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Published August 27, 2004 | Published + Erratum
Journal Article Open

Global radiative forcing of coupled tropospheric ozone and aerosols in a unified general circulation model


Global simulations of sea salt and mineral dust aerosols are integrated into a previously developed unified general circulation model (GCM), the Goddard Institute for Space Studies (GISS) GCM II′, that simulates coupled tropospheric ozone-NO_x-hydrocarbon chemistry and sulfate, nitrate, ammonium, black carbon, primary organic carbon, and secondary organic carbon aerosols. The fully coupled gas-aerosol unified GCM allows one to evaluate the extent to which global burdens, radiative forcing, and eventually climate feedbacks of ozone and aerosols are influenced by gas-aerosol chemical interactions. Estimated present-day global burdens of sea salt and mineral dust are 6.93 and 18.1 Tg with lifetimes of 0.4 and 3.9 days, respectively. The GCM is applied to estimate current top of atmosphere (TOA) and surface radiative forcing by tropospheric ozone and all natural and anthropogenic aerosol components. The global annual mean value of the radiative forcing by tropospheric ozone is estimated to be +0.53 W m^(−2) at TOA and +0.07 W m^(−2) at the Earth's surface. Global, annual average TOA and surface radiative forcing by all aerosols are estimated as −0.72 and −4.04 W m^(−2), respectively. While the predicted highest aerosol cooling and heating at TOA are −10 and +12 W m^(−2), respectively, surface forcing can reach values as high as −30 W m^(−2), mainly caused by the absorption by black carbon, mineral dust, and OC. We also estimate the effects of chemistry-aerosol coupling on forcing estimates based on currently available understanding of heterogeneous reactions on aerosols. Through altering the burdens of sulfate, nitrate, and ozone, heterogeneous reactions are predicted to change the global mean TOA forcing of aerosols by 17% and influence global mean TOA forcing of tropospheric ozone by 15%.

Additional Information

Copyright 2004 by the American Geophysical Union. Received 16 December 2003; revised 30 March 2004; accepted 14 June 2004; published 21 August 2004. This work was supported by the NASA Earth Observing System-Interdisciplinary Science Program (NASA EOS-IDS). The authors gratefully acknowledge Joe Prospero and Dennis Savoie for providing sea salt and dust measurements. We thank Brent Holben, Giuseppe Zibordi, Mary J. Bartholomew, Robert Frouin, Didier Tanre, Chuck McClain, and Arnon Karnieli for their effort in maintaining AERONET measurements used in this work. We would also like to acknowledge the Center for Advanced Computing Research at Caltech for computing resources. Corrected by: Aerosol and Clouds: Correction to "Global radiative forcing of coupled tropospheric ozone and aerosols in a unified general circulation model" Vol. 109, Issue D24, Article first published online: 21 DEC 2004

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