Within the World Climate Research Program (WCRP) and its Global Energy and Water Cycle Exchanges Project (GEWEX), the GEWEX Data and Assessments Panel (GDAP) was organized to bring together theoretical and experimental insights into the radiative interactions and climate feedbacks associated with cloud processes. The most fundamental scientific question GDAP must answer is: how sensitive is the Earth’s climate to changes in radiative and other forcings? Answering this question will enable improved prediction of transient natural climate variations, such as El Niño, and provide better understanding of the consequences of natural and human-induced climate changes.
In climate research, radiative processes are central to the climate’s energy cycle: climate is determined by the imbalances of solar radiative heating and longwave radiative cooling. The circulation of the atmosphere and ocean, the environment on land, and the biosphere are all driven by local radiative imbalances. Changes in climate can be caused by alterations of the radiation budget at the top of the atmosphere or at the surface, such as those induced by changing amounts of greenhouse gases or aerosols in the atmosphere or by changing land surface properties. The sensitivity of the climate response to changes in the radiative forcing is determined by many feedback processes that alter the radiation budget, especially the processes involved with clouds and water vapor. Within WCRP, GDAP remains focused on understanding and coordinating both observations of the incident and outgoing radiation, as well as advances in radiative transfer methods needed to understand these observations.
Changes in atmospheric water vapor, precipitation, clouds, and aerosols affect the energy balance of the Earth and since these processes are intertwined, they are complex and simultaneous. Considerable uncertainty and controversy remain concerning the quantitative impact of these feedback processes. In order to make progress in this difficult area, the GEWEX Data and Assessments Panel currently seeks to first describe the complete Water and Energy budgets using consistent, long term, global datasets of radiative fluxes and surface energy exchanges as well as the atmospheric parameters affecting the energy balance. The products currently being coordinated by the GEWEX Data and Assessments Panel consist of Clouds (ISCCP); Precipitation (GPCP); Aerosols (GACP); Ocean Sensible and Latent Heat Flux (SeaFlux); Land sensible and latent Heat Flux (LandFlux) and Surface as well as TOA radiative fluxes (SRB). An integrated product, using common assumptions across the suite of GEWEX products listed above, is expected to be released in the summer of 2014.
In addition, GEWEX coordinates the assessment of existing and new parameters related to the global water and energy balance. These assessments strive to document strengths and weaknesses of long term data sets, often by comparing these to shorter term, higher quality data sets available from research missions. The assessments further strive to create databases against which future products may be compared to provide consistent information to the user community.
Key questions considered by GDAP are: