The 14th Conference on Hydrology

5A.11
THE RELATIVE INFLUENCE OF LOCAL VERSUS FAR-FIELD EFFECTS ON WARM SEASON PRECIPITATION OVER THE GCIP REGION

Robert J. Oglesby, Purdue Univ, West Lafayette, IN; and S. Marshall, J. O. Roads, and F. R. Robertson

Of considerable interest and debate are the relative influences of local effects (e.g., soil moisture) and far-field effects (e.g., SST anomalies) on warm season precipitation over the GCIP Mississippi Basin region. To better understand these influences, model results and observations are used to make detailed analyses of the energy and water budgets for North America (with an emphasis on the central U.S. GCIP region) on interannual time scales. The primary modeling tool was the new generation NCAR climate model (CSM/CCM3). Model simulations include a 45-year CCM3 run with SSTs specified according to data supplied by NMC for the years 1950-1994, and a 300-year run with the fully-coupled ocean-atmosphere version of CSM. Our analysis emphasizes time series of key variables (including lagged correlations), and constructing composites of wet and dry years. Where possible, the model results are compared with reanalyses from NCEP and NASA/DAO, as well as with available observational datasets, including GPCP and Xie and Arkin for precipitation, and SRB and ERBE output for surface and atmospheric energy components. A particular emphasis is on the comparative roles of moisture flux from the Gulf of Mexico and that associated with the Mexican monsoon. Initial findings suggest: a) Tropical SST anomalies and GCIP precipitation anomalies have a strong correspondence. The exact nature of this connection is not yet clear. b) Remote atmospheric forcings produce a clear response in soil moisture anomalies over the GCIP region. c) Local effects (particularly precipitation) have a clear diagnostic relationship with soil moisture anomalies

The 14th Conference on Hydrology