Atmospheric boundary layer characteristics in severe smog episodes

Summary The article brings together theoretical knowledge about the structure of the atmospheric boundary layer (ABL) which should be typical for smog situations and ABL features observed during two severe smog episodes. It can be shown that the convective boundary layer (CBL) as a special ABL type is very favourable for the occurrence of smog and that at first glance simple modelling of the CBL seems to recommend itself for forecasting purposes.However, the real smog situations show much more complexity, and even high reaching (up to 1500 m) stable boundary layers (SBL) occur. Simple modelling fails because important input parameters (such as vertical wind and advection terms) cannot be derived neither from measurements nor from meso-scale models in sufficient accuracy. Even the most advanced forecast models cannot describe the ABL structure correctly or in sufficient detail to estimate the development of a smog situation.With 19 Figures