Statistical Relationship between the Snowfall Amount and the Appearance of Tropospheric Mid-Level Jet

Abstract

   Based on the snowfall data and the upper-air wind data over the Niigata district for 13 months of cold seasons from 1978 to 1984, the relationship between the snowfall amount and the appearance of tropospheric mid-level jet is examined. The statistical relationship between them is highly significant as a result of chi-square test though the individual correspondence between them is not necessarily found. Statistical analysis indicates that the jet tends to appear over the north of snowfall region nearly at the same instant as snowfall. The vertical structure of the jet in the north-south cross section, which is obtained from averaging strong snowfall cases accompanied by the jets, shows that the jet's horizontal scale is less than four degrees in latitude and the vertical wind profile near the jet has the super-geostrophic characteristic of about 10 m/s.