Remote Sensing Of Land Uses In Dust Source Regions Of East Asia

Aeolian dust,in meteorology,is a weather phenomenon that strong winds entrain small soil particles into the atmosphere.It is a common meteorological disaster in arid and semi-arid areas.Dusty weather not only endangers the ecological environment seriously,but also threatens human health and civilization.East Asia is a main source of global aeolian dust.In recent years,dust emissions from East Asia have been decreasing due to the attention of the countries in the world on environmental protection.However,in order to further clarify the occurrence patterns and dust sources of dusty weathers,it is necessary to study the spatial distribution and land uses of dust sources.East Asia was divided into seven sub-areas: Mongolia,Tibetan Plateau,the Tarim Basin,Hexi Corridor,the Loess Plateau,Xilingol Grassland and Horqin Sandy Land.Nineteen years'(2000~2018)MODIS(Moderate Resolution Imaging Spectroradiometer)L1B(Level 1B)data were used to remotely monitor and analyze the temporal and spatial patterns of dusty weather over East Asia and multiple spatial resolution satellite images were employed to identify dust sources.The study found that the dusty weather of 2000~2002,2004 and2006 were frequent in East Asia.During the 19 years from 2000 to 2018,dust event records over Mongolia,Tibetan Plateau,the Tarim Basin,HexiCorridor,the Loess Plateau,Xilingol Grassland and Horqin Sandy Land were 86?60?399?140?102?85 and 63,respectively,totaled 935.The dusty weathers in April over these sub-areas accounted for 36%,45%,18.3%,27.9%,23.5%,38.8% and 34.9%,respectively.The dusty weathers in spring accounted for 82.6%,86.7%,52.6%,58.6%,49.0%,81.2% and 79.4%,respectively.It can be concluded that dusty weathers were the most frequent in spring(March to May),with April as the most frequent month.Except for the Tarim Basin(summer is the second dusty season),winter ranked as the second dusty season in other subareas.In recent years,the frequency of dusty weather has been decreasing generally,which might be related to the greening project such as afforestation,returning farmland to forests,and the “three norths' protection forests”.Increasing the coverage of surface vegetation can curb the occurrence of aeolian dust.Dust sources in East Asia are mainly distributed over Mongolia and the northwest of China,where locate in fragile ecological environments such as desert,Gobi,farming-pastoral zone and oasis-desert ecotone.Including the south of Mongolia,the northwest of the Tibetan Plateau,the northwest edge of the Taklamakan Desert in the Tarim Basin,the north and east of the western entrance area of the Hexi Corridor,the northwest of the Loess Plateau,Otintag sandy land in Xilingol League,and the southwest of Horqin Sandy Land,53 counties are involved.The mainland use types of dusty sources in East Asia include dry lake,salt lake,river channel and lake bed sediment,piedmont deposit and flood deposits active sand dune,salinized land and land for resource and agricultural development.Dry lake,salt lake,water body,river channel and riverbed are common types of dusty sources in East Asia.It can be concluded that the formation of dusty sources is mainly related to hydrological conditions.The study showed that factors responsible for aeolian dusts are from both natural and human aspects.Natural factors include climatic characteristics,topographic features,soil conditions and vegetation coverage;however,the formation of most dust source also connected with population pressure,human economic activities,over-exploitation and unreasonable use of natural resources by human activities.Satellite remote sensing of aeolian dust demonstrated the temporal and spatial characters of dusty weathers,and efficiently determined dust emission regions and dust sources,as would be of great significance in guiding studies on the ecological environment improvement of the dust sources in East Asia.