HR: 0800h
AN: A31B-0841 [Abstracts]
TI: A "Cloud Clock": Coupling laboratory data of the accommodation coefficient of HNO3 on ice with field
surface coverage data to determine the age of a cloud parcel.
AU: * Gamblin, B
EM: gamblin@colorado.edu
AF: Laboratory for Atmospheric and Space Physics, Campus Box 392, University of Colorado, Boulder, CO
80309-0392
United States
AU: Toon, O
EM: btoon@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, Campus Box 392, University of Colorado, Boulder, CO
80309-0392
United States
AU: Toon, O
EM: btoon@lasp.colorado.edu
AF: Program in Atmospheric and Oceanic Science, Campus Box 392, University of Colorado, Boulder, CO
80309-0392
United States
AB:
Measurements of HNO3 condensation on cirrus particles sampled during the SOLVE-I mission are analyzed and compared with
data from other field studies of HNO3 or NOY condensation on ice. Each field study exhibits an order of magnitude
data spread for constant HNO3 pressures and temperatures. While others assumed this distribution is due to random
error, the data spread exceeds instrument error and instead suggests HNO3 removal had not attained equilibrium at the
time of sampling. During the SOLVE-I mission, condensation on ice was a significant sink for HNO3 despite submonolayer
surface coverages; we therefore propose condensation of HNO3 on cirrus particles is controlled by kinetics and will
occur at a kinetically limited rate. A solution for the condensation of HNO3 on ice is developed. Furthermore, we
suggest the low accommodation coefficient for HNO3 on ice combined with relatively short-lived clouds causes highly
scattered, limited HNO3 uptake on cirrus particles. It is possible to couple laboratory data of the accommodation
coefficient of HNO3 on ice with field surface coverage data in order to generate a ``cloud clock'': a calculation to
determine the age of a cloud parcel. A calibration of the ``cloud clock'' is discussed using HNO3 surface coverage data
from the CRYSTAL-FACE mission.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005