Real–time Regional Automatic Mapping of Nocturnal Winter Road Temperatures: Application of a Methodology of Analogous Situations, The Case of the Walloon Region (Belgium)

Wallonia is the French-speaking and southern region of Belgium. Its winters are humid, often rainy and with road temperatures around 0 °C ( or 32 °F). For this region, it is thus extremely important to have a winter service struggling against the accidents that may be caused by the icy patches or snow conditions. The altitude of the Walloon Region varies between around 20 m and 700 m (or between 65 and 2295 ft). Its density of regional roads ( 0.4 km/km²) , express roads ( 0.03 km/km²) and motorways (0.05 km/km²) are very great.

Since 1993, the Walloon Ministry of Equipment and Transport (M.E.T.) has financed a project of automatic real-time cartography of nocturnal surface road temperature for its winter maintenance of its regional roads and motorways. For five years, this cartography has become well synchronized with the complexity of the spatiotemporal variability of nebulosity and salt can be spread on the roads and motorways more parsimonious that before.

The best way which has been chosen to answer correctly to this mission was firstly to install a specific network of 16 principal (PRMS) (nearly 1 per 1000 km²) and 35 secondary (SRMS) (nearly 2 per 500 km²) road meteorological stations. These stations where as best as possible installed by the Walloon M.E.T. through the whole area of the concerned region (16844 km² or 60506 square miles).

Secondly, it has been necessary to keep up to date a set of data files of reference containing longitudinal profiles of nocturnal road surface radiation temperature for three specific types of radiation and wind conditions. It was made by mobile campaign with recording of radiation surface road temperature, air temperature and balance of radiation during the second part of the dry nights in winter season. It was started again each winter where significant changes were detected in the environment of the roads or if road surfaces were replaced.

The principal partners are the Military Wing Meteo of Belgium for the weather forecast conditions necessary for the model of predicted three-hourly cartography and the team of computer analysts of company Cap Gemini-Ernst & Young.

However, meteorological radar information are still important for the best forecasting of time of precipitation on cold surface road. The new radar of Wideumont (near Libramont or Saint-Hubert) is very efficient for this purpose.

The cartography is establish in real time thanks to the combination of PRMS surface road temperatures, radiation and wind speed data with the best set of reference radiation surface road temperature. The SRMS surface road temperature are used for the control of the thermal cartography of the road and motorway surfaces.