The surface and atmospheric radiation budget (vertical profiles of SW and LW fluxes) have been determined using CERES TRMM observations of TOA fluxes for broadband SW, broadband LW, and 8-12 micron window; retrievals of clouds and aerosols from the VIRS narrowband imager; data from the MATCH aerosol assimilation; and ECMWF temperature and humidity. A constrainment algorithm adjusts both the radiation fields and key inputs for radiative transfer calculations at each CERES footprint.

Maps of the cloud forcing to the radiative divergence for broad layers, the surface to 500 hPa (lower troposphere ), 500 hPa to the tropopause (upper troposphere), and tropopause to TOA span the low latitude TRMM orbit. While the radiative divergences in the lower and upper troposphere have comparable means, radiative divergence in the lower troposphere is much more dynamic. Net (LW+SW) radiative cooling of the atmosphere over the tropcial ocean is larger than over the tropical land; much of the difference is due to the greater LW cooling of the lower troposphere over the oceans during clear conditions, because of higher maritime boundary layer humidity. Over much of the tropical land mass, the absorption of SW is sufficiently large to cause a slight convergence of net radiation in the lower troposphere during the day. A focus on January 1998 reveals that in a region south of the ITCZ in the Central Pacific with significant uplift at 500 hPa, clouds force an especially significant LW heating (convergence). Areas throughout the tropics with positive vertical velocity at 500 hPa display large cloud induced LW heating for the layer from the surface to 500 hPa, due to the suppression of lower tropospheric cooling by high clouds.

TOA aerosol forcing computed from satellite-based AOT compares well with the same quantity inferred by differencing observed fluxes with calculations for an aerosol-free sky. Aerosol forcing to radiative heating of the atmosphere, however, is here quite dependent on aerosol properties assumed from MATCH.