101. Precipitation Mechanisms in Stratiform Snow Clouds Associated with a Mid-Level Trough over the Sea of Japan.
- Author
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Masataka MURAKAMI, Yoshinori YAMADA, and Koyuru IWANAMI
- Subjects
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STRATUS clouds , *SEA level , *DOPPLER radar , *VAPOR-plating , *CLOUD droplets , *ICE nuclei , *PARTICLE size determination - Abstract
Various cloud systems responsible for snowfall along the western coast of Japan are formed over the Sea of Japan. In the present study, stratiform snow clouds associated with a mid-level trough were investigated using an instrumented aircraft and dual Doppler radars. The snow clouds exhibited a double-layer structure with thermodynamically and kinematically different characteristics. The top height and base height of the clouds were 4.5 km and 0.9 km at temperatures of -29 °C and -5 °C, respectively. The layer below 2 km mean sea level (MSL) had turbulent air, which reflected its convectively unstable stratification. The maximum updraft exceeded 4 m s-1 at approximately 1 km MSL, and the maximum cloud water content was 0.6 g m-3. The layer above 2 km was less turbulent and characterized by a weak updraft of < 2 m s-1 and maximum cloud water content of 0.1 g m-3. These values were considerably lower than those in the lower layer. The weak updraft was likely caused by an approaching mid-level trough. Ice crystal and precipitation particle concentrations, measured using two-dimensional cloud and precipitation optical array probes, respectively, were almost constant with height and measured several tens of particles L-1 and several particles L-1, respectively. Precipitation particles grew by the seeder-feeder mechanism in the two-layer stratiform snow cloud. In the upper layer (2 - 4.5 km), precipitation particles increased in size by vapor deposition and showed a remarkable broadening of size distributions toward large sizes. In the lower layer (0.9 - 2 km MSL), the precipitation particles grew further via accretion of supercooled cloud droplets and produced denser particles like graupel with no substantial change in the size distribution. Below 0.9 km MSL, particle concentrations decreased at all sizes due to sublimation and melting. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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