The Study Of Evapotranspiration In An Alpine Meadow In The Laohugou Catchment In Qilian Mountains

Evapotranspiration?ET?is one the most important process of land surface hydrological cycle and energy cycle,plays an important role in maintaining the earth's surface water balance and energy balance.High altitude mountains glaciers widespread but is numerous rivers source region,alpine meadow ecosystem under the background of climate warming,sensitive and fragile.Therefore,to estimate the ET,not only for the local farming and animal husbandry development and rational allocation of water resources to provide decision-making services,can also be to study alpine meadow ecosystem response to climate change research provides data base.Based on the analysis of local climate characteristics in Laohugou catchment in Qilian mountains,meteorological data of automatic meteorological station and the Penman-Monteith formula were used to calculate the ET of the grow-ing season in 2010-2014,and the ET was analyzed from the years,the growing season,the month,and the day scales and typical year respectively,and then discussed from three aspects such as the results from field observation and comparison,compared with other studies,parameters sensitivity analysis and so on.Also,Landsat8 remote sensing data,combined with the surface energy balance system model?SEBS?was used to estimate the ET of typical sunny day,compared glacier surface,grassland,bare land and water,and also made the discussion.The relevant conclusions are as follows:?1?The ET of alpine meadow was positively correlated with the temperature,wind speed and net radiation,and negatively correlated with relative humidity.2010-2014,annual ET changed from 170.7 to 238.2mm and the average was 205.4 mm;the order of total and average ET in different growing stages was the middle growing period > the end growing period > the initial growing period,accounted for the total was 20.0%,51.5%,28.5% respectively;the order of the total month ET was August > July > June > June > September > May,from May to September,accounted for the total was l4.9%,16.1%,29.8%,33.2%,16% respectively;the daily average:August > July > September > June > May;day scale:the ET was low before mid-July,it was the highest after mid-July until late August and decreased in late August to the end of the growing season.Typical year 2014: the growing season ET amount was 212.1 mm,daily average was 1.59 mm·d^-1,daily ET for three growth stages were 0.90mm·d^-1,2.53mm·d^-1,1.85 mm·d^-1 respectively.Comprehensived field observations and the related scholars research,the calculation results were reasonable.Sensitivity experiments showed that the ET was sensitive to the relative humidity and the net radiation.?2?For the average daily ET of remote sensing typical sunny day was July 13> August 14>August 30>May 26,and the glacier surface<grass<bare rock and bare soil fertile land<waters.Alpine meadow area ET was to meet on May 26<July 13<August 30<August 14,spatial difference in the growing season ET was small.Extracted value of station compared with the calculated value of P-M doing,difference between them in a reasonable scope,based on the basic SEBS model can satisfy the estimation accuracy.