石羊河流域1961-2005年蒸发皿蒸发量变化趋势及原因初探

 利用1961—2005年石羊河流域上、中、下游当地气象站的逐月20 cm口径蒸发皿蒸发量、平均气温、平均相对湿度、降水量、平均风速、日照时数、最高气温和最低气温资料,研究了近45 a石羊河流域蒸发皿蒸发量变化趋势及原因。结果表明,45 a来,石羊河流域及上、下游年蒸发皿蒸发量呈上升趋势,中游年蒸发皿蒸发量呈下降趋势,上游上升趋势最明显。四季中,春、秋、冬季蒸发皿蒸发量呈上升趋势,上升最明显的是冬季,其次为秋季,春季变化不明显,夏季蒸发皿蒸发量变化呈下降趋势。石羊河流域在不同时段不同区域年蒸发皿蒸发量都存在明显的6～7 a周期和1～2 a的短周期,并都发生了突变。相关系数法分析表明,影响石羊河流域及中、下游年蒸发皿蒸发量变化的主要影响因子是相对湿度和降水,上游的主要影响因子是相对湿度和气温。四季中,春季的主要影响因子是相对湿度和降水；夏季影响石羊河流域及上、中蒸发皿蒸发量变化的主要因子是相对湿度和气温,下游的主要影响因子是相对湿度和降水；秋季影响石羊河流域及中、下游蒸发皿蒸发量变化的主要影响因子是相对湿度和气温日较差,上游其主要影响因子是相对湿度和降水；冬季的主要影响因子是气温和相对湿度。影响年以及春、夏、秋最显著的因子是相对湿度,冬季最显著的影响因子是气温。

Change Trend of Pan Evaporation and Its Causes in Shiyang River Basin during 1961--2005

Based on observation data of monthly pan evaporation,mean air temperature,mean relative humidity,precipitation,average wind speed,sunshine hours,maximum temperature and minimum temperature from meteorological stations in the Shiyang River basin during the period of 1961-2005,the change trend of pan evaporation and its causes in these 45 years are analyzed.Results showed that there were increasing trend of annual pan evaporation through the river basin,in the upper reaches and the lower reaches of the Shiyang River basin,and there was a decreasing trend in the middle reaches.The pan evaporation increased in spring,autumn,winter and decreased in summer in 1961-2005.The most significant increase of pan evaporation occurred in winter.There were variation periods of 6-7 years and 1-2 years and abrupt change for annual pan evaporation in Shiyang River basin.We calculated the correlation coefficients between 6 climate factors and pan evaporation.Relative humidity and precipitation were main influencing factors of annual pan evaporation variation in the entire river basin,and middle reaches and lower reaches of the basin;relative humidity and air temperature were main influencing factors in the upper reaches.Main influencing factors of spring pan evaporation change were relative humidity and precipitation;main influencing factors of summer pan evaporation change were relative humidity and air temperature in the entire basin,the up reaches and the middle reaches,and those were relative humidity and precipitation in lower reaches;main influencing factors of autumn pan evaporation change were relative humidity in the entire basin and the up reaches,and was diurnal temperature range in the middle reaches,and were relative humidity and precipitation in upper reaches;main influencing factors of winter pan evaporation change were relative humidity.In a word,relative humidity was the most significant influencing factor of pan evaporation in spring,summer and autumn,and the most significant influencing factor was air temperature in winter.