Diagnosing the Global Energy-Water Cycle with
Satellite Observations
William B. Rossow
As part of the World Climate Research Program, the Global Energy and Water Experiment
(GEWEX) is, as its name suggests, attempting to diagnose the atmospheric energy-water cycle
and its variations. Note that this cycle is central to determining the climate's sensitivity
(feedbacks) to forced changes and plays a role in determining unforced climate variations by
connecting all of the other components of the climate system. To achieve this, the GEWEX
Radiation Panel (GRP) is working to assemble a complete diagnostic dataset that describes the
main components of the energy-water cycle and its weather-scale variations over a period of a
few decades to support research on these topics. Some of these datasets are ready now and appear
to be of useful accuracy, some exist but their accuracy is not well known and some do not exist at
all. The rationale for assembling this data collection and a summary of the current status will be
presented. Since these data are now being used for climate research, the GRP is proposing that a
careful assessment of their quality be carried out to: (1) set the stage for re-processing (if needed)
to improve quality, (2) provide a better understanding of these data when used for analyses of the
energy-water cycle and (3) to support the next IPCC assessment, which will focus on water.
Given the expertise in the ITWG, GRP proposes to partner with ITWG for the assessment of
satellite-based tropospheric water vapor data products. It might make sense for this task to be
combined with a complete assessment of tropospheric and surface temperature measurements
from satellites as well.