Seasonal Inter-comparison of Fine Particulate Matter (PM<sub>2.5</sub>) Over Addis Ababa, Ethiopia

The seasonality of meteorology significantly influences the distribution of atmospheric pollution that have harmful effect on human, environment and economy. Similarly, Ethiopia has erratic seasons, this can impact air pollution. Thus, this study focused on intercomparison of PurpleAir PM<sub>2.5 </sub>measurement at Addis Ababa city. The existing data processed by R software. Accordingly, the finding show that, during the rainy season, PM<sub>2.5 </sub>levels exhibit a consistent pattern with concentrations peaking in the early night and reaching their lowest at midday. At Black Lion Hospital (BLH), peak concentrations extend to midday due to <i>due to heavy traffic and cross-sectional jams to travel commercial areas</i>. In contrast, during the semi-rainy and dry seasons, PM<sub>2.5 </sub>levels peak in the early morning and decrease by midday. Hourly variations in PM<sub>2.5 </sub>concentrations could be influenced by factors such as temperature inversion, wind, relative humidity, and solar intensity, alongside transportation and industrial activities. Analysis reveals that a significant proportion of the seasonal hourly mean trend during the rainy season, vary in between 30 µg/m3 to 50 µg/m3 of the hourly data while 15 µg/m3 to 40 µg/m3 of data in both the semi-rainy and dry seasons also surpass these guidelines. Despite the general reduction in pollution levels due to rain, the rainy season still contributes to elevated PM<sub>2.5 </sub>concentrations, posing substantial risks to human health, the environment, and development activities. The monthly mean pattern further highlights a peak in PM<sub>2.5 </sub>concentrations during the rainy season, underscoring the complex dynamics of air quality. This finding emphasizes the need for targeted strategies to manage pollution throughout the year. The finding suggest that, expand air quality monitoring, and reduce traffic emissions, strengthen industrial regulations and increase public awareness. It may relevance for air quality management strategies for local and regional governments.