• Study of mixing ratios of $\rm{SO}_{2}$ in a tropical rural environment in south India

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    • Keywords


      $\rm{SO}_{2}$; FLEXPART; $\rm{NO}_{2}$; India; CAMS reanalysis

    • Abstract


      Sulphur dioxide is a toxic pollutant in the atmosphere emitted from natural sources and human activities. Normally, $\rm{SO}_{2}$ has a life-time of about 2 days in the atmosphere and is not transported to long distances from its source region. However, under favourable circumstances such as low humidity or high wind speed, it can travel intercontinental distances from the point of emission. In this article, we have analysed the surface mixing-ratio of $\rm{SO}_{2}$ measured over the time period from January 2010 to April 2012 at a rural region in south India. It is found that $\rm{SO}_{2}$ mixing-ratio is very low over this region with an annual mean value in the range of 0.21–0.24 ppbv. OMI satellite estimates an annual mean value of 0.5 Dobson Units (DU) over the same location and period. However, during January to May relatively higher concentrations of $\rm{SO}_{2}$ are observed, mainly coming from power plants located in southern and eastern India as indicated by higher $\rm{SO_{2}/NO_{2}}$ ratios of greater than 0.5. In one instance, on June 20th, 2011, it is found that the OMI $\rm{SO}_{2}$ value was a factor of 13 higher than 2011 annual mean at Gadanki. Using the FLEXible PARTicle dispersion model (FLEXPART) and satellite data, it is found that the observed higher $\rm{SO}_{2}$ value on 20th June was due to intercontinental transport of $\rm{SO}_{2}$ from Nabro volcanic eruption. Using the FLEXPART model with ECLIPSE-v5 emission inventory, the observed seasonal variation of $\rm{SO}_{2}$ could be well reproduced; however, the mixing ratios are found to be overestimated. CAMS (Copernicus Atmosphere Monitoring Service) $\rm{SO}_{2}$ reanalysis values available through its implementation in the ECMWF Integrated Forecasting System are a factor of 7.8 higher than observations, possibly due to incorrect vertical profile used in the model.

    • Dates

  • Journal of Earth System Science | News

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