THE SPATIAL NAND TEMPORAL VARIATIONS OF SPRING DUST STORMS IN CHINA AND ITS ASSOCIATIONS WITH SURFACE WINDS AND SEA LEVEL PRESSURES

Using the methods of EOF and SVD,the spatial and temporal characters of spring dust storms in China and its associations with surface winds and sea level pressures in recent half century have been studied.In most part of China,the spring dust storms have the same trends.The dust storms have shown a decreasing trend in the recent half century.Dust storms occurred more frequently from 1957 to late 1970s.However,since the end of 1970s they have decreased and reached the lowest point in 1997.Butin latest years the dust storms increased slightly.The spring surface wind speed in China has also ilustrated a decreasing trend during the recent half century.There are significant correlations bet ween dust storms and surface wind speed.The surface wind speed has impact on the frequency of dust storms directly.The surface wind speed and dust storms have both shown a decreasing trend in recent half century.In 1997,the wind speed and dust storms both reached the lowest point. Since 1997,the wind speed has increased slightly and the dust storms have also increased.The sea level pressures in spring are closely related to dust storms and they have effects on the dust storms ultimately.During the recent half century,the sea level pressures have decreased at the mid high latitudes while increased at the mid low latitudes which leads to the change of pressure gradient.The surface wind speed has decreased because of the change of pressure gradient and this has eventually resulted in the decreasing of sand storms.Furthermore,the contrary changes of sea level pressures in north and south parts of China and over ocean and land have close correlations with the local variations of dust storms.