[Jakerin]

I’m watching the NHRA qualifying in Norwalk OH. They put up the track temp, air temp, barometer and then listed this,

Density altitude 2,310’
Elevation 651’

WTH? What is this and how is it calculated, measured, guessed?

What’s the density altitude at 2,310’ elevation? Higher? Lower? I don’t get it.

 

[Ranger]

Density altitude is basically altitude adjusted for temp and humidity, both of which affect air density. It's used more in aviation than anything else.

Here's a better explanation.
https://www.aopa.org/training-and-safety/active-pilots/safety-and-technique/weather/density-altitude

 

[Submariner409]

The big NHRA stuff is so fast that air density affects run times. Air drag.

Same sort of reason why golfers adjust stroke and club number for Mexico City and Pebble Beach. You hit longer balls in Mexico City - 7400' altitude.