GEOG3-Activity02-SurfaceEnergyBudget-W22
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Geography
Date
Dec 6, 2023
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GEOG3 –
Oceans & Atmosphere (W22, Prof. Ian Walker) –
Section Activity 2 1 Department of Geography, University of California Santa Barbara GEOG 3 Ocean & Atmosphere –
Winter 2022 –
Prof. Ian Walker Activity 2: Surface Energy Budget
Introduction In lecture we discussed how the surface energy budget must be balanced, in accordance with the Law of Conservation of Energy. Thus, the energy coming into the Earth’s surface (Q
in
) must equal the energy leaving the surface (Q
out
). We also discussed that this budget situation is a global average and that there can be variations over space and time. For instance, if Q
in
= Q
out
, and the energy budget is balanced, the temperature of the surface at a given location would not change. However, we often see daily (diurnal) variation as the sun rises and sets, which results from changing the amount of insolation and heat energy at Earth’s surface. Although the budget must balance globally, locally there are variations that give rise to temperature gradients in response to changes in the relative amounts of energy in various components of the budget. There are 3 main terms in the energy budget: 1) shortwave solar radiation
(Q
sw
); 2) longwave heat radiation
(Q
lw
); and 3) convective heat transfer
, which is the sum of latent heat from evaporation/condensation (Q
lh
) and sensible heat from convection (Q
sh
). Energy coming downward to the surface is shown with a down arrow (↓). Energy leaving the surface is shown with an up arrow (↑). Therefore, the balanced surface energy budget can be written as: Q
sw
↓ + Q
lw
↓ + (Q
lh
+Q
sh
)↓ = Q
sw
↑ + Q
lw
↑ + (Q
lh
+Q
sh
)↑
(equation 1) Recall also that the amount of longwave heat radiation (Q
lw
) emitted by an object depends on its temperature: hotter objects emit more radiation
. Outgoing shortwave energy from the Earth’s surface (Q
sw
↑) is simp
ly reflected sunlight and the amount reflected depends on the surface albedo: Q
sw
↑ = albedo* Q
sw
↓
(equation 2) Learning Objectives Through this activity, you will: 1.
Investigate the surface energy budget of several different surfaces around the UCSB campus. 2.
Improve your understanding of the controls on the surface energy budget of the Earth. 3.
Learn how the surface energy budget can change over time, or from one place to another. Note: This activity works best on a warm, sunny day. Materials •
Thermal radiometer
•
Kestrel weather tracker
•
Data spreadsheet
GEOG3 –
Oceans & Atmosphere (W22, Prof. Ian Walker) –
Section Activity 2 2 Procedure •
Your TA will organize your section into groups. •
Obtain instruments from the TA - 1 thermal radiometer and 1 Kestrel weather tracker per group. •
Your TA will demonstrate how to use the instruments to collect measurements. Pay careful attention and take notes as necessary. Please take care of the instruments. •
Visit each of the locations listed in the table below. Measure the temperature of the surface using the thermal radiometer. Next, measure the temperature and relative humidity of the air 5 cm (2 in) above the surface using the Kestrel weather tracker. Record these measurements in your data table. •
Repeat each measurement (temperatures and humidity) 3 times for each surface, by 3 different people (once per person) in your group. Record the 3 measurements and their averages in your table. •
Take field notes while you are taking your measurements on general conditions, weather, instruments, etc. You would be surprised at how useful these might be later when you are trying to make sense of your observations. Results (35 points)
1.
Describe the weather conditions during your data collection. Be sure to include: date and time of data collection (from when to when), average air temperature, wind conditions, amount of sun/cloud cover, rainy, foggy, etc. If you forgot to take notes during your data collection or if they are incomplete, you can find past weather conditions for the Santa Barbara Municipal Airport (KSBA) from the National Weather Service, ‘Past Weather’ link (see: https://forecast.weather.gov/MapClick.php?lat=34.4357&lon=-119.825#.YeCRmhPMJqt
) (5 marks) 2.
Compile your group’s measurements to complete
the attached spreadsheet. Calculate average and standard deviation values for each. Turn this spreadsheet in in addition to this handout. (30 marks)
GEOG3 –
Oceans & Atmosphere (W22, Prof. Ian Walker) –
Section Activity 2 3 Data Analysis (45 points) Environmental measurements often vary over space and time for a variety of reasons (natural variability, changing conditions, instrument or measurement errors, etc.). As a result, we often take more than one measurement and use care with our instruments and measuring methods to ensure repeatable, consistent results
. Basic statistics, like average and standard deviation, are also commonly used to describe mean conditions as well as the range in observations obtained
. Refer to the data your group collected when answering these questions. 3.
Which surface’s 3 measurements had the greatest standard deviation values? (2 point)
4.
What does a standard deviation value mean statistically? (2 point) 5.
In terms of your measurements, what might the standard deviation values indicate about what happened during your measurements and/or how you collected your observations? (2 points) 6.
List the albedos of the surfaces that you measured. Approximate values can be found online. (2 points) 7.
Which surface reflects the most
sunlight and why? (2 points) 8.
Which reflects the least
sunlight and why? (2 points)
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