HR: 1340h
AN: B43A-0133    [Abstracts]
TI: Drop-size Characteristics and Evolution of Widespread Nocturnal Light Rainfall in Forested Western Amazonia
AU: * Rickenbach, T M
EM: rickenbach@met.sjsu.edu
AF: San Jose State University, Department of Meteorology San Jose State University One Washington Square, San Jose, CA 95192 United States
AU: Tokay, A
EM: tokay@radar.gsfc.nasa.gov
AF: Joint Center for Earth System Technology, University of Maryland Baltimore County NASA GSFC Code 912.1, Greenbelt, MD 20771 United States
AU: Albrecht, R I
EM: rachel@master.iag.usp.br
AF: Institute of Astronomy and Geophysics, Institute of Astronomy and Geophysics Rua do Matao 1226 University of Sao Paulo, Sao Paulo, SP 05508-900 Brazil
AB: The Tropical Rainfall Measuring Mission / Large Scale Biosphere - Atmosphere (TRMM-LBA) and the coincident Wet-season Atmospheric Mesoscale Campaign (WETAMC) examined wet-season precipitation in southwestern Amazonia, focusing in part on the relationship between precipitating systems and land-use patterns. One interesting result from the campaign was the observation of nocturnal weak, widespread rainfall often covering much of the forested western portion of Amazonia. Satellite, radar, and sounding observations suggested that the origin of this rainfall was stratiform cloud in the mid-troposphere (6 km - 9km AGL), not associated with deep convection in any part of its lifecycle. The origin of this widespread, mid-level nocturnal cloudiness is an intriguing mystery. The present study places observations of surface raindrop size and number concentration via disdrometer measurements in the context of radar, satellite, and sounding observations of this phenomenon in order to shed light on its origin. A working hypothesis centers on precipitation formation above the freezing level by destabilization of pre-existing cloud by nocturnal cooling. This phenomenon, though likely a small contributor in the water cycle in Amazonia, may have implications for the total radiation budget in western Amazonia.
DE: 3354 Precipitation (1854)
DE: 3359 Radiative processes
DE: 3374 Tropical meteorology
DE: 3314 Convective processes
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting