Influence of street trees on modification of radiation revenue and expenditure element in city canyon and temperature and humidity

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11680090
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 自然地理学
• Research Institution: University of Tsukuba
• Principal Investigator: KOBAYASHI Mamoru University of Tsukuba, Institute of Geoscience, Lecturer (10153644)
• Project Period (FY): 1999 – 2000
• Keywords: City canyon / Street trees / City side structure / Screening effect / Transpiring on leaf side / Thermal imagery / Urban climate

Research Abstract

It is a purpose of the present study that street trees (green space) paid attention to as a relieving factor of the thermal environment of the city in recent years furthermore clarify the influence on the temperature and humidity to the radiation revenue and expenditure element of the city ground level, especially the downward radiation element in detail based on the observation and the analysis. Study results at current year are as follows. 1Do the investigation of actual conditions of the city canyon structure and street trees in a local midsize city (Kumagaya and Ota city) and Shinjuku high-rise complex, many used the sky photograph in the point, and the cover rate of the building wall and street trees was analyzed. The upper bound value of an urban cover rate was large also in the old urban area in about 45% and big cities though the street was wide though it was this almost level with about 70% on the skyscraper street in the midsize city. Moreover, the point where it reached 40% was seen on the skyscraper street though the cover rate of street trees was similar 20-investigation % or less last year. However, it has been understood that it is a result almost similar to the investigation last year though there are some special examples. 2. Eight days in total of the piling summer (the beginning of August the end of July ) and the measurements of transpiring on the leaf side (Only in daytime when it is positive every) with the polo meter during a day of the strictness wintertime (the middle of January). It went in detailed meteorological observations of the surface thermometry (Every 30 minutes or hours) by [sa-motore-sa-] and the temperature, humidity, the shortwave, and the long wave radiation element, etc. (continuous observation of the mean value for five minutes) in the city canyon on the east and west street. As for transpiring according to the azimuth, the look south is the maximum, and it has been understood to become small in order in the west, the east, and the north from catching the change type of the day of the amount of the leaf scatter according to the weather, the leaf side, and the azimuth. A day maximum value appears on the west side on the east side in the look south in the afternoon in the morning around noon. The main decision factor of the transpiration is an amount of the light quantum (insolation), humidity, and maximum about 8～10&#13197 at about fine weather and noon of the piling summer;/?^2・s (twice or more autumn measured last year), and it is complex, slight, and influence that transpiration exerts on surrounding temperature and humidity keen examination though it is. It is always considerably maintained from the building wall to the low temperature, and however, the leaf temperature remarkably controls the downward radiation element, and is extremely plain the palliative efficacy of street trees to the radiation because of the transpiration.