HR: 1330h
AN: A22A-1046    [PDF]
TI: Measurements of Water Vapor and Total Water on the NASA WB-57: Validation and Determination of Cirrus Ice Water Content
AU: * Weinstock, E M
EM: elliot@huarp.harvard.edu
AF: (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Smith, J
EM: jxsmith@huarp.harvard.edu
AF: (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Sayres, D
EM: sayres@huarp.harvard.edu
AF: (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Pittman, J
EM: vellovic@huarp.harvard.edu
AF: (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Anderson, J
EM: anderson@huarp.harvard.edu
AF: (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Herman, R
EM: rherman@mail2.jpl.nasa.gov
AF: (2) Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: We describe an instrument that makes accurate in situ measurements of total water. Cloud ice water content is determined using simultaneous water vapor measurements. The total water instrument integrates an aerodynamically shaped inlet and an in-stream heater with photofragment resonance fluorescence detection to quantitatively measure the total water content of ambient air. The air is isokinetically drawn into the instrument through the inlet positioned about a meter from the skin of the WB57 fuselage. The instrument detection axis is in principle identical to that in the water vapor instrument that has flown on the NASA ER-2 research aircraft since 1992. Ice water content measurements is critically important for: (1) determining effective ice densities as a function of ice particle size; (2) relating the microphysical properties of ice particles to their radiative properties; and (3) validating cloud ice water content measurements from remote and space-based instrumentation. We submit that validation of the total water measurements first requires validation of the instrument in clear air. We present validation data illustrating detailed in-flight intercomparisons with the Harvard and JPL water vapor instruments, and in-flight absorption measurements during the CRYSTAL FACE mission that illustrate instrument performance in clear air. Laboratory calibration procedures for it and the accompanying water vapor instrument are identical, and provide an accuracy of 5% for water vapor measurements. The close agreement between these three water vapor measurements on the WB57 helps provide convincing evidence of their accuracy, and has important implications for the upcoming validation plans for AURA instrumentation. We also discuss the uncertainties in the total water measurement caused by particle sampling issues, the possibility of incomplete particle evaporation, and instrument modifications to be implemented before the next mission. Data taken during a mission based out of San Jose Costa Rica in August 2001 and the CRYSTAL FACE mission based out of Key West, FL during July 2002 highlight instrument performance and illustrate instrument capability and the scientific utility of simultaneous measurements of water vapor and total water in the tropical tropopause layer.
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0365 Troposphere--composition and chemistry
DE: 3362 Stratosphere/troposphere interactions
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting