Open AccessA physically based estimate of radiative forcing by anthropogenic sulfate aerosol
Author(s) -
Ghan Steven J.,
Easter Richard C.,
Chapman Elaine G.,
AbdulRazzak Hayder,
Zhang Yang,
Leung L. Ruby,
Laulainen Nels S.,
Saylor Rick D.,
Zaveri Rahul A.
Publication year - 2001
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jd900503
Subject(s) - aerosol , radiative forcing , atmospheric sciences , sea salt aerosol , sulfate , radiative transfer , environmental science , cloud condensation nuclei , sulfate aerosol , sea salt , troposphere , relative humidity , forcing (mathematics) , effective radius , climatology , meteorology , chemistry , physics , geology , organic chemistry , quantum mechanics , galaxy
Estimates of direct and indirect radiative forcing by anthropogenic sulfate aerosols from an integrated global aerosol and climate modeling system are presented. A detailed global tropospheric chemistry and aerosol model that predicts concentrations of oxidants as well as aerosols and aerosol precursors, is coupled to a general circulation model that predicts both cloud water mass and cloud droplet number. Both number and mass of several externally mixed aerosol size modes are predicted, with internal mixing assumed for the different aerosol components within each mode. Predicted aerosol species include sulfate, organic and black carbon, soil dust, and sea salt. The models use physically based treatments of aerosol radiative properties (including dependence on relative humidity) and aerosol activation as cloud condensation nuclei. Parallel simulations with and without anthropogenic sulfate aerosol are performed for a global domain. The global and annual mean direct and indirect radiative forcing due to anthropogenic sulfate are estimated to be −0.3 to −0.5 and −1.5 to −3.0 W m −2 , respectively. The radiative forcing is sensitive to the model's horizontal resolution, the use of predicted versus analyzed relative humidity, the prediction versus diagnosis of aerosol number and droplet number, and the parameterization of droplet collision/coalescence. About half of the indirect radiative forcing is due to changes in droplet radius and half to increased cloud liquid water.