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.


  1. If people are anything like me, they need to see the numbers themselves, so here is the site for Washington Department of Health air monitoring data, updated daily:
    and Radiation Network, now updated each minute:
    Please read the Message page linked on that latter site; natural background levels vary quite a bit.
    Think of how many Americans are looking at meteorological sites for the first time in their lives!

  2. Thanks for this information. It is reported that radiation levels above the reactor:

    4.13 Millisieverts/hr @ 1000 feet
    87.7 Millisieverts/hr @ 500 feet
    3 Millisieverts/hr on plant grounds (higher numbers have been reported elsewhere)

    This is at the source so I don't want to imply that the levels are this high elsewhere. However it does indicate that the reactor is producing significant amounts of radioactive particles that are falling somewhere. It doesn't just go away, and these particles will be transported by wind and water over the next several decades.

    Would a good thunderstorm carry particles high into the upper atmosphere?

  3. Thanks a bunch for the periodic updates. If things get really bad you might modify your predictions. So as the situation has deteriorated, the periodic updates have allowed me to feel comfortable in not relocating my kids. Also, your web site is very cool, starting to understand the weather in the Seattle area in this way seems interesting.

  4. NYTimes is now saying it has reached Sacramento

  5. Thanks for keeping us posted, Dr. Mass. There are so many Chicken Littles out there predicting the end of humanity from this very tragic situation that it's good to get information we can rely on and understand that there is no need to panic or even worry much about our own situation -- we can focus instead on ways we can help the Japanese recover and rebuild, as we did 65 years ago.

  6. Dr. Mass, thank you for attempting to quell the fear exhibited by those who really don't understand the situation. However, with even respectable media outlets like the New York Times printing the most sensationalistic headlines, you're swimming upstream against a current of ignorance.

  7. While I agree that there is a great potential for people to panic without reason, it is not correct to say that " Measurement by the U.S. assets during the past day have shown that significant radiation has not spread beyond the immediate facility."

    There is an exclusion zone of 20km around the facility where all people have been evacuated, and people from 20-30km are being told to stay inside. Some elderly have died from this decision, so it was not made lightly. The levels of radiation within 30km of the plant are harmful according to the Japanese government. That doesn't mean that you die right away, but there are reasons that we limit the number of chest X-Rays and CAT scans that patients are allowed to receive.

    I'm afraid that by over minimizing the risks we will actually cause panic. The Japanese government is not helping things by censoring their real-time radiation sites for the states around the reactor.

    According to the Wall Street Journal, trace amounts of Xenon-133 were detected in Washington State -- two days ago. Thanks for the warning, guys!

  8. Off note, I'm at Suncadia for the weekend. Its more like Snowcadia. Really heavy wet snow tonight and the wind is blowing hard from the east. Kinda different.

  9. unfortunately, the media is running with this one because it's a great headline and works on very basic fears. too bad it's taking attention away from other pressing matters (incl. the humanitarian crisis in Japan).

  10. There is no safe dose of radiation.

  11. Cliff: Thank you for your posts on the radiation trajectories from Japan. I hate to quibble, but wouldn't the the strong flow aloft can move it eastward rather than westward?

    Thank you again.

  12. Why do you post maps of where radiation would go if it isn't a risk? I don't think you should post any maps because it assumes that we should care about the air currents, which is not true.

  13. Has anyone posited the thought that BP (remember the Gulf Catastrophe?) might be a distant relative of Tokyo Electric, known as Tepco?

    Maybe they are not blood relatives per se, but it certainly seems as if they have a similar modus operandi when it comes to getting the truth 'out there'.



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