青藏高原冬、春季沙尘暴频次时空分布特征及其环流背景

Spatiotemporal distribution characteristics and circulation background of sandstorm occurrence frequency in Qinghai-Tibet Plateau in winter and spring

利用1961-2002年青藏高原29个气象台站的沙尘天气资料,分析了冬、春季沙尘暴频次的时空分布和变化,并结合欧洲中心再分析资料的200 hPa高度场数据,分析了冬、春季沙尘暴异常年份对应的环流特征。结果表明:青藏高原的沙尘暴主要集中发生在12月至次年5月,1961-2002年间其发生频次呈显著减少的趋势;阿里高原、柴达木盆地、三江源区和雅鲁藏布江中游地区为沙尘暴的高发区域;沙尘暴高发中心随季节的推移由藏南逐渐北移至羌塘高原及塔里木盆地;冬、春两季200 hPa高度场在沙尘暴强年均表现出纬向西风气流增强,传输到地面的能量增加,利于沙尘暴天气的形成,而在沙尘暴弱年均表现为经向环流增强,阻碍了能量的向下传输,不利于大风天气的形成。

Based on the daily data of sandstorm events from 29 meteorological observation stations on the Qinghai-Tibet Plateau from 1961 to 2002 and the reanalysis data of 200hPa height of European Center of Medium Range Weather Forecast,the spatiotemporal distribution characteristics and variation of sandstorm occurrence frequency in winter and spring were analyzed,the circulation background in sandstorm anomalous years were also discussed.The results show that,sandstorm events mainly occur in the Ali Plateau,the Qaidam Basin,the source of the three rivers and the middle reaches of the Yarlungzangbo River from December to next May,and its occurrence frequency present a significant decreasing trend from 1961 to 2002.The high incidence areas of sandstorm gradually shift from south to Qiangtang Plateau and Tarim Basin in the north with seasons change.In both winter and spring of strong sandstorm years,the distribution of 200 hPa height field tends to be smoother compared with normal years when zonal westerly wind is enhanced,and the energy transmission to the ground is increased;while in weak sandstorm years,it shows the opposite situation.