Lee wave

A cikin ilimin yanayin yanayi, **raƙuman ruwan lee** sune raƙuman ruwa a tsaye. Mafi na kowa nau'i ne na **dutse taguwar ruwa**, wanda shi ne yanayi na ciki taguwar ruwa . An gano waɗannan a cikin 1933 ta wasu matukan jirgi biyu na Jamus Hans Deutschmann da Wolf Hirth, a saman Giant Mountains .    Waɗannan su ne canje-canje na lokaci-lokaci na matsa lamba na yanayi, zafin jiki da tsayin orthometric a cikin iska na yanzu da ke haifar da motsi a tsaye, misali ɗaga orographic lokacin da iska ta buso kan dutse ko dutse . Hakanan ana iya haifar da su ta hanyar iskar saman da ke kadawa a kan tudu ko tudu,  ko ma ta iskar sama da ke karkata a kan titin zafi ko titin girgije .

Motsi na tsaye yana tilasta sauye-sauye na lokaci-lokaci a cikin sauri da shugabanci na iska a cikin wannan halin yanzu. Kullum suna faruwa a cikin rukuni a gefen gefen ƙasa wanda ke haifar da su. Wani lokaci, raƙuman tsaunuka na iya taimakawa wajen haɓaka yawan ruwan sama a ƙarƙashin iska na tsaunuka. Yawancin lokaci ana samar da vortex mai rikitarwa, tare da axis na juyawa a layi daya da tsaunuka, a kusa da rami na farko; wannan ana kiransa **rotor**. Ana samar da raƙuman ruwa mafi ƙarfi lokacin da ƙimar guguwa ta nuna wani nau'i mai ɗorewa sama da toshewa, tare da wani nau'in da ba shi da ɗorewa a sama da ƙasa.

Ana iya ƙirƙirar iska mai ƙarfi (tare da iskar iska sama da mil 100 a kowace awa (160 km / h)) a ƙarƙashin tuddai na manyan tsaunuka ta hanyar raƙuman tsaunuka. Wadannan iskõki masu ƙarfi na iya ba da gudummawa ga ci gaban gobarar daji ba zato ba tsammani da yaduwa (ciki har da gobarar daji ta 2016 Great Smoky Mountains lokacin da aka hura wuta daga gobarar daji a cikin Smoky Mounts zuwa cikin Gatlinburg da Pigeon Forge yankuna). 

## Ka'idar asali

Raƙuman ruwa na Lee wani nau'i ne na raƙuman ruwa masu nauyi na ciki wanda aka samar lokacin da aka tilasta kwarara mai ɗorewa a kan cikas. Wannan rikici yana ɗaga sassan iska sama da matakin tsaka-tsaki. Saboda haka, dakarun maido da tashi suna aiki don tayar da jujjuyawa iska a cikin Brunt-Väisäla mita, wanda ga yanayi shine:

Oscillations da aka karkata daga madaidaiciya axis a wani kusurwa na 

φ 

{\displaystyle \phi } 

zai faru a ƙananan mitar 

N cos din 

φ 

{\displaystyle N\cos {\phi }} 

. Wadannan oscillations na iska suna faruwa a cikin kide-kide, a layi daya da guguwar guguwa (layin lokaci na yau da kullun). Wadannan guguwar guguwa suna wakiltar matsananci a cikin filin matakin lamba (watau, layin mafi ƙasƙanci da mafi girman matsin lamba), yayin da yankunan da ke tsakanin guguwar ruwa suna wakiltar tsananin gaske a cikin filin motsin lamba (wato, yankunan da suka fi samun ko rasa motsin rai).

Ana watsa makamashi tare da bangarorin raƙuman ruwa (daidai da oscillations na iska), wanda shine jagorancin saurin ƙungiyar raƙuman. Sabanin haka, yaduwar lokaci (ko saurin lokaci) na raƙuman ruwa suna nunawa a tsaye zuwa watsa makamashi (ko sawun rukuni).

## Girgije

Dukkanin raƙuman ruwa da rotor na iya nunawa ta hanyar takamaiman tsarin girgije idan akwai isasshen danshi a cikin yanayi, da isasshen motsi na tsaye don sanyaya iska zuwa ma'anar raɓa. Raƙuman ruwa na iya samuwa a cikin iska mai bushe ba tare da alamun girgije ba. Girgije na raƙuman ruwa ba ya motsawa zuwa iska kamar yadda girgije ke yi, amma yana ci gaba da kasancewa a cikin matsayi dangane da toshewar da ke samar da su.

* A kusa da saman raƙuman ruwa, sanyayawar fadada adiabatic na iya samar da girgije a siffar ruwan tabarau (lenticularis). Za'a iya tara girgije masu yawa a saman juna idan akwai nau'o'i masu yawa na iska mai bushewa da mai laushi a sama.
* Rotor na iya samar da cumulus ko cumulus fractus a cikin ɓangaren da ke tasowa, wanda aka fi sani da "girgije". Girgizar rotor tana kama da layin cumulus. Yana samuwa a gefen lee kuma a layi daya da layin tudu. Tushenta yana kusa da tsawo na tsaunin dutse, kodayake saman zai iya fadada sama da tsaunin kuma zai iya haɗuwa da girgije na lenticular a sama. Rotor girgije sun ragged gefen leeward kuma suna da haɗari mai haɗari.
* Wani girgije na bango na iya kasancewa a gefen dutsen, duk da haka wannan ba abin dogaro ba ne na kasancewar raƙuman ruwa.
* A pileus ko cap girgije, kama da lenticular girgije, iya zama sama da dutse ko cumulus girgije samar da raƙuman ruwa.
* Adiabatic matsawa zafi a cikin ramin kowane sautin sautin saurin sautin sabili sautin saiti na iya kuma fitar da cumulus ko stratus girgije a cikin iska, samar da "window na sautin sayin sautin saitin sautin safin sautin sahun sautin sawun sautin saunin sautin saƙin sautin saukan sautin saumin sautin sacin sautin saicin sautin saukin sautin sa.

## Jirgin sama
Raƙuman ruwa na Lee suna ba da damar da masu sauka don samun tsawo ko tashi mai nisa yayin tashi. An yi rikodin Jiragen sama na duniya don sauri, nesa ko tsawo a cikin tsaunukan Sierra Nevada, Alps, Patagonic Andes, da Kudancin Alps. Shirin Perlan yana aiki don nuna yiwuwar hawa sama da tropopause a cikin jirgin sama mara ƙarfi ta amfani da raƙuman ruwa, yana yin canji zuwa raƙuman raƙuman ƙasa. Sun yi wannan a karo na farko a ranar 30 ga watan Agusta, 2006 a Argentina, hawa zuwa tsawo na mita 15,460 (50,720 .  The Mountain Wave Project of the Organisation Scientifique et Technique du Vol à Voile yana mai da hankali kan bincike da rarraba raƙuman ruwa da masu alaƙa.

Yanayin da ke goyon bayan raƙuman ruwa masu ƙarfi waɗanda suka dace da tashi sune:

* A hankali karuwa a cikin iska gudun tare da tsawo
* Hanyar iska a cikin 30 ° na madaidaiciya zuwa dutsen dutse
* Iska mai ƙarfi a cikin yanayi mai ɗorewa
* Iska ta Ridgetop na akalla 20 knots

Rotor turbulence na iya zama mai cutarwa ga wasu ƙananan jiragen sama kamar balloons, rataye gliders da paragliders. Har ma yana iya zama haɗari ga manyan jiragen sama; an yi imanin cewa lamarin yana da alhakin hatsarori da abubuwan da suka faru na jirgin sama da yawa, gami da fashewar jirgin sama na BOAC Flight 911, Boeing 707, kusa da Dutsen Fuji, Japan a 1966, da kuma rabuwa da jirgin sama a kan jirgin sama na Boeing 747 a kusa da Anchorage, Alaska a 1993.

Rashin iska na raƙuman ruwa, wanda ke ba da damar masu sauka su hau zuwa manyan tsawo, na iya haifar da tashin hankali mai tsawo a cikin jirgin sama na jet da ke ƙoƙarin kula da jirgin sama a cikin raƙuman lee. Hawan, saukowa ko iska mai rikitarwa, a cikin ko sama da raƙuman ruwa, na iya haifar da wuce gona da iri, tsayawa ko asarar iko.

## Sauran nau'ikan raƙuman ruwa

Akwai nau'ikan raƙuman ruwa daban-daban waɗanda ke samuwa a ƙarƙashin yanayi daban-daban.

* Rashin iska na iya haifar da raƙuman ruwa. Wannan yana faruwa ne lokacin da juyawa na yanayi ya raba yadudduka biyu tare da bambanci mai mahimmanci a cikin hanyar iska. Idan iska ta fuskanci karkatarwa a cikin juyawa Layer wanda ya haifar da zafi jiki da ke fitowa daga ƙasa, zai haifar da manyan raƙuman ruwa a cikin karkatarwa da za a iya amfani da su don tashi.

* Hydraulic tsalle-tsalle induced raƙuman ruwa wani nau'in raƙuman da ke samuwa lokacin da akwai ƙananan iska wanda yake da yawa, duk da haka mai laushi dangane da girman dutsen. Bayan ya kwarara a kan dutsen, wani nau'in raƙuman ruwa ya samo asali a cikin kwararar kwararar, da kuma tsinkaye mai tsayi da ake kira siffofin tsalle-tsalle na hydraulic wanda zai iya zama sau da yawa fiye da dutsen. Gudun hydraulic yayi kama da rotor saboda yana da matukar damuwa, duk da haka ba a cikin sararin samaniya kamar rotor ba. Gudun ruwa da kansa yana aiki ne a matsayin cikas ga kwanciyar hankali na iska da ke motsawa sama da shi, don haka yana haifar da raƙuman ruwa. Za'a iya rarrabe tsalle-tsalle na hydraulic ta hanyar girgije mai tsawo, kuma an lura da su a yankin Sierra Nevada  da kuma tsaunuka a kudancin California.
* *Raƙuman ruwa* na ruwa suna yaduwar raƙuman ruwa waɗanda ke samar da manyan shingen sarari. A cikin daidaitattun hydrostatic, matsin ruwa na iya dogara ne kawai akan tsawo, ba a kan motsi a kwance ba. Hydrostatic raƙuman ruwa suna samun sunansu daga gaskiyar cewa suna bin dokokin hydrostatics, watau matsin lamba ya bambanta da farko a cikin madaidaiciya maimakon a kwance. Ganin cewa na al'ada, raƙuman ruwa marasa hydrostatic suna da halayen kwance na ɗagawa da nutsewa, galibi masu zaman kansu ne na tsawo, raƙumomin hydrostatic ana nuna su ta hanyar ɗagawa na ɗaga da nutse a tsawo daban-daban a kan wannan matsayi na ƙasa.
* Rashin daidaituwa na Kelvin-Helmholtz na iya faruwa lokacin da saurin shear yana cikin ruwa mai ci gaba ko kuma lokacin da akwai isasshen bambancin saurin a fadin dubawa tsakanin ruwa biyu.
* *Ruwa na Rossby* (ko raƙuman ruwa na duniya) manyan motsi ne a cikin yanayi wanda ƙarfin dawowa shine bambancin tasirin Coriolis tare da latitude.

## Manazarta