Abstract:

Potential evapotranspiration（ET0）， as an estimate of the evaporative demand of the atmosphere， has been widely discussed in researches on irrigation management， crop water demand and predictions in ungauged basins Analysis of ET0spatial and temporal variation is the basic research on the impact of climate change on water resources， and also is important to the optimal allocation of agricultural water resources In this study， based on the daily data from 54 meteorological stations in Northern and Southern Regions of the Qinling Mountains between 1960 and 2011， with the help of FAO PenmanMonteith formula， ET0 was calculated By using the Spline interpolation method， climate trend rate， Pettitt abrupt change point detection， correlation analysis and other methods， we analyzed the distribution and temporal and spatial variation characteristics of ET0 as well as the meteorological elements which influenced evapotranspiration The results are as follows. （1）Average annual ET0 was 9642 mm， with the spatial distribution pattern of higher in east and lower in west According to the size of evapotranspiration， the order was northern and southern region of  the Qinling Mountain， the Han River Basin， the BaWu Valley ET0  in four seasons had the same distribution characteristics as the annual ET0， the order was summer， spring， autumn and winter （2）According to the percent of stations with decreasing trend accounted for the whole stations， the order was the Han River Basin， southern slope of  the Qinling Mountain， the BaWu Valley， northern region of  the Qinling Mountain The decreasing trend was more obvious in southern region than that in northern region  ET0 of most stations in spring， which accounted for 78%， increased while  ET0 in summer， which accounted 91%， decreased significantly No obvious increasing or decreasing trend was founded in autumn or winter The departure of ET0 in summer and annual between 1960s and 1970s was positive while negative between 1980s and 2000s; ET0 in autumn experienced negative and positive departure in the past 50 years， which appeared alternatively ET0 in spring decreased in 1960s， then increased until 1980s， since then presented a downward trend， finally increased significantly in 2000s; ET0 in winter fluctuated in the past 50 years， the order was positive， positive， negative， positive and negative The spatial and temporal distribution of ET0 illustrated the difference of ET0 in different latitude zone under the background of climate change On the other hand， it could also be concluded that complicated terrain could influenced the distribution of temperature， precipitation， wind speed and other meteorological factors， which would finally influenced ET0.  （3）The abrupt change of annual and spring ET0 happened in 1993 or between 1979 and 1981， while  ET0 of  85% stations in summer changed in 1979 There was no obvious abrupt change points in autumn or winter （4）Precipitation and ET0 of 70% stations in summer presented an negative correlation relationship， as for autumn the number accounted for 76% Sunshine hour， maximum temperature， average temperature and wind speed correlated positively with ET0， which reached 001 significant level According to size of correlation coefficient， the order was sunshine duration， maximum temperature， average temperature and wind speed The decrease of sunshine duration and wind speed leaded to ET0 decreasing in summer and winter while temperature increasing caused ET0 increased in spring and autumn 