this report, the science and implementation plan will be referred to simply as “the plan” or “the GAPP plan.” This plan describes strategies for achieving two broad science objectives on the topics of prediction and decision support in the hydrologic sciences (see Box 1). It organizes the program’s research into seven components (NOAA-NASA 2004, Figure 1.1) and describes implementation activities for these components. (Chapter 3 of this report provides detailed analysis of each of the seven components and their associated activities.)

The Science Missions of GAPP

  • Prediction: To develop and demonstrate a capability to make reliable monthly-to-seasonal predictions of precipitation and land-surface hydrologic variables through improved understanding and representation of land-surface and related hydrometeorological and boundary-layer processes in climate prediction models.

  • Decision support: To develop application products for resource managers by interpreting and transferring the results of improved climate predictions for the optimal management of water resources.


Through 2007, GAPP will continue to be one of the GEWEX continental-scale experiments and a component of the GEWEX Hydrometeorology Panel. GAPP will continue to receive scientific guidance from the GEWEX Scientific Steering Group and the GEWEX Hydrometeorology Panel. Until 2004, the GAPP program within the National Oceanic and Atmospheric Administration (NOAA) was a program line of NOAA’s Office of Global Programs. GAPP has since been merged with the NOAA Climate Variability and Predictability (CLIVAR)-Pan American Climate Studies (PACS) program to form the new Climate Prediction Program for the Americas (CPPA), also within the Office of Global Programs. The rationale for the integrated CPPA is that intraseasonal-to-interannual climate variability is determined by a combination of ocean and land processes and their impacts on the atmosphere. A list of research programs related to GAPP is presented in Table 1-1.


GCIP, the predecessor to GAPP, benefited greatly from a National Research Council (NRC) review published in 1998 (NRC 1998). A number of recommendations were made in the NRC review, including extension of the study beyond the Mississippi Basin to include the semiarid Southwest and the orographic regions of the western United States. In response to the NRC report on GCIP, the GAPP program was initiated with an expanded geographic domain. In 2004, GAPP program managers approached the NRC and requested

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