You only need a temperature difference of 0.4 to 0.5 degrees C to create a heat haze effect just above a road surface and whilst its commonly seen during summers, you can see it when the road surface is just above freezing as it requires a lot of solar energy to create that wibbly wobbly effect.
It will be interesting to see how BAE compensate for that wibbly wobbly mirage, are they giving pilots 15 pints of wife beater to compensate for this effect?
The HAARP antennas also heat up the atmosphere, but these heat the atmosphere 200km+ which have the effect of expanding the atmosphere into the path of satellites which can then make them fall to earth. Radio telescopes can pick up the electron density change as explain around the 50min mark in this program. http://www.bbc.co.uk/programmes/b01d99vb