1:45 PM - 2:00 PM
[AAS08-01] Multiscale environmenal factors leading to regional heavy snowfall events in Hokuriku district
★Invited Papers
Keywords:teleconnection pattern, JPCZ, regional heavy snowfall
This study investigated the multiscale environments leading to local heavy snowfall events in Hokuriku district, a Japan-Sea side area of Japan, using composite map analyses and high-resolution weather simulations.
Composite map analyses revealed that the teleconnection pattern along subpolar jets facilitates the development and southward progression of high-pressure systems over a continent, while also promoting the intensification of an extratropical cyclone. Under the synoptic-scale environments, the outflow of cold air from the continent is enhanced, consequently organizing a robust Japanese Polar Cyclone Zone (JPCZ). In contrast, in the subtropical teleconnection pattern, only the promotion of extratropical cyclone development was observed, and the cold air outflow and JPCZ were less clear.
In the case study, we specifically focused on the heavy snowfall event in December 2022 in Niigata, Japan. Based on the characteristics of the environmental fields during the heavy snowfall event, the Niigata heavy snowfall was interpreted as a typical case under the multiscale environmental conditions, ranging from large-scale to meso-scale, induced by the subpolar teleconnection pattern. Numerical simulations captured the northwesterly winds, generated through the combination of continental high-pressure system and extratropical cyclone cyclones, intricately bifurcated and converged due to the Changbai Mountains. Such a mesoscale wind field, distorted by the Chubu mountains, converges along the Hokuriku coastal area. This convergence led to the establishment of a local-scale coastal convergence line, resulting in the occurrence of heavy snowfall in Niigata.
Composite map analyses revealed that the teleconnection pattern along subpolar jets facilitates the development and southward progression of high-pressure systems over a continent, while also promoting the intensification of an extratropical cyclone. Under the synoptic-scale environments, the outflow of cold air from the continent is enhanced, consequently organizing a robust Japanese Polar Cyclone Zone (JPCZ). In contrast, in the subtropical teleconnection pattern, only the promotion of extratropical cyclone development was observed, and the cold air outflow and JPCZ were less clear.
In the case study, we specifically focused on the heavy snowfall event in December 2022 in Niigata, Japan. Based on the characteristics of the environmental fields during the heavy snowfall event, the Niigata heavy snowfall was interpreted as a typical case under the multiscale environmental conditions, ranging from large-scale to meso-scale, induced by the subpolar teleconnection pattern. Numerical simulations captured the northwesterly winds, generated through the combination of continental high-pressure system and extratropical cyclone cyclones, intricately bifurcated and converged due to the Changbai Mountains. Such a mesoscale wind field, distorted by the Chubu mountains, converges along the Hokuriku coastal area. This convergence led to the establishment of a local-scale coastal convergence line, resulting in the occurrence of heavy snowfall in Niigata.