Estimation of the radiative forcing by key aerosol types in worldwide locations using a column model and AERONET data

Abstract

The aerosol direct radiative forcing (ADRF) is calculated using aerosol robotic network (AERONET) data, and based on aerosol categorization results, the global ADRF is estimated. The CRM-2.1.2, a stand-alone version of the radiative transfer model implemented in NCAR's community climate model, CCM-3.6, is used for the evaluation. A method of determining the aerosol optical parameters is proposed for the ADRF calculation using AERONET data. Linear regression in the log-log plane makes it possible to represent the wavelength-dependent optical properties in the model using AERONET measurements. The local ADRF is estimated at Gosan, Jeju in Korea in Spring from 2001 to 2003, and the ground-based radiation measurements during the ACE-Asia IOP are used to validate the calculation. Using 3 years of AERONET data, the mean forcing efficiency at 500 nm at Gosan in Spring season is evaluated as -80.5±13.2 Wm-2 at the surface and -29.9±4.9 Wm-2 at the top of atmosphere (TOA). The seasonal variations of the ADRF at eight AERONET sites are calculated from AERONET climatology data. The ADRF calculation at the TOA is compared with the CERES/Terra measurement, and the comparison verifies that the methodology used in this study is suitable for the global ADRF evaluation. Finally, the ADRF values in 14 regions are evaluated. Large ADRF values in Asia and Sahara regions suggest the relative importance of the aerosols on the energy budget in these regions. © 2005 Elsevier Ltd. All rights reserved.