Time series of observed (dots) and two-model ensemble mean (lines) atmospheric 137Cs concentrations (Bq m−3) from 14 to 24 March a in the Tohoku region at sites J, B, C, and E (see Fig. 15) and b in the Kantou region at sites 9, 12, 15, K1, K2, and K3 (see Fig. 15)