Name:________________________________________________             Section:________________

part 1:  Seasonal Changes in the Radiation Balance

Use the following data to answer questions in Part 1. The data were collected at the same midlatitude location but on different days, one summer, the other winter.

TABLE 2.2  Radiation Balance Data

      S     =   280 W/m²                      S     =   11 W/m²

      D    =   44 W/m²                        D    =   33 W/m²

      a     =  0.23                               a     =  0.87

      L¯   =   419 W/m²                      L¯   =   284 W/m²

 

1.   Calculate total incoming solar radiation (S+D) for each day. 

      Day 1   324                                                      Day 2   44

DAY 1: (280+44)                                             DAY 2: (11+33)

2.   Calculate the amount of reflected solar radiation (S+D)a

      Day 1   74.52                                                   Day 2   38.28

            DAY 1: (280+44)0.23                                      DAY 2: (11+33)0.87

3.   Calculate the net radiation (Q*) for each day. 

      Day 1   202.48                                                 Day 2   15.72

DAY 1: [(280+44)-((280+44).23)] + (419-466)      DAY 2: [(11+33)-((11+33).87)] + (284-274)

 

 

4.   Use the value of the albedos and Table 2.1 to determine the type of surface over which the data was collected.

      Day 1   Grass (growing & healthy)                  Day 2   Fresh Snow

[Be very careful here; light, high-albedo substances are not necessarily snow! NEVER RELY SOLELY ON ALBEDO TO JUDGE SEASON. Albedo of an asphalt road surface in winter will be low if there's been no recent snow. Conversely, the blinding brightness of evaporite salt flats in a desert doesn't automatically mean winter snow cover!  The best judge of season is (S+D), on the logic that you receive stronger sunlight during summer.]

5.   a.   Carefully examine the values of L¯ and L­ on Day 1.  Which is warmer, the surface or the air on Day1?

The surface, as the source of an upward (negative) net Longwave flux.  (419-466)= -47

b.   Carefully examine the values of L¯ and L­ on Day 2.  Which is warmer, the surface or the air, on Day 2?

The air, as the source of a downward (positive) net Longwave flux.   (284-274)= +10

6.   a.   Based on the values of L¯, which day had a higher air temperature, Day 1 or Day 2?

Longwave radiation has a direct relationship with source temperature.  Since Day 1 had a larger L¯, it had warmer air.

b.   Based on the values of L­ which day had a higher surface temperature, Day 1 or Day 2?

Since Day 1 had a larger L­, it also had the warmer surface.

7.   a.   Using your answers to questions 1 through 6 above, suggest the time of year, summer or winter, for each day? 

      Day 1   Summer     (S+D)=324                      Day 2   Winter     (S+D)=44

b.   Explain how you came to your conclusion.

Higher (S+D) indicates greater or prolonged sunlight, which occurs during summer

8.   a.   Calculate the percent of diffuse radiation on each day as:   [D/(S+D)] X 100  

      Day 1   (44/324)100 = 13.6%                         Day 2   (33/44)100 = 75.0%

b.   What likely accounts for the differences in the percent diffuse radiation on these two days?

Diffuse (D) is a greater proportion of all sunlight (S+D) when clouds scatter the light, so Day 2 was probably cloudier.
Name:_________________________________________             Section:________________

part 2: Geographical Variations in the Energy Balance

Use the data in Table 2.3 to answer questions in Part 2.  The data below were collected at three different locations on the same day. 

TABLE 2.3  Energy Balance Data

   Q*  =181 W/m²                      Q*  =181 W/m²                      Q*  =30 W/m²

   H    =      10 W/m²                  H    =   137 W/m²                  H    =     - 39 W/m²

   G    =      18 W/m²                  G    = 15 W/m²                       G    = 7 W/m²

 

1.   Calculate the values for Q* and enter in the blanks above. 

Location 1: 10 + 18 + 153

Location 2: 137 + 15 + 29

Location 3: -39 + 7 + 62

2.   Diagram the energy fluxes in the space below.  Refer to Figure 2.1.

Earth surface

3.   What percent of Q* is H for Locations 1 and 2?

Location 1   (10/181)100=5.5%                            Location 2   (137/181)100=75.7%

4.   What percent of Q* is LE for Locations 1 and 2?

Location 1   (153/181)100=84.5%                        Location 2   (29/181)100=16.0%

5.   a.   Which location, 1 or 2, probably had the warmest air temperature?     Location 2

b.   What evidence did you use to support your answer?

Much more available heat energy at Location 2 went into the air as sensible heat.

6.   a.   Which location, 1 or 2, probably had the highest rate of evaporation?  Location 1

b.   What evidence did you use to support your answer?

Much more of the available heat energy at Location 1 went to the air as latent heat.

7.   Describe the climate conditions (hot/cold – humid/dry) that are represented by Location 1?

After sustaining a positive LE dominance, and far less positive H:  relatively cold and humid

8.   Describe the climate conditions (hot/cold – humid/dry) that are represented by Location 2?

After sustaining a positive H dominance, and far less positive LE:  relatively hot and dry

9.   What evidence did you use to support your answers for questions 7 and 8 above?

The relative proportions of available heat (Q*) expenditure

10. a.   The sensible heat flux for Location 3 is a negative value. What does this mean about the relative temperature of the ground and air at this place?

The negative indicates net heat flux from the air towards the ground, and the Second Law of Thermodynamics says the flux source has the higher temperature.  Therefore, the air is warmer.

b.   Suggest environmental conditions under which this could occur

·         a hot summer DAY, as when the soil feels cool under your bare feet

·         a spring thaw, when the ground is still frozen and the air feels warmer