How Do You Dew? My Introduction to Psychrometry

I'll start off by introdewcing myself to the STEEMIT community by briefly talking about everyone's favorite topic: Psychrometrics. Although this is my second post, I haven't really had a chance to provide anyone with some real mind altering, brain stimulating content that will leave you scrolling mindlessly on your phone for hours on end - so here it goes.

Psychrometrics
What the hell is Psychrometrics? Well, according to my good friend Merriam, Psychrometrics, or Psychrometry, is a term used to determine the thermal and physical properties of a gas/vapor mixture. I like to think of it more along the lines of what air is going to do when we heat, cool, remove, or add moisture to it. Believe it or not, anytime you hear your local Meteorologist throw the terms "dew point", "wet bulb", and "relative humidity" around as he points to a giant map of your state with daily temperatures for every city but the city you live in, he is referring to Psychrometry and has probably referenced the Psychrometric chart sometime in the past.

Behold - the chart of all charts, king of multiple axis, champion of confusion, the Psychrometric chart:

This magical chart provides a visual representation of almost any property of air you can think of. Although it can easily be mistaken for the exponential rise of STEEM's value over the course of the next 2 years (for your own free advertisement, feel free to contact me at 555-5555. SP accepted), this chart has nothing to do with STEEM or its growth over time.

So what is actually going on here?

To keep it simple, I'm only going to go over some of the main properties of air that everyone is familiar with.

Dry Bulb Temperature

This is what you and I know as plain old temperature. When it reaches 105 degrees and the soles on your shoes begin to melt, the dry bulb temperature is 105. It is represented as a horizontal axis with each temperature running vertically up and down, increasing to the right and decreasing to the left.

Relative Humidity

Why does everything have to be relative? Humidity follows suit. The relative humidity of air at any given point will be dependent on how much moisture is in the air, and what the air's dry bulb temperature is. We can see this represented on the Psych chart as exponential lines. Lower relative humidities are towards the bottom, higher relative humidities are towards the top. It's important to note that 95 degree air at 80% relative humidity will have about twice the moisture content than 75 degree air at 80% relative humidity. Twice! This explains why when you leave a cold bottle of water out on a hot humid day, it begins to condense almost instantly to the point you think you have a hole in your water bottle. Which brings me to my last point - that of the dew.

Dew Point

If you've made it this far, kudos. You are either on your way to becoming an air property master genius, or are so bored with the internet that you have nothing else better to do than to read on. So, dew point. What is it, and why do we care? Air's dew point, or saturation temperature, is the temperature at which air will condense. This occurs at 100% relative humidity, and pretty much is the reason it begins to rain on a cloudy day. This is represented on the psych chart on the left/top most exponential curve where dry bulb = wet bulb temperature (I'll get more into wet bulb temperature in a followup post). Remember that cold bottle of water on that hot muggy day? The reason water began to condense on the bottle is because it was cold enough on the bottle's surface to cool the air to it's saturation temperature. Only when air reaches its saturation temperature will moisture begin to be removed. This sole concept is the underlying principle behind every AC unit in your home. It allows the inside air to stay cool and dry, ultimately preventing mold growth.

Now that you've had a crash course on psychrometry, you can head into work today and boast to your coworkers how it won't rain because the relative humidity is only 50% and rain requires 100% relative humidity to form. If you are so bold to actually do this, make sure you check the weather before going in. Actually, with today's meteorologists, you may be better off guessing.

Please let me know if you enjoyed this post in the comments. Depending on the feedback, I may write a followup post going into the psych chart in more detail.

Thanks for reading!

P.S. I accidentally selected a terrible username for a sincere account. It's easy to be oblivious when your heart is set on rhyming with steemroller.