DataStreme Activity 4B:

HEATING DEGREE-DAYS AND WIND CHILL


Note: New WET Table!

The U.S. National Weather Service and Environment Canada have revised the Windchill Equivalent Temperature (WET) values based on new research involving better science and perceptions of temperature by people under various combinations of air temperature and wind speeds. The discussion of this research and the revised WET values are given at: http://www.noaanews.noaa.gov/stories/s720.htm. An adaptation of the NWS table of new WET is provided as Image 1. Use this Image 1 table to answer questions on WET in this activity, including #8, 9 in the printed portion.


Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1, Image 2, and Image 3 Files.
  3. Print (when available) the Thursday, 4 October 2001, Daily Summary File.

To Do Activity:

  1. Read Chapter 4 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 4B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 4B Now


WELCOME BACK: Procedure continued from STUDY GUIDE.

  1. Heating and Cooling Degree Days and wind chill values are calculated with the use of observational data collected at weather stations. The DataStreme homepage delivers 24-Hour Maximum and Minimum Temperature Maps which can be used to calculate these values. Image 2 is the map of maximum temperatures, in degrees Fahrenheit, at selected stations across the coterminous US during the preceding 24-hour period, ending at 12Z on 03 OCT 2001. The highest maximum temperature reported on the map was ______ °F at [(Phoenix, AZ) (Sacramento, CA)]. The lowest maximum temperature was ______ °F at [(International Falls, MN) (Portland, ME)].

  2. Image 3 is the corresponding map of minimum temperatures across the coterminous US during the same 24-hour period also ending at 12Z on 03 OCT 2001. The lowest minimum temperature reported on the map was _______ °F at [(International Falls, MN) (Havre, MT)]. The highest minimum temperature was _______ °F at [(Key West, FL) (Blythe, CA and Phoenix, AZ)]. The maximum and minimum temperature patterns reflect the cool air mass that has settled into the northern Plains and the warmer air that has been entrenched in the Southwestern states.

  3. The following table lists some selected cities from the maps with their temperature maxima and minima. For each, calculate the average daily temperature and determine whether Heating Degree Day units or Cooling Degree Day units were produced and how many. (Following NWS practices, the mean daily temperature is rounded up to the nearest whole degree, if necessary, before calculating HDD or CDD.)
    Degree Day Units
    City Max. T (°F) Min. T (°F) Mean T (°F) HDD/CDD Units Circle which
    International Falls, MN 54 37 ________ ________ HDD / CDD
    Sacramento, CA 104 57 ________ ________ HDD / CDD
    Portland, ME 73 39 ________ ________ HDD / CDD
    New York City, NY 75 49 ________ ________ HDD / CDD
    Phoenix, AZ 92 78 ________ ________ HDD / CDD
    Orlando, FL 81 59 ________ ________ HDD / CDD

  4. Comparing the maximum and minimum temperatures shown on the maps with the degree day values you calculated, it can be seen that utility energy usage in the US during this period was probably most needed for heating across the [(southwestern) (north-central) (southeastern) (northeastern)] US.

  5. The Image 3 map shows that Glasgow, MT, had a minimum temperature of 40 °F during the previous 24 hours. Assume that Glasgow had a wind speed of 10 miles per hour when the temperature was 40 °F. Using the windchill equivalent temperature (WET) Table provided as Image 1, the WET for this combination of temperature and wind speed would have been ______ °F. This was the minimum temperature reported at [(Burns, OR) (Boise, ID)] and would also have been the WET experienced there if the wind were calm.

  6. For a temperature of 30 °F, if the wind speed were 5 mph, the WET would be ______ °F. And for 30 °F and 15 mph, the WET would be ______ °F. The 5 to 15 mph wind speed increase produces an WET difference of ______ F° in equivalent heat loss to the body. For 30 °F and 25 mph, the WET would be ______ °F. The 15 to 25 mph increase brings only a WET difference of ______ F° in equivalent heat loss to the body. The WET table shows that increasingly higher wind speeds produce proportionately less additional cooling effect in WET values.

The DataStreme homepage also provides current hourly data at many locations within each state in the Surface section, under "State Surface Data - Text" and graphically as "Meteograms for Selected Cities". These data can, among other uses, be employed to calculate WET for your location. For updates on the Heating and Cooling Degree Days accumulations for the US, see the Wednesday Supplemental Information File for Week 4.

The National Weather Service Internet site provides current meteorological data for any selected station (by state and city) for the US. These data also include a station's daily maximum and minimum temperatures. The Web address is: http://weather.noaa.gov/weather/ccus.html.


Note: If pressure blocks were already distributed to you, be sure to bring them to the Mid-course meeting. See Study Guide Part B: Applications, Activity 5B.

If you witness or experience unusual or interesting weather events, please email them to Ed Hopkins (address at end of Daily Summary files) for possible inclusion as a "Report from the Field". Your experience may be of interest to other DataStreme participants and their students. They add the human element to weather.


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday,
8 October:

  1. Chapter 4 Progress Response Form from the Part B: Applications binder, Week 4, or the DataStreme Homepage Progress Response Form,
  2. 4A and 4B Activity Response Form,
  3. STUDY GUIDE, Part B: Applications, page 4A-2, and
  4. STUDY GUIDE, Part B: Applications, page 4B-2.

Return to DataStreme Homepage

URL: datastreme/learn/b_act.html
©Copyright, 2001, American Meteorological Society