The present study involves a discussion of nocturnal temperature variation due to topography and prevailing wind speed. It is part of the ongoing project "Applied climatology for increased traffic safety and road maintenance", which aims at a development of a local climatological model applicable to winter road conditions. The temperature recordings which are used are from sensors in the Swedish Road Weather Information System in the county of Skaraborg. During clear and calm nights, local air temperature differences have been related to different topographical environments. The main factors resulting in large temperature differences are the effect of wind shelter, stagnation or production of cold air, and of cold air advection. Variation in air temperatures during clear and windy nights has also been studied. At wind speeds higher than 4-5 m/s, the temperature variation is low. With decreasing wind speed the variation in temperature increases, but only for sensor sites which have some wind shelter by topography or vegetation. The air temperature variation which develops during clear nights affects the road surface temperature. In this paper, the connection between road surface temperature differences and air temperature variation is discussed. A linear relationship between the two variables exists. © 1990 Springer-Verlag.
