HR: 1340h
AN: GC43A-0933    [Abstracts]
TI: Projected Evolution of Atlantic Tropical Cyclone Activity in the 21st Century
AU: * Enfield, D D
EM: David.Enfield@noaa.gov
AF: Atlantic Oceanographic & Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Wang, C
EM: David.Enfield@noaa.gov
AF: Atlantic Oceanographic & Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Lee, S
EM: David.Enfield@noaa.gov
AF: Cooperative Institute for Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AB: Vecchi and Soden (2007) have shown that the vertical wind shear projected by multi-model ensembles for the 21st century increases in the tropical North Atlantic, favoring a reduced tropical cyclone activity, contrary to some expectations based on the increased maximum potential intensity (MPI) of hurricanes. By considering the results of several recent studies, together with the projections of the Intergovernmental Panel on Climate Change (IPCC), there emerges a consistent physical rationale for expecting that, on the time scale of the 21st century, Atlantic tropical cyclone activity could gradually decrease overall. Recent research based on observations and model studies confirms that when the tropical North Atlantic is cool (warm) and the Atlantic warm pool is small (large), both the vertical wind shear and the moist static stability over the main development region (MDR) for hurricanes are increased while tropical cyclone activity decreases, accordingly. Whether or not this relationship holds as tropical Atlantic sea surface temperatures (SST) trend upwards, should depend on the relative rate of SST increase in the Atlantic as compared with the Pacific and Indian Oceans. If, as suggested by the IPCC multi- model data set, the North Atlantic warms more slowly than other oceans as the Atlantic meridional overturning circulation (AMOC) decreases, then a physically consistent scenario suggests that both the vertical wind shear and the moist static stability over the MDR should gradually increase, thus causing tropical cyclone activity to decrease. This should occur on the centenary time scale for which the AMOC is expected to decrease, but could be preceded by shorter term changes in activity in either direction due to multidecadal climate fluctuations. It is also possible that the expected decrease could be at least partially offset by an increase in the MPI of major hurricanes due to the absolute increase in local SST.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1626 Global climate models (3337, 4928)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3374 Tropical meteorology
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting