The Source Area,Transport And Contribution Of Mechanisms To The Total Amount Of Dust Aerosols In North Africa

Based on the analysis of the spatial and temporal distribution of sandstorm,floating dust,wind field and Aerosol Index(AI)of 300 weather stations in North Africa over the past 20 years,this paper discusses the long-distance transport path of the sandstorm and dust plume.At the same time,combined with model simulation of dust storms and dust devil on spatiotemporal distribution of sediment and compare with AI,determined the sandstorms and the dust devil sand area respectively and their contribution to the amount of dust.The main conclusions are as follows:(1)According to the meteorological station data,850 h Pa wind field and AI spatial distribution information in winter and summer in North Africa,it is considered that there are two main transmission paths of dust in North Africa,the main transmission path ? from Algeria to the Mediterranean,Egypt and Sudan in the East,then to the Sahel,from the east to the West to the Atlantic Ocean;II from Algeria,South to Mauritania and west to the Atlantic Ocean;at the same time,there are four branches in the main transmission path I.(2)In North Africa,there are two kinds of sand raising mechanisms,one is dynamic sandstorm,the other is thermal wind.The total amount of sand raising is not only significantly related to AI,but also the spatial distribution of each month is very similar.(3)Based on the observation and Simulation of Sandstorm in North Africa,the high occurrence period of sandstorm mainly occurs in spring,and the source areas of sandstorm are mainly from the western desert to the Chech desert,the northern part of the eastern desert,the Mediterranean coast,the eastern side of the Nubia desert,the Atouila desert to the Ouarane desert and the Bodélé depression,among which Bodélé depression is the most important source area of Sandstorm in North Africa,while northern Eritrea and Sudan's border region is also a dust storm sand area in North Africa from June to August.(4)April to August is the high incidence period of dust devil,and its source areas are mainly concentrated in the central part of North Africa,especially in the southwest of the Hoggar mountains to the west of the Air mountains,the border area of Egypt-Sudan-Libya and near the Tibes plateau,which happen not to be the source areas of dust storms.In addition,the contribution of dust devils to the Atlas Mountains and a strip south of 15°N in the Sahel region is also greater than 50%.(5)Although the sand-raising area of dust entrainment in north Africa is smaller than that of sandstorm,its annual dust emission accounts for 38.7% of the total amount of sand entrainment in north Africa,and it is one of the most important sand entrainment mechanisms in north Africa.