Controls on Turbulence, Kelvin-Helmholtz Waves, and Gravity Waves Observed within Melting Layers and Their Effect on Melting Layer Evolution: Results from WINTRE-MIX

The Winter Precipitation Type Research Multiscale Experiment (WINTRE-MIX) investigated the diverse processes impacting the variability and predictability of winter precipitation types (encompassing rain, drizzle, freezing rain, freezing drizzle, wet snow, ice pellets, and snow) by collecting observations over the St. Lawrence and Champlain River valleys. During February and March 2022, 11 intensive operation periods took place where two X-band Doppler on Wheels (DOWs) and a C-band on Wheels (COW) radars were deployed. These radars routinely performed Range-Height Indicator (RHI) scans to sample precipitation and its variation over the region.

This study will use gradients in radial velocity to detect instances of turbulence, Kelvin-Helmholtz (KH) waves, and gravity waves within RHI data. RHI data will be overlaid with model reanalysis and sounding data to diagnose potential causes of these features. Notably, our observations reveal the frequent occurrence of turbulence and waves in melting layers, associated with shear zones generated by interplay between frontal structures and valley flows. Turbulence, KH-waves, and gravity waves were also frequently observed when melting layers were decreasing with height, in the absence of cold air entrapment within the valleys. Null cases where turbulence, KH-waves, and gravity waves were not observed within melting layers will also be discussed.

The influence of turbulence, KH-waves, and gravity waves on the evolution of the melting layer, will also be examined. This presentation provides insights into the intricacies of these features within the melting layer and their potential impact on observed p-type observed over the region during WINTRE-MIX.