Article did not spesifically mention air layers, temperature inversion and downward refracted sound waves. Curved waves in the images imply this condition, no?

Article did not spesifically mention air layers, temperature inversion and downward refracted sound waves. Curved waves in the images imply this condition, no? Tropospheric propagation in hamspeak. Changing the color of the landscape might also have a small effect on how the area heats up on sunlight and so how often unusual sound propagation develops. silly...