Topic 5:
Regional & Southwest Climate Patterns
Announcements:
Field Wednesday - Meet at lab room; need one or 2 people to drive private vehicles... We're going outside, so dress accordingly. Bring water, rain gear, walking shoes, hat, sunscreen, tree book, lab handout, notebook.
Homework - Do Activity for Question 3 below!
MORE Announcements:
SW Climate Homework - Due next week Tuesday
Learning Goals for Day:
Ø Understand how the location of oceans (or other large water bodies) and mountain ranges affect regional climate
Ø Define the term “rain shadow”
Ø Explain how the 4 abiotic factors that define “climate” change as you go up in elevation
Ø Homework: Describe the overall climate of the Southwest, especially in terms of precipitation – based on your individual & group summaries of precip. patterns at different locations in the SW
o when is most moisture delivered?
o when is it driest?
o **what types of storms are most likely to deliver moisture at different times of year?
Defining the Southwest:
Shaded relief map of the southwestern U.S. (from: http://rst.gsfc.nasa.gov/Sect6/Sect6_8.html )
Movement of moisture over the SW:
http://cimss.ssec.wisc.edu/goes/burn/wfabba/wfabba_rt66nmex.html
Question 1: How do mountain ranges affect precipitation?
Rain Shadows (The "Orographic Effect):
Question 2a: How do the four abiotic climatic factors change as you climb up a mountain (go up in elevation)?
Temperature:
Moisture:
Wind:
Sunlight:
Question 2b: Why does temperature change with elevation - is there a predictable pattern?
Adiabatic Lapse Rate : Change in temperature of a moving air mass, as it rises or falls.
Dry Rate: 10oC/1000m (5.5oF/1000')
Wet Rate: variable, but lower because along with cooling due to expansion, get heating due to condensation (ave. wet rate = 5oC/1000m)
Environmental Lapse Rate for temperature change with elevation: Change YOU feel in temperature as you move up in elevation through a stationary air mass
the cooling is slower than for a moving air mass
Ave. rate = 6.5oC/1000m (3.6oF/1000')
Our elevation: 6500' (2250 m); Andrew's Lake Elevation: 9500' (3250 m); so....?
Question 3: What is the climate like in the Southwest? In particular, what are the patterns of precipitation here?
Small Group Activity & HOMEWORK
Activity Goals:
For this exercise, each
person should choose a weather station from a site in the southwestern US:
Visit the Western Regional
Climate Center website: http://www.wrcc.dri.edu/Climsum.html.
The climate summaries you access contain data on mean total monthly precipitation.
Temperature data are also provided, but we will focus on precipitation patterns today.
Using your carbonless paper, plot the monthly precipitation data on a graph. What type of graph (line, bar, other?) is appropriate for these data?
What information will be presented on each axis?
A standard way to plot monthly moisture data is by “Water Year” (as opposed to calendar year). What are the standard beginning & ending dates for a "water year?" And why would a “water year” be different than a standard calendar year?
Once your data are plotted, compare your graph with the others in your group. Are similar patterns present across different sites/different regions of the SW?
When is the driest month at most sites?
When is the wettest month(s)?
What is the wettest season? Is there more than one “wet” season?
What types of moisture probably arrive during the different wet seasons, and what types of storms deliver this moisture?
Do any sites exhibit a “bimodal” moisture distribution? What does “bimodal” mean?
Be sure to include both the site name & the site elevation (along with your name) in the graph's title. (...and make sure the title is complete & explanatory!)
Compare your results & your answers to these questions with other groups in the class, and be sure to put your original graph in your folder at the end of the class session.
Assess – Goals for Day:
Ø Draw a diagram of western North America showing prevailing wind direction, locations of major mountain ranges, and relative location of wet & dry areas. Where do rain shadows occur?
Ø Review your & your classmates’ graphs of monthly precipitation distribution. The SW is often described as having a “bimodal” precipitation pattern (meaning precip. occurs in 2 distinct time periods or seasons). Does this make sense in light of the data you summarized? How was that moisture delivered? (what kinds of storms)
Ø When is the driest month of the year for most of the SW? Why do you think this is the case?
9/15/06
Of Interest in the local News:
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