Within the World Climate Research Program (WCRP) and its Global Energy and Water Exchanges Project (GEWEX), the GEWEX Data and Analysis Panel (GDAP) was organized to bring together theoretical and experimental insights into the radiative interactions and climate feedbacks associated with cloud processes. The central question that governs the GDAP mission 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.
Key questions considered by GDAP are:
- How can we better measure and characterize the state and the variations of the climate using satellite observations?
- What are the changes in radiative forcing that cause climate change?
- How do the interactions of radiation with changes of the internal state of the climate (a.k.a. radiative feedbacks) affect the climate’s sensitivity?
- How do the internal water exchange and transport processes in the climate (a.k.a. water feedbacks) affect the climate’s sensitivity?
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. Understanding and quantifying the climate response to changes in radiative forcings requires consistent, global-scale, observations of the principal energy fluxes in climate system. GDAP focuses on coordinating observations of these fluxes and evaluating their consistency as well as advancing analysis methods to apply them in climate change assessments.
Changes in atmospheric water vapor, precipitation, clouds, and aerosols also 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 Analysis Panel seeks to describe the complete Water and Energy budgets using consistent, long term, global datasets of radiative fluxes and surface energy and water exchanges as well as the atmospheric parameters affecting them. In support of these goals, GDAP sponsors the GEWEX Integrated Product, a consensus gridded energy and water cycle data product that combines the suite of data products initiated by GEWEX on a common time and space grid.
GDAP also has a long legacy of assessing existing and new global water and energy balance products. These assessments 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. A unique component of GDAP energy and water cycle assessments is a focus on evaluating consistency in the context of energy and water balance constraints. To these ends, GDAP also supports integrated assessments focusing on Earth’s energy imbalance and land surface-atmosphere heat and water exchanges.
