夏期の関東地方における対流性降水の発現率の経年変化  [in Japanese] Secular Variation in the Occurrence Rate of Convective Rainfall across the Kanto District during Summer  [in Japanese]

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Abstract

<p>本研究では,関東地方における対流性降水の発現頻度とその経年変化の地域性を明らかにし,風系との関連を検討した.アメダスの毎時資料(1980~2009年7, 8月)に基づき対流性降水を抽出し,各年における対象領域全体の発現頻度に対する各地点の降水発現率を算出した.対流性降水発現率の経年変化型は,大きく三つに類型化され,I型は北部山岳地域,II型は北部山岳地域の山麓域,III型は南関東の平野域にまとまって分布する.I型とIII型の対流性降水発現率の経年変化には有意な負の相関関係が認められ,I型で対流性降水発現率が高い(低い)年は海風の内陸への進入が明瞭(不明瞭)である.また,III型地域で対流性降水強度の経年変化が明瞭でない一方,その他の要因を含む降水全般の降水強度は増大傾向にある.これらの結果は,降水発現頻度や強度に関する経年変化を,従前活発に議論された南関東より大きな空間スケールからとらえ直すことの必要性を示唆している.</p>

<p>This study was undertaken to clarify the secular variation in the occurrence rate of convective rainfall across the Kanto district during summer. The data used for this study were hourly precipitation (108 locations) from AMeDAS observation sites in July and August between 1980 and 2009, and daylight hours and wind direction/speed (73 locations).</p><p>First, 850 sunny days were selected for which synoptic-scale disturbances in and around the target study area were not analyzed with the data from the 00UTC weather chart and AMeDAS daylight hour data. The rainfall occurring on these sunny days was considered to be due to a convective system accompanying the solar heating of the ground surface.</p><p>There are three types of secular variation in the occurrence of convective rainfall. When there was an increase in the occurrence rate of type-I convective rainfall, there was a secular decrease in the occurrence of type III. Consequently, a negative correlation between types I and III was confirmed. When the geographic distribution of each type was compared by quantity, type I was distributed in the northern Kanto mountain ranges, while types II and III were distributed the foothills of the northern mountains and southern Kanto. An increase in the occurrence rate of convective rainfall and secular tendencies were confirmed for type I. In contrast, for type III, while the intensity and frequency of convective rainfall both decreased, the intensity of overall rainfall increased.</p><p>In conclusion, this study highlights the importance of discussing the secular variability in the occurrence of rainfall in southern Kanto including the Tokyo metropolitan area in relation to secular variation on the Kanto district scale. Furthermore, the variability should be analyzed while taking the speed of land and sea breezes into account, along with synoptic-scale disturbances in rainfall intensity.</p>

Journal

  • Geographical review of Japan series A

    Geographical review of Japan series A 89(3), 107-117, 2016

    The Association of Japanese Geographers

Codes

  • NII Article ID (NAID)
    130007724136
  • NII NACSIS-CAT ID (NCID)
    AA11591990
  • Text Lang
    JPN
  • ISSN
    1883-4388
  • NDL Article ID
    027421023
  • NDL Call No.
    Z8-571
  • Data Source
    NDL  J-STAGE 
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