ChEg 498X

Homework #5

Due 3/25

1. Calculate the Peclet number and terminal velocity of a spherical water droplet for the following conditions at 25 C and one atmosphere. Be careful about the larger diameters.

Diameter = 1 mm, .01 mm, .1mm, 1 mm, 1 cm

2. Calculate the Peclet number and terminal velocity of a spherical water droplet for the following conditions at 5 C and 10000 ft above sea level.

Diameter = 1 mm, .01 mm, .1mm, 1 mm, 1 cm

3. Suppose that a cloud of dust is injected into the lower stratosphere, 20 km. Provide some arguments about how long the dust will be in the atmosphere. Assume it is all quartz, SiO2, (spherical – quartz does not cleave into spheres…) with sizes ranging from 1 mm to 1 mm.

Work with this one a little and provide an insightful answer.

4. When discussing the effect of Aerosols on the radiative forcing of the earth, explain the terms direct and indirect forcing. What are the relative strengths of these two effects?

5. Explain how aerosols could either cause cooling or warming depending upon (which?) factors?

6. What size aerosol particles are most effective at causing cooling? Explain why.

7. List the major sources of CH₄ in the atmosphere. How much has atmospheric CH₄ changed in the industrial era? What is the mean atmospheric lifetime for methane and what is the primary mechanism responsible for removing it. What is the relative contribution of CH₄ compared to CO₂ for atmospheric warming?

8. Explain the link between CFC’s and ozone destruction. Use the chemical equations and tell where they occur. Explain how chlorine is acting as a catalyst for this reaction and thus is not consumed.

9. How is ozone formed? Where does this occur?

10. What is the importance of the hydroxide radical in the lower atmosphere? What is the mechanism for formation of OH^- in the atmosphere?