Author(s)

A Tal

Abstract

The Urban Heat Island (UHI) arises from the essence of urban development i.e the substitution of natural surfaces with vegetative cover, with surfaces of asphalt, concrete and other heat absorbing materials. The thermal image of Tel Aviv-Jaffa, from LANDSAT satellites’ thermal band , displays features of cooler and warmer areas, very similar in their distribution over the 11 years and over different seasons studied in this work. From many UHI studies, it is apparent that surface temperatures are influenced by: building density, construction materials, inter-building land-use ( including parking lots), vegetation, directions of main streets with relation to the dominant breeze direction, obstacles to the breeze, human activities - e.g. transportation, industry. Over 50 locations representing the hotter and cooler parts of the city were chosen to investigate this thermal pattern. With cooperation of the Tel Aviv-Jaffa Municipality’s GIS unit, tree density, building density and parking lot maps were produced from the relevant data layers Hand-held camera ground photography was also taken for most of the chosen locations around the city. The determining factor for lower surface temperatures appears to be trees, Even in more densly built areas, trees in inter-building spaces are responsible for reduction of surface temperatures. Furthermore, in some less dense parts of the city with few inter-building trees, the surface temperatures are high. The hottest locations are in general open spaces of bare ground or asphalt covered parking lots or built areas without trees. Tel Aviv-Jaffa is hot and rainless at least 8 months of the year. Therefore, in order to improve the climatic quality of the city and to reduce the use of energy for cooling, it is recommended to aforest the city. An ongoing study for the Ministry of Housing , to be completed during the first quarter of 2002 is a studying of the UHI of 4 other cities in Israel: Beer-Sheva, Haifa, Jerusalem and Natanya – cities in different geographical regions, the objective being to provide government level decision makers with a basis for guidelines for UHI considering urban planning policy.

Keywords