Lab Six: Insolation and Temperature

This lab is designed to introduce you to the number of factors that influence temperature at Earth's surface.

First, we will begin by studying how the amount of insolation received at the Earth's surface varies from

place to place. The variation of insolation leads to variations in temperature. Other factors, such as, land-

water contrasts, ocean currents, and wind patterns and air masses also influence temperatures. In addition,

we will explore how altitude affects temperatures.

Objectives:

Measure surface variation in temperature

Construct a temperature graph

Calculate temperature range

Name

Part 1: Incoming Solar Radiation & Surface Variations

The amount of incoming solar radiation (insolation) varies by latitude and by season. Since the sun's energy is

our primary source of energy, this radiation imbalance leads to temperature differences. Why do we see this

variation in insolation received?

Atmospheric Obstruction- clouds, haze, etc.

** Both of these factors vary by latitude and by season

Insolation received depends on:

Angle of Incidence**- the angle at which the sun's rays hit the Earth's surface- direct vs oblique angles.

Day Length**- the amount of time the sun is above the horizon

Exercise 6.1:

Calculate average annual temperature

Identify global temperature patterns and to

explore the reasons for these patterns.

Calculate the Average Lapse Rate

Recap from Lab 5. Select the BOLD word that is correct.

1. Places closer to the equator have HIGHER or LOWER solar altitudes and MORE or LESS variation in

daylength.

2. Places closer to the poles have HIGHER or LOWER solar altitudes and MORE or LESS variation in

daylength.

Let's explore how surface variations affect the energy received.

Albedo- the ability of an object to reflect radiation

Low Albedo surfaces: asphalt, aged concrete, dark roof/paint, dark soil, dark rock, forests, grass

High Albedo surfaces: snow/ ice, new concrete, light roof/ paint, sand/desert

Select the BOLD word that is correct.

3. Light colored surfaces have a HIGHER or LOWER albedo, thus reflecting MORE or LESS energy.

4. Dark colored surfaces have a HIGHER or LOWER albedo, thus reflecting MORE or LESS energy.

1 5. Relating this to Earth, which of the following surfaces reflect more and which reflect less? Classify the

following locations as having a low or high albedo.

a. Antarctica (ice sheet)

b. Lava Flow in Hawaii (black)

c. Aged Concrete Sidewalk

d. Greek Village with white houses

Part 2: Annual Temperature Variations

Temperature - sensible heat (energy that you feel)

Air is heated from the ground up by outgoing longwave radiation emitted from the Earth, not by

incoming shortwave insolation.

There is a lag time between the Earth receiving the shortwave insolation and remitting the energy as

longwave radiation. Although insolation peaks at noon, net radiation (the difference between

incoming and outgoing energy) continues to be positive (i.e. there is a surplus of energy) until the early

afternoon, causing temperatures to rise. Net radiation is negative (i.e. there is a deficit of energy) from

early afternoon until sunrise, causing temperatures to cool down. This also happens on an annual basis-

think about the hottest month of the year compared to the month seeing the highest solar altitude.

There are two important measures of annual temperature. The first measure is the temperature range-

the difference in temperature between the warmest month and the coldest month. This value is a very

useful indicator of seasonality of temperature- the amount of temperature change over the year. The

second is annual average temperature, which we will look at in Part 3.

Maximum Temperature - Minimum Temperature

Temperature Range:

Exercise 6.2:

Use the temperature graphs at the end of the lab to complete this section.

1. Calculate the Temperature Range for the following locations. Note: the temperatures displayed on the

graphs are the average temperatures for each month. St. Louis has been completed for you.

St. Louis, MO

=

Fairbanks, Alaska

Lihue, HI

Warmest Month-

Average Temperature

78° F

Coldest Month-

Average Temperature

2. How does latitude affect temperature range?

30° F

Temperature Range

78° -30° 48°

2 3. How does latitude affect temperature?

Part 3: Coastal Versus Continental Locations

Land heats and cools faster than water for the following reasons:

LAND

Lower Specific heat

Immobile - prevents mixing

Less Evaporation

Radiation concentrated at surface

Specific Heat: Amount of energy needs to raise 1 gram of a substance 1 degree of Celsius.

Results: Continental locations experience greater seasonal extremes- hotter summers and colder

winters (larger temperature range).

Coastal locations experience more moderate, uniform temperatures (lower temperature

range).

Annual average temperature averages all high and low temperature values for a location over the

course of the year to give a single, coarse measure of temperature.

Average Annual Temperature = Sum of the temperatures/ Number of temperatures

Exercise 6.3:

Average Monthly Temperatures for 3 Cities:

San Francisco, CA-- 37.6°N, 122.4°W

Temperature

| (°F)

Temperature

(°F)

J

49

Wichita, Kansas-- 37.7°N, 97.4°W

J

7

30

Temperature

(°F)

52

J

39

F

33

Norfolk, Virginia-- 36.9°N, 76.2°W

M

53

F

41

M

44

M

49

A

56

A

56

A

57

M

58

M

65

M

66

J

61

WATER

Higher Specific Heat

Mobile- allows mixing

More Evaporation

Radiation penetrates below surface

J

74

J

74

J

63

J

80

J

78

A

64

A

79

A

77

S

64

S

70

S

72

O

61

O

58

O

61

N

55

N

44

N

52

D

49

D

34

D

44

1. Compute the Temperate Range and Average Annual Temperature for San Francisco, Wichita, and

Norfolk. Check Your answer using the Lab Six Temperature Data Excel file.

3 2. Construct a temperature graph by plotting the Average Monthly Temperatures on the Graph below or

by using Excel.

Use red to plot San Francisco, blue for Wichita, and green for Norfolk.

Annual Temperature Graph

°F

90

80

70

60

50

40

30

20

10

O

-10

J

F

M

A

M

J

J

A 'S

O

N

D

10°C(50°F)

5°C(41°F)

0°C(32°F)

-5°C(23°F)

3. Based on the data provided, describe the relationship between continental/coastal locations and

temperature range.

4. Why does San Francisco have a smaller temperature range than Norfolk, Virginia, even though both are

located on coasts? Keep in mind that the prevailing winds are from the west.

4 Part 4: Average Lapse Rate- change in temperature as a result in altitude change.

Average Lapse Rate: 3.6° F/ 1000 feet or 6.5° C/ 1000 meters

Steps for calculating the Lapse Rate

Example: If the temperature is 93.6° F at 1000 feet, what would the temperature be like at 5000 feet?

Step 1: Find the Elevation Difference: Maximum – Minimum

5000-1000 = 4000 feet

Step 2: Set up equivalent fractions and cross multiply:

(Temp)

3.6° F

X

(Elevation)

1000 ft

4000 ft

=

(4000* 3.6)/1000 = 14.4° F

Step 3: If calculating for a higher elevation, subtract degrees from starting temperature. If calculating

for a low elevation, add degrees to starting temperature.

93.6° F 14.4° F = 79.2° F at 5000 ft

Exercise 6.4:

Calculate the temperature using the average lapse rate for the locations listed below. Round your answers to

one decimal place.

1. Currently the temperature is 99° F in San Bernardino (elevation 1200 ft). Using the ALR, calculate the

temperature in Big Bear Lake (elevation 6,752 ft) and San Gorgonio Peak (elevation 11,499 ft). You may

want to sketch a diagram to help you visualize the problem.

2. Looking at the temperature graph for Lihue (elevation 103 ft) and Kilauea (elevation 1134 ft). Does the

environmental lapse rate explain the temperature differences between these two locations? Explain

your reasoning.

5/n