Here are month and year average charts of local background radiation levels from November 2007 to 2016 for Caloundra, located in the Southern Hemisphere on the East coast of Australia. Historically, the recorded pre-Fukushima local background here was low, averaging around ~0.1 uSv/hr. This data has allowed the tracking of changes in local background levels, plus the detection of radioactive clouds passing through.
This community radiation monitoring station was created in response to detections of multiple radioactive clouds passing through. Click these links to find detailed documented information on these significant detections in Australia, and New Zealand.
Here are two examples.
Australian Radioactive Cloud Detection
New Zealand Radioactive Cloud Detection
This short animation of Northern, and Southern Hemisphere air circulation, shows why we can get detections so far south. Wind direction can significantly influence the background levels here. Observations show that when the Southern Ocean air reaches this location, we see lower background averages. More Southern Ocean air reaches this location in the cooler months and winter, hence the significant seasonal variation in background levels.
The long term data collected here before and after Fukushima, has become a valuable resource. It has enabled the tracking of changes in background levels since the nuclear catastrophe. After Fukushima, the recorded data showed an increase in background levels. The most recent data suggests this increase has stabilized, and the amount of airborne contamination reaching this location has decreased.
The GammaScout Alert Geiger Counter model pictured here, was used to log background level data once a week prior to the Fukushima Nuclear Catastrophe. After the Fukushima event it was set up to log background levels every minute, so the data collected after Fukushima is statistically much more accurate. The dotted line through the monthly charts is the year average local background, and through the year chart, it represents the overall trend since Fukushima.
What does the chart colour code mean?
Click on the charts to see larger version.
The data logging of the older local GammaScout Alert Geiger counter stopped on March 14th 2011 for some reason. High demand at the time meant that the newly ordered GammaScout did not arrive until late November 2011. So there is a gap in the data collection from the middle of March 2011 to December 2011. The 2011 year average in this chart, represents the average of the collected data, up until March 2011.