Impact of wind pattern and complex topography on snow microphysics during ICE-POP 2018

Abstract

Abstract. Snowfall in north-eastern part of South Korea is the result of complex snowfall mechanisms due to a highly-contrasting terrain combined with nearby warm waters and three synoptic pressure patterns. All these factors together create unique combinations, whose disentangling can provide new insights into the microphysics of snow in the planet. This study focuses on the impact of wind flow and topography on the microphysics drawing of twenty snowfall events during the ICE-POP 2018 (International Collaborative Experiment for Pyeongchang 2018 Olympic and Paralympic winter games) field campaign in the Gangwon region. The vertical structure of precipitation and size distribution characteristics are investigated with collocated MRR (Micro Rain Radar) and PARSIVEL (PARticle SIze VELocity) disdrometers installed across the mountain range. The results indicate that wind shear and embedded turbulence were the cause of the riming process dominating the mountainous region. As the strength of these processes weaken from the mountainous region to the coastal region, riming became less significant and gave way to aggregation. This study specifically analyzes the microphysical characteristics under three major synoptic patterns: air-sea interaction, cold low, and warm low. Air–sea interaction pattern is characterized by more frequent snowfall and vertically deeper precipitation systems in the windward side, resulting in significant aggregation in the coastal region, with riming featuring as a primary growth mechanism in both mountainous and coastal regions. The cold low pattern is characterized by a higher snowfall rate and vertically deep systems in mountainous region, with the precipitation system becoming shallower in the coastal region and strong turbulence being found in the layer below 2 km in the mountainous upstream region (linked with dominant aggregation). The warm low pattern features the deepest system: precipitation here is enhanced by the seeder–feeder mechanism with two different precipitation systems divided by the transition zone (easterly below and westerly above). Overall, it is found that strong shear and turbulence in the transition zone is a likely reason for the dominant riming process in mountainous region, with aggregation being important in both mountainous and coastal regions.

Implementation of Prognostic Cloud Ice Number Concentrations for the Weather Research and Forecasting (WRF) Double‐Moment 6‐Class (WDM6) Microphysics Scheme

“…Figure 12 represents the accumulated surface precipitation amounts from WDM6_ICE and the difference in precipitation and surface snow amounts between WDM6_ICE and WDM6 (WDM6_ICE minus WDM6). Northeasterly winds are predominantly simulated in WDM6_ICE at 850 mb, consistent with the observed data (Kim et al., 2021) (Figures 12a and 12d). The simulated surface precipitation in WDM6_ICE is closely comparable with the observed data, showing abundant precipitation amounts along the mountain range (compare Figures 12a, 12d and 3c, 3d).…”

“…Cold-low and warm-low categories contain two and five events, respectively. Our study simulates two events for each cold-low and warm-low category because the air-sea interaction category contains only one event among eight snowfall events during the ICE-POP (Kim et al, 2021). Two warm-low cases are the selected based on the study of Ko et al (2022), in which selected cases show the lowest Root Mean square Error (RMSE).…”

Snow Microphysical Retrieval from the NASA D3R Radar During ICE-POP 2018

“…These include the snowfall rate (volumetric and water equivalent), mean volume-weighted particle size, and effective density (Tokay et al, 2021), as well as parameters describing the mean aspect ratio and orientation distribution. We validated the retrieval during 3 events representing both warm and cold snow regimes Kim et al (2021). These events were chosen based upon availability of both PIP and D3R data, significant accumulation at the MHS site, and absence of any mixed-phase precipitation which the algorithm does not account for.…”