Sensitivity of simulating a dust storm over Central Asia to different dust schemes using the WRF-Chem model

Abstract

Frequent dust storms have harm to human health and agricultural activities in Central Asia. However, there has been a great deal of uncertainty in prediction of dust storms in Central Asia. One of the important reasons is that the adaptability of different dust emission schemes has not been evaluated. Here, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), Air Force Weather Agency (AFWA) and Shao2004 (Shao04) dust schemes coupled to the WRF-Chem model were used to simulate the severe dust storm occurred in Central Asia on 12–15 July 2016. Generally, this dust storm was initialed by a vortex at 500 hPa and surface cold front, and then swept across Turkmenistan, Uzbekistan and Tajikistan. The Shao04 case could represent the spatial-temporal evolution of the dust storm well, especially at the northern Iran and Turkmenistan, due to its better description of the physical process of dust emission. But it overestimated the aerosol optical depth (AOD) to the southeast of the Aral Sea, which might be associated with the uncertainties of the soil particle distribution dataset. The AFWA case simulated AOD as better as Shao04 case with improved soil moisture correction factors, saltation algorithms and particle size distributions although it had smaller particle size, indicating that smaller particles are assignable. The GOCART case showed the largest dust emission areas due to the low threshold velocity. Yet both the AFWA and GOCART scheme underestimated the high AOD over northern Iran owe to its low erodibility factors. The total dust emission of the four-day period in the Shao04 scheme was 11.9 Tg, which was 2–3 times larger than those obtained in the AFWA and GOCART schemes. The significant differences of dust emission between three dust schemes may essentially depend on the sensitivities of threshold friction velocity on surface property.