山風の流入による夏季の都市気温への影響

概要

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To clarify the effects of mountain winds on urban temperatures, meteorological observations were conducted in the summers of 2008 and 2009 in Nagano City, central Japan. Hamada et al. (2006) showed that mountain winds blew along the Susobana River, extending into the center of Nagano City. This study selected Nagano Prefectural Office (NPO), which is near the center of Nagano City as a site to observe mountain winds blowing into the city, while Nagano Local Meteorological Observatory (NLMO) at the periphery of the city was selected as an observation site not to mountain winds. Wind conditions at NPO and NLMO were classified as days with (15 cases) and without (37 cases) mountain winds, respectively. Average air temperature, wind direction and speed, and relative humidity at the two points were compared for each case. As a result, at NPO, average wind speed was about 5 m/s, air temperature dropped, and relative humidity increased on days with mountain winds. On these days, air temperature was reduced by up to 2°C, with an average drop of 0.5°C. The drop in temperature with the mountain winds was negatively correlated (r = -0.46, p < 0.001) with wind speed, and the relationship depended on the strength of radiative cooling.
2011-04-25