Climate is weather averaged over a long period of time.

• To quantify "average weather," scientists measure things such as temperature and rainfall / snowfall (precipitation) over many years.

Ecological regions are tied to physical setting and climate.

• To better understand this, you will compare two U.S. cities -- Phoenix, Arizona and San Diego, California.
• These cities are separated by about 300 miles.
• We will also investigate another pair of U.S. cities that are separated by about the same distance: Portland, Maine and Presque Isle / Caribou, Maine).
• You can also conduct the same study for other pairs of U.S. cities. A good place to begin is the "National Weather Service Offices for the U.S." website.
  • They have a "clickable map" that features links to many U.S. cities.
  • Look for the either the word "climate" or "climatology" (which is the study of climate) to find "average weather" data.

Phoenix, Arizona facts:

• Region has a desert climate: arid ("dry and barren") with marked seasonal temperature extremes;
  • See monthly average temperature plot (right, >>>).
• It is located in the "rain shadow" of high mountain ranges that intercept wet winter air masses blown by winds (Click here to see a movie about this type of "orographic precipitation"; 1 MB);
• Average annual precipitation is about 7.7 inches per year;
  • See plot of monthly average rainfall (below, VVV);
• It is part of the "North American Desert" ecological region;
• Physical setting consists of plains with hills, plains with mountains, and tablelands of high relief.

San Diego, California facts:

• Temperatures are characterized by hot, dry summers and mild winters (see above, ^^^);
• Rainfall is mostly from winter frontal storms that sweep in from the Pacific Ocean;
• Yearly precipitation total is about 9.9 inches.
• Rain falls mostly from November to April (see graph at left, <<<). Year-to-year rainfall totals can vary a lot and extreme droughts are not uncommon;
• Coastal fog is common, particularly from May through July.
• It is part of the "Mediterranean Californian" ecological region.
  • This ecological region is found ONLY in parts of California and northernmost Mexico (Tijuana);
• The physical setting is an urban area that stretches over low hills and mesas, occupying a rectangle of about 50 miles by 12 miles (80 km by 20 km) along the Pacific Coast.

Now that you know more about analyzing climate data, you will research similar data from Portland, Maine and Caribou, Maine.

• Go to Maine's National Weather Service Forecast Office website and click on the "Climate Information" link.
  • You will see a table similar to the one below (VVV).
  • Click on "Caribou" link to access climate data for that area (you may want to print it for later use);
  • Click on "Portland" to see its climate data.

You can do the same type of analysis for other places, starting at the "National Weather Service Offices for the U.S." website.

• For each city, find either the word "climate" or "climatology."
  • From there, look for "Monthly Climate Normals" or "Monthly Climate Summaries." These usually have data that are averaged over 30 YEARS (from 1961-1990).
    • You should see (or can easily estimate) ONE average mean temperature for each month.
    • Likewise, you should be able to find (or easily sum up) ONE average mean precipitation for each month.
• Alternatively, you can access "Normal Mean Temperature" (in degrees Fahrenheit) for many U.S. cities by clicking here.
  • Note that the first column of this chart shows that the climate data have been collected over many (usually 30) years, the last column shows the normal ANNUAL mean temperature, and the middle 12 columns are January through December.
• Click here to see "Normal Monthly Precipitation" (in inches) for many U.S. cities.

1. Graph "Monthly Temperature Normals" for two cities (either Portland/Caribou or another city pair). You can create a graph similar to the one shown for Phoenix and San Diego with horizontal gridlines every 5°F.
   • How do the month-to-month DIFFERENCES in normal (average) temperature between these two cities compare to the month-to-month DIFFERENCES in temperature between Phoenix and San Diego?
     • Can you explain why you observe these trends?
2. Graph monthly "Precipitation Normals (water equivalent)" for two cities (either Portland/Caribou or another city pair).
   • How do the month-to-month DIFFERENCES in normal (average) precipitation compare to the month-to-month DIFFERENCES in precipitation between Phoenix and San Diego?
     • Can you explain why you observe these trends?
3. Consider what you've learned about physical setting and ecological regions from the Phoenix and San Diego examples.
   • Do you think that the two cities (either Portland/Caribou or another city pair) are in the same ecological region?
   • Discover more about ecological regions by clicking on the following descriptions (that include most of the U.S. ecological regions): | NORTHERN FORESTS | NORTHWESTERN FORESTED MOUNTAINS | MARINE WEST COAST FORESTS | EASTERN TEMPERATE FORESTS | GREAT PLAINS | NORTH AMERICAN DESERTS | MEDITERRANEAN CALIFORNIA |
   • Given your climate data, which ecological region best describes each city you've studied?
   • Does other information about "Physical setting" help you categorize your cities' ecological region(s)?
   • Click here to see names assigned to ecological regions in all of North America.