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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D23, 8659, doi:10.1029/2002JD003210, 2003

Aerosol distributions and radiative forcing over the Asian Pacific region simulated by Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS)

Toshihiko Takemura

Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan

Teruyuki Nakajima

Center for Climate System Research, University of Tokyo, Tokyo, Japan

Akiko Higurashi

National Institute for Environmental Studies, Tsukuba, Japan

Sachio Ohta

Graduate School of Engineering, Hokkaido University, Sapporo, Japan

Nobuo Sugimoto

National Institute for Environmental Studies, Tsukuba, Japan

Abstract

A three-dimensional aerosol transport-radiation model coupled with a general circulation model, Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS), simulates atmospheric aerosol distributions and optical properties. The simulated results are compared with aerosol sampling and optical observations from ground, aircraft, and satellite acquired by intensive observation campaigns over east Asia in spring 2001. Temporal variations of the aerosol concentrations, optical thickness, and Ångström exponent are in good agreement between the simulation and observations. The midrange values of the Ångström exponent, even at the Asian dust storm events over the outflow regions, suggest that the contribution of the anthropogenic aerosol, such as carbonaceous and sulfate, to the total optical thickness is of an order comparable to that of the Asian dust. The radiative forcing by the aerosol direct and indirect effects is also calculated. The negative direct radiative forcing is simulated to be over −10 W m⁻² at the tropopause in the air mass during the large-scale dust storm, to which both anthropogenic aerosols and Asian dust contribute almost equivalently. The direct radiative forcing, however, largely depends on the cloud water content and the vertical profiles of aerosol and cloud. The simulation shows that not only sulfate and sea salt aerosols but also black carbon and soil dust aerosols, which absorb solar and thermal radiation, make strong negative radiative forcing by the direct effect at the surface, which may exceed the positive forcing by anthropogenic greenhouse gases over the east Asian region.

Received 25 November 2002; accepted 24 March 2003; published 6 August 2003.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 3359 Meteorology and Atmospheric Dynamics: Radiative processes.

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Citation: Takemura, T., T. Nakajima, A. Higurashi, S. Ohta, and N. Sugimoto (2003), Aerosol distributions and radiative forcing over the Asian Pacific region simulated by Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS), J. Geophys. Res., 108(D23), 8659, doi:10.1029/2002JD003210.

Copyright 2003 by the American Geophysical Union.