Radio interference

The two images show radio frequency interference (RFI) at northern latitudes in February 2011 and February 2012. Several radars are observed (the red ‘dots’, visible because they exceed the natural variability for brightness temperature measurements over land) over Northern Canada and at the southern tip of Greenland. The authorities from Canada and Greenland were informed, and requested to take actions. Canada started to refurbish their equipment in autumn 2011, while Greenland switched off their transmitters in March 2011. At least 13 RFIs have been switched off in the northern latitudes. However, the few remaining RFIs can contaminate areas 3000 km away from the original source, especially in passes ascending towards North America.