EGU22-537, updated on 26 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Evaluation of the MERRA-2 PM2.5 mass and its constituent chemical species concentrations over a COALESCE network site in Bhopal, India 

Sandeep Devaliya, Prem Maheshwarkar, Ankur Bhardwaj, Diksha Haswani, Deeksha Shukla, and Ramya Sunder Raman
Sandeep Devaliya et al.
  • Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh, Earth and Environmental Sciences, India (

Modern-Era Retrospective analysis for Research and Applications (MERRA-2) generated  PM2.5  concentrations are widely used to understand the spatio-temporal variability of PM2.5 across the globe. Only PM2.5 data from black carbon, organic carbon, sulphate, sea-salt, and dust are provided by MERRA-2. However, previous studies validated MERRA-2 PM2.5 concentrations obtained by combining all five species data against in-situ ​total PM2.5 concentrations. To the best of our knowledge, this is the first study over India to validate MERRA-2 species wise PM2.5 concentrations utilizing in-situ surface measurements made over a site at Bhopal (23.285° N, 22.277° E). Bhopal is one of the eleven COALESCE (Carbonaceous Aerosol Emissions, Source Apportionment and Climate Impacts) network regionally representative sites in India. 24 hour integrated filter-based samples (N = 165) collected during 2019, using the MetOne SASS® speciation sampler were used to measure mass and aerosol species concentrations by a variety of analyses. Our results show that the MERRA-2 well captures the aerosol species data at Bhopal. However, MERRA-2 underestimated the annual mean in-situ concentration of organic carbon, black carbon, and sulphate by 1.9 µg m -3 (~22 %), 1.3 µg m -3 (~47 %) and 0.9 µg m -3 (~11 %), respectively and overestimated the sea salt and dust components by 0.75 µg m -3 (~95 %) and 8.5 µg m -3 (~153 %), respectively.  It is pertinent to note that dust from surface aerosol chemical species measurements was re-constructed using elemental aluminium, silicon, potassium, calcium, titanium, manganese concentrations. Further, the annual mean MERRA-2 PM2.5 mass (reconstructed from its constituent species) underestimated the average in-situ PM2.5 mass by 13.55 µg m -3 (~26.16 %). This underestimation is likely due to aerosol nitrate not being included in the MERRA2 PM2.5 mass and uncertainties in aerosol species concentrations resulting from limitations in the chemical transport model set-up and emissions inventories. This study discusses the possible causes of disagreements between in-situ measurements and MERRA2 products, in addition to estimating the effect of including nitrate in the MERRA2 PM2.5 mass reconstruction.

How to cite: Devaliya, S., Maheshwarkar, P., Bhardwaj, A., Haswani, D., Shukla, D., and Sunder Raman, R.: Evaluation of the MERRA-2 PM2.5 mass and its constituent chemical species concentrations over a COALESCE network site in Bhopal, India , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-537,, 2022.

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