HR: 08:45h
AN: A31D-04 INVITED    [Abstracts]
TI: The effects of convective ice lofting on H2O and HDO in the tropical tropopause layer
AU: * Dessler, A
EM: adessler@tamu.edu
AF: Dept. of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, United States
AU: Hanisco, T
EM: hanisco@huarp.harvard.edu
AF: Dept. of Chemistry, Harvard University, Cambridge, MA 02138, United States
AU: Fueglistaler, S
EM: S.Fueglistaler@damtp.cam.ac.uk
AF: Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
AB: We have derived a climatology of TTL-penetrating convective events from measurements of Ice-water content (IWC) from the Microwave Limb Sounder onboard NASA's Aura spacecraft. Using this climatology, we have added convective ice lofting to a Lagrangian trajectory model of TTL water vapor (H2O) and its stable isotopologue, HDO. The Lagrangian model has been previously shown to accurately simulate H2O in the TTL and lower stratosphere. We show here that the model without convective lofting does a poor job reproducing the observed HDO depletion (dD) in the TTL. When convective ice lofting to altitudes below the cold point (the point where air experiences its lowest H2O saturation mixing ratio) is added to the model, there is little change in H2O in the lower stratosphere, but a large change in dD throughout the TTL that brings the model into better agreement with measurements. Thus, convective ice lofting has the capacity to improve the model's dD simulation while not significantly degrading the agreement between simulated and measured H2O. Convective ice lofting to altitudes above the cold point, on the other hand, has a large effect on lower stratospheric H2O, suggesting that changes in convection reaching these altitudes could drive changes in lower stratospheric H2O. This suggests a mechanism by which lower stratospheric H2O trends may be at least partially decoupled from tropopause temperature trends. Such a disconnection was suggested by previous observations of simultaneously increasing stratospheric H2O and a cooling tropical tropopause.
DE: 0321 Cloud/radiation interaction
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting