| The arid and wet conditions of climate largely determine the type of agricultural production and the distribution of crops in a region.In the agricultural climate division,the arid and wet climate index is an important reference index,so it has been paid more attention by the climate scholars.In recent years,the global environmental problems represented by global warming have been concerned by all circles of society.Existing researches show that under the trend of global warming,evaporation potential change caused by climate warming has an important influence on arid and wet conditions of the earth surface,in this case,agricultural production pattern has produced different degrees of changes,the traditional arid and wet index can not meet the agricultural regionalization need under the conditions of climate change.Therefore,this study simulates and analyzes the temporal and spatial variation characteristics of land surface evapotranspiration from 1983 to 2012 in china through localization and validation of BEPS(Boreal Ecosystem Productivity Simulator)model.Based on this,the study constructs the wet and arid climate index combining with reference crop evapotranspiration calculated by P-M equation,and compares them with the other two kinds of arid and wet climate index,to analyze its temporal trends and variability and so on.The study has provided technical reference for future climate division in China with certain research value and significance.The main conclusions are as follows:(1)This study uses the flux data,the site scale watershed balance method and compared with existing results,which show that three kinds of verification methods have achieved good results.It also indicates that the BEPS model and parameter scheme and driving data are suitable for simulation of surface evapotranspiration in terrestrial ecosystem in China.(2)The spatial distribution characteristics of land surface evapotranspiration in China from 1983 to 2012 is basically consistent with the spatial distribution of precipitation and NDVI,which show that the gradient variation characteristics of the southeast coast to the northwest inland.Moreover,the seasonal variation of surface evapotranspiration in China is obvious and the variation of surface evapotranspiration is a single peak curve,whose annual variation is going up.There are significant differences in the annual and inter annual variations of surface evapotranspiration based on the different land cover facility.(3)This study constructs arid and wet climate index(EDI)with surface evapotranspiration and the reference crop evapotranspiration of 30 years,and carries on contrast analysis of it with precipitation index and humidity index.The three kinds of arid and wet climate index are basically the same in distinguishing wet and arid climate zones,and the EDI index is significantly better than the others.From the trend of area change,China climate change toward two extremes,severe arid climate zone and humid climate zone show the trend of expansion,and arid,semi-arid,semi-humid climate areas decrease or remains unchanged.In the moist degree,our country becomes moist on the whole,among which severe arid and semi-humid climate zones are showing a drier trend,humid climate zone are showing a more moist trend,arid and semi-arid climate zones are basically unchanged.(4)The principal component analysis show that the average temperature and other thermodynamic factors are the dominant factors affecting the dry and wet conditions in China,followed by the water factor and power factor.For the whole country,the correlation of precipitation and EDI is the highest,and the correlation coefficient between EDI and meteorological factors in different regions is obvious.The comparative analysis of dry and wet climate index with LAI and NDVI show that EDI and vegetation index also has good consistency. |
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