Collaborative Research: West African Mesoscale Convective Systems and Their Interactions with the Synoptic Environment

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The interactions between mesoscale convective systems (MCSs) and the synoptic scale environment over West Africa are crucial for determining the nature and variability of the weather and climate of the region. In addition to their important role in influencing West African rainfall, the mesoscale and synoptic scale weather systems (African easterly waves, AEWs) also have a key role in mobilizing and transporting dust. General understanding of the scale interactions including their impact on dust is poor and has until now been severely hindered by lack of useful observations. The related overarching aims of this research are: (i) To improve our knowledge and understanding of the interactions between MCSs and the synoptic environment, and (ii) to improve knowledge and understanding of the role MCSs and AEWs play in mobilizing and transporting dust. Intellectual Merit Central to addressing both aims are the special observations that were made as part of the African Monsoon Multidisciplinary Analysis (AMMA), a special observing campaign over West Africa in summer 2006. Of particular importance to this research are the observations from the MIT Doppler radar. These observations will be used by the PIs to highlight the nature and variability of the intensity and structure of the MCSs. A particularly novel aspect of this work is the estimation of the 4-dimensional diabatic heating fields associated with the MCS passages. The impact these heating fields have on mesoscale potential vorticity structures will be investigated by imposing diabatic heating fields (guided by the observations) in an idealized version of the WRF regional model. A case study will be carried out that explores the multi-scale aspects of the PV field associated with the passage of an AEW and embedded MCSs during the summer of 2006 - something that has not been possible previously. The MIT radar data will also be combined with several ARM (Atmospheric Radiation Measurements) observations, including the 95 Ghz vertically-pointing Doppler radar, to explore in detail how the dust is mobilized in association with the passage of the MCSs. This analysis will be compared to the nature of the synoptic environment, discussed above, and will help to shed light on the relative contributions of Sahelian and Saharan dust to the total dust amounts observed over West Africa (and the tropical Atlantic). Broader impacts The research has broad impacts that include:- Improving knowledge and understanding of the key weather systems in the West African Monsoon. - Educating and training three graduate students who will develop their understanding of weather and climate as well as their skills in data analysis and modeling. - Contributing to knowledge of how the variability of West African weather climate impacts downstream tropical cyclogenesis, through providing detailed analysis of the weather systems before they reach the tropical Atlantic and head for the U.S.