Sierra Nevada, Death Valley and the rain shadow effect
By Judy Lehmberg, CBS News
The beautiful Sierra Nevada’s name translates very literally from Spanish as “mountain snowfall,” meaning snow-covered mountains. The reason why the peaks are snow-covered and why hot, dry Death Valley is east of the Sierra Nevada range is the same: They are both the result of the rain shadow effect.
To understand how this terrain-induced meteorological effect causes precipitation to occur in one place and dry, hot deserts in another, a little knowledge of relative humidity is needed.
The Earth’s atmosphere contains water molecules in the gaseous state, and these create pressure; the more water molecules, the greater the pressure. The higher the temperature, the greater maximum amount of water the air can hold, and therefore higher vapor pressure.
