Friday, March 18, 2011
Latest On Japanese Radiation
There is still a huge amount of interest and publicity over the radiation emitted by the damaged Japanese reactors in Sendai and the potential for radiation spread to the U.S.
As before, there is little if any risk of significant landfall of radioactive materials on the West Coast due to the mixing, settling, decay, and rainout of radioactive materials...even if the trajectories were straight into us.
Consider the issues. First, you need a large source injected into the atmosphere. THIS HAS NOT HAPPENED YET! Measurement by the U.S. assets during the past day have shown that significant radiation has not spread beyond the immediate facility. Then you have to effectively loft the material higher into the atmosphere, where the strong flow aloft can move it westward. THEN, you got to bring it back down to the ground. Mixing will continuously reduce the concentrations as the material spread across he Pacific with plenty of opportunity for precipitation to reduce the concentrations farther.
Here are the latest trajectories from the hysplit model (see graphic). The lowest level starting trajectory heads to the Bering Sea due a strong storm in the western Pacific. And the stuff gets lofted away from the surface. The middle trajectory (starting at 4500 meters) heads to Calfornia, but takes a week to get there...plenty of time for concentrations to dwindle. The highest level moves faster but the stuff stays high while it crosses the West Coast.
Anyway, although the trajectories will change day to day as the flow changes, there is little to be worried about for us.
Posted by Cliff Mass at 11:50 AM