Open AccessCase studies of the vertical structure of the direct shortwave aerosol radiative forcing during TARFOX
Author(s) -
Redemann J.,
Turco R. P.,
Liou K. N.,
Hobbs P. V.,
Hartley W. S.,
Bergstrom R. W.,
Browell E. V.,
Russell P. B.
Publication year - 2000
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1999jd901042
Subject(s) - aerosol , radiative forcing , radiative transfer , troposphere , shortwave , atmospheric sciences , radiative flux , environmental science , atmospheric radiative transfer codes , forcing (mathematics) , optical depth , single scattering albedo , meteorology , physics , optics
The vertical structure of aerosol‐induced radiative flux changes in the Earth's troposphere affects local heating rates and thereby convective processes, the formation and lifetime of clouds, and hence the distribution of chemical constituents. We present observationally based estimates of the vertical structure of direct shortwave aerosol radiative forcing for two case studies from the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) which took place on the U.S. east coast in July 1996. The aerosol radiative forcings are computed using the Fu‐Liou broadband radiative transfer model. The aerosol optical properties used in the radiative transfer simulations are calculated from independent vertically resolved estimates of the complex aerosol indices of refraction in two to three distinct vertical layers, using profiles of in situ particle size distributions measured aboard the University of Washington research aircraft. Aerosol single‐scattering albedos at 450 nm thus determined range from 0.9 to 0.985, while the asymmetry factor varies from 0.6 to 0.8. The instantaneous shortwave aerosol radiative forcings derived from the optical properties of the aerosols are of the order of −36 W m −2 at the top of the atmosphere and about −56 W m −2 at the surface for both case studies.