Thermodynamics of Atmospheres and Oceans
Planetary Radiation (9.1)
Worksheet 18
1. Calculate the solar constant of Mars, using the following information (see page 332) The solar constant for the Earth is 1370 W m-2, and the ratio of the mean distance from the sun for Mars to that the mean distance from the sun to Earth is 1.52 (Table 14.1). Compare this value with the value in Table 14.6 (p 404).
compared to 600 in the table
Consider Fig 12.3 for the following questions:
2. Averaged over the annual cycle, more radiation is received at
a) the North Pole
b) the equator
c) 30oN
3. The annual cycle of solar radiation is greatest at
a) the North Pole
b) the equator
c) 30oN
4. At the summer solstice, the latitude receiving the greatest amount of solar radiation is
a) the North Pole
b) the equator
c) 30oN
Ocean surface radiative flux
1. What is the value of the surface albedo of the ocean under overcast conditions?
~7%
2. In clear-sky conditions, the surface albedo (increases, decreases, remains the same) as the solar zenith angle increases. Increases
3. The equation for the net surface radiation flux is (9.2; note errata)
where 1-0 is the surface longwave reflectivity. If 0=0.97, what is the surface longwave reflectivity? 1 – 0.97 = .03
4. An increase in atmospheric water vapor will (increase, decrease, not change) the downwelling surface longwave radiation flux. Increase
5. An increase in atmospheric water vapor will (increase, decrease, not change) the downwelling surface shortwave radiation flux. Decrease
6. Clouds (increase, decrease, not change) the downwelling surface longwave radiation flux relative to clear sky conditions. Increase
7. Clouds (increase, decrease, not change) the downwelling surface shortwave radiation flux relative to clear sky conditions. Decrease
8. An increase in air temperature will (increase, decrease, not change) the downwelling surface longwave radiation Increase
9. An increase in air temperature will (increase, decrease, not change) the downwelling surface shortwave radiation. Not Change
Go to
6. Determine the sunrise and sunset times for Atlanta for December 7
7:29am5:29pm
7. Determine the date of onset of the polar night for Barrow Alaska (go down towards the bottom of the city list)
Nov 19, 2006
8. Determine the noon solar zenith angle for Atlanta on Dec 21
(note elevation angle is one minus the zenith angle; see the solar calculator glossary)
Solar Elevation 32.2290 – 32.22 = 57.80
9. Determine the day length for Atlanta on Dec 21 (hint use sunrise/sunset)
7:38am to 5:33pm = 9h 55m
10. Determine the noon solar zenith angle for Atlanta on Jun 21
Solar Elevation 76.5790 – 76.57 = 13.50
11. Determine the day length for Atlanta on Jun 21 (hint use sunrise/sunset)
5:27am to 7:51pm = 14h 22m
Go to for an interactive shortwave radiative transfer code. Perform the following calculations, for Instrument Filter Solar Flat, to determine the surface shortwave radiation flux under the specified conditions. Ignore the date, lat, lon, and specify the solar zenith angle. Unless otherwise specified, use the default values.
1. Atmospheric Profile: Tropical
Zenith angle 10o
Surface albedo model: sea water
Aerosol profile: oceanic
Net Surface Flux=___975.65_____
2. Perform the same calculation as for #1, except change the solar zenith angle to 60o.
Net Surface Flux=___420.79____. Compare the surfaces fluxes for #1 and #2. Explain.
The change is due to the increase in zenith angle causing more reflection, 1>2
3. Perform the same calculation as for #2, except change the aerosol model to urban (note an example of this would be polluted air from India being advected out over the Indian Ocean). Net Surface Flux=___370.31______. Compare the surface fluxes for #1 and #3. Explain
Pollutants scattering/reflecting more of the incoming solar radiation, 1>3
4. Atmospheric Profile: Subarctic winter
Zenith angle: 60o
Surface albedo model: sea water
Aerosol model: oceanic
Net Surface Flux= ___470.79______
Downwelling Surface Flux=___481.40______
Compare surface fluxes for #2 and #4. Explain
Larger aerosol content in the tropics limits downwelling and net flux in 2, so 4>2
5. Perform the same calculation as for #4, except change the surface albedo model to snow. Net Surface Flux=___104.10_____. Downwelling Surface Flux= __544.16_____ Compare the surface fluxes for #4 and #5. Explain.
Snow reflects more because of increased albedo, so net 4>5. Downwelling is likely increased due to less aerosol content reflecting in coming SW radiation so 5>4.
6. Perform the same calculation as for #4, except add 1 cloud layer at 3 km, with optical depth=2, effective radius=8 microns. Net Surface Flux = __359.85____ Downwelling Surface Flux = __351.54_____ Compare the surface fluxes for #4 and #6. Explain. Is this effective radius more typical of ice or liquid clouds?
The addition of clouds limits SW radiation reaching the surface so for both fluxes 4>6. It is more typical of water
7. Perform the same calculation as for #5, except change the optical depth to 4. Downwelling surface flux = __442.75______
8. Perform the same calculation as for #5, except change the optical depth to 6. Downwelling surface flux=__426.87_____. Compare the surface fluxes in #6 and #7, and the fluxes in #7 and #8. Does the surface flux decrease linearly with increased optical depth?
The increase from 6 to 7 is due to the removal of clouds. The change from 7 to 8 is a decrease due to the increased optical depth. The flux decreases via a powered decay and therefore is not linear.
9. Perform the same calculation as #6, except click the box for cirrus cloud. Downwelling surface flux = ______. Compare the surface fluxes for #6 and #9. Explain.
Gives error in calculation