HR: 10:50h
AN: A11H-03    [PDF]
TI: Evidence That Most Florida Anvil Crystals Derive From Midtropospheric Aerosols
AU: * Fridlind, A M
EM: ann.fridlind@nasa.gov
AF: NASA Ames Research Center, Atmospheric Physics Branch Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Ackerman, A S
EM: ack@sky.arc.nasa.gov
AF: NASA Ames Research Center, Atmospheric Physics Branch Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Jensen, E J
EM: ejensen@sky.arc.nasa.gov
AF: NASA Ames Research Center, Atmospheric Physics Branch Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Stevens, D E
EM: dstevens@llnl.gov
AF: Lawrence Livermore National Laboratory, Center for Applied Scientific Computing, Livermore, CA 94551 United States
AU: Wang, D
EM: d.h.wang@larc.nasa.gov
AF: Hampton University, NASA Langley Research Center Mail Stop 420, Hampton, VA 23681 United States
AU: Heymsfield, A J
EM: heyms1@ncar.ucar.edu
AF: National Center for Atmospheric Research, Mesoscale and Microscale Meteorology Division, Boulder, CO 80301 United States
AU: Poellot, M R
EM: poellot@aero.und.edu
AF: University of North Dakota, Department of Atmospheric Sciences, Grand Forks, ND 58202 United States
AU: Milosevich, L M
EM: milo@ucar.edu
AF: University of North Dakota, Department of Atmospheric Sciences, Grand Forks, ND 58202 United States
AU: Baumgardner, D
EM: darrel@servidor.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Centro de Ciencias de la Atmosfera Circuito Exterior, Ciudad Universitaria, DF 04510 Mexico
AU: Lawson, P
EM: plawson@specinc.com
AF: SPEC Inc., 3022 Sterling Circle Suite 200, Boulder, CO 80301 United States
AU: Wilson, J
EM: jwilson@du.edu
AF: University of Denver, Department of Engineering 2390 South York Street, Denver, CO 80208 United States
AU: Flagan, R C
EM: flagan@cheme.caltech.edu
AF: California Institute of Technology, Division of Chemistry and Chemical Engineering, 210-41, Pasadena, CA 91125 United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, Division of Chemistry and Chemical Engineering, 210-41, Pasadena, CA 91125 United States
AU: Jonsson, H
EM: hjonsson@nps.navy.mil
AF: Center for Interdisciplinary Remotely-Piloted Aircraft Studies, 3240 Imjin Road, Hangar #510, Martna, CA 93933 United States
AU: VanReken, T
EM: vanreken@its.caltech.edu
AF: California Institute of Technology, Division of Chemistry and Chemical Engineering, 210-41, Pasadena, CA 91125 United States
AU: Varutbangkul, V
EM: tomtor@caltech.edu
AF: California Institute of Technology, Division of Chemistry and Chemical Engineering, 210-41, Pasadena, CA 91125 United States
AU: Rissman, T
EM: rissman@caltech.edu
AF: California Institute of Technology, Division of Chemistry and Chemical Engineering, 210-41, Pasadena, CA 91125 United States
AB: NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and properties of cirrus cloud systems in southern Florida, including extensive measurements of aerosol number and size distribution throughout the atmospheric column. Coupling these field measurements with large-eddy simulations that resolve the size distributions of aerosols and cloud particles, we find several lines of evidence pointing to the predominance of midtropospheric aerosols as the seminal cloud nuclei for anvil crystals, in contrast to the general assumption that boundary layer aerosols are more important. Turning first to measurements made during the only penetration of a powerful updraft during the campaign, at an altitude of approximately 10 km on July 18, we find that the inclusion of tropospheric aerosols above 6 km is required to properly simulate the large number of cloud particles measured in the updraft. Furthermore, in both model simulations and observations, peak particle numbers are found not in the heart of the updraft core at 10 km, where peak supersaturations are located, but instead are found in the upwind entraining boundary of the updraft. Observed and modeled particle size distributions also demonstrate that the additional particles in the entraining region are much smaller than those in the heart of the core, consistent with cloud particle activation on recently-entrained tropospheric aerosols. Turning next to upper anvil ice crystal size distributions, observations consistently indicate peak crystal numbers in the 20 to 30 um diameter range. Model simulations reproduce this peak accurately when aerosols are included throughout the atmospheric column,but the peak shifts to 40 to 50 um when excluding aerosols above 6 km,and further shifts to 90 um when excluding aerosols above 2 km, which well exceeds the boundary layer depth. While no anvil data are available on July 18, coincident with the strong updraft measurements, we find that upper tropospheric aerosols are equally important to simulated anvil crystal numbers and size distributions on other days when cumulonimbus systems and aerosols were simultaneously measured, including July 11, 16, 19, 21, 28, and 29.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0345 Pollution--urban and regional (0305)
DE: 4801 Aerosols (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting