Allowance for urban microclimate in forecasting unfavourable meteorological conditions

Abstract

An air mass passing over a city undergoes a transformation of its vertical profiles of air temperature, humidity and the wind velocity and direction. Knowledge of these variations is essential for air pollution forecasting in large cities, which can be tens of kilometers long and wide, and for cities with a high intensity of pollution-affecting factors. It is necessary to bear in mind that in many cities air pollution is so severe that it becomes one of the major factors influencing weather conditions. Urban buildings have radiation and dynamic characteristics that differ from those of the suburban area. Of great importance is the urban emission of heat, the so-called “thermal air pollution”. The effect of all these factors can be evidenced by analysis of empirical data, but it is only in recent years that theoretical studies have made it possible to undertake quantitative refinements of weather forecasts for urban conditions.