BACKGROUND:
Growing cities in Africa are challenged by an increasing level of urban air pollution. Major cities in Africa do not regularly monitor known air pollutants such as fine particulate matter (PM2.5). Data on the effect of atmospheric temperature, relative humidity, precipitation, sunlight, wind speed, and wind direction on the concentration of fine particulate matter is limited in Ethiopia. This study examined the temporal effect of meteorological conditions on fine particulate matter concentration in Addis Ababa, Ethiopia.

METHODS:
Concentration of fine particulate matter was obtained from six years real-time measurements, April 2017 to March 2023. A Met One Beta Attenuation Monitor (BAM 1022) was used to collect fine particulate matter, ambient temperature, and relative humidity. Precipitation, wind speed, and sunlight data were obtained from the database of the Ethiopian Meteorology Agency. Descriptive trends and bootstrap generalized additive model analysis were applied to explore the relationship between fine particulate matter and meteorological variables using python notebook data analysis programming software using different packages.

RESULTS:
The effect of each meteorological variables was analyzed by controlling other variables. Meteorological variables and PM2.5 concentration varied by seasons. Categorized Ethiopian seasons were: “Bega” (dry season), “Belg” (small rainy season), and “Kiremt” (a big rainy season). From boot strap generalized additive model analysis, except relative humidity, the other meteorological variables 95% confidence interval got widen when their values got much higher.

CONCLUSIONS:
Fine particulate matter concentration was affected by relative humidity and precipitation both positively and negatively. Whereas, atmospheric temperature and wind speed majorly influenced fine particulate matter opposite. Sun hour duration effect on PM2.5 concentration was not conclusive