青海不同地形下蒸发皿蒸发量变化及其影响因子分析

Change of Pan Evaporation and Its Affecting Factors in Qinghai Province

利用青海省不同地形(河谷、盆地、高原)中36个台站1961—2003年观测的蒸发皿蒸发量及其他气象因子资料,分析蒸发皿蒸发量的变化趋势,探讨其变化形成的原因。结果表明:蒸发量在青海大部分观测站表现为下降趋势。盆地、河谷中的观测站下降较为显著,而青南高原中的观测站变化趋势并不一致,且下降趋势不显著。河谷中由于山脉的影响,大气污染物不易扩散,气溶胶粒子增加,减弱了太阳的直接辐射,使河谷中湿度增加、山谷风环流减弱、日照减小、气温日较差减小,导致蒸发皿蒸发量的下降。柴达木盆地在全球温室气体以及气溶胶浓度增加的背景下,云量增多、降水增加使该区域风速减小、日照减小、气温日较差减小,从而使蒸发皿蒸发量出现下降趋势,并呈现出盆地西部下降趋势大,盆地中东部下降趋势小的分布特征。青南高原位于青藏高原主体,各气象观测站蒸发量的变化并不是一致性的下降或上升。

The observation data of pan evaporation and other meteorological factors from 36 meteorological stations at different terrains （the river valleys, Qaidam Basin and Qingnan Plateau） in Qinghai Province during the period of 1961 -2003 were applied in the study. Results showed that the pan evaporation at the most selected stations was in an obvious decrease trend, especially at the stations in the basin and valleys. The change trend of pan evaporation at the stations in the Qingnan Plateau was different, and the decrease was not so significant. In the river valleys, the pan evaporation was decreased due to the effects of mountains, emission of air pollutant, increase of aerosol particles, weakened direct solar radiation and mountain breeze circulation, and decrease of sunshine and daily temperature range. Under the global increase of greenhouse gases and aerosols, in the Qaidam Basin the pan evaporation was decreased due to the increase of cloud cover and precipitation, and decrease of wind speed, sunshine duration and daily temperature range, and the decrease of pan evaporation in the western part of the Qaidam Basin was more significant than that in the central and eastern parts. The Qingnan Plateau is located in the main part of the Qinghai -Tibet Plateau, where the change of pan evaporation was different from different stations.