Fig. 1. Map of the high-latitude Southern Hemisphere showing the locations of the measuring sites discussed in the text. ent timescales, especially focusing on its distinct seasonal- ity. The central topic [...] for particle- bound 222Rn progenies), the characteristics of the bound- ary layer, in particular the depth of the mixing layer, co- determines the actually measured atmospheric222Rn activ- ity concentration [...] seasonality of222Rn activity ob- served from 1995 to 2011. Lines in the middle of the boxes repre- sent sample medians (mean: red line), lower and upper lines of the boxes are the 25th and 75th percentiles;