HR: 1340h
AN: A43B-1141    [Abstracts]
TI: Radar Observations of West African Monsoon Precipitation: Evolution of the 2006 Monsoon Season
AU: * Guy, N
EM: guy@met.sjsu.edu
AF: San Jose State University, Department of Meteorology San Jose State University One Washington Square, San Jose, CA 95192-0104, United States
AU: Rickenbach, T
EM: rickenbacht@ecu.edu
AF: East Carolina University, Department of Geography East Carolina University A-227 Brewster Building, Greenville, NC 27858, United States
AU: Nieto-Ferreira, R
EM: ferreirar@ecu.edu
AF: East Carolina University, Department of Geography East Carolina University A-227 Brewster Building, Greenville, NC 27858, United States
AU: Williams, E
EM: earlew@ll.mit.edu
AF: Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering Massachusetts Institute of Technology 77 Massachusetts Ave., Cambridge, MA 02139-4307, United States
AB: The African Monsoon Multidisciplinary Activities (AMMA) Intensive Observational Period, which took place during the summer of 2006, provided a wealth of information regarding the onset and development of the monsoon season over the Sahel region of West Africa. Radar observations near Niamey, Niger during AMMA documented the structure, motion, and precipitation of convective cloud systems during the monsoon season. A radar-based analysis of convective storm development and propagation, with particular focus on mesoscale convective systems (MCSs), was performed. Radar reflectivity data collected by the MIT scanning C-band radar during the months of July – September were processed and quality-controlled to remove non-meteorological echo. An objective algorithm separated radar echo into convective cell and stratiform components. Time series of rainfall produced from radar reflectivity values, partitioned by mesoscale vs. isolated convective cell organization, were analyzed. August was the most active month for precipitation, while the beginning of July and end of September corresponded to the onset and decline, respectively of the monsoon season in Niamey. As expected, MCS-scale systems produced the greatest amount of rainfall, with a near equal precipitation distribution from the convective and stratiform portions. Spectral analysis revealed significant diurnal variation of rainfall, with a late afternoon maximum, later than in other tropical land locations. The radar rainfall time series compares well with the GPCP satellite 1 deg. x 1 deg. rain product. Time variation of the vigor of convection, as measured by the 30 dBZ surface height in convective cells, revealed the strongest convection generally occurred in August, associated with organized squall line systems. A parallel analysis of MCS and isolated convection occurrence with respect to timing of the African Easterly Jet (AEJ) will be presented, to examine whether organized convective systems occurred preferentially within easterly wave troughs.
DE: 3329 Mesoscale meteorology
DE: 3354 Precipitation (1854)
DE: 3360 Remote sensing
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting