Modelling of pollution plumes using the NCEP/ETA model

Abstract

Air pollution modelling has become an important scientific tool for air quality management. Defining the initial or final position of a parcel of air, one can either predict, or trace back the path of the parcel, depending on the case in question. All this depends on changes in the meteorological parameters, which take place in the lower troposphere. Given the coordinates of the parcel and any specific boundary conditions, most of the models make use of a computer program written in a specific language to obtain the final desired output; this best viewed graphically for better understanding. This is the basic procedure followed in this case study. A ready-made Fortran program has been modified to meet the requirements of the NCEP/ETA model. The computer program makes use of a particular equation to calculate both forward and backward trajectories for three particular cases situated in the area Malta - Sicily. In this way one can deduce the area from which these pollution plumes are emitted. The prognostic period of the model is 72 hours. An emphasis is made on studying the manner in which horizontal advection varies with height. One should note that although these numerical models give a clear picture of the behaviour of the air parcel, they are not I 00% accurate for the simple reason that various assumptions are made for the process. Like all models, the ET A model has strengths and weaknesses in its design. This limits the expectations of forecasters in the quality of the final model output data. However, such models can be very useful to increase public awareness of air pollution and even serve as a tool for mitigation and prevention of emission from such identified sources.