The Global Energy and Water Exchanges Project (abbreviated GEWEX, formerly named the Global Energy and Water Cycle Experiment from 1990 to 2012) is an international research project and a core project of the World Climate Research Programme (WCRP).
In the beginning, the project intended to observe, comprehend and model the Earth's water cycle. The experiment also observes how much energy the Earth receives, and studies how much of that energy reaches the surfaces of the Earth and how that energy is transformed. Sunlight's energy evaporates water to produce clouds and rain and dries out land masses after rain. Rain that falls on land becomes the water budget which can be used by people for agricultural and other processes. GEWEX is a collaboration of researchers worldwide to find better ways of studying the water cycle and how it transforms energy through the atmosphere. If the Earth's climates were identical from year to year, then people could predict when, where and what crops to plant. However, the instability created by solar variation, weather trends, and chaotic events creates weather that is unpredictable on seasonal scales. Through weather patterns such as droughts and higher rainfall these cycles impact ecosystems and human activities. GEWEX is designed to collect a much greater amount of data, and see if better models of that data can forecast weather and climate change into the future.
Project structures GEWEX is organized into several structures. As GEWEX was conceived projects were organized by participating factions, this task is now done by the International GEWEX Project Office (IGPO). IGPO oversees major initiatives and coordinates between national projects in an effort to bring about communication between researchers. IGPO claims to support communication exchange between 2000 scientist and is the instrument for publication of major reports. The Scientific Steering Group organizes the projects and assigns them to panels, which oversee progress and provide critique. The Coordinated Energy and Water Cycle Observations Project (CEOP) the 'Hydrology Project' is a major instrument in GEWEX. This panel includes geographic study areas such as the Climate Prediction Program for the Americas operated by NOAA, but also examines several types of climate zones (e.g. high altitude and semi-arid). Another panel, the GEWEX Radiation Panel oversees the coordinated use of satellites and ground-based observation to better estimate energy and water fluxes. One recent result GEWEX's Radiation panel has assessed data on rainfall for the last 25 years and determined that global rainfall is 2.61 mm/day with a small statistical variation. While the study period is short, after 25 years of measurement regional trends are beginning to appear. The GEWEX Modeling and Prediction Panel takes current models and analyzes the models when climate forcing phenomena occur (global warming as an example of a 'climate forcing' event). GEWEX is now the core project of WCRP.
Goals and design
Predicting weather change requires accurate data that is collected over many years, and the application of models. GEWEX was conceived to respond to the need for observations of the Earth's radiation budget and clouds. Many preexisting techniques were limited to observations taken from land and populated areas. This ignored the large amount of weather that occurs over the oceans and unpopulated regions, with key data missing from these areas. Since satellites orbiting the Earth cover large areas in small time frames, they can better estimate climate where measurements are infrequently taken. GEWEX was initiated by World Climate Research Programme (WCRP) to take advantage of environmental satellites such as TRMM, but now uses information from newer satellites as well as collections land-based instruments, such as BSRN. These land-based instruments can be used to verify information interpreted from satellite. GEWEX studies the long-term and regional changes in climate with a goal of predicting important seasonal weather patterns and climate changes that occurs over a few years.
Research goals The research interest of GEWEX is to study fluxes of radiation at the Earth's surface, predict seasonal hydration levels of soils and develop accurate models of predicting energy and water budgets around the world. The project sets its goal as to improve, by an order of magnitude, the ability to model and therefore prediction hydration (rainfall and evaporation) patterns GEWEX is linked to other WCRP projects such as Stratospheric Processes and their Role in Climate (SPARC) Project, and the Climate and Cryosphere Project through WCRP. and thus shares information and goals with other WCRP projects. The goal becomes more important with the newer WCRP project, the Coordinated Observation and Prediction of the Earth System.
Complexity of the experiment Aside from fluctuations of solar radiation, the sunlight that is transformed by the Earth can vary greatly, some have concluded for instance, that ice-ages self-perpetuate once enough ice has accumulated in the polar regions to reflect enough radiation at high elevations to lower the global average temperature, whereas it takes an unusually warm period to reverse this state. Water usage by plants, herbivore activities can change albedo in the temperate and tropical zones. These trends in reflection are subject to change. Some have proposed extrapolating pre-GEWEX information using new information and measurements taken with pre-GEWEX technology. Natural fires, volcanism, and man-made aerosols can alter the amount of radiation reaching the Earth. There are oscillations in oceanic currents, such as El-Niño and North Atlantic Oscillation, which alter the parts of the Earth's ice mass and land water availability. The experiment takes a sampling of climate, with some trends lasting a million years, and as paleo-climatology shows, can abruptly change. Therefore, the ability to use data to predict change depends on factors that are measurable over periods of time, and factors that can affect global climate that abruptly appear can markedly alter the future.
Design GEWEX is being implemented in phases. The first phase comprises information gathering, modelling, predictions, and advancement of observation techniques and is complete. The second phase addresses several scientific questions such as prediction capacity, changes in Earth's water cycle, and the impact on water resources.
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