Comment on acp-2022-733

Abstract

Ice growth from vapor deposition is an important process for the evolution of cirrus clouds, but the physics of depositional ice growth at the low temperatures (<235 K) characteristic of the upper troposphere/lower stratosphere is not well understood. Surface attachment kinetics, generally parameterized as a deposition coefficient αD, are expected to limit growth rates in certain cases, but significant discrepancies between experimental measurements have not been satisfactorily explained. Experiments on single ice crystals have previously indicated the deposition coefficient is a function of temperature and supersaturation, consistent with growth mechanisms controlled by the crystal’s surface characteristics. Here we use observations from cloud chamber experiments in the AIDA Aerosol and Cloud Chamber to evaluate surface kinetic models in realistic cirrus conditions involving rapidly changing temperature, pressure, and ice supersaturation, so that depositional ice growth may evolve from diffusion-limited to surface kinetics-limited over the course of a single experiment. In part 1, we describe the adaptation of a Lagrangian parcel model with the Diffusion Surface Kinetics Ice Crystal Evolution (DiSKICE) model (Zhang and Harrington, 2014) to the AIDA Chamber experiments. We compare the observed ice water content and saturation ratios to that derived under varying assumptions for ice surface growth mechanisms for experiments simulating ice clouds between 180 and 235 K and pressures between 150 and 300 hPa. We found that both heterogeneous and homogeneous nucleation experiments at higher temperatures (> 205 K) could generally be modeled consistently with either a constant deposition coefficient or with the DiSKICE model assuming growth via abundant surface dislocations. Lower temperature experiments showed more significant deviations from any depositional growth model, with different ice growth rates for heterogeneous and homogeneous nucleation experiments.