cloud night clouds clouds cloud like phenomena ragged edge brighter polar cloud layer called polar clouds upper atmosphere visible deep twilight ice crystals roughly means night shining latin commonly observed summer months latitudes north south equator clouds observed sun horizon observer clouds sunlight highest clouds earth atmosphere located altitudes kilometres normally faint seen visible illuminated sunlight horizon lower layers atmosphere earth shadow clouds fully understood recently discovered meteorological phenomenon record observation clouds form restricted conditions occurrence sensitive guide changes upper atmosphere relatively recent classification occurrence clouds appears increasing frequency extent formation night clouds clouds composed tiny crystals water ice diameter exist height higher clouds earth atmosphere clouds earth lower atmosphere form water collects particles clouds form directly water addition forming dust particles data satellite suggests clouds require water dust cold temperatures form sources dust water upper atmosphere known certainty dust believed come dust possibilities moisture lifted gaps forming reaction exhaust entirely water detachment solid rocket height found generate individual clouds half released usually altitudes august falcon caused clouds orlando launch exhaust transported arctic region little day exact mechanism high speed transport unknown water northward falls colder occupies region atmosphere mechanism cause individual clouds thought major contributor phenomenon contains little moisture approximately air desert extremely thin ice crystals form temperatures means clouds form predominantly summer observed present inside polar circles sun low horizon season latitudes clouds form near polar regions clouds southern hemisphere higher northern hemisphere radiation sun breaks water molecules apart reducing water available form clouds radiation known vary solar cycle satellites tracking decrease clouds increase radiation solar cycles found changes clouds follow changes intensity rays year reason long known clouds known exhibit high radar frequency range behaviour understood possible explanation ice grains coated thin metal film composed iron makes cloud far reflective radar explanation remains controversial iron stripped incoming settle layer altitude clouds measurements shown elements severely depleted clouds present experiments demonstrated extremely cold temperatures cloud rapidly deposited ice surface discovery investigation clouds known observed years eruption remains unclear appearance volcano eruption discovery people observing spectacular caused volcanic debris atmosphere studies shown clouds caused solely volcanic activity dust water injected upper atmosphere contribute formation scientists time assumed clouds manifestation volcanic ash ash settled atmosphere clouds persisted finally theory clouds composed volcanic dust years following discovery clouds studied extensively germany photograph coin term cloud means night shining cloud notes provide evidence clouds appeared detailed observations unusual caused eruption previous year firmly believed clouds visible undoubtedly noticed systematic photographic observations clouds organized year continuous observations carried berlin observatory research height clouds determined project discontinued decades death new insights nature clouds composed water ice later shown correct study limited ground based observations scientists little knowledge 1960s direct rocket measurements began showed time occurrence clouds coincided low temperatures clouds detected space instrument satellite observations bright scattering layer polar caps identified extensions clouds later satellite solar explorer mapped distribution clouds clouds detected visible naked eye physical confirmation water ice primary component clouds came instrument swedish satellite performed analyses clouds produced daily global maps revealed large patterns distribution april aim satellite launched satellite dedicated studying clouds observations images taken satellite shapes clouds similar shapes clouds similarities dynamics august scientists mars express mission announced found clouds carbon dioxide crystals mars extended surface planet highest clouds discovered surface planet like clouds earth observed sun horizon research published journal june suggests clouds observed following event evidence impact caused defense space test program conducted care september exhaust particles sounding rocket launched nasa create artificial cloud cloud observed period weeks months ground instruments instrument spacecraft rocket exhaust observed reported news organizations united_states new_jersey massachusetts observation clouds generally pale blue occasionally colours including red green occur characteristic blue colour comes absorption path sunlight cloud appear bands frequently distinctive patterns streaks wave like considered beautiful natural phenomenon clouds confused clouds appear caused rocket tend colours silver blue caused uniform size water produced clouds seen observers latitude seldom occur lower latitudes sightings far south paris utah italy turkey spain closer poles dark clouds visible occur summer mid mid august northern hemisphere mid november mid february southern hemisphere faint observed twilight sunrise sunset clouds lower atmosphere shadow cloud illuminated sun best seen sun horizon clouds occur observed thousands times northern hemisphere fewer times southern southern hemisphere clouds occur frequently additionally southern hemisphere lower population land area observations clouds large variety different patterns forms identification scheme developed classified different forms classifications modified subdivided studied ground space directly sounding rocket clouds smaller crystals invisible observers ground light connection climate change proposed relatively recent appearance clouds gradual increase linked climate change author study atmospheric scientist pointed sightings coincide nascent widespread frequent twentieth century including connecting global warming clouds remains controversial penned paper hold distinction explain clouds atmospheric processes recently physics phd work supported viewing clouds possible climate change conclusion sign increasing presence water high atmosphere nasa scientists speculate driven higher clouds form climate change reactions end producing water altitudes climate models predict increased greenhouse gas emissions cause cooling lead frequent widespread occurrences clouds theory larger emissions intensive farming activities produce water upper atmosphere concentrations doubled past years suggest transition hydrogen economy result increase free hydrogen concentration atmosphere increase number clouds
Noctilucent cloud