Data and formulas at the end. Real exam is Wednesday May 8, 2002

Transcription

1 ATMS 31: Physical Climatology Practice Mid Term Exam - Spring 001 page 1 Atmospheric Sciences 31 Physical Climatology Practice Mid-Term Examination: Would be Closed Book Data and formulas at the end. Real exam is Wednesday May 8, A rectangular 10 m solar panel is inclined at an angle of 30 to the direct solar beam, the direction toward the sun. The panel has an albedo for solar radiation of 0.1 and an emissivity for thermal infrared radiation of 0.9. If the panel is such a good heat conductor that both its faces always have equal temperature, calculate the temperature of the solar panel at radiative equilibrium if the total solar irradiance is 1367 Wm -. (10 pts) sun 30 Solar Panel. Suppose the net radiative heat balance at the top of the atmosphere averages over the Northern Hemisphere to 5 Wm -, and averages over the Southern Hemisphere to -5 Wm -, over a long period of time. Calculate the northward heat flux across the equator in Joules per second necessary to balance this radiative heating difference and maintain a steady equilibrium. (10pts) 3. The Gulf Stream off the East Coast of North America loses heat to the atmosphere at the rate of 300 Wm - during winter. If the Gulf Stream current is 500 meters deep, at what rate does the water temperature change with time as a result of this heat loss through the surface? Assume all influences on the temperature except the heat flux through the surface and the storage capacity can be neglected in this calculation. Give your answer in C per day. (10pts) 4. Which continent do you think has the highest Bowen ratio? Explain your reasoning. (5pts) 5. In Oklahoma, the winds at the surface are often stronger during the day than at night. Explain. (10pts) 6. The tropical upper troposphere around 1-15 km contains a large amount of high, thin cirrus cloud that is almost invisible, but which contains enough water to be mostly opaque to IR. How do you think this type of cloud affects the temperature of the planet? Explain your reasoning. (10pts) 7. What is potential evapotranspiration? Explain thoroughly. (10pts)

2 ATMS 31: Physical Climatology Practice Mid Term Exam - Spring 001 page 9. Discuss the unusual features of this diurnal heat budget plot and speculate about what might cause these unusual features. (10pts) July Watts/Square Meter R sfc G LE SH Local Time 10. A gigantic volcanic eruption takes place. The radiative properties of the atmosphere change such that the planetary albedo is changed to 0., and the disposition of the absorbed solar radiation is changed so that 50% of the radiation that is absorbed is absorbed into the atmosphere and 50% is absorbed at the surface. Assume that the atmosphere can be represented with two layers at.5 and 5 km that are black bodies for infrared. The solar radiation is evenly distributed 5%/5% between the two atmospheric layers. a) Draw a diagram showing all of the radiative energy fluxes (be neat): (5pts) T1 T Tsurface b) Write down the radiative energy balance equations for the top of the the atmosphere, the two atmospheric layers, and the surface. (5pts) TOA Layer 1 Layer Surface.

3 ATMS 31: Physical Climatology Practice Mid Term Exam - Spring 001 page 3 c) Manipulate the 4 equations for the radiation energy balance to provide formulas for the temperature of each layer. Check to make sure that your 4 equations are consistent for the 3 temperature. (5pts) d) Solve for four temperatures, assuming that the solar constant is 1367 Wm -. (5pts) Te = e) Is this radiative equilibrium temperature profile convectively stable? Do you expect more or less rainfall than for the current climate? (5pts) Data and Formulas: σ = 5.68x10-8 Wm - K -4 π = c T Q t = G = Rs LE SH Feo I = σt 4 st 4 So e = ap 4 ( 1 - ) Area of circle = π r Area of Sphere = 4π r Density of water = 1000 kg m -3 Specific heat of water = 418 J K -1 kg -1 average radius of Earth = 6.37x10 6 m MORE EXAMPLE QUESTIONS BELOW: 1. A planet orbits about the sun in an elliptical orbit so that its closest approach to the sun(perihelion) is 80% of the mean Earth-Sun distance, and its farthest distance from the sun(aphelion) is 10% of the mean Earth-Sun distance. Calculate the total solar irradiance (solar radiation energy flux in Wm - ) at this planet at the time of perihelion and aphelion. (15pts). Mt. Fuji is a conical mountain at 38N with a side slope of 0. Calculate the insolation on the south side at local solar noon on Dec. Ignore absorption by the atmosphere. (15pts) 3. What is the Bowen Ratio and why is it important. (10pts) 4. Describe a situation in which the Bowen ratio might be negative. (10pts)

4 ATMS 31: Physical Climatology Practice Mid Term Exam - Spring 001 page 4 6. A gigantic volcanic eruption takes place. The radiative properties of the atmosphere change such that the planetary albedo is changed to 0., and the disposition of the absorbed solar radiation is changed so that 60% of the radiation that is absorbed by the planet is absorbed into the atmosphere and 40% is absorbed at the surface. Assume that the atmosphere can be represented with two layers at.5 and 5 km that are black bodies for infrared. The solar radiation is distributed 0% in the top layer and 40% in the lower atmospheric layer. a) Draw a diagram showing all of the radiative energy fluxes (be neat): (5pts) T1 T Tsurface b) Write down the radiative energy balance equations for the top of the the atmosphere, the two atmospheric layers, and the surface. (5pts) TOA Layer 1 Layer Surface c) Manipulate the 4 equations for the radiation energy balance to provide formulas for the temperature of each layer. Check to make sure that your 4 equations are consistent for the 3 temperature. (5pts)

5 ATMS 31: Physical Climatology Practice Mid Term Exam - Spring 001 page 5 d) Solve for the temperatures, assuming that the solar constant is 1367 Wm -. (5pts) Te = e) Is this radiative equilibrium temperature profile convectively stable? Do you expect more or less rainfall than for the current climate? (10pts) 7. Boundary layer clouds over the ocean have a different effect on the radiation balance at the top of the atmosphere than cirrus clouds over desert. Explain thoroughly. (10pts) 8. In the high desert, days can be 40 C and nights <0 C. Explain thoroughly using radiation and boundary layer physics. (10pts) Data and Formulas: σ = 5.68x10-8 Wm - K -4 π = c T Q t G = Rs LE SH Feo I = σt 4 st 4 So e ap 4 1 Area of circle = π r Area of Sphere = 4π r Density of water = 1000 kg m -3 Specific heat of water = 418 J K -1 kg -1 average radius of Earth = 6.37x10 6 m cosqs = sinfsind+ cosfcosdcosh So Wm * Pa L E = Mc e= 0. 6 q = e 611 exp 1 - p R Ł v 73 Tł Rv JK kg -1-1 R= 87 JK kg d Q = cosqs Ł d ł