Simulation of atmospheric dispersion of NOX over complex terrain region of Ranchi with FLEXPART-WRF by incorporation of improved turbulence intensity relationships

• Published in: Atmospheric environment (1994) 2015-12, Vol.123, p.139-155
• Main Authors: Madala, Srikanth, Satyanarayana, A.N.V., Srinivas, C.V.
• Format: Article
• Language: English
• Subjects: Air quality; Complex terrain; FLEXPART-WRF; Turbulence intensity
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2015.10.090

Accurate representation of air pollutant dispersion is essential for environmental management and planning purposes. In this study, semi-empirical relationships of turbulence intensity (σu/u*, σv/u* and σw/u*) as a function of surface layer scaling and local stability are developed following boundary layer similarity concepts at Ranchi, a complex terrain in Jharkhand, Eastern India for various seasons. The impact of the new turbulence parameterization for air pollution dispersion simulation is studied by incorporating the same in the Hanna scheme of FLEXPART-WRF Lagrangian Particle dispersion model over study region. The model is used to estimate the ground level concentrations of nitrogen oxides (NOx) due to industrial and vehicular sources in study region. The meteorological parameters needed in air-quality simulation are simulated using the Advanced Research WRF (ARW) mesoscale model at high resolution (3 km). Three turbulence schemes (YSU, MYNN2 and ACM2) in ARW are alternatively tested in dispersion simulation and comparisons are made with available air quality data for eight days in different seasons (winter, pre-monsoon, monsoon and post-monsoon). Simulations with FLEXPART revealed distinct seasonal variation of dispersion patterns. It has been found that the new turbulence intensity relationships in FLEXPART improved the NOx concentration estimates by reducing the negative bias seen with default Hanna scheme. Further, the ARW simulated meteorological parameters using ACM2 and MYNN2 significantly reduced the bias in modeled pollutant concentrations. The study demonstrates the utility of high quality seasonal turbulence measurements in pollution dispersion model for better diffusion parameterization needed in air quality modeling. •Seasonal boundary layer turbulence intensity relationships developed at Ranchi.•Hanna scheme of FLEXPART-WRF modified using new turbulence intensity relationships.•Ground level concentrations of NOx in Ranchi region simulated using FLEXPART-WRF.•Modified Hanna scheme considerably improved NOx concentrations over default scheme.•Study demonstrate utility of seasonal turbulent observation in air quality modeling.