Sensitivity of PBL parameterizations on PM10 and ozone simulation using chemical transport model WRF-Chem over a sub-tropical urban airshed in India

Publication date: July 2018
Source:Atmospheric Environment, Volume 185
Author(s): Manju Mohan, Medhavi Gupta
Meteorology plays vital role in predicting air quality parameters in regional chemical transport models. WRF-Chem is one such chemical transport model that includes various physics and chemistry options for simulating ozone and PM10 concentrations. In this study, WRF-Chem model was used to compare the performance of different Planetary Boundary Layer (PBL) parameterization namely, the Yonsei University (YSU) and Asymmetric Convective Model v2 (ACM2) PBL schemes, over the Delhi megacity urban airshed. Surface observations were used for comparisons and evaluating model performance for both meteorological and air quality variables. The ACM2 PBL scheme resulted in better model performance for simulating ozone and PM10 concentrations along with an improvement in temperature and wind speeds due to incorporation of both local and non-local characteristics. The dependency of ozone and PM10 concentrations on meteorological parameters temperature and wind speed were studied. The influence of PBL height and ventilation coefficient on model performance was analysed as dispersion of pollutants strongly depend on these factors. The PBL height was highly over estimated during evening hours which was also reflected in the corresponding ventilation coefficient values. Even though ACM2 PBL scheme was concluded as the best PBL scheme for the study region, it still requires significant improvement for simulating air quality parameters. Further, ozone and PM10 concentrations were scrutinized for varying ranges of temperature and wind speed. Model performance for ozone and PM10 concentrations was good for temperature values below 40 °C and wind speed ≤8 m/s. A poor model performance was observed for regions with high wind speed values. Even though certain limitations were observed in the model evaluation of PBL height and high wind speed values, WRF-Chem model can be effectively employed for simulating ozone and PM10 concentrations giving due considerations to limitations on high temperature and high wind speed regime.



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