Another dumb question about planes.

[rmissbrook]

In A Pirate Looks at 50, Jimmy uses the word ADIABATIC in a couple of different places as part of his descriptions when flying. For example:

"Now there is a sweetness in the air that signals altitude, adiabatic cooling, and fertile fields below."

I've looked the word up but I am just not grasping what it means or how it is used.

Any pilot out there that can explain it for me?

[Dutch Harbor PH]

Adiabatic process is a thermodynamics term in which there is no heat input to a process.....in simpler terms...adiabatic winds form from the heating of the land mass causing the air to heat (Or cool) and causing winds..... There are several examples...the Santa Anna winds of southern California are Adiabatic in nature..... the typical winds experienced in mountain canyons in both the morning and evening are often caused by heating and cooling in the valleys and mountain tops many many miles away....

This is different from Catabatic winds which is due to air cooling on a surface (Such as a glacier). The air becomes colder and subsequently denser and it essentially "falls" to lower elevations...the dense cold air falls so quickly that is causes a wind.....

[rmissbrook]

So in essence Jimmy is talking about a cool wind created by this process, is that right?

[Bicycle Bill]

In the novel "Dr. No", one of Ian Fleming's characters ('Quarrel') described similar winds in Jamaica:
the offshore Undertaker’s Wind that “blow de bad air out of de island night-times” and, in the morning, “de Doctor’s Wind that blow de sweet air in from de sea”.

-"BB"-

[flyboy55]

The phrase you quoted from A Pirate Looks at Fifty is describing part of Jimmy's flight from Georgetown on Grand Cayman Island to San Jose, Costa Rica.

I think Dutch Harbor PH hit all the right notes, but let me amplify a little . . .

"We break through the overcast at five thousand feet, and I get my first look at Costa Rica. We are flying in a long, beautiful valley surrounded by mountain peaks. Rays of sunlight shoot through breaks in the cloud cover like transporter beams from the Enterprise. A rainbow arcs in the sky to an isolated rain shower farther down the valley, and the vast Pacific peeks at us from the western horizon . . . The feel and smell of salt that accompanied us across the Caribbean is gone. Now there is a sweetness in the air that signals altitude, adiabatic cooling, and fertile fields below."

Jimmy is flying down into Costa Rica's Central Valley from east to west, heading for the Costa Rican capital of San Jose, which sits in the valley at an elevation of around 3500 feet above sea level. The westerly airflow from the Pacific moves up the Central Valley from the coast, and as the rising terrain forces the air higher, the pressure in the ascending air drops and it expands and cools, just like the air released from a car tire. This process of rising air undergoing cooling is, in meteorological terms, termed "adiabatic cooling". No doubt the air in the valley was also suffused with the aromas of agriculture, which he would also notice as he flew down the valley towards his destination.

The term "adiabatic" is a technical term from the study of thermodynamics (as Dutch Harbor PH said) which is used to describe an ideal process in which heat is neither added to nor subtracted from a mass undergoing changes in pressure, volume and temperature.

As a former seaplane pilot myself at an earlier stage in my career, I appreciate Jimmy's descriptions of flight because they convey many of the sights and sounds and smells so well.

I hope the technicalities of the explanations don't ruin your enjoyment of Jimmy's writing.

Now I want to be in Playa Tamarindo, sipping an Imperial and watching the surfers from a beach-side bar.

[rmissbrook]

Thank you both for your explanations. I think I have grasped the idea if not the complete theory. In any case, the technicaclities will not spoil my enjoyment of reading Jimmy's descriptions. It's my personal opinion that the descriptions he does of land, sea and air are his stongest points in his writing.

[JollyMon66]

I don't fly (unless someone else has the controls and a nice lady gives me a Coke) but I'm glad I opened this thread - I learned something new. Thanks guys

[rmissbrook]

This is the one you want.

Could somebody tell me how to pronouce this word.

[Dutch Harbor PH]

This is the one you want.

Could somebody tell me how to pronouce this word.

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[Bicycle Bill]

This is the one you want.

Could somebody tell me how to pronouce this word.

Go here, or go here and click on one of the little horn-shaped icons. Make sure your speakers are turned on.

-"BB"-

[rmissbrook]

This is the one you want.

Could somebody tell me how to pronouce this word.

Go here, or go here and click on one of the little horn-shaped icons. Make sure your speakers are turned on.

-"BB"-

That is cool. Thank you.