Simulation of Aerosol Optical Properties and Direct Radiative Forcing with RAMS-CMAQ in East Asia

摘要

The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements. It is determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the strongest forcing effect ranging from -12 to -8 W/m2 was mainly distributed over the Sichuan Basin and the eastern China’s coastal regions in the all-sky case at TOA, and the forcing effect ranging from -8 to -4 W/m2 could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan. Additionally, the model domain is divided into seven regions based on different administrative divisions or countries for investigating the detail information about ADRF spatial and temporal variations over East Asia in this paper. The model results indicate that the ADRF of sulfate, ammonium, BC, and OC were stronger in summer and weaker in winter over most regions of East Asia, except the South East Asia. However, the seasonal variation for ADRF of nitrate exhibited opposite trend. The strong ADRF of dust mainly appeared in spring over Northwest China and Mongolia.