Re-evaluating cloud chamber constraints on depositional ice growth in cirrus clouds – Part 1: Model description and sensitivity tests

Abstract

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.

Ice Supersaturation Variability in Cirrus Clouds: Role of Vertical Wind Speeds and Deposition Coefficients

“…We support the notion that supersaturation‐ and size‐dependent deposition coefficients resolve an apparent contradiction between high versus low values previously inferred from measurements (K. D. Lamb et al., 2022). The fact that overall water vapor uptake is not strongly inhibited suggests that the use of constant, high values (>0.1) for the ice deposition coefficient might be appropriate in cirrus models.…”

“…Here, we focus on potential growth limitations and employ supersaturation‐dependent deposition coefficients conflating two major growth modes (dislocation and step nucleation growth), generalizing the approach used by K. D. Lamb et al. (2022) to analyze laboratory measurements. We thereby provide insights that are needed for improved model simulations and better validation of ice supersaturation and cirrus.…”

“…They not only limit vapor growth rates, but also determine the development of ice crystal shapes (habits) and are therefore an important component in simulating the ice content and radiative response of cirrus. Here, we focus on potential growth limitations and employ supersaturation-dependent deposition coefficients conflating two major growth modes (dislocation and step nucleation growth), generalizing the approach used by K. D. Lamb et al (2022) to analyze laboratory measurements. We thereby provide insights that are needed for improved model simulations and better validation of ice supersaturation and cirrus.…”

Opinion: Tropical cirrus — From micro-scale processes to climate-scale impacts

“…Ice crystal growth from water vapor is known to be sensitive to crystal surface properties (Magee et al, 2014) as well as the ambient temperature and supersaturation. Many laboratory studies have tried to quantify the water vapor deposition coefficient (Skrotzki et al, 2013;Lamb et al, 2023), which influences cirrus cloud microphysical and radiative properties. Moreover, changes in the preferential partitioning of water isotopes by non-equilibrium kinematic effects during ice deposition gives insight into ice crystal surface kinetics and deposition coefficients (Nelson, 2011;Lamb et al, 2017).…”

“…Theory development will most likely be based on controlled laboratory experiments. Measurements in large aerosol chambers may provide a link between laboratory and real-world conditions (Lamb et al, 2017). Any progress in this direction will improve estimates of ice crystal fall speeds and aggregation efficiencies and thus the simulation of anvil life cycle (Sect.…”