#1Recent Changes in Pressure Patterns and Their Regional Occurrence at Times of Heavy Snowfall and Blizzard Events in Hokkaido, Japan Masaru Matsuzawa, Yusuke Harada, Satoshi Omiya, Hirotaka Takechi Civil Engineering Research Institute for Cold Region, PWRI, Japan#2Annual Maximum Depth of Snow Cover 401 124 128 128 130 132 154 年最深積雪(1971~2000年の平年値) Annual maximum depth of snow cover (Normals for the period 1971-2000) 0 5 10 20 50 100 150 200 300 cm Japan Sea Honshu Island 34 140° 142 Sapporo Tokyo 130 134" 185 24 140 144 Sea of Okhotsk Hokkaido Pacific Ocean 142 144 14 148" 40 南大東島 愛島 南島島 Japan Meteorological Agency(2001)#3Introduction Recent Winter Events in Hokkaido Jan. 13-16, 2004 Feb. 23-24, 2008 March 2-4, 2014 Photos: Hokkaido Regional Development Bureau#4Introduction Typical pressure patterns in winter in Japan High pressure Siberia (Cold air) Low pressure Seasonal winds Backbone Japan range Sea Pacific Ocean Siberia Seasonal winds Japan Backbone Pacific Sea range Ocean#54000 3500 3000 2500 2000 Road closure time (hour) 0 1500 1000 500 1971-72 1972-73 1973-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 Introduction on national highways in Hokkaido Cumulative hours of road closure by snowstorms 1986-87 1987-88 1988-89 89-90 94-95 95-96 Winter of Year 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 222 2014-15 0 250 200 150 100 350 300 400 Installation length of snow fences (km) 50#6Study Purpose Recent trends in the frequencies of heavy snowfall and severe blowing snow events •Areas of heavy snowfall and severe blowing snow Relation between routes of low-pressure systems and/or pressure distributions and areas of heavy snowfall or severe blowing snow Changes in charted weather patterns at times of heavy snowfall and severe blowing snow#7Investigation Method Heavy Snowfall and Severe Blowing Snow: Case extraction (1) Data Hourly data on snow depth, air temperature and wind velocity at 77 weather stations 46° Rumoi Asahikawa 0 Wakkanai Abashiri Right-hand figure: 44° Locations of the 77 stations in the 10 national road maintenance districts Winter: Nov. 1 to Apr. 30. 42° Sapporo Otaru Kushiro Muroran Obihiro Hakodate 41° 139° 140° 141° 142° 143° 144° 145° 146"#8Investigation Method Heavy Snowfall and Severe Blowing Snow: Case extraction (2) Extraction method Heavy snowfall criteria Snowfall >40cm /24hr, or >60cm /48hr, or >80cm /72hr Severe blowing snow criteria 24hr estimated snow drift transport* > 1,750 kg/m If any of the criteria are met at no fewer than 5 of the 77 stations, that case is extracted as a case of heavy snowfall (or severe blowing snow). Snow drift transport rate: the mass of snow passing a unit width perpendicular to the wind direction per unit time [gm-¹s-¹]. Q=0.05V1.2 [gm¨¹s¨¹] Where V1.2: wind velocity at 1.2 m in height#9Classification of Charted Surface Weather (L1, L2, L3, L4, L5) L3. L2 L1 L1-3. L5 ᏓᏎ L4-5#10Classification of Charted Surface Weather (L6, L7, L8, L9, L10) L8 L7. L9 16 L10 L6-8 L9-10.#11Classification of Charted Surface Weather (L11, L12) L11. L12#12Classification of Charted Surface Weather (Wn, Ww) Low Pressure Wn+ *1 Low OW Pressure WW+J#13Number of cases Number of cases of heavy snowfall and severe blowing snow classified by the route of the low- pressure system and winter pressure distributions 1984/85 - 2014/2015 30 20 10 0 70 60 50 40 ±±₹E6664666656#14Rumoi Wakkanai 100% 100% 50% 0% 45° L6 L9 L11L12 Asahikawa 100% Occurrence rate of heavy snowfall and severe blowing snow for L6, L9, L11 and L12 46° 50% 44° 0% L6 L9 L11 L12 Otaru 100% 100% Sapporo 50% 50% 50% Abashiri 100% L6 L9 L11L12 50% 0% L6 L9 L11 L12 43° 0% 0% Kushiro L6 L9 L11 L1 16 19 11112 100% 50% 0% L6 L9 L11L12 42° Hakodate Muroran 100% 100% Obihiro 100% 50% 50% 50% 0% 0% 0% L6 L9 L11 L12" L6 L9 L11 L12 L6 L9 L11L12 41° 139° 140° 141° 142° 143° 144° 145° 146°#15Occurrence rate of heavy snowfall and severe blowing snow for Wn and Ww 46° Wakkanai Rumoi 100% 100% 50% Abashiri 100% 50% 45° 0% 50% 0% Wn Ww Wn Ww Asahikawa 0% 100% Wn W 44° 50% 0% Otaru Wn 100% Ww 100% Sapporo Kushiro 100% 50% 50% 43° 0% 0% Wn Wn Ww 42° 100% 50% Hakodate Hakodate 50% 0% Wn Ww Muroran Obihiro 100% 100% 50% 50% 0% 0% 0% Wn Ww Wn Ww Wn Ww 41° 139° 140° 141° 142° 143° 144° 145° 146°#16The occurrence frequency of charted surface weather patterns for the winters of 1985/1986 to 2014/2015 Classification Period 1985/86- 1995/96- 2005/06- 1994/95 2004/05 2014/15 L6 3 (1) 6 (3) 0 (0) Location and L9 5 (1) 4 (1) 3 (2) route of the low-pressure L11 3 (3) 4 (3) 5 (2) system L12 5 (2) 5 (4) 11 (9) Wn 20 (10) 20 (11) 20 (10) Typical winter pressure Ww 7 (1) 5 (3) 8 (4) distribution#17Number of events of heavy snowfall and severe blowing snow per winter 0 L 2 3 + UT 10 6 1984 1986 1988 1990 1992 ས 7 Number of events of heavy snowfall and severe blowing snow per winter, and the lowest pressure each winter Winter (Year) 1000 990 980 970 960 950 940 Lowest pressure each winter (hPa) 930 948hPa bomb#189 a.m. 12/16 The case of December 17, 2014 1038 稚! 利尻馬 232 23 400 天亮島pe 燒尻器 オホーツク海 知床岬 1024 1006 1006 hPa 1038- 9 a.m. 12/17 948 每 留萌⊗0 旭 12757 小樽 岩内 37 口干 214 237 235 室蘭 浦宮 江憲 函館 太平洋 根室 Hokkaido Development Bureau, "Road information in Hokkaido”, http://info-road.hdb.hkd.mlit.go.jp/RoadInfo/index.htm 948hRa 140 17日09時 Japan Meteorological Agency, Every day's weather chart, http://www.data.jma.go.jp/fcd/yoho/hibiten/ 国行 沙#19Conclusion • Cases of heavy snowfall and severe blowing snow resulting from the L12 pattern, in which one of two low-pressure areas is absorbed by the other, were found to have increased recently. • In this pattern, heavy snowfall and severe blowing snow are likely to occur in the Abashiri and Kushiro areas of Eastern Hokkaido. • In Eastern Hokkaido, the occurrence rates of heavy snowfall and severe blowing snow are low for the typical winter pressure distributions. Further efforts must be made to clarify the regional conditions under which disasters from heavy snowfall or severe blowing snow tend to occur, by integrating the results of this study and analyses of disaster records and road closures.#20Thank you for your attention. Snow and Ice Research Team Civil Engineering Research Institute for Cold Region, Japan www2.ceri.go.jp