Density Altitude which is used for calculating runway length due to higher temperatures and moisture in the air

This is calculation is used at higher altitude and higher temperatures. Example: the actual altitude of an airport at 2500 feet will affect aircraft performance as if it were over 7000 feet when outside air temp is above 100 degrees and 50% humidity. This causes the takeoff and landing distances to increase and you then may not have enough runway to land or takeoff.

Can you post a link to some more information?

This would probably be easy to implement in at least a 3rd party program.
Air Density is given, so it would probably be an offshoot of that, I just don’t have enough info to know what exactly you are asking for.

Personally, I have found that some of the best websites to explain weather are flying related.