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Lanzhou University (2020)

The North-south Pattern of Aerosols and Their Formation Mechanisms in North Africa

邸文婧

Titre : The North-south Pattern of Aerosols and Their Formation Mechanisms in North Africa

Auteur : 邸文婧

Grade : Master 2020

Université : Lanzhou University

Résumé partiel
The climate effect of aerosols is an important factor in air pollution and surface radiation balance.As one of the most important components of atmospheric aerosol,dust is an important link in Global Ocean-Atmosphere-Land System.North Africa,one of the most important dust sources in the world,is considered as natural source,where dust can be transported to the Atlantic,Mediterranean and Caribbean oceans.It affects Marine ecosystem and provides nutrients to the amazon rainforest.Besides the natural dust,studies also show that there are a lot of anthropogenic aerosols in north Africa.Therefore,it is very important to analyze the spatial distribution of aerosols in North Africa.The optical properties and microphysical features of aerosol and spatial distribution of dust in North Africa regions from 2007 to 2017 are analyzed using MODIS and CALIPSO remote sensing,along with MERRA-2 reanalysis data.The reasons for the spatial distribution pattern are also investigated.The results are as follows :(1)The spatial distribution of AOD of dust(DU),black carbon(BC)and organic carbon(OC)shows significant seasonal variations,while there were no significant seasonal variations in AOD of sulfate(SU)and sea salt(SS).The North Africa is dominated by dust aerosol and it shows significant difference of content in different areas.The proportion of dust in northern North Africa is more than 80%.The proportion of dust in southern North Africa decreased significantly and the proportion is only 46%in summer.In addition,the proportion of BC and OC in southern North Africa shows greater increase than that in the north,especially for OC,which reaches up to 27%in summer and winter.(2)Emission of dust is mainly located in Sahara and its surroundings.The regional averaged emission of dust in northern North Africa is as high as 3×10-99 kg m-22 s-1.Emission of BC,OC and SU are mainly located in southern North Africa,and were the highest in winter and the lowest in summer.Dry deposition rate of BC and OC are significantly lower than that of dust,the high-value area of BC and OC is located in northern North Africa in summer and in southern North Africa in winter.The high-value area of wet deposition rate of dust is located in Sahara in summer and is located in Guinea coast and Atlantic coast.The high-value area of wet deposition rate of dust is consistent with the seasonal variation of the precipitation.Wet deposition rate of BC and OC is higher in southern North Africa than that in the north in summer.

Mots clés : North Africa regions ;aerosols;spatial distribution pattern ;dust aerosols ;atmospheric circulation ;

Présentation (CNKI)

Page publiée le 8 novembre 2021