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Lanzhou University (2021)

Sources and Transport of Light-absorbing Aerosols over the Tibetan Plateau


Titre : Sources and Transport of Light-absorbing Aerosols over the Tibetan Plateau

Auteur : 元天刚

Grade : Master 2021

Université : Lanzhou University

Résumé partiel
The Tibetan Plateau(TP),which is known as the“water tower”,embraces the largest magnitude of glacier in the midlatitude region.Because of its high elevation and therefore unique thermal and dynamic effects,it significantly influences the Asian weather and climate.A large number of observations have indicated that the TP has been suffering from foreign pollutants,and some of them such as dust and black carbon(BC)aerosols,showed an upward trend.Due to their strong solar absorption,light-absorbing aerosols can change the atmospheric stability and accelerate snow melting through snow-darkening effect,which is also one of the important factors for TP warming.Therefore,it is of great significance to clarify the source of light-absorbing aerosols over the TP for protecting the ecological security barrier and predicting the future weather and climate change in the TP.In this study,the Weather Research and Forecasting coupled with chemistry(WRF-Chem)model combined with multiple observations was used to investigate the sources and potential transport mechanisms of dust and black carbon aerosols.The major results are shown below :(1)Compared with the observations from surface weather stations,we found that the WRF-Chem model reproduced the spatial-temporal distribution of temperature and precipitation over model domain.The correlation coefficients between modeling temperature and observations exceed 0.96.Model also captured the variability of Aerosol Optical Depth(AOD)in Taklimakan desert(TD),northern India,TP,northern and eastern China,as well as aerosol extinction coefficient.The correlation coefficients between Aerosol Robotic Network AOD and WRF-Chem AOD in SACOL and Kanpur reach 0.6.Regarding near surface BC,the WRF-Chem reasonably simulated its distribution in comparison to samples.However,the WRF-Chem model underestimated the AOD over India and Bangladesh,which may be possibly associated with the uncertainty of anthropogenic emission inventory in South Asia,the difficulty of parameterization schemes in complex terrain and the neglect of year-to-year growth in BC emission.(2)The relationship of dust aerosol between TP and TD and their internal mechanism were investigated.In spite of higher dust emission flux in spring over the TP and TD,the dust mass loading in summer is 90 mg-2 higher than that in spring over the northern TP and Tianshan Mountains.Satellite observations also confirm that higher dust extinction coefficient occurred at 3-8 km over the TD where the dust concentration in summer is 30μg m-3 larger than that in spring.Further analysis of the transport fluxes of TD dust in four directions showed that the meridional output is only inferior to the eastward output of TD dust,especially in summer.From spring to summer,the proportion of eastward transport flux decreased from 74%to 61%significantly,while the southward transport flux increased from 21%to 30%.

Mots clés : WRF-Chem model ;Tibetan Plateau ;Light-absorbing aerosols ;East Asian atmospheric circulation ;Transport;

Présentation (CNKI)

Page publiée le 18 novembre 2021