AIRBORNE VIDEO THERMAL RADIOMETRY AS A TOOL FOR MONITORING MICROSCALESTRUCTURES OF THE URBAN HEAT-ISLAND

An advance thermal video radiometer (TVR) was mounted onboard a helico pter and used to collect data over Tel-Aviv, Israel, from an altitude of 7000 feet. The sensor, sensitive to the 3-12 mu m spectral region, consisted of an onboard calibration device and a 1.8 mRad instantaneou s field of view (IFOV), which enabled direct assessment of surface rad iometric temperature patterns in very high spatial and thermal resolut ions. The TVR capability was examined by studying the microscale struc tures of the urban heat island (UHI) of Tel-Aviv, Israel, during a sta ble calm night on 28 February 1995. The TVR data were found to be of h igh quality in terms of signal to noise ratio, reproducibility, stabil ity, thermal sensitivity and spatial resolution capabilities. The radi ometric data were analysed against air temperature acquired during the flight time by four mobile traverses that crossed the city from north to south. A significant heat island was identified over the inner cit y areas, which was found to be 5 degrees C warmer than the rural areas located 4 km to the south-east. Throughout the city, asphalt was foun d to be the major heat source whereas vegetation was found to be the m ost cooling element. A linear regression analysis between the air and radiometric temperatures showed that in general, good agreement exists between the two temperatures. Along the western routes (A and B) the correlation was relatively higher than that along the eastern routes ( C and D) and was significantly different in the linear regression slop e a. We assume that differences in atmospheric conditions, especially in the water vapour variation throughout the city, caused these incons istencies. We concluded that the examined TVR is a very promising, low -cost remote sensing sensor, which can rapidly and quantitatively moni tor the UHI in very high spatial and thermal resolutions from a high a ltitude. Based on these results we strongly recommend that the TVR be further examined in other remote sensing applications.