Kinematic structures, diabatic profiles, and precipitation systems in West Africa during summer 2006

• Main Author: Davis, Adam James
• Other Authors: Johnson, Richard, Maloney, Eric, Kirby, Michael
• Format: Text
• Language: English
• Published: Colorado State University. Libraries 2007
• Subjects: North Atlantic
• Online Access: http://hdl.handle.net/10217/79032

2013 Spring. Includes bibliographical references. West Africa is a region characterized by great spatial contrasts in temperature, precipitation, and topography, which combine to create many complex and interesting weather phenomena. In particular, the area is home to a seasonal monsoon, propagating easterly waves, and some of the most intense thunderstorm systems on Earth. These types of events have both local and global effects - precipitation variability has a major bearing on regional water resource issues, while West Africa is also the source of many of the disturbances that develop into tropical cyclones in the North Atlantic Ocean. Unfortunately, atmospheric data has historically been very sparse in West Africa, leading to an incomplete understanding of many of these meteorological features and a corresponding difficulty in modeling them accurately. An exceptional opportunity for improvement on these fronts exists thanks to the African Monsoon Multidisciplinary Analysis (AMMA) field campaign, which collected an unprecedented quantity of observations throughout the region, with the most concentrated effort during the summer of 2006. This work uses a gridded analysis of radiosonde measurements obtained during AMMA and places those observations in the context of AMMA radar data and satellite rainfall estimates to examine the patterns of kinematic and diabatic quantities in West Africa relative to the summer monsoon phase, easterly wave disturbances, precipitation systems, and the diurnal cycle. Many unique aspects of West African weather compared to conditions elsewhere in the tropics are revealed by this study. The meridional transitions related to the West African monsoon comprise the predominant control on the location and intensity of precipitation at seasonal time scales, with variations in convective activity related to the Madden-Julian Oscillation contributing at 25 to 60 day periods. On shorter time scales of two to six days, easterly wave disturbances look to be the principal factor governing ...