“…(Cigolini et al., 2013 ; Iwata et al., 2018 ; Mentes, 2018 ; Morales‐Simfors et al., 2020 ; Papachristodoulou et al., 2020 ). Radon time series may present: (a) multiple seasonality (hourly, semidiurnal, diurnal, yearly) (D'Alessandro et al., 2020 ; Siino et al., 2019 ; Steinitz & Piatibratova, 2010 ; Steinitz et al., 2007 ), (b) non‐stationarity behavior (Barbosa et al., 2007 ), (c) long‐term memory (Donner et al., 2015 ; Siino et al., 2019 , 2020 ), (d) synchronization with other factors (Siino et al., 2019 ), (e) intermittence (Crockett et al., 2010 ), and (f) not constant variance over the time (Barbosa et al., 2007 ). For these reasons, radon time series were characterized here using different time series approaches such as ARMA, ARIMA, SARIMAX, and ARFIMA methods (Siino et al., 2019 , 2020 ; Stránský & Thinová, 2017 ).…”