Climatology and trends derived from columnar aerosol measurements in Cluj-Napoca, Romania.

It is well known that in the climate and air quality studies, the monitoring process of aerosols and their temporal evolution is very important as they generate a significant impact on meteorology, air quality, climate, and human and ecosystem health. In this study, we present an overview of aerosol optical and microphysical properties over Cluj-Napoca, Romania- based on more than 12 years of observations from a Cimel sun-photometer operating in the framework of AErosol RObotic NETwork (AERONET) and part of the Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). This site is located in the north-western part of Romania and contributes to AERONET with sun photometer observation since 2010. As the atmosphere in the region is characterized by a mixture of aerosols from multiple sources: urban/industrial (dominant) biomass burning, Saharan dust, etc., this study aims to present the aerosol trends and the temporal variation of their properties based on long-term observations. The analysis highlighted that the aerosol load over the area is characterized by high inter-annual and seasonal variation of AOD due to variation of local sources and long-range transport. The same variability was observed for the Ångström Exponent, suggesting the presence of aerosols of different sizes. The methods used in this study can be extended to other stations for identifying the long-term variability of aerosols.