Weather control in radon flux time series from Schleswig-Holstein, Germany

Indoor radon exposure is a serious hazard to human health. The radon concentration in surface air varies spatially as a result of the uranium content in the underlying rocks. However, there exist also considerable knowledge gaps about temporal variations. Here we document the high temporal variability of radon flux from exhalation in high-resolution (hourly) time series from a site near Kleinneudorf, Schleswig-Holstein, Germany. By means of advanced techniques of statistical time series analysis, we show a close association between radon and meteorological variables (air temperature and air pressure). We identify four principal weather regimes that lead to different radon exhalation modes. For each of the modes, we construct a statistical linear model for radon prediction via the meteorological variables and their derivatives or time-lagged versions. The model explains between 53 and 86 percent of the variance. Many model deviations consist in excessively high measured radon values and hint at nonlinear effects. Other model deviations hint at non-meteorological forcing.