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Nanjing University of Information Science and Technology (2018)

Modeling Study on Temporal and Spatial Variation and Regional Transport of Dust Aerosols during A Typical Dust Storm Over the Tarim Basin


Titre : Modeling Study on Temporal and Spatial Variation and Regional Transport of Dust Aerosols during A Typical Dust Storm Over the Tarim Basin

Auteur : 孟露;

Grade : Master’s Theses 2018

Université : Nanjing University of Information Science and Technology

Résumé partiel
As one of the largest shifting sand dunes in the world,the Taklamakan Desert(TD)covers the wide central region of the Tarim Basin(TB)with the mean elevation of 1.1 km.Strong sandstorms occurred frequently.Dust emission,sedimentation,transport and spatiotemporal variations are controlled by the special boundary layer(BL)and unique terrain effect over the basin.Characterization of forming the unique spatiotemporal variations and regional transport of the dust aerosol over the TB is still a challenging issue in environment sciences.Aiming this scientific issue,this thesis,by employing the air quality model WRF-Chem(The Weather Research and Forecasting model with chemistry)simulates a dust storm event over the TB to investigate dust aerosol spatiotemporal variations,regional transport and its radiative forcing over the TB with the selecting appropriable PBL scheme over the desert region.The main research contents and results are summarized as follows:1.An assessment of atmospheric boundary layer schemes over the hinterland of TDDust emission,sedimentation and transport are controlled by the BL over the deserts.The observational data in desert areas limit the examination on BL simulations.In this study,the performances of five BL parameterizations of ACM2,BL,MYJ,MYNN2.5 and YSU in the mesoscale numerical model WRF were assessed by simulating the BL in the TD in April 2014,compared with the observations of a 80m tower and wind profile radar under sunny weather at Tazhong in the TD hinterland.The comparison results reveal that five PBL schemes could reasonably capture the diurnal variations of near-surface air temperature,surface temperature,boundary layer height,sensible heat,latent heat and surface heat flux,excepting for wind speed.Regarding the vertical BL structures,all the simulated temperature,wind and moisture profiles within BL can be well reproduced only with the underestimated simulations of wind speed during the daytime.The dry desert’s thermal heat capacity is low to easily form convective unstable BL in sunny days.The non-local ACM2 scheme is a more appropriable BL scheme for simulating the BL in the desert area.2.Numerical simulation of spatiotemporal variations of dust aerosols during aspringtime dust storm over the TBThe air quality model WRF-Chem was employed to simulate a dust storm event in spring,2015 over the Taklamakan Desert of the Tarim Basin(TB),Northwest China.Based on the reasonable evaluations with the ground observations and CALIPSO satellite data of meteorology and aerosols,the simulation was used to characterize the three-dimensional distribution of dust aerosols for this springtime dust storm over the TB.Under the impact of unique basin topography on a cold frontal system,a large amount of cold air invading the TB in three main tracks of near-surface winds :(1)westerly winds across the Pamirs Plateau,(2)northerly air flows crossing the Tianshan Mountains,and(3)strong northeast winds passing the northeast mouth of TB,building three main dust plumes over the TB for the dust storm process.The strong dust plume swept southwestwards across the basin with dominating over two weak dust plumes,and the mechanical effect of Tibetan Plateau on the dust plumes could determine the surface dust aerosol distribution over the TB.Based on observation and simulation,the extremely thick boundary layer was identified with the height of 3-5km from the surface over the TB for the vertical distribution of dust aerosols.Dust aerosols were lifted up to 7km in the free troposphere over the southern TB driven by the northern slope of the Tibetan Plateau.

Mots clés : Tarim Basin; dust aerosols; WRF-Chem simulation; spatiotemporal variations; regional transport;

Présentation (CNKI)

Page publiée le 14 mai 2019