Transcript Document

EARTH SYSTEM SCIENCE STUDENT PERFORMANCE AT THE INTRODUCTORY LEVEL WITH THE CLARK ATLANTA UNIVERSITY ENERGY BALANCE MODULE
Randal L. N. Mandock
STUDENT EVALUATION OF MODULE
Earth System Science Program, Department of Physics, Clark Atlanta University, Atlanta, GA 30314
Presented at the "Infusing Quantitative Literacy into Introductory Geoscience Courses" Workshop, Carleton College, Northridge, Minnesota, 26-28 June 2006
Student evaluation of the energy balance module consisted of circling the
level of agreement with each of 10 statements about the student's
experience with the project and the module. Student answers to eight of
these statements are tallied in Table 1. The statements are listed here.
INTRODUCTION
The Earth System Science Program (ESSP) at Clark Atlanta University is developing
an instructional module to study energy balance at the land and water surfaces. A
graphical user interface (GUI) has been developed which is used to model each of the
components (net radiation, sensible and latent heat fluxes, ground heat flux, storage,
anthropomorphic, and residual) involved in the partitioning of energy at the air/land and
air/water interfaces. The GUI consists of a graphical model in the form of an energy
balance diagram (e.g., Figure 1).
The energy balance equation for an "ideal" land surface may be represented in the
following form: Q* = HS + HL + HG
1. The training I received in lecture and laboratory adequately prepared
me to complete the energy balance project.
2. As a result of completing the project, I now understand evaporation and
other atmospheric energy fluxes better than I did before.
3. I learned about solar radiation, temperature, wind, and other
meteorological sensors during completion of the project.
4. The energy balance module helped me learn about energy fluxes and
partitioning of energy at the land surface.
5. The energy balance module's graphical interface was easy to use.
6. The energy balance module's graphical interface was well designed.
7. The instructions accompanying the energy balance module adequately
explained how to use the module to solve energy balance problems.
8. The energy balance module really helped me understand difficult
concepts that I encountered in the project.
Figure 5. Air temperature.
Q* (also written as RN) represents the net transfer of radiation through the atmosphere,
HS represents the atmospheric flux of "sensible" heat, HL represents the atmospheric
flux of water vapor (also referred to as "latent" heat), and HG represents the heat flux
through the ground.
Figure 10. Scenario prior to energy flux estimation.
Figure 1. Energy balance diagram.
Question Strongly Agree Disagree Strongly
No
No
Number Agree
Disagree Comment Answer
1
39
52
2
0
3
2
2
23
70
2
1
2
0
3
14
53
5
0
4
22
4
23
63
2
0
4
6
5
22
58
7
0
5
6
6
30
55
2
0
4
7
7
26
55
1
0
10
6
8
16
47
4
0
8
23
DESCRIPTION OF GUI
The GUI graphically models energy balance components.
An energy balance diagram consists of the following:
Sky elements: sun, moon, clouds
Line or box representing air/surface interface
Arrows to indicate magnitude and direction of fluxes
Figure 6. Soil temperature.
Table 1. Frequency of student responses to module evaluation statements.
The module includes 8 model scenarios which vary by:
STUDENT PERFORMANCE ON MODULE TESTS
EXPLANATION OF PROJECT
Module applications include not only theoretical elements but measured data.
Figure 3 shows one of the more than 60 surface meteorological stations of the
Georgia Automated Environmental Monitoring Network (AEMN).
The module was tested in a project assigned in the
freshman Physics 104 "Introduction to Earth
System Science" course during Spring and Fall
semesters 2005 and Spring semester 2006. The
first part of the project used one year of archived
data from the AEMN to illustrate how variations in
solar zenith angle influence air temperature, the
soil temperature profile, and evapotranspiration. In
the second part of the project the students used
daytime and nighttime 15-minute averaged surface
weather data to infer the directions of net radiation
and sensible, latent and ground heat fluxes for
clear-sky, ideal land-surface conditions. Ideal landsurface conditions are approximated at most of the
AEMN sites by either bare soil or short grass
canopies on relatively flat ground. Links to NWS
and Unisys weather were provided to aid in
identification of days with clear-sky conditions.
Figure 7. Evapotranspiration.
Figure 3. AEMN station at Bledsoe Farm.
PROJECT: ENERGY BALANCE AT AEMN SITES
Goals
• Student will infer energy fluxes for one AEMN surface meteorology site
• Student will explore day and night scenarios for uniform ground cover
• Student will explore consequences of the earth-sun relationships
Figure 8. Insolation (downwelling solar radiation).
Method
• Student goes to AEMN web site at: http://www.griffin.peachnet.edu/bae/
• Student clicks on assigned station location on map of Georgia
• Student clicks on "Graph Daily Data" (Figures 5-8)
• Student is to explain the peak in July and dip in January for:
STUDENT PROFILE
Nearly all of the 317 undergraduate
students enrolled in the course for the three
semesters consisted of liberal arts and
education majors.
Air temperature
Soil temperature at all depths
Evapotranspiration
Solar radiation
• Student prints out "Current Conditions" for assigned site (Figure 9)
• Student runs the Energy Balance Module for current conditions (Figure 10)
• Student is to estimate the magnitude and direction of these fluxes (Figure 11):
Net radiation flux
Sensible heat flux
Latent heat flux
Ground heat flux
• Student verifies that solar radiation is zero at night
ACKNOWLEDGEMENTS
Figure 4. AEMN stations in Georgia.
Figure 9. AEMN "Current Conditions" web page.
1. Heat is transferred from (circle answer): (a) cold to warm regions, (b) warm
to cold regions, (c) cold to cold regions, (d) warm to warm regions.
2. Describe what is meant by energy balance at the atmosphere/earth
interface.
3. Describe the flux of net radiation.
4. Describe sensible heat flux.
5. Describe latent heat flux.
6. Describe ground heat flux.
7. What source of energy normally drives the earth/atmosphere system
during daylight hours?
8. Write the energy balance equation for a moist, bare ground surface.
9. Draw a typical energy balance diagram for a moist, bare ground surface
on a sunny afternoon.
10. Draw a typical energy balance diagram for a short, weed-covered surface
late on a humid night.
12
10
8
Fal l 2005 Post
Mean = 66%
Medi an = 70%
Std. Dev. = 23%
6
4
2
0
0
20
40
60
Test Score
80
100
Figure 12. Fall 2005 post test scores.
F r eq u en cy o f Occu rr en ce
ENVIRONMENTAL DATA
Surface wind speed and direction
Air temperature
Relative humidity
Atmospheric pressure
Insolation
Rainfall rate
Subsurface temperature profile
Student performance with the module was assessed by 10-question
preliminary and post tests. The questions were the same on each test and are
listed here. Histograms of results are plotted in Figures 12 and 13.
Figure 11. Scenario after estimation of energy fluxes.
Figure 2. Graphical user interface.
F r eq u en cy o f Occu r ren ce
Climate or microclimate
Day and night
Cloudiness and sunshine
Windy and calm conditions
Land or water surface
Freezing and nonfreezing temperatures
25
20
Spri ng 2006 Post Test
Mean = 54%, Medi an = 55%
Std. Dev. = 19%
15
10
5
0
0
20
40
60
80
Test Score (%)
100
Figure 13. Spring 2006 post test scores.
CONCLUSION
Given that the mean score for the module preliminary examinations in the Spring 2006 semester was
8.3% for the 110 students tested, the results shown in Figures 12 and 13 promote confidence that use
of the module is an effective way to teach energy balance to non-science university students. The
student evaluation results support this conclusion as well.
Support for this project was provided by National Oceanic and Atmospheric Administration (NOAA) Environmental Entrepreneurship Program Grant #
NA030AR4810132, and Universities Space Research Association (USRA) Earth System Science Education for the 21st Century Grant #
NNG04GA82G.
Corresponding author: Randal L. N. Mandock ([email protected]).