Spatiotemporal Changes And Trend Prediction Of Water Surface Evaporation In The North-South Transitional Zone Of China

China's north-south transition zone is a sensitive area in response to global climate change.It is also the main water source of the middle route of the South-to-North Water Diversion Project and the key area of the western development.However,in the current research,there is little research on the evaporation of the whole north-south transition zone.Therefore,this paper takes the north-south transition zone of China as the research area,and analyzes the data of 43 meteorological stations in the north-south transition zone e of China Meteorological data network from 1980 to 2017 by using climate tendency rate,Mann Kendall(M-K)trend test method,cumulative anomaly method,sliding test method,grey correlation analysis method and R/S analysis method.The temporal and spatial variation characteristics of water surface evaporation in the north-south transition zone of China from1980 to 2017 are obtained,and the future trend is simply predicted,which provides a basis for further understanding of the hydrological change law and its response to climate change in the north-south transition zone,and further understanding of the differentiation law of physical geography in China.Research shows:(1)From the time change,the average annual evaporation of water surface in the northsouth transition zone is 806.2 mm,and the climate tendency rate is 19.3 mm/10 a,which shows a significant trend in the research year.The evaporation of water surface increased significantly in summer,but not in spring,winter and autumn;The abrupt change of water surface evaporation occurred in 2004 in spring,about 1990 in summer and 1985 in autumn;The average evaporation of water surface in 1994 had a sudden change.Before 1994,the evaporation of water surface decreased,and from 1994,the evaporation of water surface was on the rise;The evaporation of water surface also increased gradually in the 's.From the perspective of spatial change,the climate tendency rate of water evaporation is lower in the middle and northeast of the study area,higher in other regions,the evaporation of some stations in the north is decreasing,and the evaporation of other areas is increasing;The evaporation range of high water surface in Wudu area is expanding with the time.(2)From 1980 to 2017,the annual average temperature in the north-south transition zone was 12.86 ?.The average temperature of four seasons increased significantly;The annual average temperature showed a downward trend before 1996 and an upward trend after 1996;In the whole study period,it showed a significant upward trend.From 1980 to2017,the annual average relative humidity of the north-south transition zone was 70.67%.In spring and summer,the relative humidity showed a significant downward trend,but not in autumn;The relative humidity showed an upward trend before 1994 and a downward trend after 1994;In the whole study period,the relative humidity showed a significant downward trend.From 1980 to 2017,the annual average sunshine hours in the north-south transition zone was 1774.33 h.It increased slightly in spring and summer,and decreased slightly in autumn and winter;Before 1993,the sunshine hours decreased,from 1993 to 2002 the sunshine hours increased,and after 2002 the sunshine hours decreased;During the study period,there was a weak downward trend.From 1980 to 2017,the annual average wind speed in the north-south transition zone was 1.72 m/s;In the whole study period,the trend of spring slightly decreased,summer obviously increased,and autumn and winter slightly increased;The average wind speed fluctuates slightly.(3)The main reason for the increase in annual average water surface evaporation in the transitional zone between north and south is the increase in average temperature.The main reason for the insignificant upward trend of average water surface evaporation in spring is the weak upward trend of sunshine hours.The main reason for the significant increase in average water surface evaporation in summer is the significant increase in average temperature.The main reason for the weak upward trend of average water surface evaporation in autumn is the result of the combined effect of the weak downward trend of sunshine hours and the significant upward trend of average temperature.The main reasons for the weak increase in average water surface evaporation in winter are: a slight decrease in sunshine hours,a slight increase in average wind speed,and a significant increase in average temperature.From the perspective of future trends,the average water surface evaporation in the north-south transition zone will continue to rise,the average water surface evaporation in spring will continue to show a slight upward trend,and the average water surface evaporation in summer will continue to show a relatively significant increase.The average water surface in autumn and winter will continue to rise slowly.