P2.42 Application of WRF to investigate the moisture regime associated with the preonset of Sahelian rains

Friday, 13 November 2009
Roberto J. Mera, Union of Concerned Scientists, Washington, DC; and F. H. M. Semazzi

The present study seeks to understand the predictability of the primary attributes associated with the moisture regime in the preonset period of Sahelian rainfall. The moisture regime associated with the preonset of the West African monsoon is of primary concern for the population in the region due to its influence in areas such as health and agriculture. In addition, the variability of the intertropical front (ITF) is linked with the advancement and retreat of rains in West Africa and the associated African Easterly Waves (AEWs). We use the Weather Research and Forecasting (WRF) model as a tool to diagnose the main factors that dictate predictability of the moisture regime. We explore the dynamics associated with the Saharan heat low, sea surface temperatures, mid-latitude systems, variability of the ITF and westward-propagating convective systems during the preonset period of the West African monsoon. As part of the project, data assimilation will be included using both in-situ and satellite information to create a high resolution reanalysis using WRF at 30km for the period 2000-2009, during which the NCEP Final Analysis contain global data at 1 degree resolution. Preliminary results include model configuration and optimization for the region of study, real-time ensemble forecasts for the relevant variables during the 2009 season, air parcel trajectory analysis for the region of study, and analysis of model skill using gridded reanalysis and in-situ observations. We find that westward-propagating systems have an important influence in the modulation of moisture regime at latitudinal and temporal scales.
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