HR: 15:30h
AN: A43E-07    [Abstracts]
TI: Effects of Saharan dust on the diurnal and seasonal variability of the West African Monsoon
AU: Lau, W K
EM: william.k.lau@nasa.gov
AF: Laboratory for Atmospheres, NASA/GSFC, MD 20771U, United States
AU: * Kim, K M
EM: kmkim@climate.gsfc.nasa.gov
AF: Goddard Earth Science and Technolgy Center, U. of Maryland at Baltimore County, Baltimore, MD , United States
AB: The effects of Saharan dust on the West African Monsoon (WAM) are investigated using the NASA finite-volume general circulation model (fvGCM). Seasonally evolving, 3-dimensional global radiative forcing of Saharan dust is derived from the GOddard Chemistry-Aerosol-Radiation Transport (GOCART) and incorporated into the fvGCM. By comparing control experiments with no dust forcing, to identical experiments with dust forcing, we examine the impact of dust forcing on the diurnal and seasonal variability of the WAM. Results show that the amplitude of the diurnal cycles of rainfall and temperature over WAM land is generally reduced by dust forcing, but increased over the adjacent oceans. The diurnal cycles are also found to be dependent on the synoptic scale conditions. On daily to seasonal time scales, dust radiative forcing induces a cloud-precipitation-dynamic feedback that draws moisture and rainfall inland toward the elevated dust layer, analogous to the "Elevated Heat Pump" (EHP) effect found for the South Asian Monsoon (Lau et al. 2006). The net effects are manifested in a northward shift of the WAM rainbelt and an advance of the rainy season. The interaction of land surface and atmospheric processes associated with the EHP are discussed.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1626 Global climate models (3337, 4928)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly