HR: 1340h
AN: A13C-1367    [Abstracts]
TI: Water Vapor in the Tropical Upper Troposphere and Lower Stratosphere over Costa Rica: Insights from In Situ Measurements from the TC4 and CWVCS Summertime Missions
AU: * Smith, J B
EM: jsmith@huarp.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: Weinstock, E M
EM: weinstock@huarp.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: Moyer, E J
EM: moyer@huarp.harvard.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Ave., Chicago, IL 60637, United States
AU: Pittman, J V
EM: Jasna.Pittman@nasa.gov
AF: NASA Marshall Space Flight Center, Global Hydrology and Climate Center 320 Sparkman Drive, Huntsville, AL 35812, United States
AU: Hanisco, T F
EM: tfh@huarp.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: Sayres, D S
EM: sayres@huarp.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: St. Clair, J M
EM: jstclair@fas.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: O'Brien, A
EM: aobrien@fas.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AU: Anderson, J G
EM: anderson@huarp.harvard.edu
AF: Harvard University, Anderson Group, CCB 12 Oxford Street, Cambridge, MA 01238, United States
AB: In situ measurements of water vapor and its isotopologues from the suite of Harvard University instruments, in combination with simultaneous measurements of other tracers and meteorological parameters acquired aboard the WB-57 aircraft during two summertime missions out of San Jose, Costa Rica, are used to investigate the processes controlling water vapor in the tropical upper troposphere and lower stratosphere. Measurements from both the Clouds and Water Vapor in the Climate System (CWVCS) mission during August 2001, and the recent Tropical Composition Cloud and Climate Coupling (TC4) mission during August 2007, provide an excellent combined data set for investigating the causes of observed short-term (i.e. flight-to-flight) variability in water vapor concentrations in the UT/LS, and differences between the data sets provide a means of assessing inter-annual variability in this region. Both data sets show evidence of extreme short-term variability in UT water vapor, with the near-tropopause concentrations in both missions differing by more than 10 ppmv from flight to flight. Very low near-tropopause mixing ratios are coincident with the cooling of the upper tropical troposphere and tropopause. However, whether this is evidence of local in situ dehydration or part of a mesoscale change in the temperature and humidity structure of the tropical UT remains to be determined. Additionally, does this variability propagate into the lower tropical stratosphere? The data from both missions show no evidence of the dehydrated air masses impacting lower stratosphere humidity, however, the data do show evidence of the convective injection of water vapor and/or ice directly into the tropical lower stratosphere. Back-trajectory analyses, as well as MLS tracer contour maps, will be used to pinpoint the location, again whether local or remote, of these large-convective events. In general, the combined data set provides a rich set of examples of different processes that affect water vapor in the tropical UT/LS.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting