Spatiotemporal Patterns of Nitrogen Dioxide and Aerosol Optical Depth: A Case Study of Lahore Division

Abstract

Abstract To understand the relationships among atmospheric trace gases, aerosol variability, and climate change, as well as to inform next-generation climate change and air quality models, a precise understanding of the intricate relationships between these variables and their sources is needed. Therefore, this study aimed to investigate the spatiotemporal variability of tropospheric nitrogen dioxide (NO2), aerosol optical depth (AOD), and particulate matter (PM2.5) retrieved from both satellite and ground-based data for the period of 2006 − 2023. Tropospheric NO2, obtained from the Ozone Monitoring Instrument (OMI)/Aura, has shown that the Lahore Division frequently has high annual mean NO2 concentrations (3.87 − 6.34 x1015 molecules.cm− 2). Seasonally, winters (4.86 − 8.09x1015 molecules.cm− 2) and autumns (4.18 − 6.85 x1015 molecules.cm− 2) are mainly affected by high NO2 levels during 2021 − 2023 due to intense biomass and crop residue burning activities. Satellite AOD from data Moderate Resolution Imaging Spectroradiometer (MODIS)/Tera indicated that summers and autumns have greater AOD levels, with a mean value of 0.59 − 0.69. More variability in AOD was recorded just after the COVID − 19 lockdown. The NO2 − AOD correlation plots (maps) indicated a positive correlation coefficient R = 0.13 (0.02 to 0.19) in 2023, attributed to more NOx emissions. High concentrations of PM2.5 were recorded specifically in December and January, with the highest average AQI 374.96 µgm− 3, occurring on December 2022, which are the consequences of smog formation and other respiratory disorders during the winter season.