雨氷発生日数の地域分布に関する統計的解析 Statistical analysis on the areal distribution of annual number of days with glaze

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雨氷発生の気候学的な地域特性を調べるため, 長野県を解析対象地域として, 雨氷発生日の特定を行い, その年平均日数の地域分布を求めた.<BR>雨氷は, 過冷却の雨滴が地物などにあたり氷になる着氷現象の一種で, 上空暖気層 (気温0℃以上) で雪片が融解して雨滴となり, それが地表付近の寒気層で冷されて過冷却の雨滴 (気温0℃以下の降水) となり発生する (melting ice process).その他, 大気全層の気温が0℃以下の場合 (supercooled warm rain process) でも発生することがあるが, ここではmelting ice processのみを対象とした.<BR>高層資料から上空暖気層の有無を, AMeDAS資料から地表付近の寒気層と降水の有無を調べ, 二つの気象条件を満たす日を雨氷発生日と定義した.過去20冬季 (1979年11月~1999年4月) について調べた結果, 雨氷の発生は3月に最も多く, 次いで12月に多いことがわかった.また, 最近6年間は雨氷発生日数が少ない傾向にある.<BR>次に, 地形因子値を用いた重回帰分析から, 年平均雨氷発生日数のメッシュマップを得た.その結果, 年平均雨氷発生日数は長野県中部と東部で多いことがわかった.特に標高との関係が強く, 山岳地域や高原地域で多くなる傾向が得られた.一方, 北部と南部の低標高地域では少ない傾向にある.

To examine the climatological features of glaze occurrence, in Nagano prefecture, where there have been many reports on the glaze, glaze occurrence days were defined and their areal distribution was statistically analyzed.<BR>Glaze forms on exposed objects at the ground by the freezing of supercooled water droplets, in a kind of ice accretion. For glaze to occur, in general, two meteorological conditions must be satisfied. One is the existence of a warm air layer (air temperature above 0°C) in the upper air, for melting of dry snowflakes into rain drops; the other is the existence of a cold air layer (air temperature below 0°C) near the ground, for cooling of rain drops into supercooled water droplets. This is called a “melting ice process”. Although glaze also occurs at air temperatures below 0°C at all levels (no warm air layer), in what is called a “supercooled warm rain process”, only the term “melting ice process” is used in this study.<BR>Aerological data were used to examine the warm air layer in the upper air, AMeDAS data were used to examine the cold air layer near the ground and precipitation, during 20 winter seasons (November 1979-April 1999). A day that satisfied these two meteorological conditions is defined as a glaze occurrence day. As a result, there are frequent peaks of glaze occurrence in December and March. The number of days with glaze has been decreasing in the past 6 years.<BR>Next, a mesh map of annual mean number of days with glaze was obtained by multiple regression analysis using a factors that represent a topographical features as independent variables. The mesh map shows a high number of days with glaze in central and eastern Nagano prefecture. In particular, because of the close relationship between the annual mean number of days with glaze and the altitude, a high number of days with glaze were estimated to occur mountain areas and highlands, while a low number of days with glaze occurred in low altitude areas of northern and southern Nagano prefecture.

収録刊行物

  • 雪氷

    雪氷 62(4), 355-365, 2000-07-15

    公益社団法人 日本雪氷学会

参考文献:  38件中 1-38件 を表示

被引用文献:  2件中 1-2件 を表示

各種コード

  • NII論文ID(NAID)
    10004644939
  • NII書誌ID(NCID)
    AN00131221
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    03731006
  • NDL 記事登録ID
    5415779
  • NDL 雑誌分類
    ZM43(科学技術--地球科学--気象)
  • NDL 請求記号
    Z15-23
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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