GEOG 3601 (ENVS/ATOC 3600), Principles of Climate, Spring 2008
Tues/Thurs 11:00 - 12:15, GUGG 205

Assignments

Assignment # 1 - What is Climate?
Assignment # 2 - Analyses of Climate Data
Assignment # 3 - The Solar Constant?
Assignment # 4 - The Surface Radiation and Energy Balance
Assignment # 5 - Changing the Water Cycle
Assignment # 6 - It's Up to You

Assignment 1: What is Climate?

Due: January 24
Total Possible Marks: 10 (7 for content; 3 for style, grammar, presentation)
We have compared and contrasted some of the various definitions of climate. The terms climatology and meteorology are often confused (what's the difference?). Find someone's definition of climate (other than your text or from lectures!), reference it, and describe why or why not you think it's a good definition. Then write in your own words (in one sentence) what you think is the best, most complete definition of climate, and explain why. Your answer must not exceed 1 page of typed, doubled-spaced text.

Assignment 2: Analyses of Climate Data

Due: February 7
Total Possible Marks: 60

Introduction
We have defined climate in terms of some statistical properties of long-term weather observations. The purpose of this assignment is to examine some local long-term air temperature records to see how you interpret these records, and if your interpretation changes depending on how you present the data. This will give you practice at summarizing and interpreting large volumes of data.

You are provided two data sets (found at the class web site; click on the station name to get data) of mean monthly air temperatures for the two stations summarized below (year followed by Jan-Dec. mean monthly air temperatures all in degrees C):

Station	Period	Latitude	Longitude	Elevation (m asl)
Denver WB City 52225	1872-1972	39 deg 45' N	105 deg 00' W	1591
Boulder 50848	1931-1997	40 deg 01'N	105 deg 16' W	1646

Questions
1. The air temperature at a given location often displays a distinct seasonal pattern. To investigate the seasonality of the air temperatures at Denver and Boulder, at each location calculate the mean, standard deviation, minimum, and maximum, for each month for the entire length of records (ignore missing values as indicated by NaN). Construct two tables, (one for Denver and one for Boulder) to show your values. Marks: 10 total, 5 per table.

2. A. For both stations, plot the mean monthly temperatures and the standard deviation (plot the mean plus and minus one standard deviation). Your graph must have a title and have the axes appropriately labeled. Make two separate graphs, one for each station. Marks: 10 total, 5 per graph.

B. With the aid of your graphs, describe the seasonality in the air temperatures (e.g. when is the air temperature most variable), any differences you observe between the two stations, and anything you think could affect the quality of these measurements. Marks: 5 total.

3. A. To investigate any long-term trends in the annual air temperature patterns at each station, calculate the mean annual air temperature for both stations (if a month or more of data are missing, you may simply exclude the entire year). Rather than show all your values, what was the mean temperature during 1940-1970 period (inclusive) at both stations (again, just ignore any missing data)? Do get this number, simply calculate the mean annual air temperature for all the years between 1940-1970 (you will get one number for each stataion). Marks: 5 total, 2.5 for each.

B. Plot the mean annual temperature for all years between 1872-1972 (Denver) and 1931-1997 (Boulder) against year for both stations (make two separate graphs). Connect all the points with a line. Don't use bars please. Appropriately label the axes and give each graph a title. Marks: 10 total, 5 per graph.

C. Describe and try to explain any trends you observe. How do any trends at the two stations compare? If you plot (no need to show) both annual means on the same graph to create on longer-term "regional" picture (both stations are close together), does your interpretation of the "regional" trend change? Marks: 5 total.

4. A. On separate graphs, plot the mean annual air temperature anomaly against year for both stations using a bar graph (see Plate 8a in your text). To do this, simply subtract the 1940-1970 mean temperature you calculated in 3A from the mean annual temperature for each year (do this for both stations). To aid interpretation of possible trends, also plot the five-year running mean with a line (you're trying to create a graph that looks like those shown in Plate 8a). Marks: 10 total, 5 per graph.

B. Describe and explain any trends you observe. Does looking at theses new graphs (as compared to those you make in 3B) change your description and explanation of any trends you observe? Marks: 5 total.

Assignment # 3: The Solar Constant?

Due: February 28
Total Possible Marks: 30

Introduction
Is the solar constant (S_F) really constant? We've learned that for examining relatively short-term climate, it's a reasonable simplification to assume that S_F is constant. We know, however, that over the long term, S_F is increasing as the Sun ages. Superimposed on this long-term trend are short-term decreases in S_F due to sun spot activity.

So what has this got to do with the Earth's climate? The Earth's climate it ultimately driven entirely by S_F. The objective of this assignment is therefore to quantify how sensitive S_F is to fluctuations in changes in photosphere's radiative surface temperature.

Questions
1. Plot the Planck (blackbody) curve for the Sun at its current temperature of 5800 K. Use wavelengths between 0.01 and 3.00 um, in increments of at least 0.01 um. Add to this graph Planck curves for the Sun at temperatures 15% and 30% above and below 5800 K. Your final graph will have a total of five plots. As before, your graph must be properly annotated. Marks: 20 total, 3 per plot, 5 for annotation and neatness.

2. Calculate the wavelength of maximum emission for the Sun at each of the five temperatures (the peaks of your five plots). What's happening to the wavelength of maximum emission as the temperature changes? Marks: 10 total, 5 for each maximum wavelength, 5 for description/explanation.

3. Calculate the total energy emitted from the Sun at each of the five temperatures (the area under each plot). What's happening to the energy emitted by the Sun as the temperature changes? Marks: 10 total, 5 for each total energy, 5 for description/explanation.

4. How does S_F vary with the Sun's surface temperature? To make this calculation:
a. The solar luminosity (in Watts) = E (from question 3) x area of the Sun (4pr ² where r = 6.96 x 10⁸m)
b. S_F = solar luminosity / (4pr ²) where r is the mean Earth-Sun distance of 1.50 x 10¹¹ m
Make a graph (Sun's surface temperature on the x axis, S_F on the y axis) to help with your description and explanation. In terms of Earth's climate, should we be worried about a change in S_F, or are they insignificant? Marks: 10 total, 5 for graph, 5 for explanation.

Assignment # 4: The Surface Radiation and Energy Balance

Due: March 13
Total Possible Marks: 53

Introduction
Use this data for this assignment. The columns of data are the following measured variables:

    1. Time: day of year (211 = July 30) before decimal. After decimal is the hour divided by 24 (e.g. noon July 30 = 211.5)
    2. Incident solar radiation (W m^-2)
    3. Reflected solar radiation (W m^-2)
    4. Net radiation (W m^-2)
    5. Latent heat flux (W m^-2)
    6. Sensible heat flux (W m^-2)
    7. Air temperature (deg. C)
    8. Surface temperature (deg. C)
    9. Relative humidity (%)
    10. Vapor pressure (kPa)
    11. Horizontal Wind speed (m s^-1)

Questions
1. Make a graph of the incident and reflected solar radiation against time. Next, make a new graph of the surface albedo against time. Comment on the nighttime albedo (why is it so crazy?) Describe how and why the albedo of this surface changes with time during the day. Give the albedo around noon for each of the three days. Describe how and why the noontime albedo varies with cloud cover for the three days. Marks: 10 for graphs, 10 for written.

2. Calculate the emitted long-wave radiation from the surface using the measured surface temperature and the Stephan-Boltzmann Law (use emisivity = 0.97). Next, calculate the incident long-wave radiation (emitted from the sky downwards to the surface) as a residual of the radiation balance. Plot the incident short- and long-wave radiation as a function of time (one graph with two lines). Describe and explain any patterns you observe in the incident long-wave, using the incident short-wave to help you. Marks: 8 for graph, 5 for written.

3. Make a graph of the latent heat flux and sensible heat flux against time (one graph with two lines). Which variable(s) do the two fluxes appear to be responding to and why? Marks: 5 for graph, 10 for written.

4. Using your answers to the questions above, describe the surface (bare soil, short vegetation, forest, wetland, lake, ocean, urban?) that these measurements were taken from and why you think so. Marks: 5.

Assignment # 5: Changing the Water Cycle

Due: April 10
Total Possible Marks: 32

Introduction
The linkage between the global water cycle and climate is evaporation and precipitation. The Earth's surface experiences changes in its vegetation types and coverage due to both natural and anthropogenic disturbances. Therefore is this assignment, you will investigate what changes would occur in the globally averaged precipitation on the land surface and globally averaged runoff from the land to the sea, given a 20% decrease in evaporation from the land surface due to, for example, deforestation or desertification. The illustration of the hydrologic cycle below will help in your answers.

water cycle

Where:

P_L = rate of precipitation on the land
P_S= rate of precipitation on the sea
R = rate of runoff from the land to the sea
E_LL = rate of evapotranspiration from the land that falls as precipitation on the land
E_LS = rate of evapotranspiration from the land that falls as precipitation on the sea
E_SS = rate of evaporation from the sea that falls as precipitation on the sea
E_SL = rate of evaporation from the sea that falls as precipitation on the land

Questions

1. Give your immediate rough guess to the answer. Justify your rough estimate stating why you feel it's right or wrong. Marks: 5.

2.Given the illustration above, we can now refine and restate our problem as "How will R and P_Lchange if E_LL and E_LS both decrease by 20%?" To get us started on the answer, first give three water conservation equations, as water must be conserved in this problem (water inputs = water outputs). With the aid of the illustration above, write the simple equations for the water conservation: 1) in the sea (vertical exchange), 2) on the land (vertical exchange), and 3) rate of water flow from the land to sea equals the rate from the sea to land (horizontal exchange). Write a brief explanation describing each equation. Marks: 6 (2 per equation).

3. Using your three equations above, and given the additional facts: P_L = 108 x 10³ km³/y, P_S = 410 x 10³ km³/y, R = 46 x 10³ km³/y, and E_LL = 3E_LS, determine the values in km³/y for E_LL, E_LS, E_SS and E_SL. Marks: 8 (2 per value).

4. Now let's decrease evapotranspiration over the land by 20%, while keeping evaporation over the sea the same (as per the original question). Expressing the new rates (after the 20% increase) as primes ('), we can write:

_LL

_LS

_SS

_SL

Now, the new R (R') and P_L (P_L') can be expressed as:

R' = E_SL' - E_LS'
P_L' = E_LL' + E_SL'

Give the values of R' and P_L' using the information given above, and realizing that R + E_LS = E_SL and P_L = E_LL + E_SL. (Hint: Manipulate the equation to get rid of the unknown prime values, replacing them with your known values). Marks: 8 (4 per value).

5. Now let's answer the question as originally stated at the beginning of the assignment. By how much will the total global precipitation rate change? Compare this answer to the rough estimate you give in question 1. (Hints: P_GLOBAL = P_S + P_L, P_S + R = E_SS + E_SL). Marks: 5.

Assignment # 6: It's Up to You

Due: April 24
Total Possible Marks: 30 (20 for content; 10 for style, grammer...)

Write a brief essay on any climatologically-related topic that interests you. You are limited to three single-sided, double-spaced pages, and you must included a minimum of five current references (excluding web site references). Your essay must have an introduction, main body, and summary or conclusions. You may summarize the current state of knowledge of some aspect of climatology, or you may prefer to, for example, describe the pros and cons of global climate warming (for example). If you are not sure if your topic is acceptable, ask the Instructor for approval.