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The 1988 and 1990 Summer Season Simulations for West Africa Using a Regional Climate Model

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  • 1 Earth System Science Center, The Pennsylvania State University, University Park, Pennsylvania
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Abstract

Simulations have been undertaken using a regional climate model (RegCM2) developed at the National Center for Atmospheric Research for the West African growing season (June–September) periods of 1988 and 1990. The regional climate model simulations are driven at the lateral boundaries every 12 h by data from European Centre for Medium-Range Weather Forecasts (ECMWF) analyses, with a horizontal grid spacing of 110 km using the Grell cumulus parameterization. An additional simulation during the 1988 growing season also uses the Kuo cumulus parameterization. Furthermore, a review of the differences in the tropical circulation from the ECMWF analyses during 1988 and 1990 are reviewed. The climate simulations using the Grell parameterization during the 1988 and 1990 growing seasons capture many of the observed atmospheric features and depict drier conditions during 1990. Precipitation amounts are underestimated for both the Kuo and Grell parameterizations when compared to observations during 1988, with the largest differences occurring in the Kuo parameterization. In comparison to the ECMWF analyses, both models produce a dry bias in the lower troposphere over land areas. Even with the shortcomings in the RegCM2 simulations, the model correctly develops easterly waves when compared to ECMWF analyses and observed cloud fields. The results presented here offer promise for the use of regional climate models for the study of climate variability and possibly climate change scenarios in West Africa; however, significant challenges still exist.

Corresponding author address: Dr. Gregory S. Jenkins, Earth System Science Center, The Pennsylvania State University, 503 Walker Building, University Park, PA 16802.

Email: osei@essc.psu.edu

Abstract

Simulations have been undertaken using a regional climate model (RegCM2) developed at the National Center for Atmospheric Research for the West African growing season (June–September) periods of 1988 and 1990. The regional climate model simulations are driven at the lateral boundaries every 12 h by data from European Centre for Medium-Range Weather Forecasts (ECMWF) analyses, with a horizontal grid spacing of 110 km using the Grell cumulus parameterization. An additional simulation during the 1988 growing season also uses the Kuo cumulus parameterization. Furthermore, a review of the differences in the tropical circulation from the ECMWF analyses during 1988 and 1990 are reviewed. The climate simulations using the Grell parameterization during the 1988 and 1990 growing seasons capture many of the observed atmospheric features and depict drier conditions during 1990. Precipitation amounts are underestimated for both the Kuo and Grell parameterizations when compared to observations during 1988, with the largest differences occurring in the Kuo parameterization. In comparison to the ECMWF analyses, both models produce a dry bias in the lower troposphere over land areas. Even with the shortcomings in the RegCM2 simulations, the model correctly develops easterly waves when compared to ECMWF analyses and observed cloud fields. The results presented here offer promise for the use of regional climate models for the study of climate variability and possibly climate change scenarios in West Africa; however, significant challenges still exist.

Corresponding author address: Dr. Gregory S. Jenkins, Earth System Science Center, The Pennsylvania State University, 503 Walker Building, University Park, PA 16802.

Email: osei@essc.psu.edu

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