SNOW HYDROLOGY (GEOG 4321/5321): HOMEWORK ASSIGNMENT 5

Instuctor: Mark Williams
Telephone: 492-8830

TA: Qinghuan Zhang
Email: qinghuan.zhang@colorado.edu

Homework 5

1. Do a unit analysis of wind speed as a function of shear stress and friction velocity (5 pts).
2. You are working for the highway and need to protect the road from blowing snow using a snowfence. The site is flat, and the road is perpendicular to the prevailing wind. You decide to install a 3-meter high snowfence with 50% porosity. (10 points)
   • How far from the road must the snowfence be in meters so that the lee drift ends at the edge of the road?
   • For the lee drift, what is the maximum snow depth?
   • What is the cross-sectional area of the lee drift?
   • What is the total water storage from both windward and leeward drifts per meter of fence?

3. We are going to examine radiation data from the Niwot Ridge LTER site in order see how the radiation balance of a mountain snowpack changes over the snow season. Go to the Niwot Ridge Data Catalog at http://culter.colorado.edu/. Clik on Available Data. Click on Subnivean Laboratory Data. Next click on Snowmelt and Meteorological Data from the Subnivean. Now go to Level 2D data. Acquire the Level 2D data from January through July 2000 (0001 to 0007). To complete the question, you will need the 4 components of Net Radiation (Incident and Reflected Shortwave and Atmospheric and Terrestrial Longwave) as well as measured Net Radiation. Under Data Level Selection, check Level 2D (Daily).  Under Radiometric Data, select the five components listed above. Click Send Document. Next select either viewing option to work with the data. (20 points total)
   1. Create 3 graphs with the data you obtained (5 points):
      • Net radiation versus time for the 7 months of record
      • Incident and reflected solar radiation versus time for the 7 months of record on the same graph
      • Terrestrial and atmospheric longwave radiation for the 7 months of record on the same graph

   2. Describe the trends in net radiation. When does net radiation become positive? When does it peak? Why? (5 points).
   3. How does the relationship between incident and reflected shortwave change over the season? Calculate an albedo value for one day in February, May, and July. How and why are they different? (5 points)
   4. What is the relationship between incoming and outgoing longwave over the season? Is longwave more or less variable than shortwave? Take a guess at why this is. (5 points).
   5. Overall, what factors are most responsible for the seasonal increase in net radiation measured at Niwot Ridge? (5 points).