Air Temperature?

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NobleStone
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Air Temperature?

Post by NobleStone » Wed Nov 03, 2010 8:55 pm

i.e he impact on ball flight & carry of colder/warmer air etc

dtutelman
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Re: Air Temperature?

Post by dtutelman » Wed Nov 03, 2010 10:37 pm

NobleStone wrote:i.e he impact on ball flight & carry of colder/warmer air etc
Duly noted!

I don't know if this will make it into the next release, but we have put it on the want list. In the meantime, here's something you can do to compute it yourself.

Note that we have a few different effects here in practice:
  • The temperature of the ball.
  • The temperature of the air.
  • The humidity of the air, which often varies with the temperature.
  • The effect of cold weather on the golfer. (Stiffer muscles, more clothing, etc.)
The humidity is a very minor effect; higher humidity gives slightly longer flight.

The golfer is such an intangible that I wouldn't want to begin to add it into the program. Unfortunately, it is arguably the biggest effect. Too bad.

The combination of ball and air temperature is probably what we want to focus on computationally. A bit of research shows that the difference between 10C and 30C (equivalent to 50F and 86F) is about 5-6 yards with each club in the bag. That's a much bigger percentage difference with a short iron than with a driver.

Hope this helps,
DaveT

fschmidberger
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Post by fschmidberger » Sun Nov 07, 2010 8:17 pm

Hi Dave,

at least we have the air temperature in the program already.

Sorry, I am very busy at the moment.

Cheers
Frank

dtutelman
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Post by dtutelman » Wed Nov 10, 2010 8:53 pm

fschmidberger wrote:at least we have the air temperature in the program already.
Sorry, forgot about that. Not on my own computer this week, and my host doesn't have TrajectoWare.

(My usual Wednesday foursome was invited for the week to Reynolds Plantation. Fabulous golf courses here. Just got back from Great Waters, a Nicklaus course. Wonderful!)

Cheers!
DaveT

dinosaw
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Post by dinosaw » Tue Mar 27, 2012 8:59 pm

Hi Dave,

I was just wondering "How does higher humidity make for a longer ball flight?"
I would have thought higher humidity equals more water vapour in the air for the ball to penetrate resulting in a shorter ball flight?

Anyway I'd be very interested if you or anyone had some data on this.

Regards,
David

dtutelman
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Post by dtutelman » Tue Mar 27, 2012 9:56 pm

dinosaw wrote:Hi Dave,I was just wondering "How does higher humidity make for a longer ball flight?"
I would have thought higher humidity equals more water vapour in the air for the ball to penetrate resulting in a shorter ball flight?
The explanation is pretty simple; the hardest part is on the level of high school chemistry.

First, two facts that you need to buy into:

(1) If the air is denser (that is, heavier per unit of volume), the ball will not travel as far. This is well known, and I'm sure you bought into it when you asked the question. (BTW, that is not completely true. If you continue to reduce the density far enough, you will start to lose distance. This would occur at about 64% of the density at sea level, corresponding to maybe 10,000 feet altitude. But we're ignoring that here, and sticking to playing golf at altitudes where lower density gives more distance.)

(2) The "universal gas law" (pV=nRT for those of you who want the equation) says that, at the same pressure and temperature, a volume of gas holds the same number of molecules no matter what that gas is.

So the only issue is: Does adding water vapor to air make it heavier or lighter? Intuitively, everybody says, "Heavier, of course!" Bzzzzt! Wrong answer.

Let's start by looking at the average molecular weight of air. Dry air is about 20% oxygen (O2), 80% nitrogen (N2), and not enough of most other stuff to have much effect on molecular weight.

Molecular weight of O2 is 2*16=32
Molecular weight of N2 is 2*14=28
Avg molecular weight of air is: .20*32 + .80*28 = 28.8

Humidity is water vapor, which is a gas. It is not water droplets or a fine mist, it is a gas. So it obeys the gas laws. That means that if we add water vapor to air but don't change the pressure or temperature, the density of the wet air gets heavier or lighter DEPENDING SOLELY ON WHETHER THE MOLECULAR WEIGHT OF WATER VAPOR IS HIGHER OR LOWER THAN THAT OF AIR. So let's look at that.

Water vapor is H2O. Two hydrogen atoms and an oxygen atom.
So its molecular weight is 1+1+16=18

So the molecular weight of water vapor is only 18, while dry air is 28.8.

That means that the air is LESS dense when we add water vapor.
QED!

Hope this helps,
DaveT

davidlangleygolf
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air conditions

Post by davidlangleygolf » Wed Sep 02, 2015 3:49 pm

hi there is a great app that computes distance changes due to air conditions which is called FlagHiPro very cool to play around with and useful! well worth buying its only one or two dollars from the app store!

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