Does humidity change with altitude

Answer 1

Humidity is not directly affected by altitude. However, humidity is affected by air density and temperature. At high altitudes, the air is usually much thinner (lower pressure) and often the temperature is lower. At low temperatures and low pressures, air cannot hold as much water. Thus the humidity is necessarily low when the air is thin and cold. At high temperatures and high pressures, air can hold much more water. However, air that is hot and thick doesn't necessarily have a high humidity; but it does have the potential to hold more water.

Answer 2

Indirectly, in that at high altitude, and in space for that matter, its very cold, well below the freezing point of water, and there isn't much water. To have water vapour you need a source of water liquid and thermal energy to evaporated. There are lots of humidity myths. The amount of water vapour is a function ONLY of temperature, given there is water present, it has nothing to do with other gases present like air. So at high altitude, very little. Relative humidity is a measure of the amount you have vs the amount possible. So it is quite allowed to have very high rel humidity's at low temps, even though there is very very little moisture present (close to freezing point). The actual amount of water vapour (mass per unit volume) occurs irrespective of other gases present like air and is only slightly affected by air (the other gases) temp as its the temp of the liquid phase that has by far the most influence and drives evapouration.

Answer 3

Higher altitudes tend to have higher relative humidity. That is because relative humidity is determined by the amount of water in the air divided by the maximum amount the air at the current temperature can hold. Therefore the relative humidity is only affected by the temperature. The link to altitude is that higher altitudes tend to have lower temperatures, and the air at lower temperatures can hold less water. Therefore the denominator in the relative humidity is less making the relative humidity higher.