Summary

The Pan American Climate Studies (PACS) Program is a United States Federal Program in the 1995 to 2004 time frame directed towards the goal of improving the skill of operational seasonal-to-interannual climate prediction (with emphasis on precipitation) over the Americas. Although the principal focus of PACS is on seasonal and interannual variability on a regional (>500 km) scale, higher frequency phenomena such as the diurnal cycle and the 40-60 day Madden-Julian Oscillation and mesoscale phenomena such as sea breeze circulations and circulations forced by orography, coastal geometry, and contrasts in vegetation will be taken into account, as needed, with reference to the maintenance of the mean state and in the interpretation, diagnosis, and modeling of variability on the seasonal to interannual time scale. PACS falls within the scope of the U.S. Global Ocean-Atmosphere-Land System (GOALS) Program, but because of its emphasis on continental precipitation it will also have a close connection with the Global Energy and Water cycle EXperiment (GEWEX) and its subprograms. PACS will encompass a wide range of activities, including climate monitoring, modeling, dataset development, empirical studies, and intensive process studies (field projects) designed to address the third and fourth scientific objectives listed below.

Objectives:

Specific scientific objectives of PACS are to promote a better understanding and more realistic modeling of: (1) the seasonally varying mean climate of the Americas and adjacent ocean regions, with emphasis on the North and South American monsoons, the intertropical convergence zones, the equatorial cold tongues, the subtropical oceanic stratus decks, and the dominant tropical and extratropical cyclone tracks; (2) the role of boundary processes in forcing seasonal-to-interannual climate variability over the Americas, with emphasis on the influence of tropical sea surface temperature on continental precipitation; (3) the coupling between the oceanic mixed layer and the atmospheric planetary boundary layer in the tropical Atlantic and eastern Pacific Oceans; and (4) the processes that determine the structure and evolution of the tropical sea-surface temperature field.