Chapter 1

"NORMAL" TEMPERATURES

Goals: To investigate how often the "normal" daily maximum temperature for a particular date has been observed to be the maximum temperature on that date, and to compare the variability of daily temperature in winter to the variability of daily temperature in summer.


Data

Daily maximum temperature data for the first 10 days of January and July during the period 1901-1990 for the locations listed below (1895-1998 for Logan, UT). January and July are intended to be representative of winter and summer, respectively.

State College, PA January 1-10 July 1-10
Minneapolis-St. Paul, MN January 1-10 July 1-10
Charleston, SC January 1-10 July 1-10
Logan, UT January 1-10 July 1-10

("-999" in the data files indicates that temperature data is "missing" for that day)


Procedure:

For each city, do steps (1)-(4):

  1. Pick a day in January and the same calendar day in July (for example, January 7 and July 7). For each of these days, construct a histogram (a frequency diagram) that shows the number of times each maximum temperature was observed (see Figure 1.7 of Edition 2 of the book for an example of such a histogram).

  2. Compute the average maximum temperature (rounded to the nearest integer) for the two days you chose (use the 30-year period 1961-1990). Consider these averages as the "normal" maximum temperatures for your days. How many times during the full period of record (1901-1990 for State College, Minneapolis and Charleston; 1895-1998 for Logan) were these "normal" maximum temperatures the observed maximum temperatures?

  3. You should see that what is "normal" is not for the daily maximum temperature to exactly match the "normal" maximum temperature, but rather for the daily maximum temperature to fall within a range of the "normal" maximum temperature. How large of a range of temperatures (centered on the "normal" maximum temperature) encompasses 2/3 of all observed maximum temperatures for your January day? Answer the same question for your July day.

  4. To get a sense for how variable the high temperature can be on a particular calendar day, compute the difference between the highest observed maximum temperature and the lowest observed maximum temperature for the January day that you chose. Do the same for the July day that you chose.

  5. On the January day you chose, which city shows the greatest variability from the highest to the lowest maximum temperature observed? What about in July? In January, which city shows the least variability from the highest to the lowest maximum temperature observed? What about in July? What characteristics of the locations of these cities likely contributes to the behavior of the maximum temperature?

  6. In which city could a forecaster use the daily average maximum temperature (that is, the "normal" high) for a forecasted high and have the best chance of being accurate (or at least close to accurate)? During what season (summer or winter) would this technique work best? Why?


    Other "Weather on the Web" Exercises

    Chapter 2 | Chapter 3 | Chapter 8 | Chapter 9 | Chapter 10| Chapter 11 | Chapter 12 | Chapter 14