祁连山山区空中水汽分布特征研究

将卫星遥感资料与探空资料和地面观测降水资料相结合,分析了祁连山山区空中水汽含量和云迹风的空间分布特征。并且,以此为基础,研究了祁连山大气水汽和地面降水的空间分布及其与大气环流和地形的关系。结果表明:祁连山大气水汽和地面降水受西风带、偏南季风(南亚季风和高原季风)和东亚季风的共同影响,在祁连山西北部大气水汽主要受西风带气流控制,在祁连山中南部偏南季风占主导地位;在祁连山的东北部则是东亚季风的影响比较明显。同时,祁连山大气水汽、降水和降水转化率与海拔高度和坡向以及环流影响区的关系均十分密切。一般,迎风坡上大气水汽含量在3500—4500 m海拔高度会出现一个峰值;而在背风坡上除东亚季风影响区外大气水汽含量只出现随海拔高度单调递减趋势,基本上不出现任何峰值。背风坡大气水汽含量总体上要比迎风坡少得多,最多大约能少4.49 kg/m2。无论是大气水汽含量、地面降水还是降水转化率均在东亚季风影响区最大;东亚季风影响区大气水汽含量在迎风坡上的峰值要更强,出现的海拔高度更低。

RESEARCH ON ATMOSPHERIC WATER-VAPOR DISTRIBUTION OVER QILIANSHAN MOUNTAINS

Based on the remote sensing data,the radiosonde data and the precipitation data observed by weather stations,distributions of water-vapor in air and cloud motion winds in the Qilianshan Mountains are analyzed.Moreover,on the basis of water-vapor and cloud motion wind analyses,relations of atmospheric water-vapor distribution with precipitation,atmospheric circulation and terrain are investigated.The results show that distributions of atmospheric water-vapor and precipitation in Qilianshan Mountains are affected by the westerly belt,the southerly monsoon(the South Asian monsoon and Tableland monsoon) and the East Asian monsoon.In the northwest region of the Qilianshan Mountains,water-vapor and precipitation are entirely affected by the westerly belt flow,and there is no other direction water-vapor transport except westerly water-vapor flux,so,the northwest region is regarded as the westerly belt region.In the south and middle region of the Mountains,water-vapor is mainly controlled by the southerly monsoon,37.7% of the total water-vapor is from the south,especially in summer,the southerly water-vapor flux accounts for 55.9% of the total,and furthermore the water-vapor content in the southerly flow is more than that in the westerly flow.The southerly monsoon water-vapor is influenced by the South Asian monsoon from the Indian Ocean and the tableland monsoon in the Qinghai-Tibet plateau,so,the south and middle region is called the southerly monsoon region.But in the northeast region of the Mountains,the East Asian monsoon is the main climate system affecting the water-vapor in this region,except west and northwest water-vapor fluxes,there are a lot of easterly water-vapor fluxes in summer.The frequency of easterly cloud-motion winds in summer half year accounts for 27.1% of the total,though the frequency is not too high,it is the main water-vapor source of summer precipitation in this region,therefore,the northeast region is a marginal region of East Asian monsoon.On the other hand,atmospheric water-vapor,precipitation and the convert rate of water-vapor into precipitation are close related with altitude and circulation systems.Generally,there is a peak value of water-vapor content at the altitude from 3500 m to 4500 m on the windward slope,but on the leeward slope,water-vapor monotunically decreases with reduce in altitude except for that in the East Asia monsoon region.Water-vapor on the leeward slope is much less than that on the windward slope,and the maximal difference in water-vapor content between both sides may reaches about 4.49 kg/m2.Whether the value of water-vapor content,precipitation or the convert rate of water-vapor into precipitation all reach their maximals in the East Asian monsoon region,and correspondingly the peak value of water-vapor on the windward slope is also larger and occurs at a lower altitude in comparison with other two regions.