Low-level jet (LLJ) simulation by different WRF_Chem boundary layer schema in ‎Khuzestan province

Volume 1, Issue 3
Autumn 2018
Pages 287-303

Document Type : Original Article

Author

Department of Atmospheric Science, Iranian national institute for oceanography and atmospheric science, Tehran, Iran

Abstract
Low-level jets play a key role in the formation of dust storms in arid regions. The ‎purpose of this study was to investigate the ability of the WRF_Chem model to simulate low-level jet ‎and determine its criteria in local dust formation in Khuzestan province.For this purpose, dust was ‎selected during March 13 and 14, 2012. The synoptic structure and wind field were ‎analyzed using ERA-Interim data. The simulation ‎was also performed with dust shceme GOCART and AFWA and planetary boundary layer ‎scheme ACM, Bo, MYN, MYJ, UW and YSU. ‎

Wind profiles with LLJ characteristics were illustrated of those stations that ‎located to the right of the maximum wind 925 hPa . The LLJ broke in the mid-day results in a increasing surface wind speed up to 13 〖ms〗^(-1)and local dust emissions.
The model simulated low-level jet metrics including wind speeds 20 to 23, positive wind shear ‎between 8 and 18 and negative shear 4 to 13 〖ms〗^(-1)‎‏.‏The WRF_Chem model simulated stronger ‎LLJ than the ERA_I data. The correlation coefficients of 0.83 and 0.7 for surface wind speed and of 0.68 ‎and 0.72 for PM10 obtained by MYN scheme with GOCART and AFWA models respectively. The most matching daily variation of PM10 were obtained ‎with the MYN boundary layer and the AFWA dust scheme. The MYN boundary layer scheme was ‎chosen as the best scheme for local dust simulation in this dust strom. However, all ‎of the schemes ‎showed a surface PM10 concentration of more than PM10 observations.‎

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