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Université du Xinjiang (2017)

Spatiotemporal Evolution of Salt Dust Aerosol in Inland Lakes in the Arid Region of the Central Asia and Its Indirect Climatic Effect

张喆;

Titre : Spatiotemporal Evolution of Salt Dust Aerosol in Inland Lakes in the Arid Region of the Central Asia and Its Indirect Climatic Effect

Auteur : 张喆;

Grade : Doctoral Dissertation 2017

Université : Université du Xinjiang

Résumé
Salt dust storm is a natural weather disaster caused by the bottom of dry lake and its adjacent strong salinized soil in arid and semi-arid areas.Central Asia had a great contribution to the global dust aerosol.Desert and semi-desert occupy the vast majority of the area and the unreasonable activities of mankind,vegetation degradation,desertification increase,dust storm frequently,rapid and serious ecological environment deterioration restricting the implementation of the local economic development and the western development strategy.In the past 50 years,the Aral Sea and Ebinur Lake have deteriorated rapidly.The shrinking lake has caused a large area of the lake to be exposed.The dry lake becomes rich dust and salt dust source,which making the region facing serious threat of salt dust disaster,aserious threate to the new Eurasian Continental Bridge safe operation and "The Belt and Road" core area construction implementation.In this study,we understand the occurrence and development of dust storms in Central Asia,and obtained the overall evolution trend of dust storms in this region from 2002 to the present using remote sensing,discussed the effects of inland lakein Central Asia degradation on aerosol spatiotemporal pattern.we obtained the aerosol optical properties during the occurrence of the salt dust disaster using satellite and ground-based remote sensing,taked the typical dust aerosol and urban-industrial aerosol optical properties as reference to realize the identification of the optical properties of the salt dust aerosol.Based on the meteorological conditions such as temperature,air pressure,relative humidity,horizontal and vertical wind speed,the diffusion traces of the salt dust pollutants originating in the dry lake(Aral Sea and Ebinur Lake)were simulated day by day,and the trajectories were grouped according to the spatial similarity to determine the salt dust pollutants seasonal potential diffusion characteristics ;The temporal and spatial distribution characteristics of aerosol-cloud-precipitation in Central Asia were analyzed from the macroscopic point of view,and the results were analyzed in detail for the area of salt dust pollution,and the results were analyzed in detail.The interaction between the aerosol and the cloud and the precipitation affects the following conclusions :(1)The spatial distribution of AOD in Central Asia showed significant seasonal variation,and the trend was increasing in 14 years.The AOD high value area was mainly concentrated in the Tarim Basin in southern Xinjiang,the lower reaches of the Ebinur lake basin and the surrounding area of the Aral Sea in Central Asia ;the degree of AOD changes in Ebinur and Aral Sea basin showed the effect of inland lake degeneration on the spatial and temporal pattern of aerosol in the surrounding area ;The change of AOD in the Taklimakan Desert area is mainly affected by both temperature and wind speed,and the dominant factors are different in different seasons.(2)The spring is the most active period of dust release and transportation movement.When the dust weather in the dust source area occurs,the dust particles with large particle size were mainly concentrated in the low-level atmosphere near the ground 0-2km,the irregularity of particles is relatively high ;With the increase of height,the irregularity and particle size of aerosol were decreased.The aerosol scattering ability was strongest in the range of 0-2km above the ground in the salt dust source area.The ratio of the ratio was concentrated in the range of 10%-30%,the color ratio was concentrated in the range of 0.3-0.8.With the increase of the height,the aerosol scattering ability was gradually weakened,the deviation ratio was about 5-15%,the color ratio was concentrated at 0.3 Compared with dust aerosol,the salt dust aerosol had a higher degree of spherical sand,and the particle size of the particles was relatively small.(3)The erosion of the lake caused by the degradation of the lakewas the main reason for the occurrence of soil salinization and salt dust storms ;Salt dust was mainly settled in Jinghe area,it was close to the dry lake bottom ;With the increase of the distance from the dry source of the dry lake,the particle size of the aerosol particles in the atmosphere decreases and the particle size of the particles increases,This indicates that the area far from the dust source area not only affected by the Ebinur Lake salt dust,but also affected by local dust source intervention.In the spring,the atmospheric aerosol was mainly in the form of coarse mode,and the dust aerosol was the main factor.The winter was in the form of fine mode,and the urban-industrial aerosol was the main factor.The wind speed was the main factor affecting the local aerosol.The aerosol particles mainly showed non-hydrophilicity when the dust storm occured,butaffected by the local aerosols,aerosol particles also showed a certain degree of hydrophilicity.(4)The potential diffusion direction of salt dust in the Aral Sea area was mainly in the northeast,southwest and south,and the diffusion distance was most distant in the northeast direction.The influence range was up to the central region of Russia,the southwest divergence path height and distance were close,the main influence Uzbekistan and Turkmenistan,but the proportion was relatively high ;Ebinur lake dust disaster affected the watershed southeast direction of the river to Wusu line,salt dust particles mainly from west to east diffusion,the proliferation of highly concentrated in the 3000 m range,including Jinghe,Wusu,Kuitun,Shawan,Shihezi,Changji,Urumqi,Hami and other regions such as Gansu,Inner Mongolia,Mongolia,Hebei,Liaoning and other regions ;43% of the diffusion trajectory concentrated in the range of 1km within the Ebinur Lake around the Bole,Jinghe,Toto Township,Wusu had a greater impact.(5)The increase in the concentration of particulates in the atmosphere significantly affects the formation and development of clouds and the accompanying precipitation processes.In dry areas or seasons,the increase in particulate matter will inhibit precipitation,in wet areas or seasons,the increase in particulate matter will increase the number of precipitation or increase the intensity of heavy rain.Overall,aerosols in Central Asia inhibit precipitation.However,in the surrounding area of the Aral Sea,there is a high pollution in the autumn,but the probability of precipitation under high pollution is higher than that of low pollution.This area shows the reason why aerosols promote precipitation and increase the incidence of high rainfall rainfall remains to be analyzed.

Mots clés : Salt dust; Aerosol optical properties; Spatial and temporal distribution; Potential diffusion path; Indirect climate effects;

Présentation (CNKI)

Page publiée le 21 janvier 2018