HR: 1340h
AN: A23B-0944    [Abstracts]
TI: The Influence of Ozone Change on the Cooling of the Tropical Lower Stratosphere: a Modeling Study
AU: * Huang, X
EM: xianglei@princeton.edu
AF: Program in Atmospheric & Oceanic Sciences, Princeton University, 300 Forrestal Road, Sayre Hall, P. O. Box CN710, Princeton, NJ 08544-0710 United States
AU: Schwarzkopf, M D
EM: Dan.Schwarzkopf@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, NOAA, 201 Forrestal Road, Princeton Forrestal Campus, Princeton, NJ 08540 United States
AU: Ramaswamy, V
EM: V.Ramaswamy@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, NOAA, 201 Forrestal Road, Princeton Forrestal Campus, Princeton, NJ 08540 United States
AB: Recent observational analysis indicates that the annual-mean tropical lower stratosphere (TLS) has been cooling faster than the extratropical counterparts in last two decades. Both tropical and extratropical ozone changes can potentially contribute to the cooling in the TLS - by directly change the local heating rate and by remotely change the strength of the Brewer-Dobson circulation, respectively. We use AM2, the new generation of atmospheric global circulation model developed at GFDL, to investigate the relative contribution of tropical and extratropical ozone changes to the cooling in the TLS. Three numerical experiments are carried out: (a) when observed time-varying ozone field from 1979 to 2000 is used to force AM2, the simulated cooling trend in the TLS is significant and larger than its counterparts in the extratropics; (b) When tropical ozone field is prescribed at the level of 1970s and the extratropical ozone field changes as observed, no significant trend can be detected from the time series of the annual-mean TLS temperature; (c) when extratropical ozone field is prescribed at the level of 1970s and the tropical ozone field changes as observed, the simulated cooling trend in the TLS is significant and, to a large extent, agrees with the trend in (a) in both the magnitude and the spatial distribution. These results indicate that the tropical ozone change is more responsible for the cooling in the TLS than the extratropical ozone change. We also examine the trends month by month. The results are consistent with what we conclude in the previous paragraph. The cooling induced by tropical ozone change is strong and significant in June and July as well as November and December. This is different from observation in which the strongest cooling happens in December and January. This suggests that additional physical processes have to bee taken into account to fully explain the cooling in the TLS and the contrast between tropics and extratropics.
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3319 General circulation (1223)
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3337 Global climate models (1626, 4928)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005