Relation Between The Sand Storm Occurrence Frequency And Climate Factors And The Analysis Of Dust Entrainment And Deposition

The spatial and temporal characteristics of sand storm occurrence arestatistically analyzed based on the meteorological records in Xilingol league of InnerMongolia for 30 years (1971～2000). The influences of climate factors on the sandstorm events are quantitatively studied. The result shows that the central-western partof Xilingol is the more frequent region of sand storm, especially in Zhurihe as thehigh value site. According to the sand storm occurrence frequency of individualstations, there is an obvious daily variation and season differences of the period ofthe sand storm occurrence. The interannual change of sand storm occurrence appearsan obvious decrease during the past 30 years in Xilinhaote and Erlianhaote. Decadalchange of sand storms occurrence also presents decreasing trend. The maximumdecreasing rate present from 1980s to 1990s: -89.5%, -9.8% and 3.8%, in Xilinhaote,Zhurihe and Erlianhaote respectively. For all the climatic factors, correlation analysisshows that wind is a key factor to the sand storm occurrence in the studied area. Thecorrelation coefficient between sand storm occurrence and monthly mean wind speedis 0.816, 0.658 and 0.661, in Xilinhaote, Zhurihe and Erlianhaote respectively; Thecoefficient between annual mean sand storm occurrence and numbers of days ofwind velocity≥5m/s is 0.769 and 0.562, in Xilinhaote and Erlianhaote respectively. Itshows a significant positive correlation between daily range of air temperature andsand storm occurrence, and the coefficient is 0.718, 0.769, in Zhurihe andErlianhaote respectively. There is significant negative correlation between sand stormoccurrence and monthly mean relative humidity. The coefficient is -0.622, -0.581 and-0.750, in Xilinhaote, Zhurihe and Erlianhaote respectively (Correlation is significantat the 0.05 and 0.01 level). Increase of precipitation over the source areas of sandstorm or so might have restrained the development of sand storm.The dust entrainment and deposition model, DEAD, has been run using boxmodel forcing dataset for 1991-2003 in Paterson, WA.produced from PAWS stationdata. The numerical results of total vertical mass flux of dust and dry depositionvelocity are estimated based on the simulation. It shows that the dust emissionthreshold velocity is 4.01 m.s^-1.