An investigation of nighttime variability in air quality of Naples (Italy) using wavelet coherence

There exists a huge gape in the accurate assessment of nighttime air quality of metropolitan cities. So, in this article, we used Aerosol Robotic Network (AERONET), and Atmospheric Infrared Sounder (AIRS) data from May 16, 2016, to April 30, 2023, to access the nighttime variability of air quality over Naples (Italy). Maximum value (0.26) of aerosol optical depth (AOD) observed during June is because of relative increase in temperature that causes the scattering of pollutants. High value (1.47) of Angstrom exponent (AE) during January indicates the dominance of fine mode particles. Maximum value of precipitable water (3.0) is observed in August. Furthermore, the classification of nighttime aerosols associated with AOD and AE reveals the dominance (73.23%) of urban/industrial aerosols. In addition, nighttime variability of CH4, CO, and O3 are observed high during October, March, and May, respectively. The 72-h air mass backward trajectories plotted on April 23, 2019, at 1500 m, 1000 m, and 500 m indicate the transportation of pollutants from the western northeastern regions of Africa which indicates the transportation of dust particles transported from the Sahara Desert. Naples has the worst air quality in the last couple of years due to rapid urbanization, biomass burning, and fuel combustion. Wavelet coherence (WTC) analysis reveals that AOD has a significant association with temperature, relative humidity, CH4, CO, and O3 in both the long run and short run. A noticeable region of co-movement is observed in the frequency band of almost 8-16 months.