How Elevation Impacts Baseball

Baseballs travel 9% farther in Coors Field than at sea level

Elevation is defined as your height above mean sea level measured usually in feet. Elevation is the only factor in air density that will not change on a daily and/or seasonal basis. It is also the most dominant of the three factors that influence air density.   

Elevation has a correlation to air density; the higher the elevation, the lower the air density. Air density is defined as the mass per unit volume of the Earth's atmosphere. In English, it means how much "stuff" (air molecules) are found in a given space of air. At sea level and at 15 °C (59 F) air has a density of approximately 1.225 kg/m3

In terms of a batted baseball, the less "stuff" the ball has to collide with on its flight, the less friction it encounters. Less friction means more energy is available for the flight, which means the ball is able to travel further. 

In MLB, the two parks where elevation comes into play the most is, of course, Coors Field in Denver Chase Field in Arizona and Turner Field in Atlanta. 

(I had a real nice graph that shows elevations of MLB stadiums and also shows that Coors, Chase and Turner are head and shoulders above every other park when it comes to elevation but I can not find it at this time. Lacking a pretty graph, I can just the elevations shown below. Coors is 5183 feet above sea level, Chase is 1082 feet and Turner is 1050 feet. The highest AL park is Target Field in Minneapolis at 812 feet.)

In fact, elevation becomes almost irrelevant in all other ballparks besides these three. To make matters even more complicated, Chase Field is a retractable roof stadium so the physics of air density become tougher to digest when the roof is closed. Coors is the only field where you can count on a dramatic influence due to elevation.  

According to Colorado.Rockies.com, "the ball still travels 9 percent farther at 5,280 feet than at sea level. It is estimated that a home run hit 400 feet in sea-level Yankee Stadium would travel about 408 feet in Atlanta and as far as 440 feet in the Mile High City." See graph below: