Towards consistent coupling of cirrus cloud scheme with gravity wave parameterization in coarse resolution models

Gravity waves (GWs) have significant effect on TTL cirrus clouds by influencing their formation and life-cycle. However, modelling such clouds in coarse resolution atmospheric models still remains a challenge since large part of the GW spectrum is not resolved and has to be parameterized. By utilizing idealized simulations of cirrus cloud formation driven by either resolved or parameterized GW dynamics, we investigate the ability of a two-moment ice scheme coupled with a GW parameterization to simulate cirrus properties. The results show that transient GW parameterizations based on ray-tracing techniques are capable of reproducing cloud structure, provided that additional phase information is incorporated in the parameterization. In coarse resolution models the statistical properties of the individual clouds populating a grid box often are represented by assuming some shape of the probability density function (PDF) for the subgrid-scale fluctuations in saturation ratio or ice water content. We estimate the parameters of the PDFs from the wave-resolving simulations and relate those to parameters from the GW parameterization. Applications of the present approach in the global ICON model are discussed.