Thermodynamics of Atmospheres and Oceans
Surface Energy Balance
What is the temperature of a raindrop as it falls through the air:
a) dew point temperature
b) wet bulb temperature
c) physical temperature of the air
d) equivalent temperature
Rainfall typically (cools, warms) the ocean surface.cools
The heat flux from precipitation will (increase, decrease, remain the same) if the rainfall rate increases increase
For the same precipitation rate, snow will cool the surface (more than, less than, the same) as rain. more than
1. Match the sign of the bulk Richardson number to state of static stability of the atmosphere:
_____c______RiB = 0a. stable
_____a______RiB > 0b. unstable
_____b______RiB < 0c. neutral
2. Match the value of the bulk Richardson number to the approximate value of the heat transfer coefficient, CDH for z/zo=550.(see Fig. 9.3)
b RiB = 0a. 5.0 x 10-3
c RiB = 0.5b. 1.33 x 10-3
a RiB = -0.5c. 1.0 x 10-4
3. The surface latent heat flux will (increase, decrease, remain the same) if wind speed is increased increase
4. The surface sensible heat flux will (increase, decrease, remain the same) if the surface roughness length increases increase
5. The surface latent heat flux will (increase, decrease, remain the same) if the ocean salinity increases. decrease
6. The surface latent heat flux will (increase, decrease, remain the same) if the sea surface temperature increases. increase
7. A crude estimate of the surface moisture flux, Ė, over a large homogeneous body of water is given by,
Ė = ρaCq ux (q0 – qa)
where ρa is density, Cq=1.3x10-3 (dimensionless), and ux is wind speed. Subscripts a and 0 represent values at 10 m above the surface and the surface value, respectively. Calculate Ė under the following conditions: ux=5 ms-1 pa= 1000mb, qa = 20g/kg and T0 = 30ºC (assume that q0 corresponds to saturation) and compare for the following situations:
a) “a fresh water” lake
b) the ocean with s=35 psu
c) the ocean with s-35 psu, where the skin SST correction is ignored (assume bulk SST is 0.3ºC warmer than T0, the skin SST)
For Part a)
Calculate virtual temp using Tv = (1+(.608)*q)T=306.7K
Calculate density of air using virtual temperature ρa =P/RdTv=100000(N/m2)/287(J/Kkg)/306.7K=1.136kg/m3
Calculate q0 = ε(es/p-(1- ε)es) = .622*(42.430mb)/(1000mb-(1-.622)42.430mb)=.0268
Now, we can calculate Ė= (1.136kg/m3)(1.3x10-3)(5m/s)(.0268-.02)=5.02x10-5kg/m2s
b) Ė = 4.65x10-5kg/m2s
8. The net surface heat flux is highest (most heat into the ocean) for
a) tropical western Pacific
b) east Greenland Sea during winter
c) Gulf Stream during winter
d) Gulf Stream during summer
e) subtropics during summer
9. The net surface heat flux is lowest (least heat into the ocean) for
a) tropical western Pacific
b) east Greenland Sea during winter
c) Gulf Stream during winter
d) Gulf Stream during summer
e) subtropics during summer
10. What causes the net surface radiation flux in the Gulf Stream and East Greenland Sea to be negative in winter?
You have lower incoming SW radiation due to the sun position yet latent heat loss from the warm waters combined with cold air masses gives you high evaporation
11. Why is the latent heat flux loss in the Gulf Stream during winter so large?
The warm water that is transported northward has a high evaporation rate
12. If the surface latent heat flux is measured, how can you determine the surface evaporation flux from this measurement?
13. Which of the following processes increase ocean salinity?
a) precipitation
b) evaporation
c) river runoff
d) melting of sea ice
e) freezing of sea ice
The fresh water balance (precipitation minus evaporation) is greater than zero, less than zero, or equal to zero, in the following oceanic regions (see Fig. 9.5):
14. Tropics 10N to 10S ___>0______
15. Subtropics 20-35N, 20-35S ___<0______
16. Subpolar 50N-70N, 50S-70S ___>0______
17. Units for heat flux FQ0 are __W/m2______
18. Units for salinity flux FS0 are __kg psu / m2s____
19. Units for heat flux FB0 are __kg/ms3______
20. The equation for ocean surface buoyancy flux (no runoff or sea ice) can be written as
Evaporation modifies buoyancy in two ways, via the latent heat flux and also via the salinity. Compare the thermal vs salinity effects of evaporation on the ocean surface buoyancy flux (e.g. determine their ratio). Which will dominate under which circumstances?
Taking the ratio between the cooling term and the salinity term from the equation you get
Salinity dominates in the polar regions, while latent heat dominates in the lower latitudes
21. Which of the following will promote instability (sinking) at the ocean surface?
a) net radiative heat loss
b) evaporation
c) precipitation
d) sea ice growth
22. Which will have a greater stabilizing effect on stabilizing the ocean surface, rainfall or snowfall??
rainfall
3. The skin temperature is typically about 0.3oC (warmer, cooler) than the bulk sea surface temperature cooler
State how each of the following processes will influence the sea surface temperature (SST) and depth of the tropical ocean mixed layer (hm) (increase, decrease, remain same). Briefly explain.
1. Increasing the cloud cover during the daytime
SST___decrease_____ hm____increase______
Most heating of SS occurs from visible spectrum, once removed cooling creates instability
2. Large rainfall
SST___increase______hm ___decrease______
Freshening allows for warmer SST increasing stability
3. increased wind speed
SST___decrease_____ hm___increase______
More turbulent mixing driven by the increase in wind brings cooler waters to the surface
4. increased evaporation rate
SST___decrease_____ hm___increase______
Typically driven by turbulent wind, so again mixes the layer, increases salinity keeping the surface cool and causing instability bringing cooler water to the surface
5. increased entrainment of deep ocean water
SST___decrease_____ hm__increase______
Caused by increased winds and mixing bringing cooler water to surface
State how each of the following processes will influence the mixed layer salinity (s) and ocean mixed layer depth (hm) under sea ice (increase, decrease, remain same). Briefly explain.
6. melting of sea ice
s__decrease______hm___decrease_____
Melting freshens the water in the ocean and allows more warming creating a stable situation
7. freezing of sea ice
s__increase______hm___increase______
Freezing removes fresh water from the ocean and causes instability producing more mixing