河北省近40年蒸发皿蒸发量变化特征及影响因素初探

利用河北省区域1963-2003年50个站蒸发皿蒸发量资料,分析了蒸发量变化及影响因素。结果表明:近40年来河北省区域平均年和四季蒸发量变化,由60、70年代偏多转为80、90年代偏少,转折年均在70年代末和80年代初。春、夏季蒸发量减少趋势明显,分别为-31.3、-27.4mm/10 a,年蒸发量的减少主要是由春、夏季减少所致;对蒸发量的空间分析表明,区域内94%的站点呈减少趋势,70%站点减少趋势显著,减少速率最大区域在冀中南部东部区域,减少速率在-100mm/10 a以上;蒸发量变化与各要素相关分析表明,蒸发量变化与日照时数、低云量、气温日较差相关显著,而日照时数、低云量、气温日较差与太阳辐射大小关系密切,因此,太阳辐射是影响蒸发量变化的主要因素,同时平均风速的减少对蒸发量的减少也起着重要作用。

Variation of evaporation capacity and influence factors in Hebei Province between 1963 -2003

The variation of evaporation and its causes are analized with the observational data set of pan evaporation from 1963 to 2003 in Hebei Province. The results show that in the latest 40 years the averaged seasonal and annual evaporation of Hebei Province are all above normal in 1960s and 1970s,while below normal in 1980s and 1990s, and the turning points are all between the late 1970s and the early 1980s. The significant decline trend of spring and summer have been detected at the rate of -31.3 mm and -27.4 mm per decade, which is the main cause of the annual evaporation decrease. The spatial analysis indicates that the annual evaporation of 94% stations has decline trend, and 70% has significant decline trend. The eastern part of south central Hebei is characterized by the largest decline rate of annual evaporation ( at - 100 mm per decade) . The correlation analysis between evaporation and other elements shows that evaporation has significant correlation with the conditions of sunshine duration, low cloud and daily temperature range, therefore, solar radiation is the key factor of the variation of evaporation since the three elements mentioned - above are all closely related to it. Meanwhile the decline of wind speed is another key contributor to the decrease of evaporation.