GHY 1011 – Global Climate Change
Laboratory #1: Surface Energy Balance
Name: ________________________ Group Members __________________ _______________
Purpose
This lab exercise will introduce students to surface energy balance processes, thereby enhancing their understanding of the importance of the different energy fluxes in influencing the climate system at various spatial scales.
Learning Outcomes

Develop conceptual understanding of major radiation laws

Develop hypotheses on factors influencing micro-scale variability of surface energy fluxes and associated influence on temperature

Assess micro-scale variability of surface energy fluxes

Analyze data collected to test developed hypotheses
Key Terms

Incoming Short-wave radiation SW↓ solar radiation reaching the earth’s surface.

Outgoing Short-wave Radiation SW↑ solar radiation reflected by earth’s surface.

Albedo – a measure of how strongly a surface reflects light from the sun.
Snow has a high albedo and reflects more solar radiation; asphalt has a low albedo and absorbs more solar radiation.

Incoming Long-wave Radiation LW↓ radiant heat from earth’s atmosphere, emitted by clouds and other components of the atmosphere.

Outgoing Long-wave Radiation LW↑ infrared radiation leaving earth’s surface, detected as
 surface temperature.
Pyranometer – measures short-wave radiation (in Watts per meter squared, or W/m 2 )

Infrared (IR) Thermometer – measures IR radiation within the visible portion of the electromagnetic spectrum, perceived as surface temperature.
Description
Students will work in groups to calculate the influence of temperature on total radiated energy and dominant wavelength from a surface. Students will develop a set of hypotheses focusing on the microscale variability of surface energy fluxes and associated temperatures. Students will collect data using hand-held Infrared thermometers, hand-held pyranometers, and web-based sources and analyze the collected data to test hypotheses. Students will provide a written report of their results. This report must be typed, on sheets other than these. Each requested response must be numbered.
*Sections modified from Carbone (2010)

Radiation Laws
As we consider the Earth’s surface energy budget it is important to review two radiation laws that help us understand how temperature affects the amount and character of radiation emitted by a body. First, the
Stefan-Boltzman law states that the total energy emitted by a body increases with temperature.
Mathematically:
(1)
4 where E = radiation emitted (W m -2 )
σ = Stefan Boltzman constant (5.67 x 10 -8 W m -2 K -4 = 0.000000057)
T = temperature (K)
Reminder:
K = °C + 273
°C = °F – 32 / 1.8
°F = (1.8 * °C) + 32
Second, Wien’s Law shows that the dominant wavelength of radiative energy depends on temperature.
Specifically, it states that the wavelength of peak emission is inversely proportional to temperature:
(2)
max
=
𝐶
𝑇 where
λ max
= wavelength of maximum emission (micrometers, μm)
C = Wien’s constant (2898 μm K)
T = temperature (K)
Radiation Fluxes
From the perspective of the surface, the radiation budget is made up of four primary energy fluxes: incoming short-wave radiation (SW↓), outgoing short-wave radiation (SW↑), incoming long-wave radiation (LW↓), and outgoing long-wave radiation (LW↑). Incoming short-wave radiation (SW↓) is the amount of global solar radiation received at the surface. It depends on location, time of year, time of day, cloudiness, and other atmospheric conditions. Some of the solar radiation reaching the surface is reflected
(SW↑) and must be subtracted from the total incoming solar radiation. This outgoing short-wave radiation depends on the surface albedo , which is influenced by characteristics of the Earth’s surface such as color and texture. Short-wave radiation fluxes are relevant only between sunrise and sunset.
SW↑
Albedo = ---- * 100
SW↓
While you will be able to directly calculate albedo for the first part of this exercise, you should use the following table as a reference for different surfaces on the Appalachian Campus to calculate SW↑ when only the SW↓ are known (e.g. if SW↓ is 180 W m -2 and the surface is asphalt, SW↑ = 180 * 0.12) (e.g., in your calculations for data in Table 2)

Surface Typical albedo
Asphalt 0.12
Deciduous Forest (winter; summer) 0.15 (0.20)
Coniferous Forest 0.14
Bare soil (dry; wet) 0.20 (0.25)
Grass (short; long) 0.25 (0.16)
Snow (fresh; old & dirty) 0.85 (0.55)
Open water (high sun; low sun) 0.05 (0.30)
Ice 0.30
We must also consider the long-wave radiation emitted by the Earth’s surface (LW↑) and long-wave radiation received at the Earth’s surface (LW↓) from the atmosphere. As you have learned, outgoing longwave radiation emitted by the Earth depends on the surface temperature. Incoming long-wave radiation received by the Earth depends on the state of the atmosphere. Unlike short-wave fluxes, long-wave fluxes occur during both during day and night.
Net Surface Radiation
The net surface radiation is calculated as the sum of incoming short-wave (SW↓) and long-wave (LW↓) radiation minus the total outgoing short-wave (SW↑) and long-wave (LW↑) radiation:
(3) Net surface radiation (Q*) = SW↓ - SW↑ + LW↓ - LW↑
The energy from surplus radiation at the surface can be used to heat the atmosphere via conduction or convection (sensible heat flux), heat the ground (soil heat flux), or evaporate/sublimate water/ice (latent heat flux). Although these other energy fluxes are extremely important in influencing weather and climate across different scales, this lab exercise focuses only on measuring and calculating net surface radiation.
Data Sources
In Part I of your assignment, incoming short-wave radiation (SW↓) and outgoing short-wave radiation
(SW
↑
) will be measured using hand-held pyranometers. Incoming long-wave radiation (LW↓) will be calculated based on data collected from an internet source. Outgoing long-wave radiation (LW↑) will be measured using hand-held IR thermometers.
The pyranometer measures incoming and outgoing shortwave radiation in W m -2 .
SW↓
: To measure incoming short-wave radiation, point the pyranometer toward the sky, and make sure it is perpendicular to flat ground. Veering off of this angle will affect the readings. Record this reading when it stabilizes (values may change from second to second).
SW↑
: To measure outgoing short-wave radiation, point the pyranometer toward the ground, again making sure it is perpendicular with the ground surface. Record this reading.
LW↓
: Incoming long-wave radiation can be calculated based on the average temperature of the lower troposphere which will be estimated for you on the day you take your measurements. Be sure to convert temperature units to Kelvins (K), then use the Stefan-Boltzman equation (1) to calculate LW↓ (1).
LW↑
: Outgoing long-wave radiation will be indirectly measured using hand-held infrared thermometers to obtain the radiant temperature of a surface (follow additional guidelines provided by your lab instructor). Be sure to take temperature measurements in °C, then convert temperature units to Kelvins
(K). LW↑ may then be calculated using the Stefan Boltzman equation (1).

In this laboratory you will develop hypotheses and then measure and/or calculate the radiant temperature
(
 C), dominant wavelength (μm), net radiation (Q*), and all components used to calculate net radiation for at least five different land cover types and/or aspects. Some possible examples include:

Sun-exposed flat grassy area

Sun-exposed asphalt or dirt road

Forested southern slope

Sun-exposed rock or boulders

Bofedale peat wetland

Fresh snow surface

Glacier or icecap
1. Develop hypotheses on which of the above surfaces will have (a) the highest and lowest measured temperature, (b) the highest and lowest measured net radiation, (c) the highest and lowest albedo. Write these down (NOTE: six hypotheses total).
In developing these hypotheses, be sure to consider the four parameters that go into calculating net radiation and how they may vary from site to site (e.g., the asphalt parking lot in the sun should have the highest surface temperature, which will result in higher values of outgoing longwave radiation; the two shaded observation sites will have very low incoming shortwave radiation values, etc.)
2. Collect needed data, make all calculations and record the parameters.
3. Draw conclusions about your experiment.
(a) did the calculated net radiation values match your hypotheses? Why or why not (speculate)?
(b) did the measured temperature values match your hypotheses? Why or why not (speculate)?
(c) did the calculated albedo values match your hypotheses? Why or why not (speculate)?

4. Choose two “extreme” locations in the world (e.g., Sahara Desert, central Greenland, etc.) and discuss how net radiation would vary over the course of the four seasons (i.e., June and December Solstice,
Autumnal and Vernal Equinox). Consider things such as sun angle, length of day, hemispheric location, and typical seasonal weather for the locations you choose. http://geography.uoregon.edu/envchange/clim_animations/