The Role of the Kelvin-Helmholtz Wave on the Precipitation Microphysics during ICE-POP 2018

An environment of strong wind shear and weak static stability is a favorable condition for the Kelvin-Helmholtz (KH) wave development. Advanced high-resolution measurements from microphysical instruments (radar and airborne instruments) suggested that the KH wave influences the microphysical processes and contributes to the increased precipitation at the surface. This is particularly evident in mixed-phase clouds, where snow growth can readily be facilitated by additional microphysical processes, such as riming, aggregation, and secondary ice production. However, due to limited observations, the microphysical processes associated with the KH wave have yet to be fully investigated. This study aims to expand the current knowledge by providing observational evidence of the microphysical impact of the KH wave in two distinct environments: a speed shear environment with a colder temperature (SKH) and a directional shear environment with a warmer temperature (DKH).
Collocated in-situ and remote-sensing measurements collected during the ICE-POP 2018 (International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games) field campaign provides a comprehensive view of the microphysics associated with the KH wave. Vertical velocity fluctuations within the identified KH wave modulated radar moments (e.g., Z, ZDR, and ρHV) and Doppler spectrum characteristics within and beneath the KH wave. The polarimetric variables, Doppler spectrum, and particle size distribution at the surface imply that the KH wave in SKH contributes to secondary ice production (SIP) by ice-ice collision. The KH wave in DKH exhibited persistent waves with much stronger amplitude due to the sustained directional shear environment. The KH wave in DKH suggested the additional SIP by sublimation and activation of ice-nucleating particles.

ACKNOWLEDGMENT
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).