Measurement-based estimation of the spatial gradient of aerosol radiative forcing

[1] This paper diagnoses the spatial mean and the spatial gradient of the aerosol radiative forcing in comparison with those of well-mixed green-house gases (GHG). Unlike GHG, aerosols have much greater spatial heterogeneity in their radiative forcing. The heterogeneous diabatic heating can modulate the gradient in horizontal pressure field and atmospheric circulations, thus altering the regional climate. For this, we diagnose the Normalized Gradient of Radiative Forcing (NGoRF), as a fraction of the present global heterogeneous insolation attributed to human activity. Although the GHG has a larger forcing (+1.7 Wm ) as measured than those of aerosol direct ( 1.59 Wm ) and possible indirect effect ( 1.38 Wm ) in terms of a spatially averaged top-of-atmosphere value, the aerosol direct and indirect effects have far greater NGoRF values ( 0.18) than that of GHG ( 0.003). Citation: Matsui, T., and R. A. Pielke (2006), Measurement-based estimation of the spatial gradient of aerosol radiative forcing, Geophys. Res. Lett., 33, L11813, doi:10.1029/2006GL025974.