Radiation in Japan after the Fukushima Incident
After the nuclear disaster in Fukushima Daiichi, I collected the available measurement data from official sources with a crawler. Most official websites only presented the latest measurement value without any history, or PDF reports with a history of some measurements (e.g. one day). However, it is much easier to get a grasp of the data if you are provided with a simple chart.
I was not able to find out why the measurement stations "Fukushima" does have one peak every day, but apart from that the data is quite nice. For example, you can see a rise of radiation on all measurement stations shortly after the begin of the chart. I guess that this was caused by the white smoke which emerged from reactor block 3 on March, 21. Since there is no rise in Niigata, I assume there was wind into the direction of Tokyo. Most of the time the wind blew to the east, but a few days it switched to south.
If you compare the charts closely, you can see that the rise at Ibaraki (prefecture of Fukushima) starts a bit earlier than the rise at Kanagawa and Tokyo. This also indicates that the reason for this rise at many stations was an event at nuclear power plant Fukushima.
You can disable individual lines in the chart by clicking on them. The diagram will autoscale after such changes, so you can disable Fukushima to see the other stations better. I deliberately did not choose a logarithmic scale, because of this functionality.