UC Irvine

Radon 222 is an inert gas whose loss is due only to radioactive decay with a half life of 3. 83 days (5. 51-day 'exponential' lifetime). It is a very useful tracer of continental air because only ground level continental sources are significant. Previously published measured **2**2**2Rn profiles are analyzed here by averaging for the summer, winter, and spring-fall seasons. The analysis shows that in summer, about 55% of the **2**2**2Rn is transported above the planetary boundary layer, considerably more than during the other seasons. Similarly, in summer, about 20% rises to over 5. 5 km (500 mbar). The average profiles have been used to derive vertical eddy diffusion coefficients with maximum values of 5-7 multiplied by 10**5 cm**2 s** minus **1 in the midtroposphere and 8 multiplied by 10**3 to 5 multiplied by 10**4 cm**2 s** minus **1 near the surface.