Spatial distribution and microscale characteristics of the urban heat island in Tel-Aviv, Israel

A significant urban heat island (UHI) was identified in Tel-Aviv on a stabl e winter day. The UHI detection was performed using air temperatures at bot h the roof and the street levels (using fixed-station and car-traverse meas urements) and at the surface level (using an airborne thermal video radiome ter [TVR]). Whereas the complex microscale characteristics of the UHI studi ed by the TVR at the surface level showed variations of up to 10 degrees C, at the street level, air temperature variations of 3-5 degrees C were iden tified between the city center and the surrounding areas. It was found that during the nighttime, the warm Mediterranean Sea has a moderating effect o n the roof-level temperatures, whereas, at the street level, the urban heat island is more pronounced. The combined method of monitoring the UHI from different levels and on different scales for the first time enabled a spati al assessment of the city's UHI and its diverse thermal coverage characteri stics. The thermal differences of neighborhoods, urban activity and urban c omponents were compared. It was demonstrated that the city cover plays an i mportant role in the thermal activity of Tel-Aviv. A similar UHI spatial pa ttern was obtained using isotherm maps, generated from the air temperatures at street level, and thermal images, generated by the TVR at the surface l evel. It war concluded that there are differences in the magnitude of the U HI at different levels of the canopy layer and at different times, but the UHI pattern has similar trends. (C) 2000 Elsevier Science B.V. All rights r eserved.