Evaluation of the Urban Background Model (UBM) and AERMOD for Mumbai City

Abstract

Air quality modelling can be a strong tool for air quality management. In the present study, the Danish Urban Background Model (UBM) and the USEPA AERMOD are applied for calculating NOx and total particulate matter (TPM) concentrations for Mumbai city of India for the years 2007 and 2012. In order to compare the results from the two models, two sets of simulations are performed using the same sets of input data for boundary conditions, emissions, and meteorology. The results showed that the NOx calculations from the UBM model were in better agreement with observed data when compared with similar results from the AERMOD model. However, the opposite was the case for TPM for which the results from the AERMOD model were in better agreement with observed data when compared with the results from the UBM. The concentration levels for 2012 were generally higher than for 2007, reflecting differences in meteorological conditions for the 2 years. When comparing the obtained model results with measurements, it should be noted, that the emission inventories have various shortcomings, and that the boundary conditions from the DEHM (Danish Eulerian Hemispheric Model) are obtained with a coarse resolution of 150 km × 150 km. One of the main shortcomings of the TPM emission inventories is that it is not accounted for all the sources. Moreover, for both TPM and NOx, the boundaries of model calculations of the UBM and AERMOD model domain are underestimating the actual concentrations due to the relatively coarse resolution. When the UBM model calculations are scaled to fit the level of the observed concentrations, it is evident that spatial and temporal variation reproduced better results when compared with the results obtained from AERMOD.