SNOW HYDROLOGY (GEOG 4321): HOMEWORK ASSIGNMENT 5

Instuctor: Mark Williams
Telephone: 492-8830

Homework 5

• Assigned 16 May.
• Due 20 May, 8 am.
• There are 30 possible points.
• WRITE NEATLY and LEGIBLY.
• INDICATE THE QUESTION AT THE START OF EACH ANSWER.

1. In recent years there has been a great deal of interest in the effects of large scale climate patterns such as El Nino and La Nina on mountain snowpacks in the Western US. Give a concise description of both El Nino and La Nina and describe how they affect climate in the Western US. In particular describe how you expect snowfall/precipitation amounts in various regions of the west to be affected by these large scale weather patterns. (1 page maximum -15 points total)

2. Looking at an index of the strength of El Nino and La Nina climate patterns , it is apparent that the 1997-8 winter was a strong El Nino winter and the 1998-9 winter was a strong La Nina winter. Use Snotel data near maximum accumulation from the following sites in the western US to see whether or not your predictions about climate patterns in the western US hold true for these two winters (10 points):
   • Compare the April 15 SWE values for 1998 and 1999 for the Stevens Pass, Washington (north of Seattle, near Mt Baker) snotel site.
   • Now compare the March 15 SWE values for 1998 and 1999 for the White Horse Lake, Arizona (just west of Flagstaff) snotel site.
   Do the SWE values from these two sites follow a pattern you would have predicted based on your answer to question 1?

   Now do a similar analysis for Colorado:

   • Compare April 15 SWE values for 1998 and 1999 for Rabbit Ears Pass near Steamboat in the northern part of the state.
   • Compare April 15 SWE values for 1998 and 1999 for Lizard Head Pass in the San Juans in the sw corner of the state.
   Based on the data from these two sites, does Colorado show a predicatble north/south gradient in precipitation during El Nino and La Nina winters? Take a guess at why or why not.

3. At the 4 snotel sites you examined, were the cumulative precipitation or SWE values higher near maximum accumulation? Why would there be a difference in cumulative precipitation measured by a Belfort gauge and SWE measured by a snow pillow at the same site? (5 points)