| Under the background of global warming,changes of wet and dry climate conditions in Junggar basin is discussed to provide scientific basis for Junggar basin ecological environment protection,the rational use of water resources and protection for fragile ecological environment in future.Daily meteorological data from 1960 to 2013 surrounding the Junggar basin from 19 meteorological stations is used to calculate reference crop evapotranspiration by Penman-Monteith model,and then dry-wet index is calculated.The methods of the linear trend method,IDW method,Mann-Kendall mutation testing method,and wavelet analysis method are used to discuss reference crop evapotranspiration,dry-wet index,the characteristics of temporal and spatial variation of main climatic factors surrounding the Junggar basin and its sub-regions.Correlation analysis method is used to discuss the main factors which affect evapotranspiration decrease.The results show that:(1)The average reference crop evapotranspiration for many years surrounding the Junggar basin and its sub-regions shows the feature that “decrease first and then increase”,with a total trend of significant decrease,and Bole Valley makes the most contribution to evapotranspiration decrease for the whole region;Reference crop evapotranspiration had mutation in 1984,transferring from a slightly high period to a slightly low period;Seasonal average reference crop evapotranspiration is that summer> spring>autumn> winter,and the four seasons are decrease trends.The decrease rate is that summer > autumn > spring > winter.(2)The reference crop evapotranspiration surrounding the Junggar basin shows the spatial differentiation feature that “high in north area and low in south area,high in west area and low in east area”.Northern slope of the Tianshan Mountains and bole Valley decrease most significantly for the reference crop evapotranspiration,and it generally shows that decreasing percentage in the western region is smaller than in the eastern region.(3)The average dry-wet index for many years surrounding the Junggar basin and its sub-regions all shows increasing trends,indicating that it has a humid climate trend in the study area,and the maximum rate of increase is in Bole Valley and dry-wet index had mutation in 1984.Climate conditions are all most humid in winter for surrounding the Junggar basin and its sub-regions,and seasonal dry-wet index shows an increasing trend,with the most significant increasing rate in winter.(4)There is obvious spatial difference for the wet and dry seasonal climate conditions surrounding the Junggar basin and its sub-regions.It has the feature that “wet in west area and dry in east area,arid in middle area” in spring.Most of the areas in summer are relatively arid and in arid and semi arid areas.Only in the Irtysh River Basin there is a high value area of a relatively humid climate;Dry-wet index generally shows the trend that it gradually becomes arid from east to west for autumn and winter;the climate is relatively humid for most regions of east part of surrounding the Junggar basin,and is significantly different from other seasons.(5)The average wind speed in recent years has a decrease trend surrounding the Junggar basin.The average temperature is a significant increase trend.There are differences for the changing trends of sunshine duration and average relative dry-wet in different sub-regions,and rainfall is a significant increase trend.To sum up,although average temperature surrounding the Junggar basin is an increase trend,the decrease of the average wind speed and sunshine duration and the increase of precipitation both make effect so that the reference crop evapotranspiration surrounding the Junggar basin has a general decrease trend and dry-wet index has an increase trend. |
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