How do wind shear and gravity waves affect the evolution of optically thin cirrus in the tropical tropopause layer?

Past investigations have shown that gravity waves can affect both when/where cirrus form in the Tropical Tropopause Layer (TTL) and the ice concentrations produced by homogeneous freezing nucleation.  Here, we use high-resolution two-dimensional simulations to investigate the impacts of wind shear and gravity waves on TTL cirrus evolution after the nucleation stage is complete.  We use a bin microphysics model to simulate the physical processes of ice crystal growth/sublimation, advection, and sedimentation.  Gravity wave temperature and wind perturbations are calculated using a Fourier series of wave frequencies with periods ranging from 1 day to near the Brunt Vaisala period, with amplitudes based on aircraft and superpressure balloon measurements.  The simulations are initialized based on high-altitude aircraft measurements of a case just after a homogeneous-freezing ice nucleation event has produced numerous small crystals in a supersaturated environment.  We show that wind shear alone rapidly alters the structure of the cloud, and strong shear can significantly reduce the cloud lifetime.  High-frequency gravity wave temperature oscillations accelerate the reduction of ice concentration as the cloud evolves.  Gravity waves can temporarily increase or decrease cloud optical depth (depending on the initial wave temperature tendencies), but the overall lifetime of the cloud is reduced by the waves.  We will further discuss the relative importance of different wave frequencies on the evolution of TTL cirrus.