Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

H. Kalesse, W. Szyrmer, S. Kneifel, P. Kollias, E. Luke
2015 Atmospheric Chemistry and Physics Discussions  
Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediments through a supercooled liquid water (SLW) layer. The observations were collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland during the BAECC (Biogenic Aerosols – Effects on Clouds and Climate Snowfall Experiment) field campaign. The presented analysis of the height evolution of the radar Doppler
more » ... spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyond the traditional use of spectral moments. Dynamical effects are taken into account by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. This suggests that in-situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.
doi:10.5194/acpd-15-28619-2015 fatcat:45ckxosrcbenlg5ifls3csoey4