Unraveling the contribution of dynamical and aerosol parameters on cirrus cloud formation in the CAM 5.1 using online adjoint sensitivity analysis (Invited Presentation)
Here we present the development and application of the adjoint of the Barahona and Nenes (2009) cirrus formation parameterization. This scheme allows for competition between homogeneous and heterogeneous freezing and is unique in the sense that it is able to consider any ice nuclei (IN) spectrum (which empirically or theoretically provides the number of crystals that freeze heterogeneously). The adjoint is then implemented in the version 5.1 of the Community Atmosphere Model (CAM5) to study the relative importance of model parameters to cirrus ice crystal number globally with respect to aerosol size characteristics, ice nuclei freezing characteristics, and meteorological parameters. Model sensitivities are computed at each model time step and grid point, providing an unprecedented insight on cirrus formation within the coupled model. Sensitivities were then used to determine to what extent input parameters contribute to crystal number variability, elucidating parameter importance spatially.