Atmospheric Moisture

The term adiabatic not diabatic refers to such

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Unformatted text preview: olume of the air. The term adiabatic (‘not diabatic’) refers to such processes. If the same amount of energy is spread out over a greater volume, then the temperature will drop. And as temperature changes, so does the relative humidity. Adiabatic lapse rates describe the changes to the air temperature and relative humidity. Recall that air temperature decreases with altitude at about 6.5°C per 1000 meters and we call this the environmental lapse rate. (This rate of 6.5°C per 1000 meters is just an average–the actual rate can vary, as we’ll see later.) Here we are only talking about the air above being cooler than the air below. The cause of the ELR is the reduction in pressure with altitude. Adiabatic lapse rates are different in that the air itself is being moved to a new location. Imagine a balloon with air in it at ground level. If we take that balloon higher up, the air around it will have lower pressure, so the balloon will expand. The same amount of air will fill a bigger volume and the temperature inside the balloon will decrease. Now imagine a cubic meter of air at the surface. If we push it up, it expands because of lower pressure. Now, that same amount of air is filling up more than a cubic meter and the temperature decreases. If we take air and push it up, it will cool at about 10°C per 1000 meters. This is called the dry adiabatic lapse rate and it is different than the environmental lapse rate because the air itself is moving. As the air continues to rise and cool, the relative humidity steadily increases. Eventually, it ma...
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