1.1. Background

The Global Energy and Water Cycle Experiment (GEWEX) Continental-scale International Project (GCIP) was established to improve scientific understanding and to model on a continental scale the coupling between the atmosphere and the land surface for climate prediction purposes. Predicting variations in the earth's climate requires improved understanding of interaction between the atmosphere and land surface. Generally, the sensitivity of the earth's climate is determined by the energetic processes of the fast climate system". The fast climate processes are manifested by clouds, insolation, precipitation, soil characteristics (moisture), vegetation, state of water resources, and the coupling processes between land surface moisture in (1) the partitioning of energy flux between latent and sensible heat, (2) interpreting precipitation variability; and (3) providing knowledge on infiltration and runoff, and its impact on energy and water budgets. The GCIP activities are focused on the Mississippi River basin (see Figure 1-1) to take advantage of the existing meteorological and hydrological networks that are being upgraded with new Doppler radars, wind profilers, and automatic weather stations. The operational or enhanced observing period (EOP) of GCIP began in October 1995 and is planned to continue for five years.


Figure 1-1 The Mississippi River basin, the focus of GCIP activities.

1.2 GCIP Objectives

A recently completed review by the NAS/NRC GEWEX Panel recommended that GCIP should focus more on the seasonal to interannual prediction problem and recommended the following scientific mission for GCIP:

"To demonstrate skill in predicting changes in water resources on time scales up to seasonal, annual, and interannual as an integral part of the climate prediction system."

The Panel further recommended some restatement of the original science objectives to more clearly focus on the seasonal to interannual prediction problem and to add an objective pertaining to data management. GCIP has adopted these modified objectives to better reflect the emphasis of the Project which has evolved over the past five years since the completion of the GCIP Science Plan (World Meteorological Organization, 1992). The GCIP objectives are:

1.3 Project Implementation

The GCIP Implementation Plan, comprising three volumes, was completed in 1993 and 1994. Volume I of the GCIP Implementation Plan (IGPO, 1993) is the overall planning document for the Project. It addresses the organizational framework for GCIP, the observational and database needs, and the upgrades to be made to existing operational analysis and prediction streams that produce routine four-dimensional data assimilation (4DDA) analyses for the GCIP and global domains. Volume II (IGPO, 1994a) examines the elements of a GCIP research program needed to assist the research community in addressing the specific scientific questions in the GCIP Science Plan. The overall plans for data management through the duration of the GCIP Project are described in Volume III of the GCIP Implementation Plan (IGPO, 1994b).

GCIP is making use of existing operational and research programs to meet the research objectives. An important example is the U.S. Department of Energy, Atmospheric Radiation Measurement (ARM) Program, whose data from the Clouds and Radiation Testbed (CART) site are being made available to the GCIP effort. Opportunities for cooperation are being exploited with projects being formulated under other streams related to World Climate Research Programme (WCRP), such as the Climate Variations (CLIVAR) and the Global Ocean Atmosphere Land Surface (GOALS) Program. For example, the Pan American Climate Studies (PACS) project is being formed as a U.S. contribution to CLIVAR/GOALS to conduct research on the role of large-scale forcing from the tropics on continental precipitation in the Americas. A more complete description of collaborative research activities is given in Section 8.

1.3.1 Research Approach

GCIP research involves a systematic multiscale approach to accommodate physical process studies, model development, data assimilation, diagnostics, and validation topics. Such a multiscale developmental framework for the GCIP effort has three attributes:

The understanding and modeling of a continental scale require, from the outset, consideration of nonlinear-scale interactions in the aggregation of smaller processes to the larger scale and vice versa. Progress in this area requires that methodologies be developed to represent the coupling of processes that are important in one medium (e.g., the atmosphere) to those that are important in another (e.g., the land surface). These techniques must be suitable at the resolution of operational prediction and general circulation models (GCM) (about 10 to 100 km) and hence must be capable of representing in aggregate the effects of high levels of heterogeneity in the underlying ground surface (WMO, 1992). Accordingly, the GCIP research approach addresses activities on four scales (IGPO, 1994a):


Figure 1-2 Boundaries for LSAs and temporal emphasis for each LSA from 1994 through 2000.

The analyses and diagnostic studies conducted on the CSA, LSA, and ISA scales will derive their data primarily from existing sources, with augmentation of some observing systems as required. A major element of the rationale for carrying out the GCIP effort in the Mississippi River basin is the potential for full utilization of a number of observing systems (e.g., wind profiles and Doppler radars) not available to the same extent anywhere else in the world. In a number of LSAs, data from the existing synoptic and climatological networks operated by the National Weather Service can be augmented by data from relatively dense climatological networks established and operated by other Federal agencies and state organizations.

To the extent possible, the SSAs will be collocated with existing research basins, for example, the Little Washita Experimental Watershed in Oklahoma operated by the U.S. Department of Agriculture. The analyses, diagnostic studies, and model development on the SSA scale will be derived from operational data sources (augmented as necessary), existing research instrument complexes, and specially designed field programs of limited duration.

1.3.2 Continental Domain Synthesis

A fundamental thrust of the GCIP implementation strategy is that although the developmental activities will be initiated in limited regions, they lead toward an integrated continental-scale capability. Full continental domain studies have been important in GCIP from the beginning of the EOP in 1995. Retrospective analyses and baseline studies of water and energy balance will continue to be the main focus in the near- term. In fact, as the EOP proceeds, the GCIP-derived budgets based on regional mesoscale models will likely be superior in accuracy to budget estimates from other sources. These diagnostic studies will also be valuable for validating hydrological aspects of climate model simulations and understanding planetary-scale influences on North American hydrology.

1.4 Accomplishments to Date

The completion of the GCIP Science Plan in early 1992 heralded the beginning of a number of major activities in GCIP that have progressed steadily over the past four years. Some of the key accomplishments during this period are summarized in the remainder of this section within the scientific/technical implementation framework as outlined in the following section.

1.4.1 Scientific/Technical Implementation Framework

The two pivotal components of GCIP are (1) the development of a comprehensive observational database for the Mississippi River basin that will be available for GCIP analyses, and (2) the establishment of an evolving program of model development that will permit the observations to be extended spatially within GCIP or applied globally with new observations. A series of planned and ad hoc research and technical activities addressing observing systems, algorithm development, quality assurance issues, and water and energy budget studies link these pivotal components, as shown in Figure 1-3 (WMO, 1992).


Figure 1-3 Strategy framework for implementing GCIP.

With the interest in climate as a science over the past decade or so, computer models of the earth/atmosphere system have taken place along two separate paths. Many of the improvements in global models for weather prediction have occurred in, or in close cooperation with, the major operational analysis centers such as the U.S. National Center for Environmental Prediction (NCEP) and the European Centre for Medium Range Weather Forecasts (ECMWF). Developments in global climate models, which have their origins in the global weather models, have generally occurred in the U.S. in large research establishments such as the NOAA/Geophysical Fluid Dynamics Laboratory (GFDL), the NASA Goddard Space Flight Center (GSFC) and the National Center for Atmospheric Research (NCAR). In the early development of strategies for implementing GCIP, it was recognized that it would be necessary to draw on the strengths offered by both of these paths. A further key strategy that was adopted early in GCIP was the need to fully exploit the high resolution, limited area models that were being applied to regional weather prediction tasks through various nesting procedures in the global models.

1.4.2 Research Path Achievements

The GCIP research activities got underway in 1993 with primary support from NOAA. The achievements to date can be grouped under four headings of data analysis, model development, diagnostics of model output, and observing system enhancements. A more comprehensive review of this activity was published in a special issue of the Journal of Geophysical Research Volume 101, Number D3, March 20, 1996.

1.4.3 Achievements in the Operational Centers

Since the approaches being taken by the principal operational analysis centers (e.g., the U.S. National Environmental Prediction Center [NCEP], the Canadian Meteorological Centre [CMC] and the ECMWF) are different, it is important that GCIP researchers have access to data from more than one assimilation scheme. The NMC Eta Model and the NOAA Forecast Systems Laboratory MAPS Model are both high resolution nested regional models, the ECMWF and NMC operate global models at coarser resolution while the CMC uses a variable grid approach with the Regional Finite Element (RFE) imbedded within a global model. All these model outputs are being made available to GCIP researchers with special efforts being made to archive the output from the regional mesoscale at a central location as described in Section 11.

Improved land surface schemes were implemented in the three regional models prior to the Enhanced Seasonal Observing Period from 1 April to 30 September 1996.

1.4.4 Database Development

The GCIP Science Plan (WMO, 1992) recognized that the building of a database for GCIP scientists would be a major undertaking and that the amount and different types of data needed for GCIP studies would require an efficient data collection and management strategy.

The accomplishments to date in database development are in the areas of Pre-EOP data collection, compilation of several initial data sets, and the implementation of a distributed data management and service system. Each of these items is summarized in Part II of this Major Activities Plan.

1.4.5 Data Management and Service System

The responsibilities of the GCIP Data Management and Service System (DMSS) are to provide data services to GCIP investigators, adapt to the evolving data requirements, and compile the information on a five-year consolidated data set at the completion of the EOP. Carrying out these responsibilities involves an implementation approach with evolutionary improvements during the different stages of GCIP.

The DMSS implementation strategy makes maximum use of existing data centers to minimize the lead time and expense required for development. These existing data centers are made an integral part of the GCIP-DMSS through four data source modules that specialize by data types (i.e., in situ, model output, satellite remote sensing, and GCIP special data) as depicted in Figure 1-4. These four data source modules are connected to a GCIP central information source that provides "single-point access" to the GCIP-DMSS. The primary responsibilities for the data source modules along with their major functions and activities were described in Volume III of the GCIP Implementation Plan (IGPO, 1994b).


Figure 1-4 Organization of GCIP Data Management System.

1.5 Role and Structure of GCIP Major Activities Plan

The purpose of the Major Activities Plan is to project a description of GCIP research and associated activities over the next two to three years to preclude the need for frequent revisions to the three volumes of the GCIP Implementation Plan. The initial version of the Major Activities Plan covered the two-year period of 1995 and 1996 with an outlook for 1997 (IGPO, 1994c) and was updated last year (IGPO, 1995).

The description of planned activities is based on what should be done in an orderly progression toward the end objectives of GCIP and with a realistic assumption about the resources that will be available to do it. Adjustments are made the following year, as appropriate, to rationalize the plans with the actual resources. The adjustments are used as a starting point for projections in the following year's update.

This update of the Major Activities Plan covers the water years of 1997, 1998 and outlook for 1999. It was shown in Figure 1-2 that during this period there will be an emphasis on the four LSAs for two or more years. The structure of the Major Activities Plan during the first two years was to concentrate on the activities in each of the LSAs. Since activities are planned for each of the four LSAs, this will spread out the descriptions pertaining to specific objectives. For this reason the Plan is divided into two parts. Part I entitled Research devotes a section to each of the four science objectives and is described in Sections 2,3,4, and 5. A number of variables were deemed critical to the success of GCIP and were designated as Principal Research Areas for GCIP. These include precipitation, soil moisture, land surface characteristics, streamflow and runoff, and, clouds and radiation. The research activities for each of these critical variables are described in section 6. A summary of the research activities planned for each of the four LSAs and the CSA is given in section 7. The increasing importance of the collaborative research activities is described in section 8.

The activities related to the data management objective are described in Part II of this plan entitled Data Collection and Management.