Variation of Density with Elevation

In summary, the conversation discusses finding an expression for the variation of density with height using a list of heights and corresponding densities of air. The suggestion of using the barometric formula is mentioned as it takes into account the value of g at sea level, while also noting the importance of considering the variation of temperature with altitude. There is also a mention of the variation of g with altitude, but it is stated that the temperature dependence is more critical in this situation.
  • #1
cruckshank
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Hi, I've been given a list of heights and corresponding densities of air at these heights. I'm trying to find an expression for the variation of density with height. From the data, it looks like the density would be equal to some kind of logarithmic relationship? However, I'm not too sure how to actually establish the equation for this.

Thanks in advance!
 
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  • #4
cruckshank said:
Hi, I've been given a list of heights and corresponding densities of air at these heights. I'm trying to find an expression for the variation of density with height. From the data, it looks like the density would be equal to some kind of logarithmic relationship? However, I'm not too sure how to actually establish the equation for this.

Thanks in advance!
Probably, a more apt equation for you problem is the barometric formula:

https://en.wikipedia.org/wiki/Barometric_formula

Here, the formulation depends only on the value of g at sea level.

If you do need to know the variation of g with altitude, there is this:

https://en.wikipedia.org/wiki/Gravity_of_Earth
 
  • #5
Much more important than the variation of g with altitude is the variation of temperature with altitude. In applying the barotropic formula to determine the variation of pressure and density with altitude, it is critical to include the temperature dependence.
 
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Related to Variation of Density with Elevation

1. What is the relationship between density and elevation?

The density of air decreases as elevation increases. This is because the air molecules are more spread out at higher altitudes due to lower air pressure.

2. Why does density change with elevation?

Density changes with elevation because the higher you go, the less air is above you, resulting in lower air pressure. The lower air pressure means that the air molecules are not as tightly packed together, resulting in a lower density.

3. How does temperature affect the density of air at different elevations?

Temperature also plays a role in the density of air at different elevations. Generally, colder air is more dense than warmer air. So, at higher elevations where the air is colder, the density will be higher compared to lower elevations with warmer air.

4. How does air density affect weather patterns?

Air density can affect weather patterns because areas with higher air density tend to have higher air pressure, which can result in clear, stable weather conditions. On the other hand, lower air density areas with lower air pressure can lead to unstable weather and potential storm development.

5. What are the practical implications of variation in density with elevation?

The variation in density with elevation can have practical implications for a variety of activities, such as aviation, hiking, and even breathing. At high altitudes, the lower air density means that less oxygen is available, making it more difficult to breathe and perform physical activities. In aviation, pilots must take into account the density of air when calculating aircraft performance and fuel consumption. Hikers may also experience difficulty breathing and exert more effort at higher elevations due to lower air density.

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