RELATIONSHIPS BETWEEN DUST STORMS AND DRYNESS-WETNESS IN MIDDLE-EASTERN CHINA DURING 1470-1950

摘要

Based on 481-year records of historical dust storm (DS) and Dryness-Wetness Index (DWI) at 120 sites,spatial distribution characteristics of dryness-wetness (DW) in typical dust storm years (DS years) and in non-dust storm years (non-DS years) were derived for continental China. In DS years, most of the sites were drier than in normal years while in non-DS years wetter than normal, and the variation of DWI in DS years was larger than that in non-DS years.The relative instability and increased regional difference of atmospheric circulation in DS years might have induced more frequent DS events and dry-wet abnormality in continental China. In DS years the latitudinal (north-south) dry-wet difference was larger than that in non-DS years, that is, north China was even much drier than south China. This might be attributed to increased latitudinal differences of thermal and pressure gradients in DS years, resulting in the southward withdrawal of precipitation and increase of DS events.