EPS 5: Midterm Review Questions

The following are some questions that you should feel comfortable with before the midterm. This is a starting point for your studying, but not exhaustive.

1. What are the two main constituents of the atmosphere? 2. What is the definition of pressure? How can we interpret the surface pressure on Earth? 3. What is a blackbody? 4. What is the concept of effective temperature? 5. In what wavelengths do the Sun and the Earth peak in emission? 6. Is infrared or visible light at longer wavelengths? 7. Which has a greater albedo: a highway or a skating rink? 8. What is the atmospheric window? 9. What is the greenhouse effect? What are greenhouse gases? 10. What is the solar constant? What would lower the solar constant? 11. If we put layers into the atmosphere does the surface temperature of the Earth increase or

decrease? Why? 12. To what radiation do we assume that the atmosphere is transparent? 13. What is the force balance that is used to derive the barometric law? 14. What is the scale height? 15. How does pressure change with altitude according to the barometric law? 16. What is one of the big assumptions used in the derivation of the barometric law? 17. What do adiabatic and isothermal mean? 18. What is the difference between the atmospheric (or environmental) lapse rate and the

adiabatic lapse rate? 19. If an atmosphere is stable, what would the vertical temperature structure look like? 20. What is the wet adiabatic lapse rate? If a parcel becomes saturated does it rise higher in

the atmosphere than a dry parcel? 21. How does the saturated water vapor pressure change with temperature? 22. If there is water in the vapor form in the atmosphere, how can we change the

environment so that it will condense? 23. Explain the idea of latent heat release and how this closes the energy loop begun by

evaporation. 24. What is convection, when will it occur and how does it affect the stability of the

atmosphere? 25. If an air parcel is buoyant in the atmosphere, when does it stop moving? 26. If the wind is carrying air with water vapor in it from W->E and there is a range of

mountains blocking the way, are clouds more likely to be observed on the western side or eastern side of the mountain?

27. In what direction does the pressure gradient force push? 28. According to the sea breeze circulation does the wind come off of the ocean or off of the

land during the day? What drives this circulation? 29. Why is the angular velocity of the Earth a constant? 30. Why do we need the Coriolis force? What do we mean when we refer to it as an apparent

force?

31. In the Southern Hemisphere in what direction does the Coriolis force push relative to the wind? Why is it different in the Northern Hemisphere?

32. What circumstances would cause the Coriolis force to be large? 33. What did Hadley’s circulation accurately reproduce? What was the fault in his theory? 34. If you are in Maui (21oN) in what direction to expect the wind to be blowing? 35. What are the main features of the general circulation? 36. Does the meandering jet stream set up with high pressure or low pressure systems to its

north in the Northern Hemisphere? 37. When can we use the geostrophic approximation? 38. If isobars are closer on a weather map, will the wind be faster or slower? 39. When friction is a significant force how does that affect the rotation around a high and

low pressure system? 40. Do we expect to see cloudy conditions associated to a high pressure system?

Sample Long Questions, 2007 Midterm 1. Ymir (15 points) Last April, a group of scientists at the University of Geneva announced the discovery of Ymir (officially called Gliese 581c), a terrestrial planet orbiting the star Gliese 581 that is about five times more massive than the Earth. Gliese 581 is much colder than our sun, but Ymir’s proximity to the star may lead to “comfortable” surface temperatures. It is hypothesized that Ymir may have properties suitable for habitation by Earthlike life forms. (a) The star Gliese 581 emits radiation at a rate of 5.07•1024 W (about 100 times less than our sun emits!). The distance between Ymir and Gliese 581 is 1.10•1010 m. What is the solar constant (flux of energy crossing a unit area normal to a beam of light from Gliese 581) at the orbital position of Ymir (in units of W/m2) (3 points)? (b) Many of Ymir’s properties are unknown, including whether or not Ymir has an atmosphere. The albedo of Ymir’s surface is also unknown. Let’s assume that Ymir’s albedo is somewhere between 0.3 (Earth’s albedo) and 0.6 (Venus’ albedo). Assuming Ymir has no atmosphere, what is the range of possible surface temperatures on Ymir? Could liquid water exist anywhere in this range (assuming the same freezing/boiling points as on Earth) (4 points)? (c) What is the range of the possible surface temperatures if Ymir has a single atmospheric layer (assuming albedo is between 0.3 and 0.6)? Could liquid water exist in this scenario? (Assume the atmosphere absorbs as a blackbody.) (4 points)

(d) Assuming the true effective temperature of Ymir is in the middle of the range calculated in part (b), its blackbody radiation curve will look like the curve shown below. In which portion of the electromagnetic spectrum (UV, visible, IR) does Ymir radiate? If Ymir has an atmosphere with the same composition as the Earth, which of the gases shown below would serve as greenhouse gases on Ymir? Why? (4 points)

3. Madagascar (20 points)

The earth’s fourth largest island, Madagascar, lies off the east coast of Africa, with its center at roughly 20°S and 47°E. The island is divided by a central North-South ridge. The eastern side of the island is characterized by tropical rainforests, while dry deciduous forests, thorn forests, and xeric (dry) shrub lands predominate to the west and south. ↑ N

(a) Which is the likely the windward side of the island? (Windward means the side towards which the winds blow.) What is the direction of the prevailing winds? (Think about the island’s latitude (0° < 20°S < 30°S) and/or what you’ve been told about the land cover). You can use the image above to draw part of your answer. (1 point)

(b) Imagine an air parcel arriving at the coast with a relative humidity of 75% and a temperature of 22oC. Use this graph to help determine the vapor pressure of this parcel of air. Next, determine its dew point. (4 points)

(c) As the air parcel blows across the island, it encounters the mountains of the central ridge, and is lifted adiabatically. The dry adiabatic lapse rate is -9.8 K/km and the moist adiabatic lapse rate is -5 K/km. Field measurements show that the background atmosphere has a temperature of 25oC at the mountain base and an environmental lapse rate of -6 K/km from the surface to the top of the highest mountain. Is the background atmosphere stable or unstable? (1 point)

(d) Assuming the dew point declines at -2°K/km, at what altitude does the parcel reach its dew point (determined in (c)), and begin to form a cloud? (3 points) (e) After the cloud begins to form, the air parcel continues rising as it is blown up the mountain by prevailing winds. (Strong prevailing winds can force air over mountainous topography, regardless of its buoyancy.) Calculate the temperature of the air parcel once it reaches the summit of Tsiafajovona (~2600m), Madagascar’s second highest peak. The moist adiabatic lapse rate is defined in (c). Assume there is plenty of water in the air parcel. (3 points) (f) At the summit, is the air parcel colder or warmer than the background atmosphere? Based on this temperature difference, will the air parcel continue to rise, or will it fall after it reaches the summit? (3 points) (g) If the air parcel falls on the other side of the peak after reaching the summit, what would its temperature be upon reaching the central ridge plateau (~1100m) on the other side? (3 points) (h) Why is the western side of Madagascar dry? (2 points)