Just want to chime in that you are doing a good job. Stitching together images like you are is not at all easy and you have done a good job. As for the ice and snow near a desert, you did mention something about winter in the South. Perhaps looking at the difference between hot deserts ( like the sahara) and cold deserts (like the Gobi) will give you confirmation on your choices. I, for one, do not know the answer.