HR: 16:25h
AN: A34A-01 INVITED     [Abstracts]
TI: How Nature foiled the 2006 Hurricane forecasts.
AU: * Lau, W K
EM: lau@climate.gsfc.nasa.gov
AF: William Lau, NASA/GSFC, Greenbelt, MD 20771, United States
AB: In this study, we present new insights from NASA earth observing satellites (TRMM, MODIS, OMI/aura), and historical data to determine the root cause of the switch from the extremely active 2005 Atlantic hurricane season to the relatively mild 2006 season. Our results suggest that the increased loading of Saharan dust in the atmosphere over the Atlantic in 2006 compared to 2005, might have been instrumental, through the shielding of solar radiation at the ocean surface, in initiating rapid drop in SST in the West Atlantic/Caribbean region at the early stage of the hurricane season (June-July). Subsequently, the Caribbean cooling metastasized into a large- scale circulation regime shift in the tropical and subtropical Atlantic atmosphere-ocean through feedback processes, manifested in a Walker-type circulation anomaly with rising motion in the eastern tropical Atlantic and the sinking motion in the West Atlantic/Caribbean region. Associated with the shift was rapid cooling of sea surface temperature over the entire North Atlantic and suppressed hurricane activities. The cooling of the North Atlantic and the warming of the Gulf of Guinea in 2006 appeared to be contrary to the impacts of El Niño from past events. Analyses of historical data also show that Saharan dust has stronger influence than El Niño in the subtropical West Atlantic/Caribbean region, while El Niño influence may be stronger in the tropical eastern Atlantic. Including the pre- and early season effects of Saharan dust on SST cooling may be important in providing better seasonal hurricane predictions.
DE: 3311 Clouds and aerosols
DE: 3314 Convective processes
DE: 3337 Global climate models (1626, 4928)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly