P23 Sensitivity of microphysics parameterizations to aerosol loading.
Grell, Evelyn, CIRES, University of Colorado Boulder and NOAA/ESRL/PSD, Bao, Jian-Wen, NOAA/ESRL/PSD, Michelson, Sara, CIRES, University of Colorado Boulder and NOAA/ESRL/PSD
The local change
of a hydrometeor due to perturbations in aerosol loading is a result of
positive and negative processes such that the tendency for the aerosol-induced
change in one microphysical process may be compensated by the response of
another. Such compensatory feedback has been discussed by, e.g., Stevens and
Feingold (Nature, 2009) and Rieger et al. (Tellus, 2014), and has made
quantifying aerosol impacts on clouds and precipitation very challenging.
In this study, the sensitivity of several microphysics schemes to perturbations
of aerosol loading is investigated and compared in the simulation of an
idealized 2-D squall line, using the Weather Research and Forecasting Model
(WRF). Analysis of the budgets for hydrometeor production and loss shows that
the microphysical response to aerosol loading varies between the
parameterization schemes. While compensatory feedback may reduce the impact of
the change to any individual term, it varies with the differences in
microphysical process parameterizations. A better understanding of these
sensitivities may provide guidance on the relative importance of both the
parameterized processes and the observational data required to evaluate and
constrain them.