Sensitivity Of The Potential Evapotranspiration To Climate And Vegetation In Hexi Area Based On S-W Model

Evaporation was the third important variables in the land and ecological system withenergy control and agent exchange, and plays a vital role to understanding climate change.Currently, potential evapotranspiration has been widely used in studies of water resources forirrigation, crop water requirements, etc..We got the meteorological data (average wind speed, relative humidity, sunshine duration,average minimum temperature and average maximum temperature) of14national referencemeteorological stations inside Hexi area and8stations around the area from2001to2012,and used the S-W model to caculate the sensitivity coefficient of PET to meteorological andvegetation factors based on the meteorological and LAI data, to study the sensibility of PETvariation to each meteorological and vegetation factor under global warming. The result asfollows:1) The potential evapotranspiration to vegetation types is more sensitive. Under thesame climatic conditions, there is a great difference in the potential evapotranspirationcalculation results of different vegetation zones. The spatial distribution of annual potentialevapotranspiration was obviously difference in Hexi area. The potential evapotranspiration ofagricultural land was higher, followed by the desert and low vegetation district, but the highvegetation coverage, the grassland and the brush area was the least. The potential evaporationof each station has an uptrend except the Yumen and Wushaoling station.2) In a certain region, potential evapotranspiration is more sensitive to the changes ofrelative humidity.In a word, the relative humidity is the main factor which controlls thechanges of potential evapotranspiration, followed by the average maximum temperature, butsunshine duration was the least sensitive factor. In space, sensitivity coefficients of thevariables have a great spatial difference because of the influence by the local climate andgeological features. Potential evapotranspiration have the different sensitivity to climate indifferent vegetation-covered areas. In grassland and the brush areas, potentialevapotranspiration is more sensitive to the average maximum temperature and the minimumtemperature. In agricultural land area, the sensitivity of potential evapotranspiration to thewind speed and sunshine duration is much greater than the high vegetation coverage. Thepotential evaporation covered by various vegetation areas has sensitivity to leaf area index. Inaddition to Mazongshan, it was greater than the sensitivity of the sunshine duration, and slightly less than the average wind speed, especially in grassy areas, the leaf area index is themost sensitive.3) The sensitive coefficient of each element has a certain degree of fluctuation from2001to2012, both the average maximum temperature and sunshine duration sensitivecoefficients were declining, leaf area index sensitivity coefficient has no significant trend, theothers were rising. Among those, the interannual variability of average minimum temperaturesensitive coefficient is the greatest change. In seasonal, the average minimum temperature andaverage maximum temperature sensitive coefficient have the maximum fluctuation, followedby the wind speed, leaf area index and relative humidity, sunshine duration sensitivecoefficient fluctuation is the most gentle change.