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Differing Impacts of Black Carbon and Sulfate Aerosols on Global Precipitation and the ITCZ Location via Atmosphere and Ocean Energy Perturbations

2019; American Meteorological Society; Volume: 32; Issue: 17 Linguagem: Inglês

10.1175/jcli-d-18-0616.1

1520-0442

Shuyun Zhao, Kentaroh Suzuki,

Atmospheric Ozone and Climate

Abstract This study explores the effects of black carbon (BC) and sulfate (SO 4 ) on global and tropical precipitation with a climate model. Results show that BC causes a decrease in global annual mean precipitation, consisting of a large negative tendency of a fast precipitation response scaling with instantaneous atmospheric absorption and a small positive tendency of a slow precipitation response scaling with the BC-caused global warming. SO 4 also causes a decrease in global annual mean precipitation, which is dominated by a slow precipitation response corresponding to the surface cooling caused by SO 4 . BC causes a northward shift of the intertropical convergence zone (ITCZ), mainly through a fast precipitation response, whereas SO 4 causes a southward shift of the ITCZ through a slow precipitation response. The displacements of the ITCZ caused by BC and SO 4 are found to linearly correlate with the corresponding changes in cross-equatorial heat transport in the atmosphere, with a regression coefficient of about −3° PW −1 , implying that the ITCZ shifts occur as manifestations of the atmospheric cross-equatorial heat transport changes in response to the BC and SO 4 forcings. The atmospheric cross-equatorial heat transport anomaly caused by BC is basically driven by the BC-induced interhemispheric contrast in instantaneous atmospheric absorption, whereas the atmospheric cross-equatorial heat transport anomaly caused by SO 4 is mostly attributable to the response of evaporation. It is found that a slab-ocean model exaggerates the cross-equatorial heat transport response in the atmosphere and the ITCZ shift both for BC and SO 4 , as compared with an ocean-coupled model. This underscores the importance of using an ocean-coupled model in modeling studies of the tropical climate response to aerosols.