我国北方沙尘天气演变趋势及其气候成因分析

VARIATION OF DUST WEATHER AND ITS CLIMATIC ATTRIBUTION ANALYSIS IN NORTHERN PART OF CHINA

利用地面气象观测资料,分析了我国北方1954～2001年年、季沙尘天气发生日数的演变规律及其与主要气候要素,风速、相对湿度、降水、气温和干燥度的相关关系,用NCEP/NCAR再分析资料分析了冬春气压梯度的变化趋势.结果表明:近50年来,造成我国北方沙尘天气频率显著下降的直接自然原因是沙尘源区和发生区平均风速和大风日数的减少、主要沙尘源区降水量特别是春季及其前冬降水量的增加以及由于源区降水增加引起的大气和土壤湿润程度的改善.冬春季节气压梯度的减小是风速减小、进而导致沙尘日数减小的关键间接因素.

Based on the surface observations from 1954 to 2001, the tendency of dust weather frequency is presented by Mann-Kendall method, and the relationships of the frequency to wind,relative humidity, air temperature and dryness index are analyzed. The Geopotential height in 1000 hPa from NCEP/NCAR reanalysis data is used to study the pressure gradient change in winter and spring from 1954 to 2001. Results show that the direct natural causes of dust weather frequency change in the recent 50 years include the decrease of daily mean wind speed, the decrease of number of days with daily mean wind speed higher than 5.0 m/s, the increase of precipitation in the same spring and last winter, and the improved condition of atmosphere and soil moisture in some potential dust resource areas. Results also show that decrease of pressure gradient in winter and spring influences dust weather frequency by affecting wind speed indirectly.