HR: 10:35h
AN: OS52A-02 INVITED     [Abstracts]
TI: Impact of the Atlantic Warm Pool on Climate and Hurricanes: An Overview of Recent Understanding
AU: * Wang, C
EM: Chunzai.Wang@noaa.gov
AF: NOAA Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Lee, S
EM: Sang-ki.Lee@noaa.gov
AF: CIMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Enfield, D
EM: David.Enfield@noaa.gov
AF: NOAA Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149, United States
AB: The Atlantic Warm Pool (AWP) with a large body of warm water is comprised of the Intra-Americas Sea (i.e., the Gulf of Mexico and the Caribbean Sea) and the western tropical North Atlantic. Located to its northeastern side is the North Atlantic Subtropical High (NASH) that produces the tropical easterly trade winds. The easterly trade winds carry moisture from the tropical North Atlantic into the Caribbean Sea where the flow intensifies forming the Caribbean Low-Level Jet (CLLJ). The CLLJ then splits into two branches: One turning northward and connecting with the Great Plains Low-Level Jet (GPLLJ), and the other one continuing westward across Central America into the eastern North Pacific. The easterly CLLJ and its moisture transport are maximized in the summer and winter, whereas they are minimized in the fall and spring. This semi-annual feature results from the semi-annual variation of sea level pressure in the Caribbean region owing to the westward extension and eastward retreat of the NASH. The summertime strong easterly CLLJ is associated with a maximum of sea level pressure, a relative minimum of rainfall (the mid-summer drought), and a minimum of tropical cyclogenesis in July in the Caribbean Sea. The NCAR community atmospheric model ensemble runs show that climate response to the AWP heating extends beyond the AWP region to the eastern North Pacific and North America, owing to the westward propagation of Rossby wave response. The effect of the AWP is to weaken the summertime NASH, especially at its southwestern edge. The AWP also strengthens the summertime continental low over the North American monsoon region. In response to these pressure changes, the easterly CLLJ and its moisture transport are weakened, but its semi-annual feature does not change. The AWP-induced change of atmospheric circulation changes the moisture convergence that results in increased rainfall in the AWP region and the eastern North Pacific. The model runs also show that the effect of the AWP is to weaken the southerly GPLLJ and its northward moisture transport and thus to decrease rainfall in the United States east of the Rocky Mountains. Finally, the AWP largely reduces the tropospheric vertical wind shear in the main development region that favors hurricane formation and development during August-October.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1854 Precipitation (3354)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly