Last week the Japan Nuclear Safety Commission (NSC) began releasing plume forecasts. The plots show where radiation would go if an incident were to occur in the future, and also display the past forecasts covering the time period since the earthquake and tsunami on March 11. (More details in my prior post.) The SPEEDI (System for Prediction of Environmental Emergency Dose) model is used to predict the plume transport and dispersion, using 2 km resolution meteorological fields. (GPV mesoscale model run by the Japan Meteorological Agency.) The SPEEDI model, and how it functions in emergency situations, is described here and here. The simulations use a hypothetical low-level release (1 becquerel of radioactive iodine an hour) as the source term.
The past plume simulation description and maps can be found on the Japanese language site of NSC. A recent YouTube video animates the maps. Plume forecasts going forward are also posted on the English language NSC site. Cumulative (since March 12) dosage maps are likewise displayed:
The one above showing March 12 – April 24 dosage illustrates the role of coastal variability in shaping plume transport. The bands of higher dosage localized near the coast is typical of regions where air-sea interaction and coastal processes dominate.(Links are to prior posts on this topic.)
In related news, a high-ranking Japan government adviser took the unprecedented step of resigning over a host of grievances against the government’s handling of the radiation projections and impacts. Specifically, University of Tokyo Professor Toshiso Kosako asserts that the threshold radiation levels for evacuation are too high, and he criticized the government for delaying releasing forecast plume maps. A detailed report and analysis of the delays in releasing plume forecasts is found in this news story.
A joint task force of the government and Tokyo Electric Power Company is reportedly planning to release tomorrow more plume data and information used to make their forecasts….”5,000 undisclosed bits of data” explaining:
“But he [Hosono, secretary-general of the joint TEPCO/government task force] said the task force now believes that panic can be avoided if it offers proper explanations on the projections. He also promised to promptly release all such data in the future. ”
Meanwhile, the Meteorological Society of Japan has been trying to tamp down the release of independent plume projections by member specialists: story here. But members are questioning this strategy: “…Toshio Yamagata, another University of Tokyo professor who is a member of the society, said meteorologists have the responsibility to encourage the government to take the right course of action by announcing their forecasts ‘especially when a country is going through a critical situation.’ “