Gravity waves and ice clouds – Interaction of dynamics and microphysics using a Lagrangian approach

Publication type:

Other

Metadata:

Abstract

Ice clouds have a significant impact on the thermodynamic structure of their environment due to diabatic effects such as latent heat release in phase transitions. On the other hand, the ice clouds themselves are crucially affected by the local dynamics e.g. due to atmospheric gravity waves generated by frontal systems or the flow over a mountain. The interaction of the relevant dynamical processes and ice cloud microphysics on different length and time scales is not yet well understood. We investigate the influence of atmospheric gravity waves on ice cloud microphysics using a Lagrangian approach.The ice cloud properties are modelled by an ODE system where the variables are number and mass concentration as well as the supersaturation of water vapour over ice, while the vertical updraft is externally driving the system. The dynamical effects due to gravity waves are described by a Taylor-Goldstein type equation, which is then used to calculate trajectories of air parcels. We investigate the ice cloud microphysical properties along such trajectories. In this framework, we are able to run many simulations and thus study the setting for several different initial and environmental conditions.While the ice cloud system can be regarded as a non-linear oscillator for constant vertical motion, more complex behaviour emerges in the case of the non-constant updraft along trajectories. Due to the non-linearity of the ice cloud model and the overall complexity of the equations of the coupled systems, the feasibility of analytical calculations is limited and the investigation of the coupled system is largely based on numerical approaches.

Autoren