AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Adjoint Analysis of Ice Crystal Sensitivity to Heterogeneous Nucleation Spectrum
SYLVIA SULLIVAN, Benjamin Sheyko, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 146 Working Group: Aerosols, Clouds, and Climate
Abstract An adjoint model of the 2009 Barahona and Nenes ice cloud parameterization (ABN09) is used to understand the changes in cirrus sensitivity caused by different heterogeneous ice nucleation spectra. Input updraft velocity; temperature; and sulfate, black carbon, and dust numbers and sizes come from the Community Atmosphere Model version 5.1, and the parameterization gradient is calculated with respect to these variables. We evaluate the importance of including aerosol description in the nucleation spectrum with a default scheme from Meyers et al. 1992, which contains only supersaturation dependence. Crystal number sensitivities are also calculated with the Phillips et al. 2008 and, for the first time, updated Phillips et al. 2013 spectra within the ABN09 framework. These two empirical spectra depend strongly on aerosol profile, and several input parameters and correlations have changed value or form between the two. Differences in their sensitivity, then, show where the formulation of different ice-nucleating aerosol groups can be most influential. We focus on the importance of aerosol surface area available for nucleation, classification of organics, and the functional representation of black carbon. Attribution plots point to the geographical regions where the results for each of these factors may have the largest impact. This attribution analysis also indicates whether more variability in output crystal number comes from inherent nucleation spectrum biases or from natural aerosol fluctuations.