HR: 0800h
AN: A21E-0772    [Abstracts]
TI: A Study of Dehydration, Low Temperatures and Supersaturations in the Tropical Tropopause Layer both Inside and Outside of Clouds.
AU: * Troy, R F
EM: Robert.F.Troy@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Herman, R L
EM: Robert.L.Herman@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Christensen, L E
EM: Lance.E.Cristensen@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Bui, T P
EM: pbui@mail.arc.nasa.gov
AF: NASA Ames Research Center, MS 245-5, Moffett Field, CA 94035, United States
AB: There are substantial, and longstanding, discrepancies among instruments on satellites, balloons, radiosondes, and aircraft as to the levels of supersaturation of air parcels in the Tropical Tropopause Layer (TTL), particularly for measurements of water vapor volume mixing ratio lower than 10 parts per million by volume (ppmv). The discrepancies are due both to the difficulty of making the measurements in situ and to the difficulty of calibrating hygrometer instruments in the laboratory. We have developed a new calibration system for laser hygrometers that has allowed us to analyze data from the Jet Propulsion Laboratory Laser Hygrometer (JLH) and derive water vapor volume mixing ratios with an uncertainty of 7%, and relative humidity over ice with an uncertainty of 10%. The Costa Rica-Aura Validation Experiment (CR-AVE) was a NASA aircraft mission to characterize composition, clouds, and humidity in the TTL. In January and February 2006, a high-altitude NASA WB-57F aircraft made a series of flights from San Jose, Costa Rica, into the TTL over the equatorial Eastern Pacific Ocean. Several of these flights were characterized by unusually cold and highly supersaturated conditions near the tropical tropopause. New laboratory calibration measurements have been applied to the CR-AVE data. We analyze the updated water vapor and relative humidity along the aircraft flight path derived from water vapor concentrations measured by JLH and static temperature provided by the Meteorological Measurement System (MMS) on the aircraft.
DE: 0320 Cloud physics and chemistry
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting