I see on weather apps that for a given temperature and humidity, the dew point is x. I looked into it and I learned that the the dew point is the temperature that air must be cooled to in order for dew to form. I also saw that the formula for the dew point (Td) is Td = T-((100-RH)/5) there T is the observed temperature and RH is the relative humidity.
If this formula is accurate, then in my mind, it means that Td would be recalculated whenever T drops, thus making the dew point impossible to reach.
For example: T = 26 and RH = 60% then Td = 18. If the temperature then drops to 18, we have T = 18 and RH = 60%, so Td = 10, and so on, meaning that the dew point for a given moment is never reached…
Where am I going wrong?
In: 3
Try stirring some salt into a glass of water. The salt will completely dissolve, up to a point. But, if you hear the water up, you can dissolve more salt into the water. Then, when the water cools down, some of the dissolved salt will “fall out” of the mixture and fall to the bottom of the glass.
Now, the water is the air and moisture is the salt. Warmer air can hold more water. So (I’m using very round numbers here), at 80 degrees the air is holding 70% of the water it can hold, but at 60 degrees it’s holding 99% of the water it can hold. Below 60, some of the water in the air has to come out, so you get dew.
More info: this is how global warming creates more snow in the winter. Air over the ocean that’s just a few degrees hotter can hold exponentially more moisture. When that moisture travels East and hits air below freezing, all that moisture has to come out, hence, more snow even though the average climate is warmer.
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