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Hunan Normal University (2008)

Persistent Decrease of Dust Burden Over Middle Upper Troposphere of the Southern Taklimakan Desert and the Analysis of the Cause of Formation

李永能;

Titre : Persistent Decrease of Dust Burden Over Middle Upper Troposphere of the Southern Taklimakan Desert and the Analysis of the Cause of Formation

Auteur : 李永能;

Grade : Master’s Theses 2008

Université : Hunan Normal University

Résumé
Glacier is the result of environment.Ice core contains small amounts of atmospheric fall-out,and the atmospheric fall-out records the change of environment.By analyzing the ice core,it discloses the change of the environment at that time.An ice core of 18.7m long from Chongce Ice Cap(at an elevation of 6350m),West Kunlun Mts.China,showed an overall decrease in magnitude of the total particle content for about 100years from the beginning of the 20 century.Three phases could be identified approximately:before 1930(going back to 1903),1931—1960, and 1961—1992.The conspicuous periods include the early 1900s,1910s, late 1920s and early 1940s,of which the dust level was much higher,and the early 1970s,of which the dust level was relatively low.The dust deposit rate at the altitude was built up for the past 60 years.The mean is 1106μg·cm-2·yr-1 with the maximum and minimum of 3462 and 77μg·cm-2·yr-1,respectively.Analyzing the volume distribution of micro particles obtained from size measurement,it is estimated that contribution of the local component is 17%of the total dust input.The rest could be taken as long range transportation,i.e,the deposit of atmospheric dust burden in meso large scale.Thus,the changing trend of dust flux at the troposphere altitude over the southern Taklimakan Desert is known.The calculated deposited dust flux for the 60 years before 1992 is 913μg·cm-2·yr-1 in average, with a decreasing rate of -120μg·cm-2 in a decade.This could be a representative of the regional record of the mid upper troposphere dust burden in temporal tendency.Through mechanism analysis,we find the mechanism:global warming results in precipitation increment in arid area.Precipitation increase should result in dust-storm decrease.Then dust-storm decrease cause dust flux decrease at Mid-Troposphere altitude.So this causes cloud condensation nuclei number decrease at Mid-Troposphere altitude

Mots clés : ice core record; dust deposition; middle upper troposphere; dust flux; persisting declination;

Présentation (CNKI)

Page publiée le 13 décembre 2017