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Elevation and Temperature Change in Dry Air
Energy from the sun is absorbed by the Earth as heat and radiated back into the atmosphere. As this warm air rises to higher altitudes, it decreases in pressure and expands. Expansion causes the air temperature to drop, which is known as adiabatic cooling. Temperature drops with elevation at a rate of 5.5 degrees F for every 1,000 feet when the rising air is dry. This is known as the dry adiabatic lapse rate.
Elevation and Humidity
Rising warm air often transports evaporated water, in the form of water vapor. At a certain altitude the air will cool to the dew point, the temperature at which air becomes saturated and water vapor begins to condense into water droplets. This is the altitude at which clouds begin to form, and is called the lifting condensation level.
Elevation and Temperature Change in Moist Air
Once condensation begins and clouds begin to form, rising air cools more slowly than it did previously, at a rate of about 5 degrees F per 1,000 feet. This is known as the saturated adiabatic lapse rate.
Precipitation
Cooler air can hold less moisture than warmer air. When water droplets in clouds (or ice crystals when the temperature falls below 32 degrees F) become heavy enough, they collect as raindrops or snowflakes and begin to fall back to Earth as rain or snow. Snow may also melt into raindrops as it falls through warming air.
Orographic Lifting
When air is pushed against windward mountains (mountains that face into the wind), cloud formation and precipitation is augmented on the mountain slopes as the air rises. But as the air passes the tops of the mountains and begins to descend their leeward sides, temperatures reverse and begin to rise, which is known as adiabatic heating. Condensation ceases and clouds lose their ability to produce precipitation. The leeward side of mountains thus receives much less rain than the windward side and is known as the rain shadow.
Slope and Aspect
Steep slopes facing into the sun are warmer than shallower slopes facing away from the sun, so there is micro-variation in temperature and precipitation that occurs with small differences in topography. The angle of the Earth's axis varies the angle at which the energy from the sun contacts Earth; thereby influencing how many hours of daylight at different latitudes and thus varying conditions from one part of the year to another.