Response of Snow Cloud Bands to Sea Surface Temperatures and Air Temperatures over the Sea of Japan

The response of snow cloud bands to the increase in air temperatures and sea surface temperatures (SSTs) over the Sea of Japan was investigated. We focused on a typical snowfall event in Japan by intense cloud bands around the Japan-Sea Polar-Airmass Convergence Zone (JPCZ) on 25-26 December 2021. After confirming that a regional atmospheric model fairly reproduced the mesoscale system in the event, we conducted two sensitivity experiments with air temperatures or SSTs imposed as boundary values uniformly increasing by 4 K. The results revealed that, in the model experiment with higher SST, more water vapor is supplied to the planetary boundary layer, which encouraged the higher clouds along the convergence zone. The experiment identified the dominance of the transversal mode (T-mode) of cloud bands in the east of the zone. This is presumably because of the cloud advection from the top near the JPCZ and vertical shear response to local SST increase over the Sea of Japan away from the JPCZ. In contrast, the experiment with higher air temperatures exhibited wider areas dominated by the longitudinal-mode (L-mode) cloud bands over the Sea of Japan.