1971-2010年三江源地区干湿状况变化的空间特征

Spatial pattern and its variations of aridity/humidity during 1971-2010 in Three-River Source Region on the Qinghai-Tibet Plateau

依据1971-2010年地面观测气象数据,计算了三江源地区湿润指数。利用经验正交函数分解(EOF)和偏相关系数,对近40 a三江源地区干湿状况变化的时空特征及其影响因素进行了分析。结果表明:三江源地区干湿状况的变化在其北部与南部、东部与西部间存在明显反相位变化特征。北部和东部的部分区域分别在20世纪90年代和21世纪后表现出气候湿润化趋势,其余大部地区的持续干旱化趋势始于20世纪80年代初,其中南部与西部变干趋势显著,其湿润指数线性趋势率达到-8%/10 a。虽然三江源地区干湿状况主要决定于降水量和相对湿度的变化,但20世纪90年代中期后气温的显著上升,使得气温也成为关键的影响因子之一,即使在降水明显增加的背景下,也引起三江源主体区域湿润指数的明显下降。气候变暖情景下,北部和东部地区在近十几年暖湿化趋势明显,其余大部地区表现为不同程度的暖干化趋势。

The Three-River Source Region River, is located in the hinterland of the Q alpine vegetation ecosystem, the water and （ TRSR）, the source region of Yangtze River, Yellow River and Mekong inghai -Tibetan Plateau. With a typical continental plateau climate and heat matching is a key to vegetation variation over region. In this study, monthly humidity indexes in TRSR were computed using ground-observed monthly air temperature, precipitation, wind speed, relative humidity and air pressure from 1971 -2010, based on the method of Ecological and Meteoro- logical Monitoring Standard which recommended by China Meteorological Bureau. The spatio-temporal variation of aridity/humidity conditions and its dominated factor were analyzed using the method of Empirical Orthogor/al Func- tion （EOF）, linear correlation and partial correlation analysis. The results show a clear of opposite mode in the zone of northern toward southern and western toward eastern in TRSR. It was found that there is a wet tendency af- ter 1990s and 21~＇ century in the zone of northern and eastern respectively, but a continual dry tendency since 1980s, especially in the zone of southern and western with a remarkable decreased trend （ -8%/10a）, occurred in other area of TRSR. Aridity/humidity conditions are controlled by precipitation and relative humidity in generally, but the situation is changed evidently after Mid-1990s in the most area of TRSR due to a significant warming, and temperature plays a key of factor to dominate a decreased trend of humidity index even if precipitation increases markedly since then. Under a scenarios of climate warming, it shows a tendency of heat and wet obviously in the zone of northern and eastern and heat and aridity in a ~rt^in ,=~t,~nt ; t ~ rr^o