Geographic Information Question

 

 

 

Objectives.  To understand how absorbed radiation (Q*) varies seasonally (Part I) and how it can be utilized different physical environments (Part II).  The differences in air to ground temperatures, cloud cover, and moisture availability as it pertains to air temperature are explored.

 

Part I.   Radiation Balance. Q* = (K¯ – K­) + (L¯ – L­)

 

S = direct or straight-line solar radiation                    L¯= incoming long wave radiation

D = diffused solar radiation                                        L­= outgoing long wave radiation

r = surface albedo (reflectance)                                  Q* = net absorbed solar radiation

K¯ = S+D

K­ = (S+D)r

 

The following data from suburban Chicago collected at different times of the year are used in answering the questions below.

 

Day 1                                                              Day 2

 

S = 33 cal cm ^–2 day^-1                                                 S = 565 cal cm ^–2 day ^–1

D = 75 cal cm ^–2 day ^–1                                               D = 90 cal cm^-2 day ^–1

r = .80                                                                          r = .20

L¯ = 620 cal cm^-2 day^-1                                              L¯ = 890 cal cm^-2 day^-1

L­ = 575 cal cm^-2 day^-1                                              L­ = 960 cal cm^-2 day^-1

 

 

Answer the following questions using the above data.

 

 

1. Calculate the amount of net radiation (Q*) available on these two days.

SHOW YOUR WORK.

 

33 + 75 = 108 (33 + 75) * .8 = 86.4. 108-86.4 = 21.6

620 – 575 =  45

 

21.6 + 45 = 66.6 cal ^{cm-2 day-1}

 

 

2. On each day, what percentage of total insolation is comprised of diffuse (D) radiation?

 

{D/(S+D)}x 100 = %.

 

 

 

3. What atmospheric conditions likely explain the percentage differences between these two days? Interestingly, Day 2 has a higher absolute total of D. What does that suggest about the seasonality of Day 2?

 

 

 

 

 

4. Based only on surface albedo (r), what seasons of the year are being exhibited?

 

 

 

 

 

 

 

5. L¯ is less than L­ on Day 2, yet L¯ is greater than L­ on Day 1.  What does this tell us about the relative temperatures of the surface and the air immediately above ground?  Which day has an “inverted” lapse rate? Which day has a “normal” lapse rate?

 

 

 

 

 

6. Thinking back to the season of each day, how can the data only for L­, be helpful in discerning seasonality?

 

 

 

 

 

7. What exactly is the definition of a calorie of energy?

 

 

 

 

 

 

 

 

 

Part II.            Energy Balance.   Q* = Q_e + Q_h + Q_g

 

Q* = Net absorbed solar radiation

Q_e = Latent heat flux

Q_h = Sensible heat flux

Q_g = Ground heat flux

The data were collected at different locations & at different times of the year.

Location 1                                           Location 2                                           Location 3

 

Q* = ____________               Q* = 400 cal cm^-2 day^-1                      Q* = 400 cal cm^-2 day^-1

 

Q_h  = 70 cal cm^-2 day^-1                Q_h = 35 cal cm^-2 day^-1                                 Q_h  = ____ cal cm^-2 day^-1

 

Q_e  = 50 cal cm^-2 day^-1                Q_e = ____ cal cm^-2 day^-1                            Q_e  = 65 cal cm^-2 day^-1

 

Q_g  = -120 cal cm^-2 day^-1           Q_g = 40 cal cm^-2 day^-1                                 Q_g  = 40 cal cm^-2 day^-1

 

 

 

1. Calculate the missing value for each location.

 

 

2. How many calories of radiant energy (Q*) are available for use at Location 1? What does this suggest about season of the year? Latitudinal location?

 

 

 

3. Examine Location 1. Where did the energy come from that was used to heat the air (70 cal cm^-2 day^-1), and evaporate water (50 cal cm^-2 day^-1)?

 

 

 

4. Notice that the Q* loads are the same at locations 2 and 3. However, their use of Q* energy is quite different.  Which site is more akin to a wetland or open water and which is more likely a desert or at least a place where water is under restricted supply?

 

 

 

 

5. Which location will have the warmest temperature? Explain.

 

 

 

Part III: Earth Sun Geometry

 

 

Calculating solar elevations above the horizon facing the Equator (0°)

 

(90-latitude) + solar declination

 

Solar declination is positive when the sun is overhead in the same hemisphere as the target location & is negative when the sun is overhead in the hemisphere opposite the target location

 

For example, Los Angeles is located 34°N.  Thus, from 3/21 thru 9/22 solar declination is positive because the sun is overhead in the northern hemisphere.  Solar declination is negative 9/23 thru 3/20 because the sun is overhead in the southern hemisphere

 

Declination changes rapidly within 5 weeks of an equinox (3/20 & 9/22) and very slowly within 5 weeks of a solstice (12/21 and 6/21).

 

Declination is 0 on 9/22 and 3/20.  It is 23.5 on 6/21 and 12/21.

On 5/20 and 7/20 it is 20°N.              On 4/20 and 8/20 it is 12°N

On 11/20 and 1/20 it is 20°S             On 10/20 and 2/20 it is 12°S

 

 

1. Calculate the solar elevations at the following places

 

 

June 21            Dec 21             Mar 20/Sept 22

 

 

Anchorage AK 61°N

 

St Paul, MN  45°N

 

Atlanta, GA 34°N

 

Honolulu, HI. 21°N

 

*Quito, Ecuador 0°                             66.5°                66.5°                            90°

 

Valparaiso, Chile 32°S

 

 

1. Which two cities will have fairly consistent daylengths?  Which will have the longest daylength yet the lowest solar elevation?

 

 

 

 

*Facing north in June and south in Dec