Insights into surface ozone variability in India (1980–2014) through CMIP6 model analysis

Abstract

This study investigates long-term (1980–2014) surface ozone (O₃) variability over India using Coupled Model Intercomparison Project Phase 6 (CMIP6) models, offering a comprehensive spatial assessment crucial for addressing air quality and climate change challenges. Model outputs were compared with Atmospheric Infrared Sounder (AIRS) derived surface O₃ to evaluate their reliability. Results reveal a persistent north-south gradient in surface O₃, with higher values over northern India, consistent with satellite data. Most models indicate a positive trend in surface O₃ across the country, while a negative trend is identified over parts of the central Indo-Gangetic Plain (IGP), a previously unreported phenomenon. Analysis of precursor gases shows significant positive trends over India, with the IGP emerging as a hotspot. Spatial correlations between surface O₃ and its precursors highlight regional heterogeneity and complex formation dynamics. VOC-limited regimes dominate across India, whereas NO/NO₂-limited chemistry prevails in the IGP, explaining the decreasing trend of surface O₃ despite rising NO/NO₂ emissions. Among the CMIP6 models, CESM2-WACCM-FV2 is identified as the most reliable for studying surface O₃ in India. The spatial distribution provided by CMIP6 models is particularly valuable in regions lacking long-term monitoring, where ground-based observations are limited to point-based measurements. This study underscores the critical role of CMIP6 models in understanding surface O₃ variability and highlights the utility of satellite-derived data as a complementary resource. The findings provide actionable insights for policy efforts to mitigate surface O₃ and its precursors, improving air quality and addressing climate challenges in India.