HR: 0800h
AN: A21A-0722    [Abstracts]
TI: A new look at - Tropical Middle-Troposphere Clouds
AU: * Zuidema, P
EM: Paquita.Zuidema@noaa.gov
AF: Paquita Zuidema, CIRES - NOAA/ETL, Boulder, CO 80305
AU: Fairall, C
EM: Chris.Fairall@noaa.gov
AF: Chris Fairall, NOAA/ETL, Boulder, CO 80305
AU: Lin, J
EM: Jialin.Lin@noaa.gov
AF: Jialin Lin and Brian Mapes, CIRES - NOAA/CDC, Boulder, CO 80305
AU: Mapes, B
EM: Brian.Mapes@noaa.gov
AF: Jialin Lin and Brian Mapes, CIRES - NOAA/CDC, Boulder, CO 80305
AB: Cloud vertical structure observations within the tropical convective atmosphere made from a cloud radar during two ship-board field campaigns are presented and interpreted using soundings, large-scale divergences calculated from precipitation radar Doppler velocities, and surface rainfall rates. The Eastern Pacific Investigation of Climate (EPIC), held in the eastern Pacific ITCZ, documented mid-troposphere layers of low relative humidity occurring within an otherwise moist environment. The dry layers, centered at about 7 km, are thought to originate from near the equator and to represent a climatological feature. The dry layers work not only to suppress surface-based convection, but also to sublimate cirrus ice from previous outflow, and may be implicated in the generally lower cloud-top heights found for the eastern Pacific ITCZ compared to other tropical convective environments. Similar data gathered during the Joint Air-Sea Monsoon Interaction Experiment (JASMINE) held within the Bay of Bengal in May of 1999 document mid-troposphere relative humidities that rarely fell below 60% once the monsoon onset began, along with more upper-level cloud. Buoyancy-sorting model calculations document more detrainment near the top of the boundary layer during EPIC than during JASMINE, suggesting air of lower initial buoyancy that is then also more sensitive to inhibition of its vertical movement by free troposphere low-relative-humidity layers.
DE: 3314 Convective processes
DE: 1655 Water cycles (1836)
DE: 1694 Instruments and techniques
DE: 1610 Atmosphere (0315, 0325)
DE: 0325 Evolution of the atmosphere
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting