This paper focuses on the the influence of meteorological conditions on the vertical variability of the optical properties of aerosols. The quantities analysed included the aerosol scattering coefficient (ASC), the scattering Angstrom exponent (SAE) and the effective radius of particles Reff depending on the degree of cloudiness, wind speed, air temperature gradient and the direction of air mass inflow. The measurements were collected from sensors placed on five levels, on the walls of the Palace of Culture and Science in Warsaw.
Measurements in the urban environment can provide thought-provoking results and conclusions, but it should be remembered that in uncontrolled conditions they are burdened with significant errors, related to, among others, local heating of the surface or presence of turbulence generated by urban built-up area.
Particular attention was paid to seasonal changes. Higher average ASC values were observed in winter, and an increase in average particle size values was also found. However, despite higher concentrations of pollutants in winter, it was observed that during favourable conditions (intense mixing), optical quantities indicated a significant improvement in air quality. In the summer season, a smaller effect of meteorological changes on optical quantities was observed, which could be related to the effective mixing of air masses, characteristic of this period.
The greatest variability of optical parameters was observed at the lowest altitudes, where emission sources are concentrated and where the atmospheric boundary layer is most sensitive to local meteorological conditions. The most significant effect on vertical differences in the aerosol light scattering coefficient was exerted by a positive temperature gradient. Changes in the Angstrom exponent and effective radius were small, but generally smaller average particle sizes were observed at higher levels. In conditions of increasing convection and boundary layer height, the vertical differentiation of optical parameters values were less noticeable.