秦岭南北地区绝对湿度的时空变化及其与潜在蒸发量的关系

基于秦岭南北地区1960—2011年的气象观测资料,分别利用绝对湿度计算公式和Penman-Monteith公式估算大气绝对湿度和潜在蒸发量,并进一步分析了绝对湿度的空间分布规律、时空变化特征及其与潜在蒸发量变化的响应关系。结果表明:(1)秦岭南北地区绝对湿度由南向北顺次递减,具有较好的海拔地带性和纬度地带性。季节平均湿度以夏季为最大,冬季最小。(2)近52年绝对湿度除巴巫谷地表现出不显著下降趋势外,其它子区均呈现出增加趋势。1986年和1998年是湿度变化的转折点,1960—1986年以微弱下降为主,此后直至1998年震荡上升,1998年以后呈下降趋势。(3)年尺度和春、秋两季,除巴巫谷地外,湿度和潜在蒸发量均表现出显著的负相关关系;而在夏季和冬季,除汉水流域和巴巫谷地不显著正相关以外,其它区域也均为负相关。年度和春、秋两季两个指标负相关的紧密程度随着区域的南移而逐渐减弱。1960—2011年间,年度和季节尺度潜在蒸发和绝对湿度呈反向变化趋势;而在1960—1989年间,两者同向变化;1990—2011年间,年度和春、冬两季潜在蒸发上升,而同期的绝对湿度则是先上升再下降。(4)实际蒸发量的增加导致空气中水汽含量(湿度)增加,反过来抑制了水面蒸发(潜在蒸发量)。秦岭以北、秦岭南坡、汉水流域和巴巫谷地部分地区绝对湿度和潜在蒸发量为互补关系,由北向南随着水分限制作用的不断减弱两者逐渐转化为不显著的正相关关系。

Spatial and temporal variation of absolute humidity and its relationship with potential evaporation in the northern and southern regions of Qinling Mountains

Based on the meteorological data from weather stations in the northern and southern regions of Qinling Mountains (NSQ), we used absolute humidity estimating formula and Penman-Monteith equation to estimate absolute humidity and potential evaporation, respectively. Furthermore, we analyzed the spatial and temporal distribution and variation of absolute humidity, and tried to give the possible explanations for the reciprocal feedback between absolute humidity and potential evaporation, the result are as following. (1) Absolute humidity presented a clear pattern that high in south and low in north, the order of it was Bawu Valley (BWV), Han River Basin (HRB), northern and southern regions of Qinling Mountains(NSQ), southern slope of Qinling Mountains (SSQ) and northern regions of Qinling Mountains (NRQ), the order of seasonal absolute humidity was summer, autumn, spring and winter. (2) In the past 52a, absolute humidity in most regions, except for BWV, had increasing trend. 1986 and 1998 are the change point, in the period of 1960-1986, it had insignificant decreasing trend, and then increased significantly until 1998, and decreased since 1998. (3) On the annual scale, spring and autumn, in most regions, except for BWV, absolute humidity negatively correlated with potential evaporation, meanwhile, in summer and winter, except for HRB and BWV, absolute humidity and potential evaporation also had the similar correlation relationship. Beside from this, the correlation coefficients on the annual scale, spring and autumn became smaller with the latitude decreased. In the period of 1960-2011, on the annual and seasonal scale, absolute humidity and potential evaporation had contrary change trend, however, in the period of 1960-1989, they showed same change trend. From 1990 to 2011, potential evaporation in year, spring and winter increased significantly, meanwhile, absolute humidity increased initially and then decreased. (4) The contrary change trend of absolute humidity and potential evapotranspiration can be explained by the evaporation complementary theory. The actual evaporation increasing will lead to the increase of water vapor content in the air, also for the absolute humidity, which will inhibit water evaporation. Absolute humidity and potential evaporation had complementary relationship in NRQ, SSQ, HRB, and part of BWV, and the correlation relationship decreased with water limitation reducing, ranging from negative correlation to insignificant positive correlation.