Mountain Weather

Over the summit

After the air mass passes over the mountain's summit, it begins to descend. Just as the air cooled and expanded as it moved up the mountain, it now begins to warm and compress as it descends to lower elevations. This process is called adiabatic warming.

In addition to becoming denser and warmer, the air's relative humidity decreases as it descends. Relative humidity is a percentage that compares the total water vapor in the air to the water vapor that the air could hold at a certain temperature.