Humidity

I just got off the phone with my friend Tressana, and told her to check out the latest observations in Rhode Island. She is sitting in her warm apartment looking out the window at 55 degree weather while I sit here freezing. I think God is answering menopausal women's prayers, because there is no way anyone could sweat in this cold. Anyways, Tressana noticed that the relative humidity is high in Rhode Island. She asked me how that could be true if the temperatures are so cold.

The answer is that relative humidity is a relative number. In other words, the higher the temperature, the more moisture that air can hold before the airmass is saturated. The opposite also holds true, in which lower temperatures are able to hold much less moisture. As a result, we could have a lot of moisture in the air, but a very high temperature would mean the air could hold a lot more moisture. Hence, the air is dry relative to the amount of water the air could actually hold. In this case, we would see a LOW relative humidity. In the case where the temperature is very cold (as in Rhode Island tonight), the air can only hold very little moisture. As it turns out, there is some moisture in the air, but only a small amount. The truth is that this cold atmosphere couldn't hold much more. In this case, we have a HIGH relative humidity because the air is already holding almost as much moisture as it possibly can.