2. Geographical range.....Global and Regional

3. Objectives
The Global Energy and Water Cycle Experiment (GEWEX) is an integrated programme of research, observations and science activities to observe and model the hydrologic cycle and energy fluxes in the atmosphere, at the land surface and in the upper oceans. GEWEX was initiated in 1988 by the World Climate Research Programme (WCRP).

The goal of GEWEX is to reproduce and predict, by means of suitable models, the variations of the global hydrological regime, its impact on atmospheric and surface dynamics, and variations in regional hydrological processes and water resources and their response to changes in the environment, such as the increase in greenhouse gases.

In order to achieve its goal, GEWEX has following objectives:

• Determine the hydrological cycle and energy fluxes by means of global measurements of atmospheric and surface properties;
• Model the global hydrological cycle and its impact on the atmosphere, oceans and land surfaces;
• Develop the ability to predict the variations of global and regional hydrological processes and water resources, and their response to environmental change;
• Advance the development of observing techniques, data management, and assimilation systems for operational application to long-range weather forecasts, hydrology and climate predictions.

4. Programme
The projects of GEWEX consist of three parts: Hydrometeorology and Land-Surface Projects, Radiation Projects, and Modeling and Prediction Projects.

• Hydrometeorology and Land-Surface Projects
  • GEWEX Hydrometeorology Panel (GHP)
    GHP is the principal group within GEWEX for considering scientific issues associated with water cycle involved in the coupling of the atmosphere and land surfaces. The main task of the GHP is to improve the collective contribution of the GEWEX Regional Continental-Scale Experiments (CSEs, see below) to global requirements. The GHP is formed from the leadership of the CSEs and the International Satellite Land-Surface Climatology Project (ISLSCP, see below) with exofficio representation drawn from the Global Runoff Data Centre (GRDC see below), International Association of the Hydrological Sciences (IAHS) and related organizations (http://www.tor.ec.gc.ca/GEWEX/GHP/ghp.html).

  • Regional Continental-Scale Experiments (CSEs)
    Various kinds of projects are implemented.
    • GEWEX Continental-Scale International Project (GCIP)
      The goal of the GCIP is to improve climate models by bridging the gap between small scales appropriate for modeling discrete processes over land and large scales practical for modeling the global climate system. The Mississippi River basin was selected as the study of the GCIP at the first phase (http://www.ogp.noaa.gov/gcip/).
    • Baltic Sea Experiment (BALTEX)
      BALTEX is a long-term multinational project to study coupled hydrological processes between complicated terrain, sea and ice and the atmosphere circulation to determine the energy and water budgets of the Baltic Sea and related river basins. The ultimate goal of BALTEX is to relate the results to the large-scale circulation systems in the atmosphere and oceans over the globe (http://w3.gkss.de/baltex/baltex_home.html).
    • GEWEX Asian Monsoon Experiment (GAME)
      The overall goal of GAME is to understand the role of the Asian monsoon in the global climate system and develop methods for long-range forecasting (http://www.ihas.nagoya-u.ac.jp/game/index.html).
    • Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA)
      LBA is a multi-disciplinary, international research effort designed to understand the climatological, ecological, biogeochemical and hydrological functioning of Amazonia, its interaction with the Earth system, and its response to land use change such as continued deforestation of the Amazon Basin (http://yabae.cptec.inpe.br/lba/).
    • Mackenzie GEWEX Study (MAGS)
      MAGS is a series of large-scale hydrological and related atmospheric and land atmosphere studies to be conducted within the Mackenzie Basin in Canada. The results of the projects are applicable to understanding cold region, high latitude hydrological and meteorological processes, and the role that they play in the global climate system (http://www.tor.ec.gc.ca/GEWEX/MAGS.html).

  • Global Runoff Data Centre (GRDC)
    The principal objective of GRDC is to collect and disseminate hydrological data to support projects within the World Climate Programme (WCP) and the WCRP of the World Meteorological Organization (WMO) as well as other related programmes. A global hydrological database includes water balance studies, investigation of trends in long-term hydrological time series, coupling of hydrological and meteorological models, flux of fresh water and pollutants into the oceans, and the coupling of runoff with water quality data (http://www.wmo.ch/web/homs/grdchome.html).

  • International Satellite Land-Surface Climatology Project (ISLSCP)
    ISLSCP promotes the use of satellite data for understanding and predicting climate changes. The goal of all activities of the ISLSCP are to assess terrestrial changes in terms of the physical and biological quantities, which can be related to the exchange of carbon, energy and water between surfaces and the atmosphere (http://www.cais.com/gewex/islscp.html).

• Radiation Projects
  
  • Baseline Surface Radiation Network (BSRN)
    BSRN is a worldwide network to continuously measure radioactive fluxes at the EarthÕs surface. Over thirty stations, which located throughout the world, provide data for calibration of the Surface Radiation Budget (SRB) Projects and other satellite-based measurements of radioactive flux. The BSRN data is also used to validate radioactive flux models. The data is archived at the World Radiation Monitoring Center (WRMC) (http://bsrn.ethz.ch/). BSRN data is also available from the Langley Distributed Active Archive Center (DAAC) (http://eosweb.larc.nasa.gov/).

  • Cloud Profiling Radar Project
    The aim of the Project is to develop a GEWEX spaceborne cloud radar system to determine the global three dimensional distribution of cloud parameters from satellite observations (http://www.cais.com/gewex/cloudradar.html).

  • Global Precipitation Climatology Project (GPCP) (see also GPCP)
    The goal of GPCP is to provide global data sets of monthly mean precipitation data on a 2.5 x 2.5 degree latitude-longitude grid for the period 1986-2000 (http://orbit-net.nesdis.noaa.gov:80/gpcp/).

  • Global Water Vapor Project (GVaP)
    The primary goal of the GVaP is the accurate global measurement, modelling, and long-term prediction of water vapor which is the most significant greenhouse gas and plays a fundamental role in the energy and water cycle processes (http://www.cais.com/gewex/gvap.html).

  • International Satellite Cloud Climatology Project (ISCCP)
    Using infrared and visible data obtained from polar and geostationary meteorological satellites, ISCCP produces data sets of global cloud cover and cloud radioactive properties (http://isccp.giss.nasa.gov/). Information about the data can also be obtained from the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) DAAC at Langley Research Center through the Internet.
    (http://eosdis.larc.nasa.gov:12000/dataset_documents/isccp.html)

  • Surface Radiation Budget Project (SRB)
    The long term objective of the SRB Project is to produce and archive a global data set of shortwave (SW) and longwave (LW) surface parameters for a twelve year period from 1983 to 1995 using the ISCCP and Earth Radiation Budget Experiment (ERBE) data and from the Goddard GEOS-1 reanalysis product (http://agni.larc.nasa.gov/Pilot_homepage.html).

  • Global Aerosol Climatology Project (GACP)
    GACP is concerned with the climate forcing due to changing aerosols, which consists of direct and indirect forcing. In Phase I of GACP, a twenty-year global climatology will be compiled from aerosol forcing data (http://www.cais.com/gewex/gacp.html).

• Modeling and Prediction Projects
  • GEWEX Cloud System Study (GCSS)
    GCSS will develop better parameterizations of cloud systems to reduce the uncertainty of climate models via an improved understanding of physical processes of cloud systems such as boundary layer, cirrus, extra tropical layer and precipitation convective.
    (http://www.cais.com/gewex/gcss.html)

  • Project for Intercomparison of Land-Surface Parameterization Schemes (PILPS)
    PILPS provides a mechanism for validating available and proposed land-surface process parameterization schemes and compares existing schemes (http://cic.mq.edu.au/pilps-rice/).

5. Data management
Much of the GEWEX project data is available (GCIP, GRDC, MAGS, ISLSCP, GVaP, ISCCP, SRB, BSRN, GPCP and GCSS). The information on this data can be acquired thorough the Internet (http://www.cais.com/gewex/datasets.html).

Many of the GEWEX data sets can also be obtained through NASA's Earth Observing System Data and Information System (EOSDIS) Earth Science Information Management System (IMS). EOSDIS V0 IMS is a cooperative effort between various archives around the U.S. and the Goddard Space Flight Center (GSFC) Earth Science Data Information System (ESDIS) project.
(http://www-v0ims.gsfc.nasa.gov/v0ims/eosdis_home.html)

6. Coordinative relations
The Executive Board of the International Council of Scientific Union (ICSU) has endorsed GEWEX as a core programme of the WCRP and a major contribution to the study of global climate change. The major international space agencies such as NASA, the National Oceanic and Atmospheric Administration (NOAA), and the National Space Development Agency of Japan (NASDA) have stated strong interest in the GEWEX Programme. The U.S. Committee on Earth and Environment Sciences has identified climate change and the hydrological cycle as the highest priority issues for research on global change. The IAHS and the WMO Hydrology and Water Resources Programme have established a joint working group on GEWEX in the field of global or large scale hydrology.

Sources
http://www.cais.com/gewex/gewex.html (last updated: 1/06/1998)

Contact
International GEWEX Project Office
1100 Wayne Avenue, Suite 1210, Silver Spring, Maryland 20910 U.S.A
Tel.: +1-301-427-2089 (521)
Fax: +1-301-427-2222
E-mail: gewex@cais.com
www: http://www.cais.com/gewex/gewex.html