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Spatio-Temporal Variation of High-Temperature Events in Hokkaido, North Japan

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Title: Spatio-Temporal Variation of High-Temperature Events in Hokkaido, North Japan
Authors: Mori, Keisuke Browse this author
Sato, Tomonori Browse this author →KAKEN DB
Keywords: Foehn
high temperature
diurnal variation
solar radiation
Issue Date: 25-Aug-2014
Publisher: Meteorological Society of Japan
Journal Title: Journal of the Meteorological Society of Japan
Journal Title(alt): 気象集誌, 第II輯
Volume: 92
Issue: 4
Start Page: 327
End Page: 346
Publisher DOI: 10.2151/jmsj.2014-404
Abstract: This study investigated the spatiotemporal characteristics of high-temperature events in Hokkaido, Japan, using observational data of 26 years. Statistical analyses revealed that the annual mean frequency of these events was lower (higher) at stations on the western (eastern) side of Hokkaido. The frequency of these events showed clear seasonal variation with two distinct peaks occurring in January and May. In addition, the local time of the high-temperature onset was strongly dependent on the season; the onset occurred more frequently from 1600 to 0400 Japan Standard Time (JST) in January and from 0700 to 1300 JST in May. The seasonal dependence mechanism of the high-temperature onset was investigated in eastern Hokkaido, where the frequencies of both January and May high-temperature events were the highest. In January, an extratropical cyclone passage caused intensified warm advection and increased precipitable water vapor, leading to weakened radiative cooling during the night. In May, the high-temperature events were triggered by two different mechanisms related to solar insolation. The first mechanism is explained by dynamic foehn, which forms the subsidence of the high potential temperature layer on the lee of mountains. However, the nocturnal inversion layer prevented vertical mixing of the foehn-induced warm air aloft and cold air near the ground. The surface air temperature dramatically increased after sunrise when the nocturnal inversion layer disappeared. The second mechanism is explained by the combination of airflow diabatically heated by surface sensible heat flux and dynamic foehn. Therefore, solar insolation is the key factor that controlled the diurnal variation in high-temperature events in May.
Type: article
URI: http://hdl.handle.net/2115/57746
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 佐藤 友徳

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