African easterly waves (AEWs) over tropical Africa and the East Atlantic influence and are themselves influenced by moist convection. Data from the Tropical Rainfall Measuring Mission (TRMM) satellite, reanalyses, and in-situ observations are used to examine both directions of this two-way interaction.
This dissertation examines the climatological properties of convection, including their modulation by the diurnal cycle, over tropical Africa and the East Atlantic. Data from the TRMM Precipitation Radar (PR) shows that most of the rainfall which occurs over the Sahel comes from large and intense convective systems. This is due to the presence of high conditional instability and shear in this location.
Both reanalysis and TRMM PR data are composited by AEW phase to examine how AEWs modulate the convective environment (lift, moisture, conditional instability, and shear) and how this affects the properties of convection. Over Sahelian West Africa, the highest rain rates are found in the northerly phase of AEWs. Large mesoscale convective systems (MCSs) account for most of the increase in rainfall in this phase of the wave. MCSs found in the northerlies are typically located just to the south of the northern low-level vortex, which is located near the Saharan heat low. This part of the AEW is favorable for convective organization due to the presence of anomalously high conditional instability and shear. Two MCSs developing in association with an intense AEW in 2006 are examined to clarify this relationship.
Regional differences in the structure of AEWs between East Africa and the East Atlantic are examined in the context of the climatological zonally varying latent heating. Although AEWs over both regions are on average cold core, much stronger cold cores are observed in AEWs over East Africa. This difference in AEW structure is due to the presence of higher values of low-level latent heating over the East Atlantic, which occurs both climatologically and with the trough of AEWs.
|Commitee:||Bosart, Lance F., Davis, Chris, Molinari, John, Torn, Ryan|
|School:||State University of New York at Albany|
|Department:||Earth and Atmospheric Sciences-Athmospheric Science|
|School Location:||United States -- New York|
|Source:||DAI-B 74/07(E), Dissertation Abstracts International|
|Subjects:||Hydrologic sciences, Meteorology, Atmospheric sciences|
|Keywords:||African easterly waves, Mesoscale convective systems, Moist convection, Trmm, Tropical meteorology|
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