HR: 11:35h
AN: A32C-06    [Abstracts]
TI: Trends and Variability of Mid Latitude Stratospheric Water Vapor Deduced From the Re- evaluated Boulder Balloon Series and HALOE
AU: Scherer, M
EM: maschere@student.ethz.ch
AF: Atmospheric and Climate Sciece, ETH Zurich, Zurich, CH-8092, Switzerland
AU: Voemel, H
EM: holger.voemel@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Voemel, H
EM: holger.voemel@noaa.gov
AF: NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States
AU: Fueglistaler, S
EM: S.Fueglistaler@damtp.cam.ac.uk
AF: Applied Mathematics and Theoretical Physics, Cambridge University, Cambridge, 00000, United Kingdom
AU: * Oltmans, S
EM: samuel.j.oltmans@noaa.gov
AF: NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States
AU: Staehelin, J
EM: johannes.staehelin@env.ethz.ch
AF: Atmospheric and Climate Sciece, ETH Zurich, Zurich, CH-8092, Switzerland
AB: An updated trend analysis of water vapor in the lower mid latitude stratosphere from the Boulder balloon-borne NOAA frostpoint hygrometer measurements and from the Halogen Occultation Experiment (HALOE) is presented. Two corrections for instrumental bias are applied to homogenize the frostpoint data series, and a quality assessment of all soundings after 1991 is presented. Linear trend estimates based on the corrected data for the period 1980-2000 are up to 40 percent lower than previously reported. Vertically resolved trends and variability are calculated with a multi-regression analysis including the quasi-biennal oscillation and equivalent latitude as explanatory variables. In the range of 380 to 640 K potential temperature (~14 to 25 km), the frostpoint data from 1981 to 2006 show positive linear trends between 0.3±0.3 and 0.7±0.1 percent/yr. The same dataset shows trends between -0.2±0.3 and 1.0 ±0.3 percent/yr for the period 1992 to 2005. HALOE data over the same time period suggest negative trends ranging from -1.1±0.2 to -0.1±0.1 percent/yr. In the lower stratosphere, a rapid drop of water vapor is observed in 2000/2001 with little change since. At higher altitudes, the transition is more gradual, with slowly decreasing concentrations between 2001 and 2007. This pattern is consistent with a change induced by a drop of water concentrations at entry into the stratosphere. Previously noted differences in trends and variability between frostpoint and HALOE remain for the homogenized data. Due to uncertainties in reanalysis temperatures and stratospheric transport combined with uncertainties in observations, no quantitative inference about changes of water entering the stratosphere in the tropics could be made with the mid latitude measurements analyzed here.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 1610 Atmosphere (0315, 0325)
DE: 1694 Instruments and techniques
DE: 3300 ATMOSPHERIC PROCESSES
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting