A radar view of ice microphysics and turbulence in Arctic stratiform cloud systems

Abstract. Ice microphysical processes are inherently complex because of their sensitivity to temperature and humidity, the diversity of ice crystal habits, and their interaction with supercooled liquid water (SCL) and turbulence. Long-term surface-based radar observations have been systematically used to unravel the different processes that affect ice particle growth. In this study, we present a statistical analysis of 6.5 years of Ka-band radar observations, combined with thermodynamic profiles derived from radiosonde measurements. For the first time, ice particle growth and sublimation—diagnosed from vertical gradients of radar reflectivity and mean Doppler velocity—are systematically mapped across a broad range of temperature and moisture conditions. These vertical gradients correspond closely with saturation levels relative to ice and exhibit a strong temperature dependence in supersaturated regions. Notably, distinct signatures near -15 °C are indicative of dendritic growth. Turbulence, quantified via the eddy dissipation rate (EDR), is most frequently observed in regions containing SCL. When SCL is located near cloud base, it often appears decoupled from high EDR values, suggesting that latent heat release from SCL alone is insufficient to generate strong turbulence. Instead, the presence of turbulence appears to actively support the formation and maintenance of SCL. The co-occurrence of SCL and elevated turbulence results in significantly enhanced ice particle growth compared to conditions in which either is present alone.

This work provides new observational constraints that are critical for improving the representation of ice microphysics in atmospheric models.