资源环境科技发展态势分析平台

The present study investigates the variability of surface ozone (O₃) and its precursors (NO_X, CO) at different time scales for 3-year period (2016–2018) using continuous ground-based observations from 25 stations located within the Indian Capital Delhi (28.83°N, 77.81°E). Observations indicate that there is a clear spatial heterogeneity and seasonality in surface O₃ where larger magnitudes (40–60 ppb) are observed during pre-monsoon season, and 10–20 ppb in other seasons. The frequency distribution exhibits that 70% of O₃ concentrations are in the range of 10–50 ppb, while 10% lies larger than 50 ppb and the remaining 20% is mostly confined within 50–80 ppb. Further, a detailed analysis on the diurnal cycle of surface ozone and its precursors performed over IMD Lodhi Road location. Analysis of diurnal cycles show maximum and minimum O₃ concentrations during the morning and nocturnal hours, with a rate of change 4.8 ± 1.96 and −7.4 ± 0.95 ppb h⁻¹, respectively. On the other hand, the rate of change of O₃ during high ozone days (HOD) is found to be 5.61 ± 2.6 ppb h⁻¹ in the morning and −8.04 ± 3.4 ppb h⁻¹ in the evening hours, respectively. It is also noted that the increase in precursor concentrations and associated titration effects appear to play a considerable role in surface O₃ depletion during the evening hours. It is also noted from the composites of HODs that there is an enhanced diurnal O₃ (80–90 ppb) concentrations compared to 3-year average (40–60 ppb). Further evaluation of associations between surface O₃ changes and meteorological parameters shows that observed surface O₃ (Copernicus Atmosphere Monitoring Service-CAMS modelled O₃) show positive correlations of R² = 0.3 (0.42) with temperature, of R² = 0.47 (0.60) with Solar Radiation (SR), of R² = 0.39 (0.59) with boundary layer height. An overall assessment shows CAMS modelled three year daily averaged ozone values are generally in good agreement with surface ozone observations with a CC value of about R² = 0.65.