Impact of wind pattern and complex topography on snow microphysics during International Collaborative Experiment for PyeongChang 2018 Olympic and Paralympic winter games (ICE-POP 2018)
2021
Abstract. Snowfall in the northeastern 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 on the planet. This study focuses on the impact of
wind flow and topography on the microphysics drawing of 20 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 weakens 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 on 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 the 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
the mountainous region, with aggregation being important in both mountainous and
coastal regions.
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