Direct radiative forcing due to aerosols in East Asia during a Hwangsa (Asian dust) event observed on 19–23 March 2002 in Korea

Abstract

The Asian dust aerosol model (ADAM) and the aerosol dynamic model with the output of the fifth generation of mesoscale model (MM5) in a grid of 30×30 km2 have been employed to simulate the temporal and spatial distribution of the Asian dust aerosol and the anthropogenic aerosol concentrations in East Asia for the period of 19–23 March 2002 when a severe Asian dust (Hwangsa) event was observed in Korea. The simulated aerosols are implemented to estimate radiative forcing at the surface and the top of atmosphere (TOA) with the use of the National Center for Atmospheric Research (NCAR) column radiation model (CRM) of community climate model 3 (CCM3). The results indicate that the ADAM model simulates quite well the spectral-mass concentration distribution with the R2 value of 0.7 whereas the aerosol dynamic model underestimates the observed anthropogenic aerosol by a factor of 4 over Korea. The estimated mean total aerosol mass in the analysis domain for the period of 19–20 March 2002 is found to be about 880 mg m−2, of which 98% and 2% are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol. However, the direct radiative forcing contributed by the anthropogenic aerosol are about 40% of the mean radiative forcing at the surface (−11 W m−2) and 45% of the mean radiative forcing at TOA (−6 W m−2), implying the importance of the anthropogenic aerosol on the direct radiative forcings at both the surface and TOA. The difference between the radiative forcing at TOA and the surface that indicates the atmospheric absorption is found to be 5 W m−2, of which 3 and 2 W m−2 are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol, suggesting the importance of the Asian dust aerosol on the regional radiative energy balance especially in the high occurrence frequency season of spring.