The Impact of Canyon Geometry on Intra Urban and Urban: Suburban Night Temperature Differences Under Warm Weather Conditions |
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Authors: | K Giannopoulou M Santamouris I Livada C Georgakis Y Caouris |
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Institution: | (1) Group Building Environmental Research Studies, Department of Physics, National Kapodistrian University of Athens, Panepistimioupolis, Building Physics 5, 157 84 Athens, Greece;(2) Department of Mechanical Engineering and Aeronautics, University of Patras, 265 00 Patras, Greece |
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Abstract: | The present paper investigates the impact of canyon geometry on the temperature regime and nocturnal heat island development
in the very dense urban area of Athens, Greece. Detailed measurements of air temperature have been carried out within three
deep urban canyons of different aspect ratios (H/W = 3, 2.1 and 1.7) during the night period of the summer and autumn of 2007. An analysis was carried out to investigate the
relative impact of the canyon geometry, the undisturbed wind velocity, ambient temperature, and cloud cover on the development
of a nocturnal heat island. A clear increase of the median, maximum and minimum values of the cooling rates has been observed
for decreasing aspect ratios. Under low ambient temperatures, high wind speeds correspond to a substantial rise of the cooling
rate in the urban canyons mainly because of the increased convective losses. On the contrary, cooling rates decrease substantially
under high-undisturbed wind speeds and ambient temperatures because of the important convective gains. The impact of cloud
cover was found to be important as cloudy skies cause a substantial decrease of the cooling rates in the urban canyons. Comparisons
were performed between the temperature data collected in the three studied urban canyons and temperatures recorded in an urban
as well as a suburban open space station. |
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