OEAS 405: Introduction to Physical Oceanography
Exercise
Heat Budgets, Mass Conservation
Due: Oct 15 as mid-term exam
As you do this if you get stuck for more than 30 minutes contact me. Include matlab script in the email so I can see where you are having problem. I’ll be online all weekend and next week.
See you Wednesday and you can explain to me what you see in the plots.
This problem uses the data sets given in PAPA11_12.mat, which is posted on the class website. Note the data are daily averages.
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 temperature (SST [oC])
Wind speed (Wspeed [m/s])
- 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 = short wave incoming radiation = SW
Qb= outgoing longwave radiation = incoming – back radiation = LW-Cs K4[note K = SST+273]
Qh= sensible heat loss= -Ch (SST-AirT) Wspeed
Qe=latent heat of evaporation = -Le Ce (Ew-Ea) Wspeed
Note – get Ew from qsat
Get Ea from EA=Relhum.*EW/100
Cs=5.67x10-8 Stefan Boltzmann [Wm-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]
Ew is the air specific humidity (kg of water vapor/kg of air) at the water surface (100% relative humidity) and
Ea is the specific humidity above the surface (nominally at 10 m elevation).
Relative humidity is (Ea/Ew)*100 with units of percent.
The matlab routine qsat.m calculates the saturation specific humidity, Ew, based on air temperature and air pressure.
MATLAB Note – when you multiply a scalar times a vector use .* as in the equation for Qh= sensible heat loss= -Ch (SST-AirT) Wspeed the Matlab code would be QH=-CH.*Wspeed.*(SST-AirT)
a)Describe the trends or patternsin 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?
- Use the net heat flux to calculate the temperature change for a mixed layer 20, 50 and 100 m deep, starting with a winter temperature of 6C at 1 January 2011. Compare this estimated temperature to the actual SST at Station Papa. Explain why these two curves are different.
Example Change in temperature = (Day in Seconds / depth*mass* specific heat).*NetHeatFlux
The plot should look like this (my version)
1