夏季夜間の局地風系に及ぼす東京都心域のヒートアイランド現象の影響(続報)局地風前線の停滞・通過と周囲の気圧場の関係  [in Japanese] Influence of Urban Heat Island Phenomenon in the Central Tokyo on Nocturnal Local Wind System in Summer(Continued Study)Relationship between Stagnation or Passage of Local Wind Front and Atmospheric Pressure Field in Surroundings  [in Japanese]

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Author(s)

    • 高橋 一之 TAKAHASHI Kazuyuki
    • 東京都環境科学研究所:首都大学東京都市環境科学研究科:(現)東京都都市整備局 Tokyo Metropolitan Research Institute for Environmental Protection:Department of Geography, Tokyo Metropolitan University:(Present office)Bureau of Urban Development, Tokyo Metropolitan Government

Abstract

本研究では,東京周辺の気象官署と,東京都内で気象観測を行ったMETROSのデータなどを用いて,東京のヒートアイランド(UHI)現象の影響を受けた,夜間の局地風前線(以下,前線と呼ぶ)の停滞・通過と,周囲の気圧場との関係を解析した.対象期間は,暑夏年であった2004年の7月~8月である.本研究の結果は以下のようにまとめられる.(1)UHIが発達する風の弱い深夜には,内陸側からの局地風系が,前線を伴って都心部に向かって進行する.この前線には,都心部付近で停滞して海上に進行しない場合(停滞型)と,時聞の経過に伴って海上に進行する場合(通過型)が認められる.(2)停滞型の場合は,UHIに伴う都心部の気圧低下域で前線が停滞し,そこで内陸側からの局地風系と東京湾上で卓越するやや強い南寄りの風が収束している.(3)通過型の場合は,UHIに伴う都心部の気圧低下が風系に及ぼす影響は停滞型の場合に比べて弱く,内陸側から進行する局地風系と,東京湾上に残る弱い南寄りの風が収束している.(4)停滞型と通過型のどちらも,関東地方南部で気圧傾度が小さい場合にあたるが,停滞型は気圧が南側で高い場合に,通過型は北側で高い場合に対応する.周囲の気圧場のわずかな違いが,夜間の局地風系の挙動や前線の停滞・通過に大きな影響を与えることが示唆された.

The present study analyzed the relationship between the stagnation or passage of the nocturnal local wind front and the atmospheric pressure field in surroundings. We used the atmospheric pressure data observed at the JMA observatories located in and around the central Tokyo, and that observed by the METROS network which had been installed in the Tokyo wards area. We focused on the period from July to August 2004 which was a hot summer. The results of the present study can be summarized as follows: 1) At midnight with weak wind when UHI developed, it was shown that local wind fronts advanced toward the central Tokyo from the inland side. The local wind fronts are grouped into two types from the behavior. One is "stagnation type" of which the front stagnates near the central Tokyo and does not head out to the sea. Another is "passage type" of which the front heads out to the sea as time passes. 2) In the case of the stagnation type, the front stagnates near the surface low pressure area in the central Tokyo, and the local wind system which advances from inland side and the southern wind which prevails on Tokyo Bay converges into the central Tokyo. 3) On the other hand, in the case of the passage type, the influence of the atmospheric pressure depression in the central Tokyo due to the UHI is weaker than in the case of the stagnation type. The local wind system which advances from inland converges with the southerly weak wind on Tokyo Bay. 4) Both types of the fronts were found when the atmospheric pressure gradient in surroundings was small. In this condition, the stagnation type front was found when the atmospheric pressure field in surroundings was higher in southern area. On the other hand, the passage type front was found when that in surroundings was higher in northern area. The present study showed that a minor difference in the atmospheric pressure field in surroundings greatly influenced the behavior of the local wind system and the stagnation or passage of the local wind front.

Journal

  • 天気

    天気 61(7), 525-540, 2014-07

    日本気象学会

Codes

  • NII Article ID (NAID)
    110009832811
  • NII NACSIS-CAT ID (NCID)
    AN00151568
  • Text Lang
    JPN
  • ISSN
    0546-0921
  • NDL Article ID
    025740060
  • NDL Call No.
    Z15-35
  • Data Source
    NDL  NII-ELS  NDL-Digital 
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