Comparison of the Linke turbidity factor in Warsaw and in Belsk

Abstract The paper describes the relationship between direct solar radiation in a city (Warsaw) and in its broadly-defined suburban area (Belsk). The analysis covers the days of 1969-2003 when observations were carried out at both sites. The degree of extinction of solar radiation was expressed by means of Linke’s turbidity factor. Its mean annual value on the selected days of the period under consideration was 3.00± 0.10 in Warsaw and 2.87±0.11 in Belsk. Average atmospheric turbidity for individual seasons of the year as well as for the whole year was higher in Warsaw than in Belsk. In all cases, except for the summer, these differences were statistically significant. The period considered was divided into two sub-periods (1969-1993 and 1994-2003), in which atmospheric turbidity in Warsaw and in Belsk was compared by individual seasons and whole years. At both analysed sites Linke’s atmospheric turbidity factor decreased in 1994-2003, compared to the values for the earlier sub-period (1969-1993). However, the average annual atmospheric turbidity in Warsaw in comparison to Belsk remained the same, i.e. greater turbidity occurred in the city in both sub-periods.