The Accuracy of Climate Data

The cooperative observing network in the United States has existed since 1890. During this time, volunteers across the country have taken daily weather observations and reported their data to the federal weather service (currently, the local National Weather Service office). Typical data from these "co-op" stations include a 24-hour maximum and minimum temperature, a 24-hour rainfall or snowfall total, and the current temperature. The maximum and minimum temperatures of a given day are averaged to obtain the mean daily temperature. The mean daily temperatures are averaged over a 30-year period for every day of the year, then these results are fit to a curve to obtain the "normal" daily temperature. A similar process is completed to calculate the normal precipitation. These normals are used in climatological records.

Objectives

1. To determine the accuracy of the cooperative observer network.
2. To understand the impact of data reporting interval on the climate record.

Notes to the teacher

1. Obtain sets of hourly ARM air temperature data for a 24-hour period beginning and ending at 6 AM. Using WxScope, create a table of these data.
2. Give each student data from a different day or a different site.
3. This lesson examines the accuracy of an observing frequency of once per day.

PROCEDURE 1. What is the maximum temperature for the 24-hour period? What is the minimum temperature for the 24-hour period? 2. Average the maximum and minimum temperatures to obtain the "mean daily temperature" at your simulated "co-op" station. (By averaging the maximum and minimum temperatures from your 24-hour data, you are simulating how the mean daily temperature is computed for the nation's cooperative observing stations.) 3. Average all 24 hourly temperatures to obtain the mean daily temperature as computed at a National Weather Service station. 4. Calculate the difference between the two mean daily temperatures. QUESTIONS 1. How do the two mean daily temperatures compare? Is one noticeably higher than the other? 2. Compare the differences among the class. Is there a trend in what type of averaging obtains higher results? 3. Which method of averaging is more accurate? Why? 4. How might the method of averaging the temperature data affect the climate record of the U.S.? 5. What type of weather events would likely result in large differences between the two methods of averaging? Why? 6. What type of weather events would likely result in small differences between the two methods of averaging? Why?

PREREQUISITES Ability to average a list of numbers MATERIALS (Per person): Table of hourly ARM air temperature data Climate data worksheet (pdf) Paper Pencil To view PDF files, get Adobe's free Reader here. VOCABULARY Climate Cooperative Observing Network Mean daily temperature Normal temperature Weather 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.