Chapter 3 THE AVERAGE ENVIRONMENTAL LAPSE RATE Goals: To investigate how temperature varies with elevation in specific locations, and to compare environmental lapse rates computed with actual climate data with the average environmental lapse rate.

Data:

Average monthly maximum temperature data for January (representing winter) and July (representing summer) during the period 1951-1990 for three pairs of nearby observing sites, where the two sites in a pair differ substantially in elevation but not in latitude or proximity to a large body of water. The three pairs of observing sites are:

1. Stroudsburg, PA(480 ft) and Freeland, PA(1900 ft)
2. Chico, CA (185 ft) and Lake Tahoe, CA(6230 ft)
3. Boulder, CO (5484 ft) and Dillon, CO (9065 ft)

Procedure:

1. Using the 40 years of data, determine the average difference in January maximum temperature between the lower elevation site and the higher elevation site in each pair. Do the same for the July maximum temperature. Express the answers in ^oF per 1000 ft. How do your answers compare to the average environmental lapse rate of 3.6^oF per 1000 ft that is given in the book?

2. From your calculations, does it appear that the difference between the higher and lower elevation stations is greater during one of the seasons (winter or summer)? If so, can you suggest any reasons why this might be?

3. The point of this exercise is simply to demonstrate that, on average, temperature decreases with elevation. But if the sun heats the ground and the ground heats the overlying air, and mountains are closer to the sun, then why aren't mountaintops hot?