近几十年来三江源地区水汽输送与 降水变化特征

Abstract

以三江源地区为研究区，采用该地区1971~2010年观测气象资料和NCEP/NCAR I再分析资料的逐日风场和比湿数据，分析了三江源地区近几十年来不同时间尺度上水汽输送及降水的时空特征和变化趋势。结果表明：1971~2010年，三江源地区水汽输送和降水的时空分布格局比较相似，但近几十年来水汽输送和降水的变化趋势并不一致。1971~2010年，三江源地区经向水汽输送呈显著减少趋势，主要是由于南边界水汽输入减少；纬向水汽输送呈显著增加趋势，主要是由于东边界水汽输出显著减少；区域边界总水汽收支变化趋势与经向水汽输送一致，呈显著减少；降水则呈一定的增加趋势，但未通过显著性检验。三江源地区特别是东南部近几十年来水汽输送显著减少，尤以6月和9月为甚，且水汽通量散度在中低层大气中辐合程度降低，但实测降水除9月明显减少外，其他月份并没有相应减少。 Based on daily meteorological factors at observation stations and daily reanalysis data (including daily wind and daily specific humidity) of NCEP/NCAR I Reanalysis data during 1971-2010, temporal-spatial distributions and variation characteristics of water vapor transport and precipitation in the Three Rivers’ Headstream Region were analyzed. The results showed that the temporal-spatial distributions of water vapor transport and precipitation were similar in the Three Rivers’ Headstream Region, but that variation characteristics were different in recent several decades. During 1971-2010, meridional water vapor transport showed the dramatic decreasing trend due to the decrease of water vapor transport on southern boundary, and zonal water vapor transport showed the significantly increasing trend due to the decrease of water vapor transport on eastern boundary. Water vapor budget in the whole region had the same decreasing trend as the meridional water vapor transport, while precipitation had a certain increasing tendency without passing the significance testing. Water vapor transport decreased significantly in the Three Rivers’ Headstream Region especially in the southern-east part during 1971-2010, while water vapor transport in June and September decreased most. At the same time, the degree of convergence of water vapor flux divergence in lower-layer atmosphere reduced. However, annual precipitation didn’t show the significantly decreasing trend in recent decades, except that precipitation in September decreased obviously.