Variability of aerosol optical depth with precipitable water vapour at different wavelengths in the recent decade

The association between aerosol optical depth (AOD) and precipitable water vapour (PWV) over the recent decade was studied using data from AERONET sites at USM-Penang, Malaysia, and the National University of Singapore. This study aimed to determine the fluctuation and quantitative relationship between the parameters at different wavelengths. The analysis focused on the variability of the parameters in response to changes in wavelengths and geographical patterns. The procedure employed descriptive statistics to calculate the mean and correlation of parameters. MATLAB 2024b was utilized for time series analysis to ensure quality resolution of plots, and the HYSPLIT model for trajectory simulation to identify pollution sources. A notable contrast in correlation was observed between AOD and PWV at both locations. A high correlation of 0.82 was observed at USM-Penang in 2020, while weak to moderate correlations of 0.36 and 0.42 were noted in Singapore. The backward trajectory simulations revealed the sources of aerosol pollution, and the pathways of the particles showed the source-receptor connection. The pollution primarily comes from dust particles, forest fires, and marine sources. The amplitudes of AOD at both stations at a common wavelength displayed similarities, indicating that similar events occurred at both stations, suggesting comparable sources of pollution. The events of some months displayed an increase in the AOD peak, which coincided with a notable decline in PWV. The positive linear relationship between the parameters was observed at 500 nm, as the identified wavelength that is most sensitive to their interactions, relevant for radiative forcing estimates.