Fun Weather Facts: Warm Air Rises and Cold Air Sinks---Doesn’t it? Part I

When my wife Helen purchased Young’s Enumclaw Flowers and Gifts we were excited to be in a “turn of the century building”.  We loved the old-fashioned high ceilings. However, in winter, as we sat shivering waiting for customers, I wondered where all the heat was going.  I could hear the furnace running its little heart out in the back, but seemingly to no avail.

One day Helen asked me to retrieve some flower thing (don’t ask me) from the loft.  I climbed up and “Eureka”!  I had found the Sierra Desert, and it wasn’t in Africa. It was in the top several feet of our flower shop.  I sent off a quick e-mail to National Geographic to correct their mistake.   

Should I have been surprised?  Probably not. Everyone knows that warm air rises and cold air sinks, doesn’t it?  Well it normally does, but a secret that scientists keep from the public (this keeps the mystic intact surrounding scientists) is that in the atmosphere that doesn’t always happen. 

Take today, for example.  It is going to get into the 70s this afternoon, but it will be much colder at 16,000 feet above us.  In fact, it will be cold enough to freeze water!  So why doesn’t that cold air plunge to the surface and freeze us and all the nice warm air at the surface go up, like in our flower shop?

My son-in-law Mark (also a scientist working on wind power) tells me that this mystery is one of the hardest concepts in the atmosphere to understand.  But, I think that you already know everything from just living your daily lives to understand it.  Today I’ll lay the groundwork from your everyday experience to be able to finish the explanation in Part II.

Open your mouth and puff out some air onto your hand.  It’s warm, isn’t it?  This is no surprise since your temperature is close to 100 degrees, and the air that comes out of our mouth is naturally close to that temperature.  Now, purse your lips (squeeze them tightly together) and force air to blow on your hand.  The air is no longer warm, but feels cold.  Why is that?

Almost everyone has blown up a bike tire at one time or another.  When you’re done the tire is hot.  Why is that?  You have stumbled onto a scientific truth without knowing it.  When air is forced out of your pursed lips it expands.  When air is forced into the bike tire it is compressed.

Aha! Expanding air cools and compressing air heats! And as a bonus we know from everyday experience that air can be compressed or can expand.  Every (still living) mechanic knows to bleed (get rid of the air in brake lines) so that the brakes will work instead of simply compressing the air in the brake lines.

Now you are ready for “Fun Weather Facts: Warm Air Rises and Cold Air Sinks--Doesn’t it? Part II”