The simulation from NOAA's HYSPLIT model shows a continuous release of tracer particles at a rate of 100 per hour representing the Cesium-137 emitted from Fukushima Daiichi. Each change in particle color (red, orange, yellow, cyan, green, blue, violet, magenta) represents a decrease in radioactivity by a factor of 10. Radioactivity decreases only due to wet and dry deposition. Decay is not a factor for Cesium in this short duration simulation compared to its long-half life. The air concentration would be computed from the particle density so it is only partially related to the color scale. Emissions occurred from 12-31 March, but the particles are followed through the end of April using meteorological data from the 1-degree resolution NOAA global analyses. The maximum cesium emissions on March 15th are shown by the red color and represent a particle activity of 5E+12 Bq. Copyright Disclaimer Under Section 107 of the Copyright Act 1976 "Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use."

• published: 30 Aug 2013
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