Monsoons are driven by the release of latent energy, which in turn comes from a surplus of radiant energy to evaporate surface water. The air which flows from the clouds, following the release of the latent energy and the consequent precipitation, must then descend to allow more air to rise to continue the rain. This outflow air can only descend by radiating away its potential energy. Monsoons are a part of a heat engine for which the heat source is the absorbed insolation and the heat sink is the radiation emitted by the atmosphere. In order to understand monsoons, it is necessary to study the effect of radiation on the energetics of the processes.

This paper discusses radiation data sets which have been developed by use of satellite measurements and the ongoing measurements which should be considered in planning of field programs for the study of monsoons. The Earth Radiation Budget Experiment (ERBE) provided radiative fluxes at the "top of the atmosphere" (TOA) from 1985 through 1990. The Clouds and Earth Radiant System (CERES) project provides fluxes at TOA, at the surface and divergence of radiative flux within the atmosphere.

The first CERES instrument flew aboard the Tropical Rainfall Measuring Mission and operated from January until September 1998. Other instruments aboard this spacecraft include the precipitation radar and the Visible and Infrared Scanning Radiometer, which give simultaneous measurements of rainfall, surface temperature, cloud cover, etc. CERES instruments have operated aboard the Terra spacecraft since March 2000 and aboard the Aqua spacecraft since June 2002 to give global coverage. The data products include pixel level, i.e. individual measurements, instantaneous fluxes averaged over a 1 degree latitude by 1 degree longitude grid, and daily and monthly average fluxes. These data products enable one to study conveniently the radiation fluxes at various space and time scales.

The Surface Radiation Budget Project has produced a 12-year data set for the period July 1983 through October 1995, covering the globe with a quasi-equal are grid which is 1 degree latitude by 1 degree longitude at the Equator. This data set includes upward, downward and net solar and longwave radiation.