Why is it cooler and more moist in the mountains than in the lowlands?

Answer 1

According to the Ideal Gas Law, if air pressure decreases, so does the temperature. Air pressure decreases with altitude and therefore the temperature of the air decreases with altitude. Orographic lifting sends air up the side of a mountain. The rate at which this happens is called the dry adiabatic lapse rate (DALR), or, if the air is saturated, then it is the moist adiabatic lapse rate (MALR). As air cools with height, it comes closer to its lifted condensation level (LCL) and its humidity increases. This increased humidity makes it feel more moist at that temperature because the moisture is more concentrated, even though it really isn't because the air has the same moisture content as it did at ground level.

Answer 2

Good question.

The answer is simple. Adiabatic cooling.

As air reaches the base of a mountain, it is normally dry. As it rises, the temperature or the air cools, at the dry adiabatic lapse rate, until the temperature drops to meet the dew point. This produces 100 percent relative humidity. If there is dust in the air, fog and or rain form. The dry adiabatic lapse rate is 10 degrees per 1000 meters. As the air continues to go up, it now cools at the moist adiabatic lapse rate of 6 degrees per 1000m.

As the air goes up ocver the mountain, it dumps most of its moisture out, and becomes dry on the leeward side of the mountain. The cooler air, now descends on the leeward side and warms using the dry adiabatic lapse rate again.

As it descends, the temperature goes up and the dew point remains steady. Making this air very dry.

So...for instance, lets say you have a 3000m hill to ascend. if your temperature is 30degrees celsius at the base, and your dewpoint is 20 degrees celsius. at 1000 meters, the air will have cooled using the dry adiabatic lapse rate to become 20 degrees and the dew point remains at 20 degrees. This is where condensation begins. Fog/rain etc...begin here.

Now the air is moist and the other lapse rate takes over...at 2000m the temp and dew point are 14/14. At the top (3000m) they are both 8/8. Now the cool 8 degree air descends and warms. It is almost instantly warming at the dry adiabatic lapse rate....

So at 2000m the temp will be 18 and the dew point 8. 1000m the temp is 28 and the dew point is 8. At the bottom you have practically desert conditions with the temperature at 38 and the dew point at 8.

For an example of this, look at nearly ANY north to south oriented mountain range. Western Washington State in the USA is a good one. Western part of the state is lush and green, the east is dry and arid.

Answer 3

You are assuming that all effects are the same. Simply, the higher you go in elevation, the lower the temp is. When the temperature drops, the relative humidity goes up, so it seems more humid. It is not always the case, but in general, this is the answer.

Answer 4

It isn't necessarily. The down wind side of mountains tends to be dry. It is usually cooler at higher altitudes and if it is moister, it tends to be even cooler because of the effects of evaporation.

Answer 5

because the mountains are higher elevation than the lowlands and receive a lot of precepation because they are higher elevated.