HR: 0800h
AN: A21A-0721    [Abstracts]
TI: Cloud Radiative Heating, Transport, and Dehydration in the Tropical Tropopause Layer
AU: * Jensen, E
EM: ejensen@cirrus.arc.nasa.gov
AF: NASA Ames Research Center, MS 245-4, Moffett Field, CA 94035 United States
AU: Pfister, L
EM: pfister@mindego.arc.nasa.gov
AF: NASA Ames Research Center, MS 245-4, Moffett Field, CA 94035 United States
AB: Recent studies have shown that thin cirrus formed in situ within the tropical tropopause layer (TTL) can effectively freeze-dry air entering the stratosphere. An important part of this process is the pathways taken by air parcels through the TTL due to rapid horizontal transport and slow ascent in balance with radiative heating. Under clear-sky conditions, the TTL experiences net radiative heating with a peak magnitude of about 0.5 K/day, corresponding to ascent rates of a few tenths of a mm/s. It has been shown that thick cirrus below can decrease (or even reverse) the TTL radiative heating, and thin cirrus within the TTL can substantially increase radiative heating. We use fully interactive simulations of transport and cloud formation in the TTL with radiative transfer calculations including clouds to evaluate the impact of clouds on TTL radiative heating, transport, and dehydration.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting