Diurnal Temperature Changes and Water Vapor Content

The moisture content of the air is one of the most important variables in the atmosphere. Even though water vapor ranges from only 0 to 4% of air's composition, it affects the earth's cloudiness, precipitation, energy transfer and greenhouse effect. In this lesson, students will examine the latter of these consequences, as they determine how moisture in the air affects the diurnal temperature range. Their investigation will help them to understand different climatological regimes of both the Southern Plains and the world.

Objectives

1. To determine the effect that atmospheric moisture has on diurnal temperature variation.
2. To better understand the greenhouse effect on the earth's atmosphere.
3. To understand the circumstances under which temperature extremes occur.

Notes to the teacher

1. Obtain Mesonet or ARM/CART air temperature and dewpoint temperature for two different days at the same station. One of the days should have dew points higher than 18 deg C (~65 deg F); the other day should have dew points lower than 5.5 deg C (~35 deg F). Both days should be clear. Create the needed tables in WxScope.

PROCEDURE Let Day 1 be the day with the higher average dew point. Let Day 2 be the day with the lower average dew point. 1. Read through the tables of data to answer the following questions: a. What is the maximum air temperature for Day 1? The      minimum air temperature? b. What is the maximum air temperature for Day 2? The      minimum air temperature? 2. Compute the temperature ranges for Day 1 and Day 2. The temperature range can be obtained by subtracting the minimum temperature from the maximum temperature. QUESTIONS 1. Which day had the largest temperature range? Which day had the most moisture in the air?  2. What relationship does the amount of water vapor in the air have with the day's temperature range? Why? What other data could be used to demonstrate the relationship better?  3. What does your investigation say about the characteristics of days when a record high or low temperature was set? 4. How can you use your knowledge to produce better low temperature forecasts for the upcoming night? 5. Where in the U.S. are daily temperature ranges probably the greatest climatologically? The least? Why?

PREREQUISITES Basic understanding of air temperature and dewpoint temperature Knowledge of latent heat MATERIALS (Per group):  Pencil Paper Tables of Mesonet air temperature and dewpoint temperature OR tables of ARM air temperature and dewpoint temperature VOCABULARY Climatological Dew point Dewpoint temperature Forecast Greenhouse effect Variable Water vapor   CORE CURRICULUM SKILLS APPLIED IN THIS LESSON Identify similar or different characteristics in a given set of objects, organisms or events. Select descriptive (qualitative) or numerical (quantitative) observations in a given set of objects, organisms or events. Identify qualitative and quantitative changes given conditions before, during and after an event. Use appropriate Systems International (SI) units (grams, meters, liters and degrees Celsius) to measure objects, organisms or events. Report data in an appropriate method when given an experimental procedure or information. Interpret line, bar and circle graphs. Select the most logical conclusion for given experimental data. Recognize and describe patterns. Create an appropriate graph or chart from collected data.