Temperature and Elevation —What Scientists Think— Did you discover that temperatures seem to go down as you go up in elevation? They do! Wouldn't you think that if you're closer to the sun (on a mountaintop, for instance), it would be warmer? Here's why that's not true: Our air is not warmed directly by the sun, but by heat from the earth's surface! (The sun's energy has to hit the surface of the earth before "radiates" back out as heat energy.) As you go higher, the air pressure decreases (because there is less air above weighing you down). As air rises up from warm surfaces to elevations with lower pressure, the air expands and cools down. Being a Better Scientist: How could you be more confident about your findings and predictions? Answer: You could compare temperatures and elevations in many different places! The more data you have, the more accurate you're likely to be. What did you find out about how temperatures change with elevation? Here are two general rules of thumb: On average, the temperature drops 3.5 degrees F for each 1,000 feet of elevation. But that's only if there are no other factors, such as moisture, that could affect the temperature. The temperature of dry air drops about 5.5 degrees F for each 1,000 feet of elevation. (The temperature of moist air drops at a lower rate.) Think! * Did either of these "rules" hold true today based on temperatures in Zitacuaro and Angangueo? If not, what else do you think might have affected the temperatures? Once you've pondered this, see below. * We don't have a link to temperatures at the sanctuaries. But think about what season they're in (wet or dry). What would the temperature be today if you followed the related rule of thumb? What did you discover about how a location's elevation affects the temperature extremes it experiences? How would you explain it? Locations at higher elevations tend to have much greater temperature extremes in a day than lower elevations do. Here's why: The air is "thinner" (has fewer molecules) at higher elevations. This makes it easier for the sun's energy to reach the surface and heat it. At night, there are fewer gases to "trap" the warmer daytime air, so the surface cools very fast. Think! What monarch behaviors help it survive in these daily temperature extremes? What aspects of its habitat help it do this? * What else could affect temperatures? Factors such as wind currents, precipitation, and intensity of sunlight hitting the ground could affect the temperatures in a location, causing them not to "fit" the standard rules of thumb! < Back to Lesson Copyright 2006 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form