Tempo-Spatial Change Of The Evaporation In Hunan Province In The Period 1981-2013

Based on the daily evaporation gauge data from 97 different meteorological stations over Hunan Province in the period 1981-2013,the spatiotemporal change,abrupt change and trends of annual and seasonal evaporation are discussed by using the linear regression,moving arithmetic average,cumulative anomaly,Mann-Kendall test,R/S analysis and the causes of increasing evaporation were analyzed by the method of time lag cross-correlation and stepwise regression analysis.The main results are as follows:(1)the annual evaporation presented a fluctuant increasing tendency in recent 33 years,the evaporation change trends of spring,autumn and winter were similar and determined the change of the annual evaporation;the evaporation in Hunan mainly concentrated in summer,in terms of the spatial distribution,the change of the decadal evaporation had obvious regional characteristics;the annual and seasonal evaporation showed a decreasing tendency from the southeast to the northwest;the results of M-K mutation analysis revealed that: spring,autumn,winter and annual evaporation presented an increasing tendency except for summer,the evaporation abrupt change occurred in spring,2000 and autumn,1983,respectively;the results of R/S analysis showed that annual evaporation presented a strongly positive persistence,and evaporation in spring was the most significant.(2)During the study period,the annual sunshine duration and annual mean temperatures of Hunan Province presented an increasing tendency,which of the change was significant and presented a strongly positive persistence.The annual sunshine duration is higher in north and south,while is low in the central.Spring,summer,autumn and winter,the increasing tendency of sunshine duration which presented a strongly positive persistence in autumn is the most significant.The tendency of average temperature is increasing in seasons.Annual average temperature presented a strongly positive persistence,and it in spring was the most significant.The sunshine duration is higher in southeast than that in northwest,annual and seasonal average temperature is high in the south,while is low in the north.The change of annual average wind speed and annual relative humidity was not significant and it showed a fluctuant decreasing,while,the future trend of change will be consistent with the present.The wind speed is the largest in winter and there is no abrupt change point.At this time,most of the areas in Hunan are positive persistence;the seasonal relative humidity is declining,except for winter,there is a abrupt change point in other seasons,and relative humidity is the largest in summer.The annual and seasonal average wind speed is larger in east than that in west,while,the spatial distribution of relative humidity is just the opposite.(3)The increasing tendency of daily range of temperature in Hunan Province is not significant and there is no abrupt change point.The annual precipitation showed a significant tendency,which had abrupt change point in the time series.The change of annual precipitation presented an anti-persistence in the north and south,but positive persistence in the middle of Hunan Province.The change of daily range of temperature which had a abrupt was decreased in spring and autumn,but increasing in summer and winter.The change of annual and seasonal daily range of temperature showed positive persistence.The annual precipitation was amount of the most in the summer,and it showed an increasing tendency,the positive persistence of annual precipitation is the most significant and there is a abrupt change point.The spatial distribution,the average annual and spring temperatures are concentrated in the southeastern and northwestern of Hunan,and the high value is shifted to the south in summer.the value of average temperatures is high in the south,while is low in the north in autumn.in the winter,the area of high value was smaller and it was at the southeast of Hunan Province;annual precipitation is higher in southeast than that in northwest,and the distribution of precipitation in spring was the same as the annual precipitation.the precipitation is generally higher in the north than that in the south in summer and autumn,the lowest precipitation in winter was decreasing from the southeast to the northwest.(4)The sunshine duration and daily range of temperature were positively correlated with annual evaporation,among which sunshine duration had the most significant effect on annual evaporation.The correlation coefficient between evaporation and sunshine duration in spring was the highest,evaporation in summer,autumn and winter have the best correlation with daily range of temperature.In terms of the spatial distribution,the Contribution meteorological variables were of temporal and regional characteristics.The daily range of temperature have a significant impact on annual and spring,autumn and winter evaporation in Hunan Province,and it were positively correlated with annual evaporation,However,annual temperature had the greatest effect on the summer evaporation in Hunan Province.