Local temperature differences in relation to weather parameters

The objective of this paper is to focus on the influence of clouds and wind on air and road surface temperature variations between different types of local climate environments. The study area covers 160 x 130 km(2) and inclu des 35 field stations in the Swedish Road Weather Information System (RWIS) and two synoptic weather stations. By combining data from the two sources, the spatial and temporal variations in air and road surface temperature ha ve been analysed. In the first part of this paper the theoretical influence of different weather parameters is determined. In the empirical part of th e study, a validation of the theoretical result is assessed using temperatu re and weather data from the study area. The results show that it is possib le to calculate the temperature variations in relation to topographical sit ing and different weather factors. During day-time conditions, the effect o f screening from the sun has a significant influence on the road surface te mperature, even with cloudiness amounting to 4-6 octas, provided that the s olar elevation is high. During night-time, the potential for pooling of col d air is determined by cloud cover and wind speed. When cloudy situations p revail during night-time, neutral stability is dominant resulting in a decr ease with increasing altitude for both air and surface temperatures. Road s urface temperatures, however, have a lower correlation with altitude than a ir temperature. The variation in surface temperature decreases with altitud e is also larger and has a more even distribution than the air temperature decrease with altitude. Wind speed was not an important factor for the vari ation in surface temperature decrease with altitude, but insolation from th e sun during day-time is one parameter to consider. Copyright (C) 2000 Roya l Meteorological Society.