THey must have put a non shadow casting light from below to simulate the look of sunlight bouncing from the sand.
Maybe something similar to what was in Battlefield 2 on PC. Most might not have noticed it being in a war scene but terrain and water reflected it's color onto atleast helicopters underside and the result was great. Maybe for other objects to but never looked for it. I am sure a DICE dev once mentioned it at B3D.