3. LSA-NW IMPLEMENTATION STRATEGY

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 3-1 (WMO, 1992).

3.1 GCIP 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:

(1) Support for a hierarchy of scales for observational work, algorithm and model development, and validation and diagnostic studies leading to a continental-scale capability.
(2) Capacity for sequential expansion to support the evolution of research themes (e.g., initial emphasis on hydrological implications of warm-season convective precipitation, moving next to issues related to midlatitude cold-season hydrology).
(3) Flexibility to develop methods and algorithms that can be applied in data-sparse areas of the globe outside the Mississippi River basin.

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 100km) 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):

Continental-scale area (CSA) activities that span the entire domain of the Mississippi River basin with a scale size of about 3.2 x106km2.
Large-scale area (LSA) activities that occur in a phased timetable and emphasize a particular region with special characteristics for a period of about two years. Scale size is about 105 to 106km2. Four LSAs have been identified that in aggregate cover most of the GCIP domain, as shown in Figure 3- 2. The time phasing of activities within each of these areas is also shown in the figure.
Intermediate-scale area (ISA) activities that will be phased in with those for the LSAs and will serve as the basis for the regionalization of the parameters and coefficients of land surface hydrological models. Scale size is about 103 to 104 km2.

Figure 3-1 The research and technical activities linking the pivitol components of GCIP, i.e.. the GCIP Database and Model Development.

Figure 3-2. Boundaries for LSAs and temporal emphasis for each LSA from 1994 through 2000.

Small-scale area (SSA) activities that typically occur in association with efforts requiring intensive observing periods (IOP) over a concentrated region to study a focused set of issues. Scale size is less than 102 km2.

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 augmentedby data from relatively dense climatological networks established and operated by other Federal agencies and state organizations.

To the extent possible, the SSAs are being 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 are being derived from operational data sources (augmented as necessary), existing research instrument complexes, and specially designed field programs of limited duration.

A fundamental thrust of the GCIP implementation strategy is that although the developmental activities are being 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 have been the main focus of the research activities. In fact, as the EOP proceeds, the GCIP-derived budgets based on regional mesoscale models are 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.

3.2 LSA-NW Implementation Approach

The LSA-NW implementation will follow the GCIP Research Approach summarized in the previous section. The schedule for the two-year Enhanced Observing Period (EOP) is set to run from 1 April 1999 through 31 March 2001. This deviates from the EOP schedules for the earlier three LSAs which started at the beginning of the water year rather then the middle of the water year.

The overall research theme for the LSA-NW research activities is:

The Hydrometeorological effects of land cover changes over the annual cycle.

Based on earlier GCIP research results and evidence shown by regional coupled hydrologic- atmospheric models we can safely assert that in the LSA-NW:

Coupled land-atmosphere interactions and terrain effects are significant modulators of the hydroclimate of the Missouri River basin,

The planning for the research activities in the LSA-NW at the Detailed Design workshop held in October 1998 led the participants to recommend the following research hypothesis:

Land-atmosphere interactions and terrain effects can be modeled with sufficient skill to provide useful predictions for hydrologic applications on daily to seasonal time scales.

The LSA-NW implementation is designed to test the validity of this research hypothesis in addition to contributing to the successful achievement of the science objectives given earlier in Section 2. The research activities planned for the LSA-NW are divided into the following three components with their associated research objective:

Land surface and hydrological characteristics: To evolve from a static and coarse resolution representations of the land surface and hydrological characteristics to a more detailed and dynamic landscape characterized by a strong annual cycle with significant spatial and temporal variability

Coupled hydrologic/atmospheric modeling: To diagnose and skillfully represent the significant regional effects of land/atmosphere interactions on the hydrometeorology and hydroclimate of the Missouri River Basin on spatial and temporal scales relevant for hydrologic applications and water resources .

Hydrometeorological prediction and water resources: To enhance the reliability of precipitation, streamflow and related hydrologic variables that impact the water supply and demand forecasts for water managers in temporal scales up to seasonal. This research objective constitutes a test of the GCIP research hypothesis for the LSA-NW stated above.

A more detailed description of the research plans for each of these components is given in next three sections. A summary of potential focus study areas, data enhancements and data collection and management plans is given in Sections 7 and 8.