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GCIP Background and Accomplishments Summary

The Problem

Predicting variations in the earth's climate requires improved understanding of interactions between the atmosphere and land surface. Generally, the sensitivity of the earth's climate is determined by the energetic processes of the "fast component" of the climate system. This fast component consists of the upper layers of the land and oceans that are closely coupled to the atmosphere, and which respond on relatively short meteorological time scales. It includes those processes that control the fluxes of solar and terrestrial radiation in and out of the planet. The "slow component" of the climate system includes processes in the atmosphere and oceans that determine seasonal to interannual variability and long-term climate change. As part of an overall scientific strategy of the World Climate Research Programme (WCRP) and Global Energy and Water Cycle Experiment (GEWEX) to improve climate predictability, GEWEX Continental-scale International Project (GCIP) has been launched to study, on a continental-scale, the mechanisms controlling incoming and outgoing fluxes of solar and terrestrial heat energy, clouds, precipitation, evaporation, river runoff, and water storage. The first continental-scale initiative is called GCIP-Mississippi.

LANDSAT photographs clearly demonstrate the devastating effects that floodwaters have on large waterways. The ability for long-term prediction has the potential to reduce costs incurred in such disasters. The left image shows normal Mississippi water flow in St. Louis. The right image shows July 1993 floodwaters. -COURTESY EARTH OBSERVATION SATELLITE COMPANY, LANHAM MD

The planners of GCIP recognized that scientific progress in climate requires a combination of modern systems for observing the environment and advanced numerical computer models of the climate system; models that realistically represent atmospheric processes, land surface characteristics and hydrological processes on a geographical domain large enough to encompass global weather patterns and varying landscapes.

The Mississippi Basin is a continental-scale domain with an excellent observing and data management system from which GCIP scientists can benefit. The rate of flow and depth of water along the Mississippi River and its tributaries reflect complex climate forcings by atmospheric and hydrologic processes. These flow characteristics can be significantly modified by human activities while extremes at either end of the spectrum can have major impacts on human endeavors. In drought years, such as 1988, there were widespread crop losses and disruptions to river traffic. The record-breaking floods of 1993 equally wrought havoc on industry, commerce, and the lives of those living and working along vast stretches of the flood plain of the Mississippi Basin and several of its major tributaries. The diagram below illustrates the components of the hydrological cycle.

The Plan

GCIP-Mississippi is a major scientific undertaking with broad international interest, since it addresses many issues at the forefront of climate research and water resources management. GCIP will use, in fact will depend upon, the modernized, ground-based US meteorological observing networks. Among these networks are the advanced Doppler weather radars and a network of profilers capable of making continuous measurements of the wind through the atmosphere. The radar data, when validated by strategic networks of conventional rain gauges, will provide accurate precipitation measurements at very high spatial resolution. These measurements can then be correlated with data from space-borne instruments to improve techniques of precipitation estimation from satellites over the whole globe.

The wind profilers, coupled with atmospheric humidity data from ground-based and airborne instruments, will enable moisture flowing into and out of the GCIP domain to be quantified and incorporated into computer models. Here too, the enhanced capabilities will improve satellite-based estimates of water vapor on a global scale.

The ambitious scientific program of GCIP-Mississippi depends upon the latest developments in atmospheric and hydrological modeling and on advances in computer technology. Climate processes involving solar driven energy and hydrology cannot be modeled separately, hence the research plan for GCIP-Mississippi includes development of improved techniques for coupling surface and atmospheric processes in climate models. One important task for GCIP scientists is to incorporate into a single consistent numerical representation, both the large-scale features of the atmospheric circulation and at a necessary level of detail, processes related to variations in land surface attributes, such as vegetation, soil type and topography. This development effort and its extension to other regions of the globe will require the cooperation of the international community of hydrologists, meteorologists and other geoscientists.

Linking hydrological processes at different scales has been hindered by poor data sets and the difficulty in representing the complexity involved. New, high-resolution measurement technologies for precipitation, wind and humidity, new methods for assimilating data into climate models, and the scientific community's recognition of the need for advanced schemes that represent the hydrological cycle in coupled models now provide the necessary capabilities and the incentive to support the GCIP effort. GCIP presents a unique opportunity to make scenarios and predictions from climate models more useful for water resource assessments, and hence to water resource managers.

The Benefits

Climate variability coupled with escalating urban, industrial, and agricultural demands will continue to place increasing stress on our water resources, even without the effects of a change in the global climate. Improved water management practices will be essential to sustain national economies, the health of the environment, and our overall quality of life. GCIP will provide much-needed information to improve assessments of flood and drought risk, and will assist in the development of better systems for water resource planning and management.

Specific outputs of GCIP-Mississippi will include:

• improved precipitation estimation through the integration of ground and remote sensing measurements;
• more precise methods of distributing precipitation estimates in high mountainous areas and estimating hydrological water budgets for the continental USA;
• more advanced drought and flood risk assessments;
• more accurate predictions on a range of time-scales;
• and improvements in the prediction of evaporation, water levels and ice cover over large lakes.

The GCIP-Mississippi initiative recognizes:

• the importance of water resources to national economies and the environment;
• that water resource operations require tradeoffs between conflicting water uses;
• that global climate change will most likely have its earliest and most serious impacts on water resources;
• that its success will depend in particular on the modernization of the meteorological observing networks and prediction systems operated by the US National Oceanic and Atmospheric Administration, the hydrological networks of the US Geological Survey and on the support of NASA, the US Department of Energy and other US agencies contributing to the US Global Change Research Program

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