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Physical and Optical/Radiative Characteristics of Small Particles in Tropical CirrusWhether cirrus clouds heat or cool the Earth-atmosphere system depends on the relative importance of the cloud shortwave albedo effect and the cloud thermal greenhouse effect. Both an determined by the distribution of ice condensate with cloud particle size. The microphysics instrument package flown aboard the DC-8 In TOGA/COARE included an ice crystal replicator, a 2D Greyscale Cloud Particle Probe and a Forward Scattering Spectrometer Aerosol Probe. In combination. these instruments permitted particle size measurements between 0.5 micrometers and 2.6 mm diameter. Ice crystal replicas were used to validate signals from the electro-optical instruments. Typical results show a prevalence in tropical cirrus clouds of micron-sized particles, in addition to cloud particles that exceed 100 micrometer radius. The mechanism of their formation is growth of (hygroscopic, possibly ocean-derived) aerosol particles along the Kohler curves. The concentration of small particles is higher and less variable in space and time, and their tropospheric residence time is longer, than those of large cloud particles because of lower sedimentation velocities. Small particles shift effective cloud particle radii to sizes much smaller than the mean diameter of the cloud particles. This causes an increase in shortwave reflectivity and IR emissivity. and a decrease in transmissivity. In the cirrus outflow of tropical cyclone Oliver on 8 February, 1993, the reflectivity increases with altitude (decreasing temperature) stronger than does cloud emissivity, yielding enhanced radiative cooling at higher altitudes.
Document ID
20020038833
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Pueschel, R. F.
(NASA Ames Research Center Moffett Field, CA United States)
Ferry, G. V.
(NASA Ames Research Center Moffett Field, CA United States)
Strawa, Anthony W.
(NASA Ames Research Center Moffett Field, CA United States)
Allen, D. A.
(NASA Ames Research Center Moffett Field, CA United States)
Howard, S. D.
(Synernet Corp. Fremont, CA United States)
Foster, T. C.
(California Polytechnic State Univ. San Luis Obispo, CA United States)
Hallett, J.
(Desert Research Inst. Reno, NV United States)
Arnott, W. P.
(Desert Research Inst. Reno, NV United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: International Union of Geodesy and Geophysics XXI General Assembly
Location: Boulder, CO
Country: United States
Start Date: July 2, 1995
End Date: July 14, 1995
Sponsors: International Union of Geodesy and Geophysics
Funding Number(s)
PROJECT: RTOP 464-14-16
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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