Treat your car with a high-grade polish and wax. If these snaps have been recently taken, i reckon you do it right away and repeat it at least twice every month. Its hot, will get humid also, and the harsh UV sun rays definitely affects the car's body, as well the dust. So, the skin has to be protected with a layer of wax.
As a word of advice, DO NOT place those aluminum reflector sheets from inside to protect the windscreen. They reflect sun rays and in turn burn in the windscreen.