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moisture and the freeze/thaw cycle), produce or will produce estimates of near-
surface soil moisture that can be used to diagnose or update model estimates, and
Gravity Recovery and Climate Experiment (GRACE) (a joint NASA/German
Aerospace Center (DLR) mission to map gravity anomalies and thus detect changes
in water storage), now provides a nearly decade-long record of total water storage,
albeit at coarse spatial resolutions. The GRACE follow on mission is intended to
enhance the spatial resolution of such measurements and provide continuity of
measurements over the future decade. The planned surface water and ocean
topography (SWOT) mission will provide observations of lake and reservoir surface
area and levels, from which changes in storage of over 7,000 km 3 of the estimated
8,000 km 3 of reservoir storage globally will be available at 1-2-week intervals. In
addition, in situ observations from buoys to Argo floats will help close the water and
energy budgets over the oceans.
4.
A dedicated snow hydrology mission such as ESA's Cold Regions Hydrology High-
Resolution Observatory (CoReH2O) will enable better understanding of the role
snow hydrology plays in the regional/global water cycle, especially in mountainous
regions of the globe that depend mainly on snow as a source of fresh water for human
consumption, food production and industrial activities (e.g., California, Tibetan
Plateau, La Plata Basin, etc.).
5.
Improvements in communication and data exchange policies help create higher
resolution global surface maps of precipitation and soil moisture based upon both
local very dense networks of high-resolution measurements as well as surface radar
networks where these are available. Significant gains are expected from high-
resolution gridded products being developed by GEWEX and other projects based on
in situ data as well as inventories of long-term in situ precipitation time series
focused on engagement of these data into validation, error estimation and
intercomparison efforts. The use of improved error statistics to develop new
blending algorithms and fusion techniques capable of bringing together precipitation
measurements with distinct error characteristics (e.g., gauges, radar, satellites and
models) into a consistent physical framework. Advances in data assimilation
techniques allow more precipitation information to be incorporated into Numerical
Weather Prediction models.
6.
Estimates of fluxes of moisture from surface are improving through the use of flux
tower
and
other
observations
over
land,
feeding
into
improved
estimates
of
evapotranspiration as part of the GEWEX Landflux and ocean flux projects.
7.
The production of an Integrated Water and Energy product by the GEWEX data and
assessments panel (GDAP) can be used to explore linkages between hydrology and
energy variables in the Earth System which in turn provides a much improved basis for
evaluating models on all aspects of the water cycle. Advanced diagnostic methods that
use the observed variables and their co-variability are used to diagnose not only problems
in the model output, but also assess model processes and potential improvements to these
processes in order to better represent the observed climate behavior.
8.
Incorporate more realistic land surface hydrology into land surface models, including
water management, land management and land-use and land-cover change, as well as
improved process representation (including cryospheric processes). The envisioned
new information is expected to be revolutionary in terms of the management of trans-
boundary rivers, but current climate models have no mechanisms for use of this
information, since most do not represent the effects of water management.
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