MISSION TO PLANET EARTH - ROLE OF CLOUDS AND RADIATION IN CLIMATE

The role of clouds in modifying the earth's radiation balance is well recognized as a key uncertainty in predicting any potential future cli mate change. This statement is true whether the climate change of inte rest is caused by changing emissions of greenhouse gases and sulfates, deforestation, ozone depletion, volcanic eruptions, or changes in the solar constant. This paper presents an overview of the role of the Na tional Aeronautics and Space Administration's Earth Observing System ( EOS) satellite data in understanding the role of clouds in the global climate system. The paper gives a brief summary of the cloud/radiation problem, and discusses the critical observations needed to support fu rther investigations. The planned EOS data products are summarized, in cluding the critical advances over current satellite cloud and radiati on budget data. Key advances include simultaneous observation of radia tion budget and cloud properties, additional information on cloud part icle size and phase, improved detection of thin clouds and multilayer cloud systems, greatly reduced ambiguity in partially cloud-filled sat ellite fields of view, improved calibration and stability of satellite -observed radiances, and improved estimates of radiative fluxes at the top of the atmosphere, at the surface, and at levels within the atmos phere. Outstanding sampling and remote sensing issues that affect data quality are also discussed. Finally, the EOS data are placed in the c ontext of other satellite observations as well as the critical surface , field experiment, and laboratory data needed to address the role of clouds in the climate system. It is concluded that the EOS data are a necessary but insufficient condition for solution of the scientific cl oud/radiation issues. A balanced approach of satellite, field, and lab oratory data will be required. These combined data can span the necess ary spatial scales of global, regional, cloud cell, and cloud particle physics (i.e., from 10(8) to 10(-7) m).