Rashin yiwuwar evapotranspiration

Mai yuwuwa evapotranspiration (***'PE***') ko mai yuwuwa (PE) shine adadin ruwa wanda za'a fitar da shi kuma ya wuce ta hanyar takamaiman amfanin gona, ƙasa ko yanayin halittu idan akwai isasshen ruwa. Yana nuna makamashi da ake samu don narkewa ko wucewa ruwa, da kuma iska da ake samu wajen jigilar tururin ruwa daga ƙasa zuwa cikin ƙananan yanayi kuma daga wurin farko. Ana nuna yiwuwar evapotranspiration dangane da zurfin ruwa ko kashi na danshi na ƙasa.

Idan ana ɗaukar ainihin evapotranspiration sakamakon sakamakon buƙatun yanayi don danshi daga farfajiya da ikon farfajiya don samar da danshi, to PET ma'auni ne na ɓangaren buƙata (wanda ake kira buƙatun evaporative). Yanayin ƙasa da iska, insolation, da iska duk suna shafar wannan. Yankin da ya bushe wuri ne inda yiwuwar narkewar shekara-shekara ta wuce ruwan sama na shekara-sheko.

Sau da yawa ana lissafin darajar yiwuwar evapotranspiration a tashar yanayi da ke kusa a kan wani wuri mai tushe, a al'ada a kan ƙasar da ta mamaye gajeren ciyawa (ko da yake wannan na iya bambanta daga tashar zuwa tashar). Wannan darajar ana kiranta evapotranspiration (ET0). An ce ainihin evapotranspiration daidai yake da yiwuwar evapotranspiracy lokacin da akwai isasshen ruwa. Evapotranspiration ba zai iya zama mafi girma ba fiye da yiwuwar evapotranspirated, amma yana iya zama ƙasa idan babu isasshen ruwa da za a fitar da shi ko kuma tsire-tsire ba su iya wucewa cikin balaga da sauƙi ba. Wasu jihohin Amurka suna amfani da cikakken murfin alfalfa wanda ke da    a tsawo, maimakon gabaɗaya gajeren ciyawa mai kore, saboda mafi girman darajar ET daga bayanin alfalfa.

Halin evapotranspiration ya fi girma a lokacin rani, a kwanakin da suka fi haske da ƙarancin girgije, kuma kusa da ma'auni, saboda matakan hasken rana mafi girma wanda ke samar da makamashi (zafi) don evaporation. Hakanan yiwuwar evapotranspiration ya fi girma a kwanakin iska saboda za'a iya motsa danshi da sauri daga ƙasa ko tsire-tsire kafin ya sauka, yana ba da damar ƙarin evaporation don cika wurinsa.

## Ma'auni

Ana auna yiwuwar evapotranspiration a kaikaice, daga wasu abubuwan yanayi, amma kuma ya dogara da nau'in farfajiyar, kamar ruwa kyauta (don tabkuna da teku), nau'in ƙasa don ƙasa mara kyau, da kuma yawanci da bambancin ciyayi. Sau da yawa ana lissafin darajar yiwuwar evapotranspiration a tashar yanayi da ke kusa a kan wani wuri mai tushe, al'ada akan gajeren ciyawa. Wannan darajar ana kiranta evapotranspiration, kuma ana iya canza shi zuwa yiwuwar evapotranspiracy ta hanyar ninkawa ta hanyar ma'auni na sama. A cikin aikin gona, ana kiran wannan ma'aunin amfanin gona. Ana amfani da bambanci tsakanin yiwuwar evapotranspiration da ainihin hazo a cikin jadawalin ban ruwa.

Matsakaicin yiwuwar eva*P* na shekara-shekara ana kwatanta shi da matsakaicin hazo na shekara-mako, alamar da ita ce *P*. Rabin biyun, P / *PET*, shine alamar busasshiyar. Yanayin zafi mai zafi yanki ne na yanayi tare da lokacin zafi da zafi, da sanyi zuwa hunturu mai sauƙi. Yankunan subarctic, tsakanin 50 ° N  da 70 ° N latitude, suna da gajeren lokaci, lokacin rani mai sauƙi da hunturu mai sanyi dangane da yanayin gida. Ruwan sama da evapotranspiration suna da ƙarancin gaske (idan aka kwatanta da bambance-bambance masu zafi), kuma ciyayi alama ce ta gandun daji / taiga.

## Kimanin yiwuwar narkewa

### Daidaitawar Thornthwaite (1948)
PET = 16 \left(\frac{L}{12}\right) \left(\frac{N}{30}\right) \left(\frac{10T_d}{I}\right)^{\alpha} 

### Daidaitawar Penman (1948)
Ma'aunin Penman ya bayyana evaporation (E) daga saman ruwa mai budewa, kuma Howard Penman ne ya haɓaka shi a cikin 1948. Daidaitawar Penman tana buƙatar matsakaicin zafin jiki na yau da kullun, saurin iska, matsin iska, da hasken rana don hango E. Ana ci gaba da amfani da daidaitattun Hydrometeorological masu sauƙi inda samun irin wannan bayanan ba shi da amfani, don ba da sakamako mai kama da shi a cikin takamaiman mahallin, misali zafi da yanayin busasshiyar yanayi.

### FAO 56 Ma'aunin Penman-Monteith (1998)
Daidaitawar Penman-Monteith tana inganta ƙididdigar evapotranspiration (ET) na yankunan ƙasa masu tsire-tsire. Wannan daidaitattun ya samo asali ne daga FAO don dawo da yiwuwar evapotranspiration ET0.  An dauke shi a matsayin daya daga cikin daidaitattun samfuran, dangane da kimantawa.

:  ET_0 = \frac{0.408 \Delta (R_n-G) + \frac{900}{T} \gamma u_2 \delta e }{\Delta + \gamma (1 + 0.34 u_2)}


### Daidaitawar Priestley-Taylor
An haɓaka daidaitattun Priestley-Taylor a matsayin maye gurbin daidaitattun Penman-Monteith don cire dogaro da abubuwan lura. Ga Priestley-Taylor, ana buƙatar lura da radiation (radiance). Ana yin wannan ta hanyar cire kalmomin aerodynamic daga ma'aunin Penman-Monteith da ƙara wani abu mai mahimmanci. α

Tunanin da ke bayan samfurin Priestley-Taylor shine cewa iska mai motsi sama da yankin ciyayi tare da ruwa mai yawa zai cika da ruwa. A cikin waɗannan yanayi, ainihin evapotranspiration zai dace da Penman rate na yiwuwar evapotranspiracy. Koyaya, abubuwan lura sun nuna cewa ainihin evaporation ya ninka sau 1.26 fiye da yiwuwar evaporation, sabili da haka an sami daidaitattun don ainihin evapotranspiration ta hanyar ɗaukar yiwuwar evpotranspiration da ninka shi ta hanyar α. Tunanin a nan shine don ciyayi tare da wadataccen ruwa (watau tsire-tsire suna da ƙananan damuwa). 

## Manazarta