17 March Good luck!

Transcription

1 ! Midterm Exam 17 March 2005 Name:! SID:!! The mid-term has a maximum of 120 points: 60 points for a section with short essays, and 60 points for a section with qualitative/quantitative problems. Remember to carefully read the questions! Think simple and do not make unnecessary assumptions! Write clearly and use the provided space. Good luck! Remember to write clearly so that your instructor can read and understand your answers! Academic Integrity. The University Senate requires that students include the following signed statement on each examination: I pledge on my honor that I have not given or received any unauthorized assistance on this examination

2 Part I: Short Essays (4 * 15 pts. max = 60 pts. max) In this section I look for a brief answers and explanations of about one paragraph in length that answer the questions. Make sure that you include the most relevant aspects of the correct answer. Answer only 4 out of the 5 questions (pick your favorites)! 1. What is the atmospheric greenhouse effect? 2. What different roles does the expression P - E (precipitation - evaporation) play for the different components of the climate system?

3 3. Can the atmosphere transport heat only by a mean circulation (characterized by a mean wind speed), or are there also other possible means? 4. Which role does vegetation play for the surface energy- and water balance? Which terms are affected, and why are these affected by vegetation?

4 5. Is the sensible heat flux always directed from the surface to the atmosphere (i.e. cools the surface, heats the atmosphere), or can you imagine a situation in which the heat flux would be reversed? Where on Earth is this likely to be found?

5 Part II: Qualitative/Quantitative (3 * 20 pts. max = 60 pts. max) This section involves interpretation of diagrams and/or some simple calculations. Make sure that you show all your work of how you got to the answer. You may use a calculator for getting the final numerical value. Answer only 3 out of the 4 problems (pick your favorites)! 1. Energy Balance. The diagram shown below shows the global energy balance of Earth, with some numbers missing stratosphere 10 7 re- 21 emitted troposphere 335 emitted re- 17 SH LH surface 171 emitted -376 re- 304 heat fluxes 99 solar shortwave terrestrial longwave turbulent fluxes all units in W/m 2 a. Fill in the missing numbers! b. How strong is the atmospheric greenhouse (in terms of units) in the diagram?

6 2. Terrestrial water balance. The diagram below shows the mean seasonal course of precipitation (solid line) and potential evaporation (dotted line) for one location in the US. a. What would be the seasonal course of evaporation if storage of soil moisture is (a) negligible and (b) sufficiently large? Draw the two cases of evaporation into the diagram, mark them clearly, and briefly explain cm/month J F M A M J J A S O N D J b. What would be the seasonal cycle in soil moisture content in the case of a large storage capacity? During which months is soil moisture recharged and depleted and in which months would the maximum/ minimum in soil moisture be found? Draw the seasonal course of soil moisture into the empty diagram below and add a scale and a proper unit. Remember that the change in soil moisture is directly related to precipitation and evaporation (neglect the effect of runoff for simplicity). J F M A M J J A S O N D J

7 3. Radiative temperature. In 2004, scientists at Caltech and Yale discovered a tenth large object orbiting the Sun, which since has been named Sedna. Sedna orbits the Sun on a highly elliptical orbit far outside from Pluto s orbit (see figure on right). The closest distance of Sedna to the Sun is about 76 AU (1 AU = km, the mean distance of the Earth to Sun), at the farthest point of the orbit, Sedna is about 1000 AU away from the Sun. a. How much incoming solar radiation does Sedna receive at the perihelion? Orbit of Sedna in relation to the other 9 planets in our solar system. b. Assuming a planetary albedo of 20%, what would be the radiative temperature of Sedna at the perihelion?

8 4. Heat Transport. Calculate the surface temperatures of polar and tropical regions from a simple energy balance approach. Use QT = 300 W/m 2 and QP = 170 W/m 2 for the amount of solar radiation in the tropics and polar regions respectively, and use QTR = A + B * T for the emission of terrestrial radiation (for a temperature T in C) with A = 204 W/m 2 and B = 2.17 W/m 2 /K -1. Neglect turbulent heat fluxes. a. What would be the tropical and polar temperatures in the case of no heat transport? b. What is the global mean surface temperature? To calculate the mean absorption of solar radiation use the numbers from above and assume that the tropical and polar regions represent equal areas (so that the mean is given by (QT + QP)/2 ). How much heat transport would be required to be removed from the tropics for it to attain the global mean value?