Field experiment on the effects of a nearby asphalt road on temperature measurement

Abstract

A field experiment to clarify the characteristics of temperature distribution near an asphalt car road was carried out at the Meteorological Instruments Center in Tsukuba, Japan. Fifteen thermometers equipped with artificially ventilated radiation shields were installed on a wide grass field within a distance of 10 m from edges of the road. At a height of 0.5 m above the ground, the temperature on the leeward side of the road was found to show substantial bias from that on the windward side of the road. The biases were positive values of 0.2-0.4°C on the average and larger when the thermometers was nearer to the road or in cases of lower wind speed. The temporal variation of the biases showed a diurnal change and had a maximum peak in the evening and negative values during some hours of the day. Smaller positive biases around 0.1°C were also found at a height of 1.5 m during some time of the day whereas small negative biases were seen at a height of 2.5 m in summer. These results indicate complicated distribution of roadside temperature, although they can partly be interpreted by advection of air heated over the road.