Simulation of trace gases and aerosols over the Indian domain: evaluation of the WRF-Chem Model

Abstract

The "online" meteorological and chemical transport Weather Research and Forecasting/Chemistry (WRF-Chem) model has been implemented over the Indian subcontinent for three consecutive summers in 2008, 2009 and 2010 to study the aerosol properties over the domain. The initial and boundary conditions are obtained from NCAR reanalysis data. The emission rates of sulfur dioxide, black carbon, organic carbon and PM_2.5, which are developed over India at a grid resolution of 0.25° × 0.25° have been used in the present study. The remaining emissions are obtained from global inventories (RETRO and EDGAR). The model simulated the meteorological parameters, trace gases and particulate matter. Predicted mixing ratios of trace gases (Ozone, carbon monoxide and sulfur dioxide) are compared with ground based observations over Kanpur. Simulated aerosol optical depth are compared with those observed at nine Aerosol Robotic Network stations (AERONET). The simulations show that the aerosol optical depth of the less polluted regions is better simulated compared to that of the locations where the aerosol loading is very high. The vertical profiles of extinction coefficient observed at Kanpur Micropulse Lidar Network (MPLNET) station is in agreement with the simulated values for altitudes greater than 1.5 km and qualitatively simulate the elevated layers of aerosols. The simulated mass concentration of black carbon shows very good correlation with observations, due to the better local emission inventory used. The vertical profiles of black carbon at various locations have also been compared with observations from aircraft campaign held during pre-monsoon period of 2008 and 2009 resulting in good agreement. This study shows that WRF-Chem model captures many important features of the observations and therefore can be used for understanding and predicting regional atmospheric composition over Indian subcontinent

WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms

“…Following up on this, here we compare modelled ozone mixing ratios obtained with these two extensively used chemical mechanisms over south Asia: RADM2 (e.g. Michael et al, 2013;Ojha et al, 2016;Girach et al, 2017) and MOZART (e.g. Ghude et al, 2014Ghude et al, , 2016, by keeping the same input emission inventory (HTAP).…”

“…Kumar et al, 2012a, b;Michael et al, 2013;Gupta et al, 2015;Jena et al, 2015;Ansari et al, 2016;Ojha et al, 2016;Girach et al, 2017). WRF-Chem simulations at higher spatial resolution employing regional emission inventories have been shown to better reproduce the observed spatial and temporal heterogeneities in ozone over this region as compared to the global models (e.g.…”

“…Despite these applications, there is room for improvement in modelled concentrations, as some limited studies evaluating ozone on diurnal scales revealed a significant overestimation of noontime ozone, e.g. by as much as 20 ppbv in Kanpur (Michael et al, 2013) and 30 ppbv in Delhi (Gupta and Mohan, 2015).…”

Response to referee 1 (RC1)

“…Radiative transfer in the model has been represented using the Rapid Radiative Transfer Model (RRTM) longwave scheme (Mlawer, 1997) and the Goddard shortwave scheme (Chou and Suarez, 1994). Surface physics is parameterized using the unified Noah land surface model (Tewari et al, 2004) along with ETA similarity option (Monin and Obukhov, 1954;Janjic, 1994Janjic, , 1996, and the planetary boundary layer (PBL) is based on the Mellor-Yamada-Janjic (MYJ) scheme (Mellor and Yamada, 1982;Janjic, 2002).…”

“…The Weather Research and Forecasting model with Chemistry (WRF-Chem) (Grell et al, 2005;Fast et al, 2006), a regional simulation system, has been popular for use over the south Asian region in numerous recent studies to simulate the meteorology and spatiotemporal distribution of ozone and related trace gases (e.g. Kumar et al, 2012a, b;Michael et al, 2013;Gupta et al, 2015;Jena et al, 2015;Ansari et al, 2016;Ojha et al, 2016;Girach et al, 2017). WRF-Chem simulations at higher spatial resolution employing regional emission inventories have been shown to better reproduce the observed spatial and temporal heterogeneities in ozone over this region as compared to the global models (e.g.…”