HR: 1330h
AN: A32B-0140    [PDF]
TI: Observations of the upper tropospheric water vapor feedback in UARS MLS and HALOE data
AU: Minschwaner, K
EM: krm@kestrel.nmt.edu
AF: New Mexico Tech, Dept. of Physics, Socorro, NM 87801 United States
AU: * Dessler, A E
EM: adessler@umd.edu
AF: University of Maryland, ESSIC/2207 Computer and Space Sci Bldg, College Park, MD 20742 United States
AB: One of the biggest uncertainties in climate science today concerns the water vapor feedback. Most climate models maintain a nearly constant relative humidity as the climate changes, which provide a strong positive feedback to warming caused by anthropogenic greenhouse gas emissions. On the other hand, it has been suggested that specific humidity in the upper troposphere (UT) may remain fixed or even decrease as the climate changes. Observational studies have attempted to resolve this disagreement, but the results have been inconclusive, and few of the studies have focused on the tropical UT. This is a significant oversight: the surface temperature is especially sensitive to changes in water vapor in the tropical UT owing to the cold temperatures found there. We present an analysis of UARS MLS and HALOE water vapor measurements at 215 hPa in the tropics. We find strong evidence that the water vapor feedback in the UT is positive, but not as strong as fixed relative humidity scenarios. This suggests that current model simulations may be overestimating the sensitivity of the climate.
DE: 0322 Constituent sources and sinks
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting