OEAS 405: Introduction to Physical Oceanography
Exercise
Heat Budgets, Mass Conservation
Due: Oct 15 as mid-term exam
This problem uses the data sets given in PAPA11_12.mat, which is posted on the class website.
This all is discussed in Knauss Chapter 3
The data sets are:
Incoming short wave radiation (SW [W/m2])
Incoming long wave radiation (LW [W/m2])
Air temperature (AirT [oC])
Relative humidity (RelHum [%])
Sea surface temperture (SST [oC])
Wind speed (Wspeedw [m/s])
1. Using the above data sets, calculate and plot the surface heat flux components using the
following information. Label all axes and give units. Heat gains are positive and losses
are negative.
Qs = SW
Qb = LW - Cs K4
Qh = -Cp Ch (SST-AirT) Wspeed
Qe = -Le Ce (Ew-Ea) Wspeed
Cs = 5.67x10-8 Stefan Boltzmann [W m-2 K-4]
Le = 2.26x106 Latent heat [J kg-1]
Cp = 3985
Specific heat [J (kg K)-1]
Ce = 1.5x10-3
Humidity exchange coefficient [nondim]
Ch = 0.83x10-3 Heat exchange coefficient [nondim]
a) Describe the trends or patterns in the heat budget components: at least 5 sentences for
each ‘Q’.
b) Calculate the net surface heat flux. Describe trends and patterns in the net heat flux and
compare this to the trends and patterns in the individual heat budget components. Which
terms are controlling the heat flux at this location?
2. Use the net heat flux to calculate the temperature change for a mixed layer 20 m deep,
starting with a winter temperature of 6C at 1 January 2011. Compare this estimated
temperature to the actual SST at Station Papa. Explain why these two curves are
different.
STOP HERE
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3. Chesapeake Bay has the following characteristics: Area = 11,601 km2, Volume = 68.4
km3, River input = 193.8 106 m3 d-1, precipitation = 0.25 cm d-1.
(40)
a) Calculate the Chesapeake Bay flushing time based on the river flow.
b) Construct the expressions for a water volume budget and a salt budget. Assume that
surface salinity at the bay mouth is 25 PSU and the bottom salinity is 32 PSU. Also
assume that net evaporation is equal to precipitation. Solve these expressions for the
inflow and outflow volume transports at the bay mouth.
c) Compare the transports at the bay mouth to the river input. Calculate the flushing time
based on the salt driven (estuarine) transport. What is the effect of the estuarine
exchange flow on the flushing time compared to the river flow?
d) The width of the Chesapeake Bay mouth is 30 km and the depth is 8 m. What is the
average speed of the inflow and outflow based on the water and salt budget, assuming
mid-depth is the boundary between inflow and outflow?
e) Compare the size of precipitation to river flow in Chesapeake Bay. Speculate on the
effect on bay conditions if there were no evaporation. What would happen if the
evaporation rate is twice the precipitation rate?
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