Evaluation of surface ozone variability using ground-based observation and reanalysis dataset over the North-West Indo-Gangetic Plain of Indian region.

In recent times, Surface Ozone has become a widely studied constituent due to its emergence as a short-lived secondary pollutant and its damaging impacts on human health and crop production. Recent studies show increased surface ozone across different parts of the world including the Indian region. The modern reanalysis dataset provides meteorological parameters as well as atmospheric chemical compositions such as tropospheric ozone etc. In this study, we validated the spatial-temporal ozone variability using ground-based observation and reanalysis datasets such as over the North-west Indo Gangetic region. Reanalysis datasets are the Copernicus Atmospheric Monitoring Service reanalysis (CAMSRA) and NASA Modern-Era Retrospective analysis for Research and Application version 2 (MERRA2) which tells the spatial-temporal variability of surface ozone over the Northwest region of India. The result shows a lesser correlation over the study region. Through a validation process, it was determined that the CAMSRA compares fairly to ground-based observations with correlations (> 0.5)  over the Northwest region of India. This agreement has also been quantified in terms of range, Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). The CAMSRA captures seasonal variations regardless of location, according to a time series analysis. Spatial distribution of surface ozone shows higher concentration during pre-monsoon followed by post-monsoon. Over the northwest region, a notable rise is noticed during May over the Indo-Gangetic Plains in particular (IGP) of the Indian region. These seasonal differences are associated with solar radiation (SR), temperature, low-level circulation, and boundary layer height (BLH).In order to further examine the spatial and temporal variability of surface ozone, we have performed the Principal Component Analysis (PCA). PCA explains the relationship between dominant modes of spatial variability and their temporal evolution. Overall, the findings show that variations in the precursors or in the meteorological conditions have a considerable impact on the surface ozone concentrations across the northwest region of India.