The impact of thermal inversion on the variability of PM10 concentration in winter seasons in Tricity

The paper concerns the effect of thermal inversions on PM10 concentrations in winter seasons between 2004–2005 and 2012–2013 in Tricity. Temperature inversions were analyzed using aerological measurements timed at 00 UTC and 12 UTC obtained from the aerological station in Łeba. The PM10 concentrations were obtained from five Agency of Regional Air Quality stations in the Gdańsk metropolitan area (ARMAAG). The effect of inversion conditions on the variability of daily PM10 concentrations was assessed using single and multiple linear regressions. The unfavorable conditions of PM10 dispersion in the lower troposphere were mostly determined by elevated inversions, which occurred with comparable frequency, nearly 90%, during the day as well as at night. Surface inversions were recorded at a frequency of 30% at night and only 10% during day-time. The strongest adverse effect on PM10 concentrations and their variability during the period of calendar winter was found to be related to the thickness of surface inversions at night. A significant yet substantially less adverse effect during both day and night, however, was found to be related to the thickness of the lowest layer of upper inversion. The high location of the base of upper inversion, primarily during the day-time, contributed to a decrease in PM10 concentration.