{"action":"created","issue":{"url":"https://api.github.com/repos/pyqg/pyqg/issues/71","labels_url":"https://api.github.com/repos/pyqg/pyqg/issues/71/labels{/name}","comments_url":"https://api.github.com/repos/pyqg/pyqg/issues/71/comments","events_url":"https://api.github.com/repos/pyqg/pyqg/issues/71/events","html_url":"https://github.com/pyqg/pyqg/issues/71","id":105114938,"number":71,"title":"instability of a QG jet","user":{"login":"francispoulin","id":8239041,"avatar_url":"https://avatars.githubusercontent.com/u/8239041?v=3","gravatar_id":"","url":"https://api.github.com/users/francispoulin","html_url":"https://github.com/francispoulin","followers_url":"https://api.github.com/users/francispoulin/followers","following_url":"https://api.github.com/users/francispoulin/following{/other_user}","gists_url":"https://api.github.com/users/francispoulin/gists{/gist_id}","starred_url":"https://api.github.com/users/francispoulin/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/francispoulin/subscriptions","organizations_url":"https://api.github.com/users/francispoulin/orgs","repos_url":"https://api.github.com/users/francispoulin/repos","events_url":"https://api.github.com/users/francispoulin/events{/privacy}","received_events_url":"https://api.github.com/users/francispoulin/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2015-09-06T20:11:01Z","updated_at":"2015-09-08T01:21:55Z","closed_at":null,"body":"Inspired by the recent advances in pyqg, I would like to put together another QG example.  Basically, I want to reproduce some of the results of Glenn's from 1987.\r\n\r\nhttp://journals.ametsoc.org/doi/abs/10.1175/1520-0485(1987)017%3C1408:NWACVS%3E2.0.CO;2\r\n\r\nHe uses the reduced gravity BT QG model but one issue is that the streamfunction is not periodic in one direction.  One way to do this is to decompose the model into a basic state and perturbation\r\n\r\npsi = Psi + psi'\r\nq    = Q   + q'\r\nu    = U   + u'\r\n\r\nThe fully nonlinear governing equations are then\r\n\r\npartial_t q' + J(Psi, q') + J(psi', Q) + J(psi',q') = 0\r\n\r\nand we can look for solutions that are doubly periodic.  \r\n\r\nI know how to solve this in general but not sure how to fit this into the context of pyqg.  I looked in BT_model and the evolution equations are not there.\r\n\r\nRyan: any ideas how best to do this? \r\n\r\nAnother option is to look how to use DCT in one direction.  I thought the first option would be easier but am very interested to know what you all think. \r\n\r\nIf you think this is too much of a pain for the moment I don't have to do it now but I thought I'd mention it since it would be a nice example. Doing the linear stability would be nice and easy too.  "},"comment":{"url":"https://api.github.com/repos/pyqg/pyqg/issues/comments/138402312","html_url":"https://github.com/pyqg/pyqg/issues/71#issuecomment-138402312","issue_url":"https://api.github.com/repos/pyqg/pyqg/issues/71","id":138402312,"user":{"login":"rabernat","id":1197350,"avatar_url":"https://avatars.githubusercontent.com/u/1197350?v=3","gravatar_id":"","url":"https://api.github.com/users/rabernat","html_url":"https://github.com/rabernat","followers_url":"https://api.github.com/users/rabernat/followers","following_url":"https://api.github.com/users/rabernat/following{/other_user}","gists_url":"https://api.github.com/users/rabernat/gists{/gist_id}","starred_url":"https://api.github.com/users/rabernat/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rabernat/subscriptions","organizations_url":"https://api.github.com/users/rabernat/orgs","repos_url":"https://api.github.com/users/rabernat/repos","events_url":"https://api.github.com/users/rabernat/events{/privacy}","received_events_url":"https://api.github.com/users/rabernat/received_events","type":"User","site_admin":false},"created_at":"2015-09-08T01:21:55Z","updated_at":"2015-09-08T01:21:55Z","body":"> Not sure where it is explicitly specified that U is constant, maybe it isn't even declared.\r\n\r\nEverything happens in the kernel's advection routine\r\nhttps://github.com/pyqg/pyqg/blob/master/pyqg/kernel.pyx#L341\r\n(Note that this is cython.)"}}