NASA flies three large, multi-sensor satellites that monitor Earth's land, atmosphere, oceans and energy balance. The relationship between snow, clouds, and sunlight is a good example. In November, the chill and snow of a Northern Hemisphere winter is on the horizon. Snow covers the far north and high elevations, as shown in the map of percent snow cover in November 2009. White areas show where snow covers the ground completely, while blue points to areas with partial snow cover. Image Credit: NASA. Buy this as a superb wall poster, a canvas print or a framed print.