Geog. 321 -- Climatology
Exercise 7 -- Recent Climatic Variations

This exercise focuses on the climate anomalies, or how recent conditions differ from the long-term averages, as well as the drought (exceptional dryness) that has prevailed over the western United States for the past year or so.  Although it has begun to rain again, as is usual for this time of year, at many locations in the Pacific Northwest precipitation has remained below normal for over a year.

Note:  The exercise once again makes use of "live" images, which might not be available at the time you work on the exercise.  Before starting the exercise, scroll down the page to make sure all images are being displayed.  There should be a total of six images.  If some of the images are missing or the pages don't open up, you could try doing the exercise later, or without losing any points, just type "image or page not available," and the time, into the answer form.

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Recent Variations in Precipitation at Eugene

The amount of precipitation received at Eugene over the past month, season (i.e. the past 90 days), and year (as of the beginning of November 2006) is shown on the top half of each figure above.  The smooth line shows the normal accumulation of precipitation over an "average" month, season or year, while the thicker jagged line shows the actual accumulation of precipitation over the interval.  Brown shading indicates when, and by how much, precipitation was below the normal amount, and green shading indicates when, and by how much precipitation was above normal.  The bottom half of each figure shows the precipitation observed each day.

Question 7-1:  Over the past month, was precipitation at Eugene above normal, normal, or below normal (hint:  it might be the case that for part of the month it was one way, and for another part of the month it was the other--visually compare the area of green and area of brown to get an idea).  What about over the past season and year?  When during the year did the greatest precipitation deficit accumulate (when did the smooth line rise the highest over the jagged line)?

Recent Variations in Temperature at Eugene

The figure above shows the variations in average daily temperatures (top), with red areas indicating days that were warmer than normal, and blue indicating days that were colder than normal, a 31-day running mean of temperature differences from the long-term average temperature (middle), colored the same way as the top panel, and the observed daily maximum and minimum temperatures over the year (bottom).

Question 7-2:  Over the past year, were conditions at Eugene warmer than average or cooler than average?  (If it's hard to tell, then overall temperatures were probably close to normal.)

U.S. Precipitation patterns

The map above shows precipitation over the most recent season for which the data have been summarized (possibly last summer), expressed as the percentage of the long-term average (with 100 percent indicating that the average precipitation was received).

Question 7-3:  Focusing on the western U.S., were recent conditions wetter than normal or drier than normal overall?  Are the conditions at Eugene displayed above consistent with the overall pattern?

 

Drought Monitor

The figure above shows a summary of current drought conditions across the U.S.

Question 7-4:  Describe the overall pattern of drought.  Where is drought occurring, and where is it not.  Compare this map with the precipitation map above.  Considering the recent precipitation anomalies at Eugene (Question 7-1) would you expect drought conditions in the Pacific Northwest to become more extreme or less extreme?

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