Comparison of Upper Air Mixing Height Estimation Methods for Urban Air Pollution Modeling

Mixing height (MH) is one of the most important parameters requested by different atmospheric pollutionmodels as an input data for forecasting the air quality. When pollutants emitted into the atmosphericboundary layer (ABL), they dispersed horizontally and vertically because of the action of convection andmechanical turbulences until it becomes completely mixed. In spite of the fact that there is still no uniquedefinition and no general accepted method for calculating the mixing height. However, the depth of themixed layer is defined as the mixing height, which determines the volume available for the dispersion ofpollutants. The greater depth of the mixed layer makes larger available volume to dilute the atmosphericpollutants. A number of indirect algorithms for the estimate of MH in upper air in stable conditions arereported in the literature. The aim of this paper is to review the different methods for the upper air mixingheight estimate and compared them with the MH derived from radiosonde measurement in order to achievea critical awareness on their application, and to identify the most suitable methods. Four indirect methodsbased on surface observations and the standard algorithm used in AERMET pre-processor is used in thiscase. The meteorological data from Jeddah in Saudi Arabia is considered to demonstrate the proposedmethodology.