The reduction of rainfall to the lee side of a mountain barrier, which results in relatively dry surface conditions, e.g. in the mountains of the south-western USA, where the wetter western slopes of the Coast Range and Sierra Nevada contrast with the desert areas of Nevada and eastern California on the lee side of the mountains. Moist air rising on the windward side cools at the saturated adiabatic lapse rate, its moisture condensing to produce precipitation. Air subsiding on the lee side is dry and warms at the dry adiabatic lapse rate, which further reduces its relative humidity.