Live from the Julia Morgan ballroom in San Francisco, extracting the signal from the noise, it's theCUBE, covering Structure 2015. Now your host, George Gilbert. This is George Gilbert. We're live at the Julia Morgan room at Structure 2015, the iconic conference. And we're with Paula Long, founder and CEO of Data Gravity. Paula, good to have you. Thank you for having me. So, for those of you who don't know your fame and fortune and glory at Equalogic, tell us what made you found Data Gravity and what its mission is. Okay, so I was the founder, co-founder of Equalogic, which we sold to Dell in 2008. In 2011, I found myself sort of unemployed and trying to think about what to do next. And I had a great ride with Equalogic. And I said, I'm never going to do IT again unless I can come up with a really good idea about a new problem. And so, right around that time, big data was coming out, there were security issues, there were storage issues. And I started to wonder if maybe storage could help you solve your big data analytics issues and your security issues right at the point of storage. So, could the storage array tell you about the data it held? And could it help you secure it, protect it, and service it in a way that was effective for the end user? And I said, yes you can. And so, Data Gravity was found. Okay, so take us then into the next, that first use case. What type of data, who was the sort of, the Zebra customer, the one you could see at 100 yards away? What were you solving for them? Okay, so what I then observed is, lots of focused on structured data, not a lot of focused on unstructured data, yet unstructured data was growing at 80% faster than structured data. It was 80% of your data, and it was most likely the mismanaged. So I said, we're going to go unstructured data for the first iteration. And then I said, your customer's going to be people who have regulatory requirements or sensitive data. So sensitive data can be personally identifiable information, like credit cards or social security numbers, but it also can be company IP like software or plans for manufacturing, et cetera. So our customers really have a pretty broad vertical market, we have customers in legal, customers in healthcare, customers in education, customers in state and local government. And the common theme is, they need to be able to understand and protect their data, both to make sure that they are in compliance, but also to get leverage from that data. Okay, so let's start with security, sort of constructs many people are familiar with. They log in, a directory says, okay, your ID is...  And you're authorized to get to these resources. So that's sort of the basic infrastructure. Now what do you layer on top of that? So what really happens is you come in and you have a set of data that you're allowed to get to. A lot of security is done by obfuscation. So a lot of times you're able to actually see stuff that you didn't know you could find, right, and then you'll just stumble into it. This is what Bill Joy used to call security through obscurity. Absolutely, security through obscurity. So what we do is we let you understand where your classified information is, what is the permissions on it, and you decide what's classified. We have some built in what we call tags or classifications, but you can build your own set as well, and we have very easy tools to do that. So then you log in and you start looking at stuff, and you'll see us over time start to create profiles. So just because you had active directory permissions to read something, if you weren't in a classification profile that matched the classification of the data, you'd still be denied access. So that's a future, but that's coming. Give us a more concrete example of that. So for example, I'm working in a database and I cut and paste some things out of the database that happen to have some security numbers and happen to have some credit card numbers from an employee, a health form or an employee. And I cut and paste that and it ends itself up in a temp directory somewhere and that inherited the permissions from the directory. So now it's wide open with your personal information in it. What you really want is that file, even though it's wide open, you want to know that George doesn't have rights to read that because he doesn't have rights to read that classified information.  Now this is all things we'll be doing. Some of the things we do now and some of the things are on the roadmap for the future. But what you really want to do is not just do things by by just plain rule, you want to do things based content and people will wear as well. Okay, tell us what that, I mean, for a directory like an access control list says these people have this type of access to these documents. So what did you have to layer on top of that? Now being a little bit more abstract than the, I can't read that temp file, tell us what did you put on that new layer to make it more general? So what we do that no one else really does today at the point of storage is we understand people and we understand people how they are identified from either active directory or LDAP or NIS, which are the name services you use to get into storage. And then we understand content. So we look at over 400 different unstructured data types and we extract content, whether that's in a file share or if that's in a VM or if that's in a block device. And then we look at time. So what we have is we have a map of you, we have a map of content and we layer on top of that classifications to say who can look at what and what can do what. So what we've built is I hate the word platform and I always rag on people who use the word platform but we've created this set of metadata and data that we can use to transform and make rules about how the data is accessed.  So if you were to take an MRI of your hand for example, you can see some bones are very healthy, some bones aren't, if you look at the hand it seems fine, but when you look inside you can see like this finger was broken once before. We can do the same thing with your data. We can take an MRI of your data and we can map to that the users and we can map to that the access. So we can do amazing things based on what we put together for data transformations and actions. Would it be a fair to call this like a forensic analysis of how your unstructured information is being accessed and used? And then. Sort of, except forensics analysis applies kind of a post-project, it kind of sounds like somebody already died and then weeks later you solve the case. We're actually actively participating in the, we're at the crime scene if you will, storage is at the crime scene. So we're actually seeing what's happening in the data as it's happening and we can be much more near real time. Nobody's really real time, right? But near time, whereas forensics is sort of more of a passive thing. So we were talking about this earlier. So SharePoint is like the sort of new file server and it's a way of, you know, people have to actively go in and classify information and set permissions and things like that. Is there a way for you to, where you're sort of automatically assigning, you know, who can get access, but also tagging that information so that when you build these policies for access, could those feed into a sharing environment to help sort of surface more information more easily? Yeah, so anything that relies on the end user tagging things is destined to have problems. Unfortunately, including myself, humans make errors. And to be honest with you, we don't really, if you look at the number of tags companies have for how they're going to classify data, no one's going to do that. So what we do is we let you create a set of, you know, basically regular expressions or ways to scan the data to tag and we'll auto tag for you. Now we aren't doing the access check based on content permissions today, but you'll see us doing that in the future. Okay, replay that last little bit because it sounded important and I'm not quite sure I got it. Okay, so end users being responsible for tagging things is destined to be problematic. What we do is we're actually scanning the content and based on rules you provided and rules we have, we're creating what we call tags or classifications on the data dynamically. Almost like we're... We're learning about your data and we're helping you put your rules on your data. Okay. And then today we are looking at reporting on who's accessing what and when and you'll see us in the future have capabilities in the not too distant futures to be able to classify who can actually access things based on content. We do not have that today, but we will have that soon. That sounds like not only who would be able to access things based on content, but you might be able to have performance tiering even behind it. You can imagine, so for example, today's storage tiering and I, with Equalogic, we were one of the people who did tiering, it was based on who was asking for performance. So the more you ask, the more you try to give it. Well, if this is a movie everybody's watching, you might not want to give that performance. What we'll know is we'll know about the content, we'll know about what's going to be ahead next because we know the structure and we'll be able to do performance work knowing about content. We're not doing that today, but it's definitely a roadmap thing we can do and we can start to say that that movie is not important, but this aura file is. Okay, so now let's jump to the sort of the value, how you deliver value. So it's O'Coran to talk about converged infrastructure and hyperconverged infrastructure and you deliver an appliance. So tell us how that fits in. Our value add is 100% software and it's delivered in a storage array. So we are a storage array that knows about your data that can help you protect it, give you information about it and how to manage it. So what we talk about is we're not converged in the traditional sense, but what we've done is we put a layer of data services next to the data that benefit from being next to the data. A lot of the converged stuff lets you put whatever application you want there, but there's no really performance benefit from living in the, it's a packaging convenience exercise, it's not a, they're leveraging the fact that they're close to the data. We leverage the fact we're close to the data. So typically storage in a converged environment might be more about sort of patching and upgrade, simplifying that sort of thing. Well, it's about scale and what you'll see in a converged infrastructure, when storage and compute scale sort of in match sets or linearly, it provides a really good value and it's an easy way to deploy when they don't actually end up scaling that way. You find yourself with either way less capacity than you wanted and you have to buy more computes than you want or you find yourself with way more computes than you want because you've got too much storage. So it's not, it's not, I say storage is a couch potato because it keeps getting bigger and growing and isn't always active, where computes are always active. So the scaling and the economics are not always right for hyperconverged but it is an important part of an overall IT strategy. Okay, can you give us a sense of how you're going to take this? It sounds like primarily files right now. We have lots of customers, I'd say 95% of our customers are running some form of virtualization and we're looking at unstructured data. Now remember unstructured data is generated by applications and humans. So we are looking at application data and we're looking at human generated content. Okay, so when you say application type data, that means application aware and looking inside. Application aware and looking inside. Not application aware and that I can take a backup because they told me to, application aware and that we know what the content is and we know who the users are and we know what the purpose of the application was. Okay, so instead of a file being something that's opaque, you know, you can add value in the way you do. Okay. So we've heard a lot about, you know, the rage right now is all these flash SSD devices and sort of no one seems to be picking on you. Sort of why is there so much activity there and how did you stake out such a defensible position seemingly on the other side? So when we started Ecologic and I will get to the point I promise, you know, we decided to go after mid-tier customers much like data gravity is going after mid-tier customers, you know, 50 to 2,000 employees, less than a quarter of a petabyte of data. So we're going after mid-tier customers. We defined a real customer problem and need in a market big enough and then we did differentiated stuff. So in the case of Ecologic, people couldn't get to a sand because nobody knew how to manage storage and didn't really, well, they did not know how to manage storage but Fiber Channel was new and complicated and storage required a lot of like a PhD and storage to manage it. We made it all self-managing. With data gravity, what we've said is not everybody's going to have a CISO, not everybody's going to have a security officer or an analytics officer, so why don't you make the storage do that for you? Right, so why don't you add the software to do that for you as opposed to having to hire people to do it. Okay, and everyone was off with a shiny new toy. Everybody else off doing Fiber Channel, trying to be the fastest guys on the planet and we were saying, you know what, we're going to be fast and we were fast and we are fast, but we don't have to be the fastest guy on the planet because you can be a jock and an intellect at the same time.  That never happened to me, just FYI. Me neither, but they don't have to be mutually exclusive. Okay, we've got to wrap it there. This is George Gilbert with Paul Along from Data Gravity and we're at the Julia Morgan Ballroom at Structure 2015 and we'll be right back in a few minutes. Thank you, George.


And that was put down saying that there are only very specific files that you should be allowed to create in the C-group file system. This was, for me, this felt like an inslexibility argument. I understand for a particular distro of some sort, this is a challenge where some user space utilities would not know these files in the standard file systems are coming from BPF and they would sort of start relying on them. But I wonder if it should be allowed in a configurable way to extend these file interfaces with BPF. So maybe I want to create something in procfs and I want to add a file there and I could implement the logic or the content of the file with BPF, similarly in C-groupfs. So does it, I know that, I saw some background in the mailing list threads that there has been, like this has been shot down many times that people don't like it. But could it be under some advanced config or like for some people who have, who know what they're doing, sort of, area? You know what you're doing, config options? Yeah, probably. Like RCU expert BPF expert, right? Yeah, exactly. But what was, like maybe how I can talk through, like what was the problem with the overlay fs, trying to combine BPFfs and C-groupfs? So what the KP talked about was the previous, the very first draft version I come up to solve my problem to talk about this morning. The initial thought I had, the solution I gave was actually to using BPF to extend the C-groupfile system interface, basically you can pin a BPF object in the C-groupfile system. When you pin that, you create an artificial file in the C-groupfile system and then you can read it and write it and it was the same. But this will be becoming very intrusive to the C-groupfile system because it's actually adding files to the C-group interfaces. And that idea was not liked by the C-group maintainers. So after that, I kind of switched to the idea to replicate a C-groupfile hierarchy in the BPF file system. So by replicating these hierarchies, you can create files in the BPF file system and then read the files there. Some thoughts I have from the very first version of the RFC patch was that there are pros and cons for that solution by extending the file system. The pro is that whenever the user creates a C-group, they don't need to have added the BPF programs to create those files because it's really, the C-group file system can create these files for you automatically. So it will be a lot simpler for us, don't have the troubles that I have for the whole complicated infrastructure introduced this morning. The cons is that that will be intrusive to our file system. So that's some kind of background or discussion here. So I think there's one more very big advantage there, right? We want to have, we currently have C-groupv1 that is creating some files in the C-groupfile system. They're not taken, they're in C-groupv2. There are programs that expect those files to be present. So there is code change required, there would be code change required, of course. It's inconvenient, right? It's inflexible, which is something we should try to solve with BPF, which is what we tried in the beginning, but this would make the migration easier because the file would effectively be in the same place implemented by BPF. The contents of the file would be implemented by BPF. The other aspect is in proc, right? I want to add my own custom statistics that would be in proc. Of course, the client library to get these statistics could be sort of, you should just move towards BPF maps and the work how I was doing where you allow certain unprivileged code to read like BPF maps, but in the true Linux sense, we should probably have files in proc that could create like statistics generated by BPF programs. This doesn't fly, people don't like other things adding random files in proc, so... I remember initially I was talking to, Yong Hong told me that when they introduced task ether, they were also thinking about extending the proc file system by using BPF. So in that way, you can parameterize the task ether program and then pin those task ether program in the proc file system under each task directory. So that would be very convenient to use, but they told me that there are some concerns there, so they didn't continue in that path. I'm trying to do very much a similar thing, but eventually we choose to do the currently using this, do it in the BPF file system. So I definitely think that being able to extend the pseudo file system interface with the BPF have some uses. Anything, any pseudo file system like proc, cgroup, whatever, like I... Can we use a relay of this? Yes, that was, I think the question was not answered yet. Sorry, sorry, my bad, my bad. There are also proposals, I tried, the solution is that we have, we use the overlay file system, have a two layers of file system, underneath is the cgroup file system and the top layer is a modifiable file system, maybe BPF file system, so you can pin the, you can have, you create a unified view and which is a combination of the cgroup file system and the BPF file system. You can pin that. The issue here is that because the underlying layers is a cgroup file system and it changes from time to time, but there is a requirement in the overlay file system is that they require the underlying file system be immutable. So if you change the underlying file system, you get undefined behaviors. I tried that, it does, it's very confusing. It causes some issues from the view of the user space. For example, if you create a cgroup in the underneath, directly from the underneath file system and then you delete it, the file is cached there and you get an inconsistent view from the unified file system view. So that doesn't work using overlay file system. So what we could do is telepathically relay this question to the file system summit there, right? Like, can we make overlay FS understand base modifiable file system? Sorry, maybe we can ask them, right? This is something they would probably use because they never considered and it's possible, right? I don't know, I can ask a number about it, but my intuition is that technically it'd be difficult to avoid this assumption, to make it work without breaking our assumption. I haven't thought about it this way. I can ask and then try. I would defer to the experts there. Is that answer to that question? Just a question for understanding, like when you have the lower and upper file system, right? Could also be the lower one BPF and BPF is not modifiable except for within the kernel, so it's more controlled. And the upper one is like the C group, which? No, the eventual file system should be the same type as the upper level, upper layer, because you are pinning from the top level and in the top layer should be the same type as it. It definitely has to be the BPF file system. It cannot be the C group file system. So on a principle standpoint, right? I mean, this is a Trojan horse sort of scenario. We're trying to create files. The files will appear on something on a principle standpoint. Is it, would it be fine to add this functionality in whatever way we can if it is under config expert? But who's the ultimate person who has to like? There's no ultimate like here. It's a combination, right? It's a, well, Linux philosophy, I don't know. Like the proc files is like everything in proc should be like maintained by proc. Like C group maintains the C group. Like overlay, I think making overlay files work in this scenario where you don't have all the rights coming through the upper file system, but lower like in this case like C group can be modified on its own. And the overlay files doesn't do the caching. And like every time for every access it like goes through. I think it should be doable. And this is more of like flexible. Then we can combine like we PFS with the group of us or we PFS with proc of us. And we any other like trace of us, debug of us, see so fast, like any other files. This is the longest overlay fs doesn't maintain this caching layer and does not assume that all of the rights going through the top. I agree with you. And on a principle standpoint, that is the functionality overlay fs is supposed to provide, it is provide extension to like a post design differently. So my understanding. Okay. But maybe it will be not won't be even called overlay fs, but it's, it's pseudo file system that combines two and potentially not being, being a master of either. Okay. Should be doable. So overlay f, you have to mount overall fs. Like it cannot just appear. No, no, no, you don't prevent you have proc of us put overall fs with FFS and it all will work in the same spot. In the same slash bar. I know, I know we use overlay fs in container optimized of us where the base images sort of like read, read only. And then there are, there are overlays that go on top of that. But that is the criteria like how was mentioning that the base file system that, that is being overlaid upon is, is, is not changing. And whereas C group currently changes stuff. I just want to have a practice that like if I want to extend be able to extend proc fs, general, not inside my C group, but like overall, right? Like, how do I do this? Like, do I talk over like fast and do time and. Yeah. And then, and then files appear there, right? Because you mounted it by overlay fs, the files would appear when you're doing like, when you're interacting with the file system. This is my understanding. You can correct me if I'm wrong, right? But my understanding is that the files appear as if it was normal proc fs. This is why I was going to the principle argument, right? In principle, that's the end result. Files appear in proc fs by using overlay fs. So you might have the same principle argument here. But proc fs doesn't appear by its own. Like somebody mounts like system d mounts proc fs. Fs tab or whatever there is. If we would do, well, if we can remount, right? It's like. Yeah, but I think. I think we should just ask the first. We should try hard in this direction. Yeah. I mean, otherwise, like, if you extend one file system specifically, it's just a hack on top of other hacks. I think there was in principle agreement on that the overlay fs approaches is reasonable. It was just the limitation of the overlay fs itself. So, like, say, for example, going back to this group fs, how I think you try to do is not only to pin to one link, one iterator into cgroup fs, but also to make cgroup fs when new cgroups are created, you would transfer the old one and put in a new location. So that's becoming like very, very like BPF specific and so on. So that's what like teaching didn't like me. Like, if it was just like, let's just pin an iterator in cgroup fs and do someone special. Well, we can try to convince like humans, other cgroup folks, at least that would be okay, I think, but like automatically now, like, oh, let's take it from here and pins another place, preserve naming convention or not, like it's just becoming like really, really custom and specific. Yeah, it's gonna be messy, yeah, it's gonna be messy. So also inheritance is also important requirement for us. For example, if you have a cgroup and then you pin to parent cgroup, if you create a Chelsea group, the Chelsea should automatically be getting those pinned objects there. And I can see that pinning on the SQL file system would be difficult to have this inheritance in force. But if we add in the sleepable hooks to cgroup creation, potentially there we can create direct, create files in the cgroup of fs. So that's the thing we can sell. Yeah, yeah, sleep file. When there's things like policy, this automatic stuff is not done by the kernel, by the cgroup code. When it's like just a hook there that can create an iterator and it will do something, then it's, I think, will be fine. Right, right. Just keep this in the back of the mind because it'll make stuff a lot simpler if the files do appear somehow in cgroup fs, right? Like either via an overlay or something. I think it's just that the overlay file system is not intended to be used this way. So it has some special... Evolution. We should, I think we should check with the people there in the fs. Glad. Yeah. Yeah. Yeah. Okay, I think this was good. That's all I had. So we asked for a small topic. Perfect. Thank you. Thanks. Thanks, folks.


Hi guys, my name is Elva and today I'm going to take you through a tutorial of Nearpod. In this tutorial you will be shown how to create a Nearpod and connect it to your Google Slides as well as add a variety of features. The first step is to go ahead and go to Nearpod's website which is nearpod.com. Once you do that, if you have not already created an account, that is what you will want to do. Nearpod has a lot of different features that can be utilized for the classroom. If you go to create and then click lesson or video or activity, you can create anything you need for your class. For example, if you click lesson, it opens up more of a cloud-based version of PowerPoint. You can add many different features on here such as Slides, Slides Classic, which is a blank slide, Slideshow, you can even turn a PowerPoint into a Nearpod. You can upload a PDF file, Sway, and even images and audio. To start, we're just going to create a slide from scratch and it looks like this. Now if you scroll down on the side, you can find many different themes. You can just choose whatever you like. I'm going to choose this one called Sky Deck. This is where you make whatever you want for your title side. I personally usually do notes. So I am just going to type in China Vocabulary specifically for our DBQ as an example. Now just like PowerPoint, it will automatically regulate itself and then after you type your title, you just type anything you need to into this box. Once you are done making any changes to the slide, you click save. It'll say it saves, but while that's saving, you can go ahead and create your next one. For the next one, let's go ahead and go to some of the interactive features. One really nice thing that Nearpod has included is flowcabulary videos. Let's go to Nearpod 3D. Once you click Nearpod 3D, it has many different applications you can use. You can look up an animal cell, the auditory system, Aztec Temple. Let's go ahead and click on plant cell and click save. Now that is added in there as well. You can add any content you want on here and it'll be so, so simple for your class. You can even take virtual field trips or do any simulation with math and science. In addition to giving basic content, Nearpod also has quizzes and other interactive features like fill in the blank where students just click and drag. They can draw it. Time to climb is a favorite among students. This is where you create your own little quiz and they get to play a game. You can choose one of these over here such as map skills and it automatically gives you the question. It says, a blank indicates a relationship between distances on the map and actual distances on earth. It gives your answers and that's it. If you click save, once again, it'll save. Once you are done with your entire lesson, you want to make sure to give it a name.  Once it's ready, you can click live participation which allows students to look along with you on the Nearpod or you can do student paste which is more of a homework assignment. But once you click live participation, a code will pop up and then students can just join. You can also copy the link, email it or put it on Google Classroom. If you are a co-teacher or have a co-teacher, there's also the option to add a co-teacher on there so they can also control what students are seeing. One other great feature for Nearpod is actually not on Nearpod itself. For this one, you will want to go to Google and you want to type in Nearpod Chrome extension. You want to go to the Google Chrome website where you can download any extension and then click add to Chrome and then you can just click add extension and once it's done, you'll see it popped up where all your extensions are. So if you click the puzzle piece and you scroll down, you can see Nearpod for classroom. Now once you click on that, it just takes you to basic Nearpod but this is where the cool stuff comes into play. If you are somebody that loves Google Slides and wants to use Nearpod but you're kind of hesitant because you don't get as much creativity as you can on Google Slides, there's no need to worry. You can create your Google Slides presentation and it can be converted into a Nearpod. For example, if I take this copy of Unit 4 for China, I have fixed everything the exact way I want it but I want to put it into Nearpod now. Well, you absolutely can. All you have to do now that extension is put into Google Chrome is click extensions, then you just go down to Nearpod and click open Nearpod. Once the sidebar loads, you can add any extension you want from Nearpod right onto your Google side. I'm going to put an example of a field trip. You can just type in anything. For example, I'll type in China and it takes me to a bunch of different places.  Now it might look a little weird because it doesn't have the actual program on there.  Now that it has loaded, I'm going to show you what it looks like during a live participation. This is my title slide and it might take a minute or so for the virtual field trip to load up because it is very heavy. Once in, students can just click and drag to view their surroundings. This is a fun way for students to be able to experience other places that they might not be able to go. One other cool thing is if you decide you wanted to add something else, you have the option to do that. So you would just go back to your Google site, say you wanted to add a quiz.   So if you want to make any type of quiz, you can make an extended question. You can do anything you want with this. Here's the quiz button. My example question will be, what country are we learning about? And then you can just add your answer choices. Mine will be China or Japan. You specify the correct answer and then click save.  I hope you got plenty of useful information and can make your own lessons very soon. Don't forget to like and subscribe to our channel.


I'm Mike Krausky and I'm the Director of Corporate Relations for the College of Engineering and Applied Science. Mike grew up on the south side of Milwaukee. His backyard actually budded up to the property of Rockwell. So it's interesting that he had these relations with Rockwell down the line while working at UWM. My father had a number of degrees. He had a bachelor's degree in engineering. I think he had like two or three master's degree. He truly was passionate about learning and education and he really felt that that was a way for people to find happiness and also financial success. As my supervisor, really let me do what I do best here but at the same time he was always there to provide support, suggestions if needed and to help make career services better for both our students and the employers that we work with. Mike could bring in terms of impact for students was obviously the sense of care and concern but more specifically a lot of the internships and a lot of the partnerships where we would have opportunities that were created by partnerships and when you think about professional schools there's not a lot that's more important than to have those types of opportunities for our students to really benefit from. I wouldn't have had my opportunity to come work at Rockwell Automation and I was very focused when I started working with Mike on pursuing a technical career. Mike convinced me that there were a ton of opportunities in corporate America in business development and business leadership and helped me find my opportunity at Rockwell and I've had a really fun career at Rockwell Automation thanks to Mike's support. In the business environment he was a true professional. I admired his technical engineering skills and he was able to connect with a lot of people. Mike and I we work closely on many industry related projects and we also work very closely in the poster competition. I think we were the ones that get this whole initiative started. The poster competition I think is a phenomenal display of our strengths of our students and of our strengths around the promotion of STEM education. There are hundreds of conversations going on between students, between faculty, between industry and just a huge technical exchange. Really something that was very important in the program for the college and really also for area businesses and area industries. His main role was to try to recruit the judges and we need 70, 80 people from industry to come in and give up a Saturday to be a part of this and this was no easy task particularly in the beginning. He loved working at the university. He really did and he always said he wanted to stay until he was 70 and he felt like that would really ground out his career nicely. He took a leave of absence from the university but was still technically an employee and I think his last day of employment was on a Friday when he officially retired and it was the subsequent Monday when he passed. So that's just a testament to how much he loved it and I don't think he can ever say he didn't want to be there. I'm Mike Krausky and I'm a Milwaukee engineer.


In the last lecture, we have started talking about what is the basic system responsible for the monsoon. We already talked about the first hypothesis for this system, namely that the monsoon is a gigantic land sea breeze. Now, in this lecture, we will talk about the evolution of the ideas about the basic system. You may recall that in the last lecture, we ended with comments by Simpson, which said that the land sea breeze theory is not tenable because we cannot understand the observed spatial and temporal variability of the monsoon on the basis of land sea breeze theory. We cannot explain it by land sea temperature contrast. So, now, let us look at how the ideas about the basic system have evolved and that is what I propose to do here. And before we do that, let us remind ourselves what is it we are trying to understand, what is it we are trying to explain. And it is of course, the seasonal variation of rainfall and wind. Now, here I have the rainfall for December, January, February and it is over the equatorial region and June, July, August and the monsoon has come over land, there is rain here. Now, the winds also change in direction. As you see, they are in December, January, February from the northeast and they change to southwest here. I want you to also note an important feature of the winds in June, July, August or summer monsoon season, namely that there is a crossing that occurs. These are the southeast trails and they cross over. They cross over into the as southwest winds when they come to the Arabian Sea. This cross equatorial flow, you will realize is very important and many theories have in fact, talked in detail about that as well. Now, so what we are proposing to do in this lecture is to see how the ideas about the basic system responsible for the monsoon have changed over time. Now, as I mentioned, the first hypothesis is that the primary cause of the monsoon is the land ocean contrast and in temperature in the summer and that the basic system is a gigantic land sea breeze. Now, Simpson, who actually pointed out that this land sea breeze model for the monsoon cannot explain the observed variation of the rainfall over India, suggested an alternative hypothesis, an alternative hypothesis to land sea breeze. He suggested that the peculiar distribution of the mountain ranges over the Indian region and regions to its north and east plays an important role in the monsoon rainfall over the Indian region. So, this is a new theory and an important element of that theory is the peculiar topographic distribution. This is the mountains over India. This you see is the huge Tibetan plateau to the north and these are the western guards and there are of course, hills in the northeast region as well. Here you see it as you see it in an atlas. So, you have these Himalayas to the north and you have also high mountains on the Burmese coast and there are the western guards and eastern guards and of course, Vindhya's and Aravlis and so on and so forth. So, this is the peculiar mountain distribution over the country and these are the surface winds which you have seen before. This is the cross equatorial flow and now here it is you can see that the winds are coming almost at right angles to the western guards. So, what is Simpson's theory? Simpson has drawn these streamlines of the flow during the monsoon. They go this way and what he says is that the mountain ranges, these mountain ranges he is talking of the mountain ranges which I have marked as red. These mountain ranges in fact, are equivalent to two sides of a box. You can see on the north and on the east, there are mountain ranges. So, there are two sides of a box into which the air streams through the other two sides. So, these are the other two sides. The air is streaming through the other two sides, but the box is closed to the north as well as to the east. There are no openings in these two sides and the air is flowing from the other two sides. So what he is saying is that the mountain ranges which I had colored red are equivalent to two sides of a box into which the air streams through the other two sides. Now, there are no openings in these two sides. As the air pours in from the other sides, it is clear that within the area shown, the air must rise at least as high as the mountains. This is his logic. So, he is saying that the simple geographical relation of the mountains around India to the main currents necessitates an essential movement of air at least up to 6,000 feet that is the height of the mountains to the east which in reality is more or near 20,000 feet. So, actual ascent of air is very up to very very high levels. He is aware of that and he is saying minimum ascent up to 6,000 feet has to occur simply because that is the height of the walls of that box on the north and east. So, he is saying because there are walls there is forced ascent of air because air that is flowing in has to get out of the box and the only way it can do it is by ascending. So, it is this forced ascent that India it is to this force ascent that India owes its rainfall the essential currents due to India being warm are absolutely insignificant in comparison. So, he is saying the fact that land is warm compared to ocean it will generate some winds and ascent, but what is more important is this forced ascent due to the mountains. Now, this is the mean average rainfall July rainfall over India and this is of course from the C map which is partly satellite derived and partly based on land gauges, but it has a course resolution compared to the rainfall maps that we see from India Med Department. So, this is the high rainfall on the west coast that you see very very low rainfall here. This is Tamil Nadu coast this is the south eastern coast of the peninsula there we have very low rain very high on the west coast then very high here in the northeast including Cherapunji which gets one of the highest rainfalls and then the rainfall decreases as we go this way this is the main pattern. So, now he actually gives us explanation for why it varies with space the way we have seen. So, the first is the wet area on the west coast that we have seen we have also seen that the main air currents are almost at right angles to the western guards and forced to rise at least 4000 feet. Now, this air is warm and with humidity around 90 percent it therefore, contains much moisture condensation sets in at a height of about 500 feet and during the remainder of its ascent condensation continues giving rise to very heavy rain. See, this is something this is a process that we have seen earlier how forced ascent due to topography in this case western guards can give rise to condensation clouds and rain. Now, the ascent is naturally most sudden in the middle of the range while at the ends where the air can escape around instead of going to the top it is less rapid. So, what he is saying is if we look at the mountain ranges then this is the mountain range of western guards and right in the center it is difficult for the air to go around whereas towards the edges like here the air can kind of skirt around the mountains and go in this manner. So, he is saying that in fact, the strongest ascent he calls it ascent is naturally most sudden in the middle of the range while at the ends where the air can escape around instead of going to the top it is less rapid. So, in fact, right near the central part near Honawar you get highest rain on the west coast. So, this is the explanation for the west coast rainfall and this is something we are all very familiar with. Then he asked for why is it dry over the rest of the peninsula we have seen that as well that compared to the rain here this is the west coast high rain here and compared to that you have a dry hole here the rain is very less on the southeastern part of the peninsula this you have seen. Now, what is his explanation for that he says after the air stream has crossed over the main ridge of the guards it continues to the east, but now instead of rising it descends to the plains right it has already gone over the mountains and now it is descending to the plains. A descending air current is warmed by adiabatic compression this causes the rainfall to seize and the cloud particles to be rapidly evaporated. So, we have descending air current over the plains to the east of the guards and there the rainfall ceases because the cloud particles get rapidly evaporated. So, this is what you see here that you have high rain here and low rain here because the air is descending over this portion here after having ascended over the western guards. Now what about the wet regions on the coast of Burma the air currents over the south of the bay strike the mountain ranges on or near the coast of Burma giving heavy rain where they meet the mountains we can see his idealized figure of mountains again and you will see here see these are the ranges high mountain ranges on the coast of Burma and the air stream that he goes right at right angles to these will naturally have to ascend and that will give very high rainfall over the coast of Burma. So, now we have an explanation for why it rains on the west coast why it is dry over the peninsula and why there is so much rain over the coast of Burma. Now heavy rain at Chirapunji practically saturated air from the bay crosses the deltaic Bengal which at this time is one great swamp because it has already rained a lot there. This air current with the velocity of many miles per hour strikes the Khasi hills at right angles. Now, this is again Simpson's view of the topography simplified view and what you see here are the Khasi hills and so this air which is coming from the bay of Bengal going over what was then called Bengal this whole Bengal region which he claims is almost a swamp now actually encounters Khasi hills at right angles to that air stream. And so this air current with a sufficiently high velocity strikes the Khasi hills at right angles and has to rise at least 4000 feet. So, now you see the situation near Chirapunji where again you have very moist air rising at hitting the mountains at right angles and therefore, rising this is the Khasi hill thing. So, this is why you have very high rain at Chirapunji. Now what happens over the Gangetic plain and the sub montain region to the north now we have seen I think we should just see what the observations are on that side as we mentioned here the highest rainfall is here near the head bay and as we go towards the north west the rainfall is decreasing that is very clear here you can see the contours here the heavier rain is here and as we go steadily towards the north west the rainfall has decreased. So, this is what now he is trying to explain why does the rainfall decrease in the Gangetic plain from here to here remember the mountains are here. So, this is where we are trying to find out why the rainfall has decreased. So, now we have so this is the Gangetic plain and this is a stream line idealized picture of the stream line which comes here. So, it is air that has come over the Bay of Bengal and now is easterly over this region. So, this is the air current so the red stream line which I just showed you represents the air flow over the west of the Bay of Bengal this current arrives at the coast of Bengal heavily laden with moisture, but it means no obstruction directly. So, this is a case in which you see there is no obstruction here all the obstructions are here this air that comes across means no obstruction, but it gradually proceeds towards the west. He says this current arrives at the coast of Bengal heavily laden with moisture, but it means no obstruction directly on crossing the coast it is deflected to the west and passes right along the Gangetic plain and reaches as far as Punjab this we have seen. It is however passing into a region from which there is no outlet for air is flowing into the same region from the west and the south and the great Himalayan barrier impedes its motion to the north. So, his picture is as follows you can see that the air is flowing into this region from Arabian Sea as well you see this is the air coming from the Arabian Sea this is the air coming from the Bay of Bengal and so air is coming together here and it has nowhere to go because there is a wall here and there is a wall here this is the way he envisages the picture. So, what we have here is that it is deflected to the west and continues going east it is however passing into a region from which there is no outlet as we have seen because the air is flowing into the same region from the Arabian Sea as westerly flow as well as from the Bay of Bengal as easterly flow and there is the great Himalayan barrier to the north. So, it cannot go north. So, this current of air must therefore rise, but it does not do so suddenly, but gradually over the whole length from the bay to Punjab. So, this is his picture then that over this region there is no over this region then it ascends the air ascends because there is a lot of convergence of air, but it does so gradually it is not like you know going coming to a mountain and suddenly there being a sharp increase and sharp ascent it does so very gradually as it moves here and actually the ascent decreases as you go from Bengal to here. So, this is why the rainfall decreases as you go from here to here this is what his claim is. So, the current of air must therefore rise, but does not do so suddenly, but it rises gradually over the entire region and that is really his explanation for the rainfall over the monsoon zone now. Remember, it depends on there being a current from the Bay of Bengal air current that is to say winds from the Bay of Bengal which go towards the northwest. So, he says since it is now ascending and ascending right from the Bay of Bengal to the northwestern parts he says and the ascent is higher near the bay and slowly decreases as you go towards the northwest he says rainfall is greatest in the stream near the coast of Bengal and decreases slowly in its intensity as it penetrates over northern India. Now this all sounds like a good theory it is a it sounds reasonable, but the catch is that it depends on the winds or what he Simpson calls air currents being the way they are ok. But you know we know very well there are breaks in the monsoon in July when actually there are no easterlies at all. So, it is not we cannot really assume a given pattern for the low level wind and then figure out the rainfall see the wind itself depends on the rainfall. So, during breaks in fact there are no easterlies and this explanation cannot hold. So, this is a rather than saying this explanation does not hold this explanation sort of does not take into account the interaction between rainfall and wind. It assumes that the wind pattern is what it is just like it assumes the mountains to be what they are, but while the mountains remain steady the wind does not ok. Then comes the very interesting question of the dry region in the northwest ok. So, the case of the dry region in the northwest is rather complex and is made up of four factors he says each of which depends on the other and they may be stated as the following. Almost the small amount of moisture which reaches the low pressure area because of its peculiar geographical position. So, we have seen earlier now we are talking of the northwest region here here. So, he is saying relatively small amount of this moisture is reaching here this is one of the reasons because of its geographical location. He says the small amount of moisture which reaches the low pressure area because of its peculiar geographical position is one reason. The dry wind from the west in the upper troposphere now low humidity at the ground caused by high temperature which prevents condensation and as the air rises below the level of the upper wind. So, there is no condensation there are no deep clouds ok and this because of this the temperature of land is high and because of that there is low humidity at the ground ok. So, this is how all these factors are interconnected and the high temperature caused by the absence of cloud and rain is what he lists as the fourth important thing ok. So, it is difficult to this is my comment on Simpson's explanation. So, difficult to take what he has given as an explanation of the lack of rainfall over the northwestern part rather all the factors are consistent with the region being what is called a heat low and I will be talking about these heat lows these are low pressure regions which have no rainfall. I will be talking about these dynamical systems a little later in the lecture as well. So, again this is a matter of things being consistent that there is no cloud and rain the temperature is high ok. So, the humidity is low and so on and so forth and there is a lot of dry air coming into the region. So, now according to Simpson what how what is the basic system responsible for the monsoon what is the primary cause of the monsoon. So, although he has short down the Land C Breeze theory of the monsoon he still says that the primary cause of the monsoon is the difference of temperature over land and sea ok. So, that he still maintains is the important thing the relatively high temperature over land in the northern hemisphere during the summer tends to lower the pressure there as the pressure falls over land air motion results and the air motion is acted on by rotation of the earth which again modifies the original pressure. So, he is bringing in a lot of interactions here and the result of all these interactions each of which affects the others is a close low pressure system over the whole of Asia and North Africa with the lowest pressure in the northwest of India. The pressure distribution in the final system bears no relationship to the actual temperature in the different parts. This is an important point to recognize that the finally pressure and temperature patterns are not by any means identical. Then he goes on to say the air over the north Indian ocean including the Arabian sea and the Bay of Bengal takes part in the general motion set up by this huge pressure system which inverse low pressure extending right from Africa to India and high pressure in the southern hemisphere and this huge pressure gradient this huge pressure system sets up the air currents or the winds ok. So, the air takes part in this general motion set up by this pressure gradient as the pressure falls over land in the northern hemisphere the pressure rises over the ocean in the southern hemisphere. So, we have high pressure in the southern hemisphere a huge low pressure belt in the northern hemisphere the resulting air motion affected by the earth's rotation and the distribution of land in the southern hemisphere modifies the pressure distribution. The final result being a closed high pressure system in the south of the Indian ocean. So, he is again talking of how the pressure gradient is set up the air over south Indian ocean moves under the influence of this pressure distribution and the rotation of the earth towards the northwest as far as the equator. So, these are the south easterly trades going from the high pressure region to the south of the equator to the equator ok. At the equator the air from the south is caught up in the circulation around the low pressure system in the northern hemisphere and moves towards the northeast now this is because the Coriolis force changes sign as the air crosses the equator instead of pushing any wind to its right now to its left in the southern hemisphere now it is pushing it to its right. So, this is why we get south westerly flow and the southwest air motion over the north Indian ocean is therefore, a continuation of the southeast air motion over the south Indian ocean. This is why I pointed out to you this important cross equatorial flow which contributes moist air to the monsoon. So, this has been again emphasized and it has been shown that in fact the air that is crossing as the southwest monsoon over the Arabian sea emnates from the southern hemisphere as southeast trades this is what Simpson has pointed out. So, in consequence the air which reaches the Indian area has travelled for 4000 mines over the ocean and is therefore, highly charged with aqueous vapor. The southwest air current over the north Indian ocean which is impaled forward by forces extending over the whole region of its motion is directed towards the high mountains of India which are so arranged as to form a barrier to the north and the east. So, now you have a the scenario that Simpson has built up that you have a pressure gradient set up with high in the southern hemisphere low in the African Asian belt in the northern hemisphere air motion results from this pressure gradient and there is rotation of the earth and in consequence of all this you get southwest flow and the air is finally directed into this box as Simpson envisaged it with a wall in the north and wall in the east. So, in consequence the air actually which crosses the north Indian ocean in fact comes into the box which is formed by the mountains there. So, the air is caught in a trap from which there is no escape, but for rising this is Simpson's thing. So, Simpson concludes that we have seen that the heavy rain characterizing the monsoon is caused by the inflow of large quantities of damp warm air into the region on account of the peculiar distribution of mountain ranges it is forced to ascend and in consequence deposit its moisture as rain. So, he is saying that mountain ranges are primarily responsible are a major driving are a major element in making it possible for the large rainfall over India which we call the monsoon. But he further remarked that we have seen that the actual temperature over the Indian land area is not directly responsible for the existential currents which cause the rain. He is saying the actual temperature is not responsible for the rain it is not responsible for the ascending currents which are related to the rain on the contrary in the regions where the rainfall is prevented the temperature is abnormally high that is in the north western part of India while the greatest rainfall is accompanied by low temperature. So, this is Simpson's theory of the monsoon. Now, so although Simpson argued against considering the monsoon as a gigantic land sea breeze the basic system that he proposed is also special to the monsoonal region. He claims that it is because of the special configuration of the mountain ranges that we get ascent of air here and therefore, in fun. So, it is a system which is special to the monsoonal region resulting from an interaction of the air motion set up by land ocean contrast with the special topography of the region. So, this is what Simpson has argued for. Now, so all along we are thinking the thinking so far has been that the monsoon is the basic system responsible for the monsoon is a special system which occurs on over the monsoonal region. Whereas, however, been a different school of thought in which the monsoon is considered to be the seasonal manifestation of the seasonal variation of the tropical circulation and rainfall in response to the seasonal variation of the incoming radiation. So, thus the basic system responsible for the monsoon rainfall is assumed to be the same as that associated with the rainfall over the rest of the tropics that is ITCG, Alaa, Charney or the equatorial trop, Alaa, Reel. So, the second school of thought says the basic system that gives us rainfall over monsoonal region is not different from the ITCG which gives rainfall over the tropical pacific. But the amplitude of the seasonal variation in the location of the system is exceptionally large over monsoonal region. Now, the implications for the variability of the monsoon from these two high two kinds of schools of thought if you wish are entirely different because if the second hypothesis is true if the system is the same then some of the feedbacks which lead to the variability of the ITCG over the pacific should also operate over the monsoonal region. Whereas, if it is a special system one has to work out what leads to the variability by looking at the special system itself. It appears very interestingly now in fact several years I would say almost 50 years, 40 years before Simpson the idea that the monsoon is associated with the upper air and so over the Indian region of the rain belt which is present around the year over the equatorial Indian Ocean was first suggested by Blanford in his classic treatise. It is amazing how many of the so called new ideas that we think have come only in the modern era can be traced to this genius Blanford and which he has in fact expounded on in his very classic treatise this is rainfall of India monographed by Henry H. Blanford who was the meteorological reporter to the government of India and this is published as an Indian meteorological memoir 1886. So, this is a very classic memoir and in that how does he talk about the basic system responsible for the monsoon. So, he begins with the spring months he says during the spring months on the Bay of Bengal and the Arabian Sea the winds are light frequently alternating with calms and somewhat variable though chiefly from the south west in the former and northerly and in May westerly on the latter sea. So, he is saying during spring months the winds are weak and variable the change that ensures at the end of May or in June remember that is when the onset of monsoon over Kerala occurs this is what he is talking about the change that ensures at the end of May or in June when the surrounding seas are swept by a strong monsoon current and heavy continued rain sets in on the coast of India is very marked and has long been recognized in popular language as the burst of the monsoon. So, this is the onset over Kerala which has been popularly called burst of the monsoon for well over a century now. Then he talks of what is the essential cause the essential cause of the change change from the spring conditions where you have light and variable winds and hardly any rain over India to what happens during the burst of the monsoon. The essential cause of the change appears to be that during the spring months the sea winds which feed the storms of that season are the relatively damp but by no means saturated air of the surrounding seas. So, during the spring he says the air that comes that generates the storms around India is actually simply the sea wind which feed the damp but by no means saturated air of the surrounding seas. So, this is a local air sea interaction kind of thing. So, these are local winds that generate the storms or if saturated at least not so to any considerable vertical height above the sea. So, what he is saying is that the water vapor in the air is constrained to the lower layers of the air in the spring lower layers of the air in the spring but in more southerly latitude that is to say in our spring itself over the equatorial region in the neighborhood of the equator is a belt of the atmosphere corresponding to the doldrums of the Atlantic into which the southeast trades of the south Indian ocean for a study study supply of almost saturated air. So, he is saying in spring itself there is a rainy belt and I believe this is a picture this is a satellite picture in spring and what you see is that there is an equatorial band here and this is the band which is what Blanford refers to as a rainy belt and into this air is flowing moisture laden air is flowing from the southeast here these are the southeast trades this is what he is talking about. So, he says that in the more southerly latitudes there is a band which corresponds to doldrums in the Atlantic which is very similar to the ITCZ what we call now the ITCZ over the Atlantic into which southeast trades of the south Indian ocean for a study supply of almost saturated air. So, at all times of the year more or less convection goes on in this belt. So, this is what we refer to as the ITCZ or the equatorial trough. So, the ITCZ or the equatorial trough is located over the equator in our spring that is April May and he says that in fact at all times of the year some convection goes on here there is always some rain here as proved by its raininess in all the seasons and consequently it affords a great reservoir of air which up to an indefinite height above the sea surface borders at all times on a state of saturation. Now, remember he is talking in 1886 where we did not have upper air measurements and so he says that there is moisture up to an indefinite height above the sea surface. Now, we know up to what height it is there, but it is up to a so he is talking of a very very deep moist layer. So, what he is describing is an ITCZ over the equatorial region and the critical characteristics of the ITCZ in terms of the moisture moist air being water vapor layer extending to very very high levels that is what he is referring to. So, now it appears to be he continues this is Blanford again talking he has described what is happening over the equatorial region in the spring and then he says now it appears to be the eventual rush of this air towards the region of low pressure developed over India gradually during the summer months during the spring months sorry that constitutes the burst of the monsoon. So, he has a very clear notion that the burst of the monsoon involves this movement of this moist air in the ITCZ over this region. So, he is saying the coming of the ITCZ over our region constitutes the burst of the monsoon one started and this is a very important point he makes one started the energy of its movement is sustained by the condensation of its own copious water vapor by the latent heat so set free. So, this is a very important point he is making that once you have a tropical convergence zone going then the it is sustained by the latent heat of condensation within its own region and the energy of convection furnished by the heated atmosphere of the planes. So, he is talking of the you know the land ocean contrast that has been often emphasized. So, the energy of convection furnished by this kind of a gradient of temperature between land and ocean furnished by the heated atmosphere over the planes he says as compared to that over the ocean is competent only to keep up the febler in drought that obtains during the spring months. So, actually as Simpson had pointed out in May India is much hotter than in July. So, actually this land ocean contrast is very very high in May. So, there is considerable energy of convection furnished by this land ocean contrast, but all it can do is to generate a feeble in drought that obtains during the spring months and indeed even this in drought is maintained partly by the moderate condensation of cumulus and local thunderstorm fed by the vapor it brings. So, even this energy is not the total energy for that feeble in drought part of the energy also comes from our pre monsoon thundershowers this is what Blanford is saying. So, then he actually puts it very beautifully I think the solar heat directly absorbed by the dry land atmosphere or taken up from the heated ground bears much the same relation to the general air movement as the pull on the trigger does to the propulsion of the rifle ball. I think this is an extremely important simile or analogy because he has expressed very beautifully I think what is the role played by the land sea contrast. He says solar heat directly absorbed by the dry land atmosphere or taken up from the heated ground bears much the same relation to the air movement that is the strong monsoon winds as the pull on the trigger does to the propulsion of the rifle ball. It determines the disturbance of atmospheric equilibrium, but it does not furnish the energy of the resulting air stream. So, just like the energy is provided by what is in the bullet itself or the rifle ball itself the trigger does not provide the energy what the trigger does is to provide the perturbation. So, similarly he says the land sea contrast provides the perturbation or a disturbance to the atmospheric equilibrium, but actually it does not furnish the energy of the resulting air stream that energy comes from the latent heat release. This is what Blanford has said and he says so long as this supply is small and limited to the shallow stratum of air immediately fed by the evaporating surface beneath it, so long is the air movement feeble and interrupted. So, he is now talking of the spring situation, he is saying so that the supply of moisture is limited to the shallow layer above the sea and is fed by the directly by the local evaporation over the sea itself. Then the air movement is feeble and interrupted it is only when the barotropic I am sorry it is only when the barometric gradient from south to north has become sufficiently great to tap the great reservoir of latent energy supplied by the evaporation of the southeast trade zone that the air current becomes strong and sustained constituting the summer monsoon. So, he this is again a very very important point that only when the barotropic barometric gradient from south to north this is something Simpson also talked about has become sufficiently great to tap the great reservoir of latent energy. So, he is saying that pressure gradient has to be great, but once that has become great then it is the latent heat tapping by the winds that lead to the monsoon. This is what he is saying sufficiently great to tap the great reservoir of latent energy supplied by the evaporation of the southeast trade zone that the air current becomes strong and sustained constituting the summer monsoon. So, strong and sustained wind can occur only when this in a great reservoir of latent energies tapped and he says sustained to long after the heated land surface has been in a great measure quenched and cooled by the rainfall. So, he is now talking of in a sense he has before Simpson pointed out the same thing again that this monsoon is sustained even when the land surface cools because of the rainfall. So, it is amazing that more than a century back Blanford has suggested that the Indian summer monsoon is associated with the appearance over the Indian region of the TCG over the equatorial Indian ocean. He called it by another name, but the physical system he described was in fact the intertropical conversion zone as Charney had conceived it. So, this is a very very interesting thing that this kind of an understanding of the basic system geniuses like Blanford had long before in fact more than one century back and now recent ideas how have how has the monsoon been talked about in recent literature. So, unfortunately what has happened is that although the view that the most fundamental driving mechanism by of the monsoon is the differential heating of land and ocean continued to be supported for a long time. So, the thing that was originally proposed by Haley actually continued to be supported for a long long time namely if you look at a important chapter the elementary monsoon in a book entitled the monsoons that came out in 87 where Peter Webster has tried to explain how monsoon arises. What he talks about also is a gigantic land sea breeze of course with modifications in the sense he puts in how the deep clouds arise over land and so on and so forth, but the basic idea remains that it is a gigantic land sea breeze and the primary cause is the land sea temperature contrast. So, this idea has continued to be in literature for a long time considering the monsoon as a manifestation of the of the tropical atmosphere to the seasonal variation of the incoming radiation began to get support in the 70s I would say in the late 60s and early 70s. So, this monsoon as a gigantic land sea breeze land sea temperature contrast being the primary cause of the monsoon and so on or monsoon being attributed to a very special system over the monsoonal regions has continued to hold sway in text books as well as in monographs and you know books specialized books on the subject even to this day I must say, but an alternative school of thought namely considering the monsoon as a manifestation of the response of the tropical atmosphere to the seasonal variation of the incoming radiation began to get support. Now, this was with Reel who was again another giant in the field of tropical metrology he is the one who formulated the concept of equatorial trough, but even his perspective of the basic system responsible for the monsoon appears to have changed between 54 and 69. So, let me just see Reel wrote two books both of them are very important one in 54 called tropical metrology and one in 79 called climate and weather in the tropics both are very good books and describe in great detail the system systems in the tropics in terms of what is observed and what is the physics and so on. Now, what you see here is what appeared in Reel's 54 books and this is the location of the equatorial trough now in January in solid and dashed in July and what you see is that the equatorial trough in fact is mostly in the southern hemisphere in this part in January, but here this is over the Atlantic and so on is straddles the equator as even north of the equator in January in July it shifts only a little bit over this region and remains in the northern hemisphere in this part of the world this is the African region you know 0 to 40 he is he claims that the equatorial trough actually shifts in July, but over the Asian monsoon region these are the Asian monsoon longitude in fact he puts a blank there he does not show any equatorial trough suggesting that perhaps something else is happening over the Asian monsoon region this was in 54, but a lot more information came in the after the mid 60s with the advent of meteorological satellites and lot of papers were written Chania and Elyson's CIS theory came out and so on and so forth and with that Reel appears to have changed his perspective and in the 79 book in fact he draws equatorial trough as a continuous line across the Asian monsoon suggesting that he now believes that the monsoon is also can also be contributed to the equatorial trough coming on to that region so this is a very interesting thing as I mentioned so Reel's perspective about the basic system responsible for the monsoon appears to have changed between 54 and 69 whereas in 54 the equatorial trough in the northern hemispheric summer was shown to be absent over the longitudes of the Asian monsoon 69 book he depicts the equatorial trough over these longitudes as well suggesting that he considered it to be the basic system responsible for the monsoon although even in that book he did not state it in that way however the system responsible for the monsoon was believed to be distinct from the equatorial trough or ITCG associated with the rainfall over the Pacific and the Atlantic oceans even with the first analysis of satellite derived cloudiness by Sadler so this is Sadler's depiction of this is in fact climatological cloud cover this is entirely derived by analysis of satellite imagery which came with the first meteorological satellites and what you see here is the situation for July and this is India here so this is the eastern hemisphere and this is the western hemisphere if you wish and this is what he calls monsoonal region here and he calls the ITCG over the Pacific here and here is the Atlantic and the East Pacific and over both those regions he attributes the high cloudiness to ITCG so Sadler also clearly hinting that you know this is the monsoonal system right here this is centered about here this is India and this is our monsoon rainfall decreasing as we go here which is reflected in the clouds so this is the heart of the Asian monsoon system and that is depicted not as ITCG but monsoonal even by Sadler so actually while there was a suggestion though nobody had put it in so many words that monsoon is could be considered as a manifestation of the seasonal migration of the ITCG there were objections raised to this concept by Murakami again in 87 same year that Webster published his elementary monsoon and what he said was the following if these are the he is looking at OLR climatology and these are the low OLR regions here in January and this is for July now what you see is that in January the latitudinal extent of this low OLR region is say about 10 15 or so but if you go to July over the same longitudes you see the latitudinal extent of the cloud band is huge it is more like 30 40 degrees in latitude here so what he is saying is somehow the band low OLR band flares up over this region occupies a huge region in comparison which say this is the ITCG over the Pacific so in comparison with the ITCG over the Pacific or the ITCG over the Atlantic both of which you see here have typical latitudinal extent of 10 degrees there is a huge thing here so how can this be the same how can the system responsible for this be the same as the system which is responsible for this now so he says considering the mean OLR distributions for January and July he says over the Indian ocean of persistent bell shaped distribution of low OLR values can be seen mainly during the December to February season along the area connecting the northern Madagascar and Sumatra the lack of similar distribution during the summer indicates that the ITCG over the Indian ocean has changed its existence drastically from winter to summer in other words Murakami suggested that the system over the Indian ocean in the northern summer is different because the latitudinal extent of the low OLR region over the Indian longitudes during the summer monsoon is much larger than that found elsewhere in the tropics such as the Pacific where it is associated with the ITCG I am going to stop at this point because now as far as we are concerned the question is still open as to whether the migration of the ITCG is what leads to the monsoon over the Asian region so we will have to look at that and that is what we will look at in the next lecture.


Welcome to All Hands Update, I'm Petty Officer Brandi Wills with your headlines from Around the Fleet. Defense Secretary Leon Panetta signed a memorandum February 11th that extends some benefits to same-sex partners of service members. Panetta said the Defense of Marriage Act will place limitations on what benefits can be prescribed, but he is confident that there will come a time when that won't be in place. To see which benefits are now available, log on to defense.gov. Commander Fleet Force's command recently discussed how he plans to maintain fleet readiness through fiscal uncertainty. He said he'll continue to look at all future deployments and promise to keep commanders informed of any decisions he makes. You can read more about these stories at navy.mil. From All Hands Update, thanks for watching.


Thanks to you for the introduction. Welcome everybody to the last talk of today. I'm Navid and I'll be talking about symmetric primitives with structured secrets. This is a joint work with Hart Montgomery and Chikar Patronubis. Let me start by considering key rotation in the cloud, which is one of the most widely used tools to protect data in the cloud. So key rotation in the cloud is one of the cryptographic applications that we encounter in many scenarios. So suppose that we have some encrypted data in a cloud using symmetric key encryption, and at the security measure, we need to do key rotation in certain time intervals. A naive approach to do this would be downloading all cipher text, re-encryption using a new key, and then uploading all cipher text back to the cloud. However, it's easy to see that such an approach would be overwhelmingly inefficient and it would require more resources. So fortunately, cryptographers came up with a more efficient approach, which is to use cryptographic primitives that allow us to transform a cipher text encrypted under certain secret key SK to another cipher text encrypted under another secret key SK prime using some auxiliary information. And as the security property, we require that the auxiliary information should not leak down the underlying data. Now let's see a couple of examples of such primitives. Maybe the oldest example of such primitives is proxy re-encryption, which has been considered in both symmetric and asymmetric setting. Proxy re-encryption has been proposed by Bonaiz et al. in 98 and subsequent works showed improved versions of this primitive both in terms of efficiency and security. A more recent example is updatable encryption, which has been formally defined by Bonaiz et al. in 2013. And recently, we have seen variants of this primitive with relatively strong security guarantees known as post-compromised security proposed by Lehmann and Taikman in 2018. In a more fundamental level, there's also a primitive called key homomorphic pseudo-random functions, which has been implicitly introduced by Naur, Pinkas, and Reingold in 99 and formally defined by BLMR 13. This primitive has also further applications, such as distributed PRFs and pseudo-random functions that are secure against related key attacks and also updatable encryption. This primitive is particularly interesting because it served as a building block to build other primitives such as updatable encryption. Now, a natural question to ask is, what would bring all these primitives under one umbrella? Although these primitives differ significantly in terms of constructions and proofs, these primitives have some common properties. So the first one is that these are ostensibly symmetric primitives that have structured secret space or extra functionality. For example, in the case of key homomorphic pseudo-random function, the key space is a group which is algebraically structured. Or in the case of updatable encryption, the extra functionality is the capability to transform a ciphertext encrypted under a secret key to another ciphertext under some other secret key. In addition, known constructions of these primitives require relatively strong concrete public key assumptions, such as DDH or Decisional Defilement or Learning with Errors. Even the constructions in the random oracle model need public key assumptions. So this may imply that public key assumptions are inherent to build these primitives. So the main question that we study in this work is are public key assumptions necessary for building these primitives? The answer is yes. And here we have an overview of our results. We show that a key homomorphic weak PRF implies a certain primitive known as input homomorphic weak PRF, which has recently been shown to imply a bunch of primitives, such as PIR, Private Information Retrieval, Lasitraptor Functions, and of course, public key encryption. In addition, we show that a proxy re-encryption with UPD security implies an updatable encryption with UPD security, which in turn implies public key encryption. More specifically, we show that a proxy re-encryption with UPD security implies an updatable encryption with a strong security guarantee known as post-compromise security. And such an updatable encryption is sufficient to realize public key encryption. This means that these primitives belong to the world of asymmetric primitives. So the green arrows are contributions from Europe 19, and the black arrows are the results from our work. In addition, we also show that certain variants of key homomorphic weak pseudo-random functions do not have post-quantum security. Now, for the rest of the talk, I'm going to focus on this particular result, and we will see how to get a key exchange protocol, which is sufficient to realize PKE, from an exact key homomorphic weak pseudo-random function. The ideas for this construction and its proof can be used in similar ways to construct a variety of primitives, such as trapdoor functions or PIR. And I'm going to also quickly recall some of the definitions that we need for this particular result. So if you are not even familiar with the weak PRF, I will show the definition. So we say that a function family is a weak PRF if an attacker cannot distinguish between samples of the form xi and fkxis from xi's and ui's, where ui's are chosen uniformly from the output space of the weak PRF. This is seemingly a weaker version of a plain pseudo-random function, where an attacker gets to see function evaluations on only randomly chosen inputs, instead of adaptively chosen inputs. Now let's see a key homomorphic weak PRF. So we say that a weak PRF is key homomorphic if the key space and output space are groups with efficiently computable group operations. And in addition, it satisfies the key homomorphism property, which is basically given any two keys, k and k prime.  We usually use plus for the group operation on the key space and times for the group operation on the output space. It's long been known that we can build weak pseudo-random functions in a generic manner from any one-way function. But with the result of this paper, it doesn't seem likely that when we augment a weak PRF with key homomorphism, we can build it in a generic manner from any one-way function, because it implies public key encryption. Now let's see a simple example of a key homomorphic weak PRF. So if GBA DDH hard group of order Q or GBA group over which DDH holds, consider the function f whose key space is ZQ and input and output space are both the group G. So if we define the function as f of k h equals to h to the k, which is a single exponentiate group element, it is easy to see that this is a weak PRF based on DDH assumption. In addition, it also satisfies the key homomorphism property, which is f of k plus k prime is going to be equal to f of k h times f of k prime h, where the multiplication is the group operation over the output space. In addition, if you define the function f as f of k x equals to h of x to the k, where h is a random oracle from bit strings to the DDH hard group, so it has been shown that this is a key homomorphic PRF in the random oracle model, which has been shown by Naur, Pinkas, and Rengold in 1999. So the definition that I give you for a key homomorphic PRF requires that the function evaluations on some of two keys is equal to product of function evaluation on each individual key. It's also possible to consider relaxed definitions. One relaxed definition is almost or non-exact key homomorphic PRF.  As a simple example, if you consider this function, where the input and key space are both zqn, and the function is defined as the dot product or inner product of these two vectors over zq, rounded some modulus p, this has been shown to be a weak PRF by Banerjee, Peichart, and Rosen in 2012. And it's kind of easy to see that this satisfies almost key homomorphism property. Because for two different keys, s and t, f of s a plus f of t a is going to be very close to f of s plus t a. Now before going into the construction of key exchange from key homomorphic PRF, I'm going to describe some notation that we'll use for the construction and proof. So if y is a vector of group elements and s is a binary vector, I'm going to use yts or sty to essentially denote the subset product over the components of y using the binary vector s. This notation can be similarly generalized into the setting where y is a matrix of group element. So if y is a matrix of group element and this is a binary vector, again, ys is going to be a vector whose components are rows of y, where you do the subset product over the rows of y. For example, the first component of ys is going to be the subset product over the first row of y. Now to make sure that everybody is following the last talk of today, I'm going to show you a key exchange protocol from a key homomorphic PRF where we don't actually use the key homomorphic PRF. So we have some key homomorphic PRF f. And suppose that n is a large enough integer, I'll talk about this later. And y is an abelian group. In addition, suppose that we also have a uniform matrix of group elements. This is a square matrix where each element of the matrix is uniformly chosen from the output group of the key homomorphic PRF. So we assume that y is our common random string. So we have two parties, Alice and Bob, and they want to do key exchange. So Alice samples a binary vector a, and Bob samples an n-bit string binary vector b. Alice sends a transpose y to Bob, which is a subset product over the rows of y. Bob sends yb to the Alice, which is a subset product over the columns of y. It is easy to see that if y is an abelian group, Alice and Bob both compute the final secret mutually, in the sense that 80 transpose yb, where a is the binary vector that belongs to Alice, is going to be equal to 8 transpose yb. So in the first one, we take the subset product over the vector yb using a. And in the second one, we do the subset product over the vector aty using b. So this is a key exchange protocol, and we haven't actually used the key homomorphic PRF. But we are going to use it for the security. To prove the security of the construction, we are going to use the pseudo randomness or hardness of repeated subset products in the output group. So consider these two vectors x and k, where x1 through xm are uniformly chosen elements from the input space of the key homomorphic PRF, and k1 through kn are uniformly chosen elements from the key space. Now, we form a matrix of big PRF outputs in the following way. So we use the key vector in each row, and we use the input vector in each column. Now, if I take a random subset product of columns of s, since f is key homomorphic, I can push the subset product of columns of s to the key space, and I can view it as a subset sum over the key space. This means that fs, using the notation that I described in the previous slides, is gonna be equal to f of k star xi's for some k star that is equal to s1 k1 plus s2 k2 through sn kn. So we use the key homomorphism of f to say that this is equal to f of k star xi's. Now, by the left over hash lemma, we know that if n is large enough, we can say that given k, k star is statistically indistinguishable from uniform. So this means that given the matrix f, fs is computational indistinguishable from random. Or essentially, this means that fs is the weak PRF evaluations on a fresh random key. So we know that f is output of the weak PRF on uniform key input pairs, and in the previous slide, we saw that given f, fs is computational indistinguishable from random. Now, we know that f itself is also computational indistinguishable from random because it's the output of uniform key input pairs. So if we combine these together, this implies that given a uniform matrix y, ys is pseudo-random. So this proof technique has some other interesting implications as well. So notice that so far, we have only used the fact that the number of columns of y are large enough so that we can apply the left over hash lemma. This means that number of rows of y play essentially no role in the proof other than the fact that we need large enough rows to do the key exchange protocol. This means that linear equations with binary coefficients over the output space of a key homomorphic weak PRF is interactable. In particular, this means that there is no exact key homomorphic weak PRF instantiation whose output group is ZQ with plain addition. The hardness of repeated subset products or the pseudo-randomness of knapsack function is versatile enough to build a variety of cryptographic primitives such as trapdoor functions and PIR. As a simple trick, one can use binary matrices instead of binary vectors to get a certain cryptographic primitives. For example, one can define a function f where the input space for the function f is the set of l-bit strings and the key is a uniformly random square matrix where the elements of this matrix lives in the output group and s1 through sl are binary matrices. If we define the function such that on this key and input outputs y times subset product of si by the key homomorphic weak pseudo-randomness of f it can be shown that this is actually as strong pseudo-random function. Although the hardness of repeated subset products is versatile enough to build many cryptographic primitives, it comes with some shortcomings as well. For example, we can use quantum algorithms to determine the structure of any Abelian group. This means that we can use these quantum algorithms to show that exact key homomorphic weak PRFs with Abelian output groups cannot be secure against quantum attack. This means that over Abelian groups approximate homomorphism is the best that we can hope for in terms of post-quantum security. The idea for the attack is pretty simple. We first use the quantum algorithm to determine the structure of the output group which is basically decomposing the Abelian group into its cyclic components and then we use such explicit representation of the output group to solve a linear system of modular equations. Such an attack can be generalized to basically any primitive with exact homomorphism over Abelian groups. I'm gonna conclude the talk with a couple of open problems. Recall that the construction of public encryption or key exchange from an exact homomorphic peak PRF or non-exact bond requires the output group to be Abelian. So the question is, can we construct public encryption from a key homomorphic peak PRF whose output group is non-Abelian? Recall that the pseudo randomness of knapsack function or hardness of repeated subset products holds if the output group is non-Abelian and we only need Abelian property to show the correctness of the key exchange protocol. The next open problem is constructing public key encryption from homomorphic pseudo random generators which is a seemingly weaker primitive. So it is easy to see that any key homomorphic peak PRF implies a homomorphic pseudo random generator just by viewing the key of the key homomorphic peak PRF as a seed for the PRG and leaving the input or inputs as the public parameter. Finally, it's also interesting to consider improved definitions or constructions of updatable encryption that does not immediately imply public encryption. Such an updatable encryption might be helpful to perform certain tasks such as key rotation in cloud using purely symmetric primitives which would be overwhelmingly inefficient. Thanks for your attention to the talk. If you have a question, please come to the microphone. I have one question. You didn't talk about proxy re-encryption and updatable encryption. In the key homomorphic peak PRF case, you use the structure of homomorphic property. But in the case of proxy re-encryption, I... So the rough idea to do that construction is that since we have indistinguishability of updates or something like indistinguishability of tokens, and it gives you the capability to transform Cypher text given under some secret GSK to Cypher text under another secret GSK prime, you essentially use this capability to sort of do a key exchange protocol where you switch the knowledge of secret key to the knowledge of tokens and use this to perform the public encryption or key exchange. Thanks. Thanks. More questions? Let's thank the old speakers again.