HR: 09:00h
AN: A31B-05    [PDF]
TI: On the Remarkable Cooling of the Tropical Lower Stratosphere Since 1990
AU: * Reid, G C
EM: greid@al.noaa.gov
AF: CIRES, University of Colorado, Aeronomy Laboratory 325 Broadway, Boulder, CO 80305-3328 United States
AB: Radiosonde measurements of temperature and geopotential height from several island stations in the tropical western Pacific have been used to look for long-term trends in the tropopause region and the lower stratosphere. The time period studied was up to 43 years in length, beginning in 1960 and extending through 2002 in some cases. Trends prior to about 1990 were small, in agreement with previous results and with model predictions of the effects of long-term ozone depletion and greenhouse-gas enhancements, but a steep cooling trend has taken place throughout the decade of the 1990s and appears to be continuing unabated to the present. The cooling appears to maximize between pressures of 80 and 30 hPa, and is small at the tropopause level, indicating a decrease in the stability of the lowermost stratosphere. The cooling trend is steepest in the northern-hemisphere winter and early spring, and weakest in the northern early summer months, suggesting that it is dynamical in origin, and related to the meridional Brewer-Dobson circulation of the lower stratosphere. The results and their interpretation will be discussed.
DE: 1610 Atmosphere (0315, 0325)
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting