HR: 12:06h
AN: A22A-08    [Abstracts]
TI: Thin cirrus clouds near the tropical tropopause during TC4 and their relation to convection
AU: * Pfister, L
EM: lpfister@mail.arc.nasa.gov
AU: McGill, M
EM: Matthew.J.Mcgill@nasa.gov
AF: NASA/Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, United States
AU: Browell, E
EM: Edward.V.Browell@nasa.gov
AF: NASA/Langley Research Center, Commander Shepard Boulevard, Hampton, VA 23681, United States
AU: Loewenstein, M
EM: mloewenstein@mail.arc.nasa.gov
AF: NASA/Ames Research Center, Moffett Federal Airfield, Mountain View, CA 94035, United States
AU: Jensen, E
EM: ejensen@sky.arc.nasa.gov
AF: NASA/Ames Research Center, Moffett Federal Airfield, Mountain View, CA 94035, United States
AB: Cirrus clouds in the tropical tropopause layer (TTL) help govern water mixing ratios at the bottom of the stratosphere and play a role in driving tropical troposphere-to-stratosphere exchange. Though some cirrus clouds are obvious convective anvils, most of the thin cirrus clouds at the tropical tropopause are hundreds of kilometers away from the deep convection that reaches to cirrus altitudes. Nevertheless, a large fraction of the clouds are downstream of convection and are probably caused by the convection in some way. Others are formed "in situ" by cooling along air mass trajectories that is induced by large and mesoscale waves. The recent Tropical Clouds, Chemistry, and Climate Coupling (TC4) experiment conducted in Costa Rica provides extensive observations of these thin cirrus clouds by lidar, some of which are coupled with in situ measurements of cloud and chemical properties. The experiment also included the usual extensive meteorological and standard cloud satellite measurements that allow us to trace the cloud air masses back to convective systems using trajectory analysis. This comprehensive dataset allows us to address some outstanding science questions, including: (1) What fraction of the clouds can be clearly tied to convection, and how does that compare with other regions and seasons?; (2) What is the vertical distribution of the clouds relative to the local temperature structure?; and (3) What tracer signal is seen in the clouds and can that be clearly tied to a convective process?
DE: 3311 Clouds and aerosols
DE: 3314 Convective processes
DE: 3362 Stratosphere/troposphere interactions
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting