Modelling the long-range transport of ²²²Rn to subantarctic and antarctic areas

Abstract

The long-range advection of ²²²Rn over the Indian Ocean has been studied using a three-dimensional coarse-grid (8° × 10°) transport model of the global troposphere based on the meteorological fields of the GWE period (December 1978—November 1979). A uniform continental source of ²²²Rn and a weak, wind-speed dependent oceanic source of ²²²Rn has been prescribed in the simulations. Model predictions are compared to observations of the ²²²Rn concentration at three Indian Ocean islands and one station located at the Antarctic coast. The advection of continental ²²²Rn to these observing sites, each being several thousand kilometers away from major landmasses, requires several days and provides a unique opportunity for the validation of the transport model on time scales ranging from a few days to the seasonal cycle induced by seasonally changing transport patterns. The model is able to simulate several features of the time series observed in the Indian Ocean; however, it fails to correctly predict the seasonal cycle and the short-term concentration variations at the Antarctic coast.