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The Global Water Cycle
Overview
Recent
Accomplishments
Near-Term Plans
Archived
News Postings [June 2000-July 2005]
Related
Sites
Calls
for Proposals
CCSP / USGCRP Water Cycle Working Group Members
For long term plans, see
Water Cycle chapter of the
Strategic Plan for the Climate Change Science Program (2003) posted
on CCSP web site. |
The
Water Cycle
Basic background information from NASA's Earth Observatory
Reference section.
Proceedings of the Tenth U.S. -Japan Workshop on Global Change: Climate
and Water. Workshop held 15-17 January 2003, Irvine, California.
Draft dated 30 May 2003. Also available as
MS Word file.
(link posted 30 May 2003) |
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Research associated with this element involves studies of the crucial role the water cycle plays both in climate variability, climate change, and the influence climate has on aspects of the global water cycle for which society and nature critically depend. Through countless interactions in the Earth system, the global water cycle integrates physical, chemical, and biological processes that sustain ecosystems and influence climate and related global change. The ultimate goal of the CCSP water cycle research is to provide a better foundation for decisions and investments by policymakers, managers, and individuals. Achieving this goal requires a program of activities that test predictions and data products in real decision contexts, demonstrate techniques and their effectiveness to potential users, and provide tools and strategies to transfer the science from the experimental realm to operations. In FY 2008, emphasis will be given to coordinated observations and modeling of selected sites, at the river basin or catchment scale, to improve understanding of terrestrial water cycle processes leading to better closure constraints on water budgets at this scale. The improvements to land surface and hydrological models resulting from this research will lead to an enhanced ability to more accurately represent global change projections at the regional scales that affect water resources and other water cycle-dependent applications sectors. |
Strategic Research Questions
5.1. What
are the mechanisms and processes responsible for the maintenance
and variability of the water cycle; are the characteristics of
the cycle changing and, if so, to what extent are human activities
responsible for those changes?
5.2.
How do feedback processes control the interactions between the
global water cycle and other parts of the climate system (e.g.,
carbon cycle, energy), and how are these feedbacks changing over
time?
5.3. What
are the key uncertainties in seasonal to interannual predictions
and long-term projections of water cycle variables, and what
improvements are needed in global and regional models to reduce
these uncertainties?
5.4. What
are the consequences over a range of space and time scales of
water cycle variability and change for human societies and ecosystems,
and how do they interact with the Earth system to affect sediment
transport and nutrient and biogeochemical cycles?
5.5. How
can global water cycle information be used to inform decision
processes in the context of changing water resource conditions
and policies?
See Strategic
Plan for the U.S. Climate Change Science Program, Chapter
5, for detailed discussion of these research questions. |
The global water (and energy) cycle plays a critical role in the functioning of the Earth system. Through complex interactions, the global water cycle integrates the physical, chemical, and biological processes that sustain ecosystems and influence
climate and related global change. Inadequate understanding of the water/energy cycle is one of the key sources of uncertainty in climate prediction and climate change projections. Clouds, precipitation, and water vapor play important roles in feedbacks that are not well represented in many climate models. These processes alter surface and atmospheric heating and cooling rates, leading to adjustments in atmospheric
circulation and precipitation patterns. Improved understanding of these processes will be essential to develop options for responding to the consequences of water cycle variability and change. For assessing the impacts of global and regional climate change on human societies, industrial and economic systems, and natural and managed ecosystems, water is considered a more rigid or critical constraint or limiting factor than temperature. To address these issues, the CCSP Global Water Cycle (GWC)
element expends considerable effort to improve observations, data assimilation, and modeling/prediction systems that in turn deliver the information necessary for
decision-support tools and assessments that provide a basis for "best practices" in the management of water resources.
The ultimate goal of water cycle research is to provide a solid foundation for decisions and investments by policymakers, managers, and individuals–be it at the Federal, state, or local level. Achieving this goal requires a program of activities that significantly improves understanding of water/energy cycle processes, incorporates this understanding in an integrated modeling/prediction framework, and tests predictions and data products in real decisionmaking contexts. In order to demonstrate techniques and their
effectiveness to potential users, the GWC program also aims to expedite the transfer of science results from the research/experimental realm to operational applications.
Conceptualization
of the water cycle.
Significant progress has been made in the understanding of cloud properties and the direct and indirect effect of aerosols on cloud and precipitation processes through field campaigns such as DOE's Cloud and Land Surface Interaction Campaign (CLASIC), and the multi-agency North American Monsoon Experiment and African Monsoon Multidisciplinary Analyses. Comprehensive satellite monitoring of water cycle parameters such as global precipitation and cloud structure in storm systems and hurricanes (with TRMM) and soil moisture and water bodies (with GRACE) as well as atmospheric profiles of temperature and humidity, and land/ocean surface parameters (Terra, Aqua) have resulted in integrated data sets and improved models of the Earth system. The incorporation of research results in models has led to better simulations of and prediction capabilities for hydroclimatic variables. Multi-model and ensemble modeling techniques developed by the NOAA Climate Prediction Program for the Americas have led to improved seasonal predictions of both the atmospheric and terrestrial hydrological cycle. Techniques have also been developed by USDA, DOI/USGS, and the DOI Bureau of Reclamation, in collaboration with NOAA, NASA, EPA, and DOE, among others, for the downscaling of seasonal precipitation forecasts to temporal scales consistent with the input requirements for agricultural management and
conservation planning decision-support tools. Experimental seasonal hydrological
prediction systems have been developed that use multiple climate forecast model products and empirical tools to "force" land/hydrological prediction models.
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