29 June 2001 Activities

---

Student Work

You are in charge of the family budget (or you are on the city planning committee for future water supplies). You must estimate how much you will spend on watering the lawn for the next three years (or hyou must estimate city water usage for the next three years). What do you need to do the planning?

• You know the usage last month. Can you assume future months will be the same?
• Or, does rainfall vary from month to month, and from year to year?
  • If so, how much?
  • Enough to worry about?

How do we find the answer?

We want you to help us.

• Determine natural variability of rainfall in a city.
• Determine natural variability of rainfall over an area.
• Can you use rainfall recorded in a nearby city to answer your question about future water usage at your house?

Activities

• Working in teams of three, determine spatial and temporal variability of rainfall in Brenham area.
• Working in teams, determine if variability in Brenham is representative of variability in other areas.

Materials

• Brenham rainfall data.
• Gif radar images of local Texas rainfall on selected dates.
• Texas county rainfall data.

Other Activities

 Look at this plot of rainfall this last year at Waco: http://www.cpc.ncep.noaa.gov/products/global_monitoring/precipitation/sn72256_1yr.gif then compare it with the plot for the same time for Houston at: http://www.cpc.ncep.noaa.gov/products/global_monitoring/precipitation/sn72243_1yr.gif
What are the similatities and differences?

Go to the NOAA weather archive at http://www.ncdc.noaa.gov/cgi-bin/fsod_state and select display one parameters for two stations for one month. Then on the next page select Texas in both windows, then seplect Bryan and College in the two windoes, then select precipitation for whatever month and year you prefer, then submit graph values.

• How does rain at the two cities compare?
• Are they identical?
• Are they different?
• If so, how different?

Here are some other images showing variation of rainfall in space:

• Rainfall at 19:08 on 05 June 2001 in Texas
• Rainfall at 15:07 on 08 June 2001 in Texas.
• Rainfall at 18:17 on 08 June 2001 in Texas.
• Rainfall at 20:58 on 08 June 2001 in Texas.
• Rainfall at 21:37 on 26 June 2001 in Texas.
• Daily rainfall from 1951 to 1996 at College Station.
• Rainfall in Brenham in September from 1885 to 1990.
• Texas rainfall from 12Z June 14, 2001 to 12 Z 15 June 2001.

---

Some suggestions for the teacher

We begin this course with a local practical problem. By looking at a long record from one point, and a map of rainfall variability over a large state we can begin to understand the natural variability of rainfall.

Students will learn that there can be large variations of rainfall in time and space, from kilometer to kilometer, county to county, day to day, and year to year.

1. Rainfall varies in time and space.

• August rainfall this year may not be the same as August rainfall last year.
• Rainfall at a gauge in one part of a county may not be the same as rainfall at a nearby place.
• Rainfall varies from city to city and county to county in Texas.

1. The work opens up the questions:

• Why does rainfall vary?
• Can the variability be predicted.

Revised 6/29/01 Robert Stewart