Downloaded 10/08/21 03:17 AM UTC 3122 MONTHLY WEATHER REVIEW VOLUME 147
SEPTEMBER 2019 V E A L S E T A L . 3121 Factors Affecting the Inland and Orographic Enhancement of Sea-Effect Snowfall in the Hokuriku Region of Japan PETER G. VEALS AND W. JAMES STEENBURGH Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah SENTO NAKAI AND SATORU YAMAGUCHI Snow and Ice Research Center, National Research Institute for Earth Science and Disaster Resilience, Nagaoka, Japan (Manuscript received 8 January 2019, in final form 6 June 2019) ABSTRACT The Hokuriku region along the west coast of the Japanese island of Honshu receives exceptionally heavy snowfall accumulations, exceeding 500 cm from December to February near sea level and 1300 cm at high elevation sites, much of which is produced by sea-effect systems. Though the climatological enhancement of snowfall is large, the lowland–upland snowfall distribution within individual storms is highly variable, presenting a challenge for weather forecasting and climate projections. Utilizing data from a C-band sur- veillance radar, the ERA5 reanalysis, and surface precipitation observations, we examine factors affecting the inland and orographic enhancement during sea-effect periods in the Hokuriku region during nine winters (December–February) from December 2007 to February 2016. The distribution and intensity of precipitation exhibits strong dependence on flow direction due to three-dimensional terrain effects. For a given flow di- rection, higher values of boundary layer wind speed and sea-induced CAPE favor higher precipitation rates, a maximum displaced farther inland and higher in elevation, and a larger ratio of upland to lowland precipitation. These characteristics are also well represented by the nondimensional mountain height H^,withH^ , 1 associated with a precipitation maximum over the high elevations and a larger ratio of upland to lowland precipitation, and H^ .
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