A Monte Carlo model of the nocturnal surface temperatures in urban canyons

A model for the urban canyon is formulated for meteorological conditions of weak winds at night time. Thermal radiation, conductivity and convection a re simulated by means of the Monte Carlo method. These are the main physica l processes of energy transfer that give rise to the characteristic tempera ture distribution in these systems. The model has been satisfactory tested under ideal conditions for which analytical solutions exist. The prediction s of the model under more realistic conditions accurately reproduce the obs ervational results. A strong temperature gradient across streets, with the canyon corners up to 4 degrees C warmer than the canyon centre, is found fo r the deepest canyons. This theoretical prediction has been successfully ve rified with measurements taken in a number of streets of the city of Granad a in Spain.