UC Irvine

The distribution of 222Rn over North America is simulated with a 3-d chemical tracer model (CTM) based on the meteorology of the GISS general circulation model (GCM). Model results are compared to surface observations from 5 sites in the United States. It is found that the 222Rn concentrations are regulated primary by dry convection. At night, the model underpredicts observations because it does not resolve the sharp 222Rn concentration gradient which forms near the surface. In daytime, the predicted and observed concentrations are usually in good agreement. Inspection of seasonal trends reveals, however, several significant discrepancies which are traced to anomalies in the GCM meteorology. -from Authors