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

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 tow ind, 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 day s with daily mean w ind speed higher than 5.0 m/s, the increase of precipitation in the same spring and last w inter, 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 w ind speed indirectly.