11:30 AM - 11:45 AM
[ACG38-10] Regional snowfall distributions in a Japan-Sea side of central Japan associated with Eurasian jet variabilities and Siberian blocking
Keywords:atmospheric blocking, 10-day averaged fields, Plain- and Mountain-type snowfall
In this study, the relationships between snowfall events in each type and intraseasonal circulation variabilities in the larger-scale circulation (∼5000–10000 km) were found out, especially for the jet variabilities in the upper troposphere, by conducting composite analyses for past heavily snowed “decades” (one-third of a month) as P-, M-, and PM-type snowfall events using a Japanese global long-term reanalysis dataset. Results indicate that all snowfall types were related to southward shift of the westerly jet over Japan with a large-scale intensified troughs (i.e., cyclonic or cold anomalies) over there. The troughs were found to be identical to blocking cyclones, because frequencies of blocking events significantly increased in the east Siberian region. Mechanisms of the trough intensification were different among the three snowfall types: Different paths of quasistationary Rossby-wave packet propagation along the Eurasian jets and relative positions of the blocks were found in between the three snowfall types. Thus, the local snowfall distributions in Japan were are determined by large-scale circulation variabilities which can be evidently distinguished in the global reanalysis.