The Global Water Cycle
USGCRP Program Element

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)

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.