Density Altitude Experiment

Module 3 – Density Altitude Experiment

This experiment is intended to further your understanding of density altitude. Before beginning the experiment, complete the background reading on density altitude in module 3. Then, follow the instructions below to complete the experiment.Submit your completed experiment file to your group discussion area by the end of Module 3.

Below are three tables – each table provides five different scenarios of pressure, temperature, and dew point temperature for the given airport.Using the data provided, utilize the NWS Density Altitude Calculatorto calculate the density altitude each scenario.

NOTE:  The NWS density altitude calculator is valid for any location. The input data includes the station pressure, air temperature, and the dew point temperature.  The input data does not include the station (airport) elevation.   Verify this by inspecting the density altitude formula used by the calculator. Think about why the station elevation is not needed to calculate density altitude if the station pressure is known (hint: recall how air pressure changes with elevation, from chapter 1).

Before doing the calculations,hypothesize on the expected results, based on your understanding of the dependence of air pressure, temperature, and humidityon air density, and the relationship between air density and density altitude. First, think about the effect of the airport elevation alone on air pressure and density, and the density altitude.* Then, for each scenario in the table, consider the effect of the change in each factor on air density, and how the calculated density altitude should compare to the airport’s elevation.

Type your hypothesis here:

Now, complete all three tables.  Be careful to match the correct units on the density altitude calculator with the units of the given data.

Table 1

Airport Location:  Phoenix, AZ                    Airport Elevation (feet above Mean Sea Level): 1,135

Table 2                

Airport Location:  Denver, CO                     Airport Elevation (feet above Mean Sea Level): 5,430

Table 3

Airport Location:  Leadville, CO                 Airport Elevation (feet above Mean Sea Level): 9,927

*Station Pressure vs. Sea Level Pressure

Station Pressure– the actual air pressure as measured at the station, and the pressure value used in the density altitude calculator.

Sea Level Pressure– station pressure corrected to mean sea level.This is basically an altitude correction to the actual air pressure at the location, so that pressure readings between locations with different elevationscan be compared.

Observing the difference between station pressure and sea level pressure at a given location gives you a sense of how elevationalone affects air pressure and air density. For reference, in a standard atmosphere, the air pressure at sea level is 29.92 in. Hg, and, in the lower atmosphere, air pressure decreases at a rate of about 1 in. Hg per 1000 feet of elevation gain (review the discussion of air pressure in chapter 1).

Read more about the differences between station pressure and sea level pressurein chapter 8.

After completing the tables, analyze your results, then draw some conclusions by answering the following questions:

1. Are the results what you expected based on the hypothesis you made?
2. What is your conclusion about the effect of elevation on density altitude?

3. What are your conclusions about the effects of changes in air pressure, temperature, and humidity on density altitude at a given location?

4. Which single factor has the greatest effect on density altitude?
5. Which single factor has the least effect on density altitude?
6. What combination of factorscreates the highest density altitude?