GEOG/ENVS 4201, Biometeorology, Fall 2009
Tues/Thurs 12:15 - 1:45, GUGG 205

Assignments

Assignment # 1 - What is Biometeorology?
Assignment # 2 - Radiation and Plant Canopies
Assignment # 3 - Biological Responses to Air Temperature
Assignment # 4 - The Human Energy Balance
Assignment # 5 - Water Potential and Flow in Plants
Assignment # 6 - Organisms and Climate Variability

Text refers to Environmental Biophysics

Assignment 1: What is Biometeorology?

Due: September 3
Total Possible Marks: 16

1. We have described what this science is, and what it encompasses in class. To show your understanding of the scope of biometeorology, choose an organism (any) and describe: 1) how it is affected by its environment (by environment, I mean the amount and exchange of energy and mass) and 2) how the organism, in turn affects (changes) its environment. Your answer must not exceed 2 pages of typed, double-spaced text. Marks: 3 for style, grammar and neatness, 7 for content.

2. To warm up on algebra and units, do questions 1.3 and 1.4 in your text. Marks: 3 each.

Assignment 2: Radiation and Plant Canopies

Due: September 17
Total Possible Marks: 22

Please show all of your calculations!

1. Question 10.4 in your text. Marks: 1.

2. Question 10.5 in your text. Marks: 3.

3. Describe in a paragraph or two, what a hypothetical forest would look like if the absorption of short-wave radiation by its leaves was large, say 90-95% (describe both the over- and understory). Marks: 4, 2 each of over- and understory descriptions.

4. You measured the following values over a forest at noon:

incident short-wave radiation = 800 W m^-2
reflection coefficient = 0.18
incident long-wave radiation = 300 W m^-2
surface temperature = 15 ^oC
emissivity = 0.97

What is the net radiation? Marks: 2.

5. Given a canopy with the following characteristics:

short-wave absorption = 0.8
leaf area index = 2 m² m^-2
Extinction coefficient at a solar zenith angle of 0^o = 0.5
Extinction coefficient at a solar zenith angle of 45^o = 0.8
clumping factor (index) = 0.9

calculate, for both zenith angles:

    A) The fraction of total beam radiation transmitted through the canopy. Marks: 2.
    B) Repeat A) with double the leaf area index. Marks: 2.
    C) Repeat A) with the leaves clumped together (clumping factor = 0.5). Marks: 2.

6.

A) What is the relationship between the extinction coefficient and the solar zenith angle for a canopy with a spherical leaf distribution (i.e. x = 1). Plot this relationship using zenith angles between 0 and 80, at increments of at least 1 degree. Marks: 2.
B) What is the fraction of the incident solar beam radiation that will reach the ground for this canopy, as a function of the zenith angles used in A)?. Plot this relationship for a canopy with a leaf area index of 2.0. Marks: 2.
C) If you double the leaf area index, what do you expect will happen to the fraction of the incident beam radiation that will reach the ground. Repeat b) for a canopy with double the leaf area index, and describe your results. Marks: 2.

Assignment # 3: Biological Responses to Air Temperature

Due: Tuesday October 27 2009
Total Possible Marks: 30

Hand-written assignments will be not be graded.

Please show all your work to get full marks!

1. Text, Question 2.4. Marks: 6 for each part.

2. Calculate the effective temperature (Te) using the equation on the wind chill handout for air temperatures between -50 and 0 ^oC (increments of 1 ^oC; that means 50 calculations of Te) at wind speeds of 6, 25, 50, and 75 km/h (equivalent to roughly 4, 15, 31, and 47 miles/h, respectively). Use a walking speed of 6 km/h. Plot and interpret your results. Marks: 8 for plot, 4 for interpretation.

3. Calculate the Humidex (H) using the equation on the Humidex handout for air temperatures between 0 and 30 ^oC (increments of 1 ^oC; that means 50 calculations of Te) at a relative humidity of 25, 50, 75 and 100%. Plot and interpret your results. Hint: You may find equations 3.8 and 3.11 useful, and note that 1 kPa = 10 mbar. Marks: 8 for plot, 4 for interpretation.

Assignment # 4: The Human Energy Balance

Due: To be annnounced in class
Total Possible Marks: 27

Introduction
The relationship between a person's mass and body surface area has implications for how we achieve temperature regulation through adjustments in our energy balance. When energy inputs balance energy outputs, a constant (steady-state) body temperature is achieved. The heat generated by metabolism (H_m), is balanced by convective (H_c), radiative (H_r), evaporative (from sweating; H_s, and from within the lungs; H_l) when body temperature is constant. In this exercise, we'll explore the relationship between human mass and the energy balance. Use your answers and constants from previous questions to answer the next.

Questions
1. What is the relationship between a person's total body area, and mass? First, write down your hypothesis on what you think the relationship is, and why (2 marks). Then, for a 2-m tall person, calculate the total body area as their mass varies from 0 to 100 kg in 2-kg increments. Plot the relationship (2 marks), and describe what the implications of your graph in terms of a person's energy balance and temperature regulation (2 marks). Hint: Equation 13.1 may be useful.

2. Based on your answer to #1, what do you think the relationship between mass, and the radiative and convective heat loss would be, and why (2 marks)? From an Ohm's Law analogy, we know that "flux = conductance x gradient". Therefore, we can write:

H_r (radiative heat loss) = D_rA(T_s-T_a) and
H_c (convective heat loss) = D_cA(T_s-T_a)

where D_rand D_c are the heat and convective conductances, respectively (D_r = 6.5 and D_c = 7.1 W m^-2 K^-1), A is the total body surface area (m²), and T_sand T_a are the body surface and air temperature, respectively (T_s = 37 and T_a = 25 ^oC, respectively). Plot the relationship between mass (for a 2-m tall person), and H_r and H_c (use one graph with two plots) (2 marks). How does a person's mass influence the convective and radiative heat losses? (2 marks).

3. How does a person's mass influence their ability to cool by sweating? To answer this, assume a person generates heat at a rate of 500 W (e.g. moderate activity), and the rate of heat loss from the lungs is 10.5 W. First, write down the energy balance for our 2-m tall person with a constant temperature (1 mark). Then, calculate the heat loss from sweating as a function of mass, and plot this relationship (4 marks). What does this relationship show? (2 marks). Is your result a surprise (why or why not?) (2 marks).

4. At what mass does the evaporative sweating, convective, and radiative heat losses roughly balance? To determine this, on one graph, plot each of these terms against mass (2 marks).

5. The heat loss from sweating can be expressed as H_s = D_sr where D_s is the "evaporative sweating conductance" (674 W h kg^-1), and r is the sweat required. Plot the sweat required to supply the sweat evaporation rate as a function of mass (2 marks). How many litres of water would a person at the mass you reported in question 4 need to drink per hour to supply this demand? (2 marks).

Assignment # 5: Water Potential and Water Flow in Plants

Due: To be annnounced in class
Total Possible Marks: 16

Please show all your work to get full marks!

In your text, questions (marks):

    4.1 (1)
    4.2 (1)
    4.3 (3)
    4.4 (7)
    4.5 (1)
    4.6 (2)
    4.7 (1)

Assignment # 6: Organisms and Climate Variability

Due: To be annnounced in class
Total Possible Marks: 20

We know that the Earth's climate is variable, even over relatively short time scales. It has changed in the past and will in the future. Organisms, to be successful, must then be capable of adapting to such climate variability.Or maybe not? (e.g. think of many reptiles, insects (coach roaches), or the plant Equisetum (horsetail))

Your assignment is to find at least one scientific paper (It must be peer reviewed. Web documents, unless on-line peer reviewed journal articles, are not acceptable) that describes how an organism adapts (or doesn't adapt) to changes in its environment. For example, inspection of plants in her bariums compared to today's plants shows that the stomata density has decreased as carbon dioxide concentrations in the atmosphere have increased (implying that the plants have become more efficient). Write a 2-5 page summary of your paper's findings, including at least one key figure or graph (10 marks). Then, on December 3, be prepared to orally present your paper to the class, using visual aids to assist you (10 marks). Your oral presentation should be 5-10 minutes.