Spatio-temporal Variation Of Land Surface Evapotranspiration In China

Evapotranspiration is a vital process of terrestrial ecosystems,which includes water,carbon and surface energy exchange.Also,it is the key aspects of water cycle.Hence evapotranspiration plays an important role in regulating local or regional climate.Better understanding of the spatiotemporal variation of evapotranspiration is very important for enhancing understanding of the interaction between surface and atmosphere,the rational management of regional water resources,analysis and monitoring and assessment of drought,application of regional hydrology,the management of crop water demanding and ecological environment and so on.Compared with the data used in the traditional evapotranspiration estimation method,the use of remote sensing data makes estimation method obvious superiority,that remote sensing data has obvious superiority on the application of the land evapotranspiration on the non-uniform underlying surface.Therefore,combining remote sensing data and meteorological data to estimate regional evapotranspiration becomes a main direction of current research.Researches of evapotranspiration in China past were based on the site with traditional method,while considering the ecological system in the regional research were less.So,this study adopts the model of global evapotranspiration estimation to estimate the land surface evapotranspiration in China,which proposed by Zhang et al.in 2010.The model based on the NDVI data received from MODIS,NECP / NCAR reanalysis meteorological data and MICLCover2000 land cover data,then used GIS to process data.This study write codes of model in Matlab.Meanwhile this study showed the rationality of the input data processing method and the accuracy of the evapotranspiration model used in this study,which validated by the data of ground station observation.At last,this study analyzed the results of actual evapotranspiration in China by Arcgis which displayed the law of spatio-temporal variation of land surface evapotranspiration in China obviously.Conclusions are as follows:Model,input data and the processing method are optical,and the estimation of the China land surface evapotranspiration is good.The month average evapotranspiration in China of a year varied obviously and presented characteristics with zonal distribution.The month average evapotranspiration in China presented a tendency to increase first and then decrease with the change of month in a year,and the difference in the variation of the different regions is obvious.The differences in evapotranspiration between different seasons in China were significant,and the distribution of high and low area was also changed.The range of high and low evapotranspiration in China from 2001 to 2014 is almost the same.The high value area of the eastern monsoon region increased obviously after 2007,and the range was obviously enlarged,which reached above 1400 mm.The spatial distribution of evapotranspiration in China has obvious ladder changes from southeast to northwest,and the spatial banding distribution of the eastern monsoon region is also obvious.From 2001 to 2014,the interannual rate of the actual evapotranspiration in China presented a significant increase trend.The rates of trend in most areas were greater than 0,and there were obvious regional differences in space.