简介：有卫星数据集的表面土壤水分蒸发蒸腾损失总量(et)的评价是在气候变化，灾难在西藏自治区域(tar)监视和水蒸汽和精力的发行量的理解的主要题目之一。这研究在1月11日选择卫星图象，在2010的4月6日，7月31日和象冬季，春天，夏天和秋天的代表的10月19日分别地，与潜在的土壤水分蒸发蒸腾损失总量(宠物)和从Penman-Monteith(下午)方法导出的et一起基于表面精力平衡系统(SEBS)估计每日的表面et的分发。结果如下被获得。(1)et和宠物的季节的分发基本上从东南部分减少到焦油的西北部分。尽管et和宠物有类似的空间分布，仍然有一些差别估计极端特别在焦油的中间、东南的部分珍视最大的价值。不管我们采用了什么样的方法，et和宠物的最大的价值总是出现在夏天，当那在冬季是最小的时，由秋天或春天列在后面。(2)在et的评价当模特儿以便更好理解SEBS的精确性，我们从从下午方法获得的SEBS和ET比较了ET。结果证明从SEBS的ET能估计实际et的变化趋势，但是它稍微总体上低估或过高估计et的价值，特别为有厚森林的那些区域。(3)规范的差别植被索引(NDVI)的空间分发从东南部分展出一个减少的趋势到显示在et和植被索引之间的分布的显著一致性的tar的西北部分。当时，et与在不同季节的NDVI，最小，平均数，最大的空气温度和阳光持续时间有关断然好否定地在夏天与降水，相对湿度和风有关加速。

简介：Abstract:Hydrologicalregimesinfluenceecologicalpatternsandprocessesaswellasalterratesofwetlandevapotranspiration.ThisstudyaimedtoinvestigatetheimpactofgroundwaterfluctuationonevapotranspirationofPhragmitesaustralis.SupportedbyfielddataobtainedfromtheBaiyangdianLakeinnorthernChina,thevariationsingroundwaterlevelswereexplored,andthechangesinsoilwaterandevapotranspirationofreedwereanalyzedtoinvestigatedifferentgroundwaterlevelscenariosusingHYDRUS-1Dmodel.Theresultsshowedthatsoilwatercontent,rechargedbygroundwater,remainedstableinthelowersoillayerbutvariedstronglyintheupperlayerofthesoilprofile;incomparisontoevaporation,Phragmitesaustralistranspirationcontributedsignificantlymoretotheoverallevapotranspirationrate;thehighlevelsofevapotranspirationcouldbemaintainedwhengroundwaterlevelsvarybetween1.0mand1.8m,whileitwasreducedwithanincreaseingroundwaterlevelsasaresultofwaterstressconditions.TheresultsalsoindicatedthattheevapotranspirationofPhragmitesaustraliscouldmaintainhigherevapotranspirationratesundernaturalwaterlevels.Theevapotranspiration,inotherwords,mightbethemainwaterconsumer,butitneverthelesshaslittleeffectonwaterlevelsduringwatershortages.TheevapotranspirationofPhragmitesaustralisrespondedtothechangesingroundwaterlevelscouldhelpresearchersunderstandwaterrequirementsofthewetlandsandestablishsuitablewaterlevelsforthewetlands.

简介：Itisaverycomplicatedproblemtoestimateevapotranspiration(ET)overalargeareaoflandsurface.Inthispaper,theevapotranspirationestimationmodelsfordensevegetationandbaresoilarepresented,basedontheinformationofparameterslikevegetationcover-degreeandsurfacealbedo.Combinedwithvegetationcover-degreedata,amodelforregionalevapotranspirationestimationovertheheterogeneouslandscapeisderived.ThroughacasestudyusingremotesensingdataoverNorthwestChina,theaccuracyofthemodelforregionalevapotranspirationestimationischecked.Theresultshowsthattheaccuracyofthemodelissatisfactory.ThefeaturesofevapotranspirationoverNorthwestChinaarealsodiscussedwiththeapplicationofthemodel.

简介：Basedontheconceptionoffluidmechanics,thepaperpropoundsamodelformonthlypotentialevapotranspirationETi(mm):ETi=22di(1.6+Ui^1/2)woi(1-hi)/Pi^1/2(273.2+ti)^1/4whereiisthenumberofamonth,Pithemeanmonthlyatmosphericpressure(hPa),tithemeanmonthlyairtemperature(℃),dithenumberofdaysinthemonth,Uithemeanmonthlywindvelocitymeasuredatheight10-12m(m/s),woithesaturatedwatervapourpressureatti(mmHg,1mmHg=133.322Pa),andhithemeanmonthlyrelativehumidity.TheannualaridityKis:K=12∑i=1ETi/rawhereraisthemeanannualprecipitation(mm).Baseduponthedataof669sitesinChinaduring1951-1980,therelationsamongthesoilmoistureregime,thevegetationandthevalueofKmaybeillustratedasfollows:KSoilmoistureregimeVegetationK<1UdicFOrest1≤K<2semi-udicFroest,froest-steppeandsteppe2≤K<3.5Semi-aridicAridsteppe3.5≤K<11AridecDesert-steppeK≥11VeryaridicDesert.

简介：TheKotoda-Bortan(KB)model(LiuandKotoda1998)usedforestimatingevapotranspirationwasmodified.ThemonthlyevapotranspirationforvarioussurfacesintheYangtzeDelta(118-123■,28-33■)wascalculatedusingthemodifiedmodel,andtheannualregionalaverageofevapotranspirationfrom1961to1998wasobtainedusingaweightingmethod.Thespatialandtemporaldistributioncharacteristicsofevapotranspirationwereanalyzed.Itisfoundthattheregionalaveragedannualevapotranspirationhasadecreasingtrendoverthepast40years;thevaluedroppedbyabout24mmfrom1961to1998.Themainreasonforthistendencyisduetothechangeoflandsurfacecondition.Comparedwiththecaseof1980,thecurrentproportionsofpaddyfield,farmlandandwatersurfacehavedecreasedby1.353%,4.42%and2.597%respectively,whiletheproportionsofurbanareaandnon-agriculturelandhaveincreasedby3.345%.Thesechangesclearlyresultinadecreaseoftheregionalaveragedevapotranspiration.

简介：Drylandsareamongthoseregionsmostsensitivetoclimateandenvironmentalchangesandhuman-inducedperturbations.Themostwidelyaccepteddefinitionofthetermdrylandisaratio,calledtheSurfaceWetnessIndex(SWI),ofannualprecipitationtopotentialevapotranspiration(PET)beingbelow0.65.PETiscommonlyestimatedusingtheThornthwaite(PETTh)andPenman–Monteithequations(PETPM).ThepresentstudycomparedspatiotemporalcharacteristicsofglobaldrylandsbasedontheSWIwithPETThandPETPM.ResultsshowedvastdifferencesbetweenPETThandPETPM;however,theSWIderivedfromthetwokindsofPETshowedbroadlysimilarcharacteristicsintheinterdecadalvariabilityofglobalandcontinentaldrylands,exceptinNorthAmerica,withhighcorrelationcoefficientsrangingfrom0.58to0.89.Itwasfoundthat,during1901–2014,globalhyper-aridandsemi-aridregionsexpanded,aridanddrysub-humidregionscontracted,anddrylandsunderwentinterdecadalfluctuation.Thiswasbecauseprecipitationvariationsmademajorcontributions,whereasPETchangescontributedtoamuchlesserdegree.However,distinctdifferencesintheinterdecadalvariabilityofsemi-aridanddrysub-humidregionswerefound.ThisindicatedthattheinfluenceofPETchangeswascomparabletothatofprecipitationvariationsintheglobaldry–wettransitionzone.Additionally,thecontributionofPETchangestothevariationsinglobalandcontinentaldrylandsgraduallyenhancedwithglobalwarming,andtheThornthwaitemethodwasfoundtobeincreasinglylessapplicableunderclimatechange.

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简介：季节的干旱是在潮湿的气候的普通出现。一年2003在时期期间是最干燥的年19852011在东南的中国。这研究的目的是阐明在2003的非凡的干旱的影响，与旋涡流动大小相比在200411期间在土壤水分蒸发蒸腾损失总量(et)和相关因素的动力学上，以及他们的内在的机制，在在东南的中国的副热带的具球果的种植园。在集中的干旱时期期间从5.34～1.84公里减少了并且在恢复干旱时期的subsquent期间恢复了到4.80公里，被发现那每日的et。路径分析显示那et被华盖传导力和深土壤水内容(50厘米)主要分别地在集中的干旱和恢复干旱时期期间决定。华盖传导力当承受干旱应力时，在et上抵消空气蒸汽压力赤字的积极效果，当华盖传导力在迟了的成长季节期间在et上提高了空气温度的积极效果时。因为这种植园的好根主要在浅土壤，和土壤被散布，流水在上面40厘米没满足需求因为et，有气孔的闭合和落叶作为对干旱应力的生理的回答明显。

简介：Moreaccurateestimationofcropevapotranspiration(ETc)inaregionalscalehasalwaysbeenoneofthemostimportantchallenges.TemporalandspatialmonitoringofETcusingsatelliteimagescanhelptoenhanceaccuracyofestimations.Inthisstudy,the(ETc)ricemapswereproducedbyusingstatistical/experimentalmethodsbasedoncropcoefficient(Kc)mapsderivedfromvegetationindex(VI).Kcwasestimatedusingfourmethods,includinglinearrelationshipbetweenKcandVI(Kc-VI),calibratedmodelofKc-VI,linearrelationshipbetweenKcb(thebasalcropcoefficient)andVI(Kcb-VI),andcalibratedmodelofKcb-VI.TheresultsshowedthatcalibratedmodelofKc-VIhadabetterperformancecomparedtotheothermethods,withnormalizedrootmeansquareerrors(NRMSE),meanabsoluteerrorandrootmeansquareerrorbeing5.7%,0.05mm/dand0.06mm/d,respectively.(ETc)ricemapswereproducedbyusingcalibratedmodelofKc-VIandreferenceevapotranspiration(ET0)fromFAOPenman-Monteithmethod.TheNRMSEwas21.3%forusingFAOPenman-Monteithmethod.Therefore,calibratedKc-VImodelincombiningwithET0basedontheLandsat7ETM+imagescouldbeprovidedagoodestimationof(ETc)riceinregionalscale,andcanbeappliedtoestimatewaterrequirementduetothefreeandfacilitateaccess.

简介：在19612009期间在Hengduan山区域基于20个车站的气象学的数据，潜在的土壤水分蒸发蒸腾损失总量的年度、季节的变化与Penman-Monteith模型一起在联合被分析。与在ArcGIS下面的花键插值的方法，潜在的土壤水分蒸发蒸腾损失总量的空间分发被介绍研究地区性的差别，并且关联分析被用来讨论影响潜在的土壤水分蒸发蒸腾损失总量的主导的因素。结果显示自从1960年代，年度潜在的土壤水分蒸发蒸腾损失总量显示出一个减少的趋势，特别从1980年代到1990年代，当自从2000，它显示出一个增加的趋势时。地区性的潜在的土壤水分蒸发蒸腾损失总量显示出0.17公里a1的率。在Hengduan山的北方，中间和南方的潜在的土壤水分蒸发蒸腾损失总量在学习时期上展出了减少的趋势，并且它的地区性的趋势在从西南的衰落上到东北。

简介：Spatio-temporalvariationofactualevapotranspiration(ETa)inthePearlRiverbasinfrom1961to2010areanalyzedbasedondailydatafrom60nationalobservedstations.ETaiscalculatedbytheAdvection-Ariditymodel(AAmodel)inthecurrentstudy,andMann-Kendalltest(MK)andInverseDistanceWeightedinterpolationmethod(IDW)wereappliedtodetectthetrendsandspatialvariationpattern.TherelationsofETawithclimateparametersandradiation/dynamictermsareanalyzedbyPersoncorrelationmethod.Ourfindingsareshownasfollows:1)MeanannualETainthePearlRiverbasinisabout665.6mm/a.Ithassignificantlydecreasedin1961-2010atarateof-24.3mm/10a.Seasonally,negativetrendsofsummerandautumnETaarehigherthanthatofspringandwinter.2)ThevalueofETaishigherinthesoutheastcoastalareathaninthenorthwestregionofthePearlRiverbasin,whilethelatterhasshownthestrongestnegativetrend.3)NegativetrendsofETainthePearlRiverbasinaremostprobablyduetodecreasingradiationtermandincreasingdynamicterm.Thedecreaseoftheradiationtermisrelatedwithdecliningdiurnaltemperaturerangeandsunshineduration,andrisingatmosphericpressureaswell.Thecontributionofdynamictermcomesfromincreasingaveragetemperature,maximumandminimumtemperaturesinthebasin.Meanwhile,thedecreasingaveragewindspeedweakensdynamictermandfinally,toacertainextent,itslowsdownthenegativetrendoftheETa.

简介：Thusfar,measurementsandestimationsofactualevapotranspiration(ET)inextremelyaridareasarestillinsufficient.BasedonsuccessiveobservationsfromJune–September2014,wesimulatedETofaPopuluseuphraticaOliv.forestduringthegrowingseasoninanextremelyaridregionofnorthwestChinausingtheShuttleworth–Wallace(S–W)model.SimulatedETvalueswerecomparedtothoseoftheeddy-covariance(EC)methodona1hinterval.Witharootmeansquareerror(RMSE),relativeerror(RE)andmeanabsoluteerror(MAE)of0.192,3.100and0.165mmh-1,respectively,modelperformancewasnotsatisfactory.Inparticular,ondayswithstrongwinds(Sep.11–13),deviationsbetweensimulatedandobservedETvaluesincreasedto0.275,0.878and0.251mmh-1,RMSE,REandMAErespectively.Thesevaluesweresignificantlygreaterthanthoseinotherstudyperiodsandweremostlikelyowingtosharpincreasesinwindspeed.Asaresult,thereweresubstantialadvectiveeffects,whichisnotconsistentwiththeassumptionoftheS–Wmodelthattherearenoadvectiveeffectsormesoscalecirculationpatternsinducedbysurfacediscontinuities.