How to compute the moist static energy (MSE)

[pybl]

Hello,

I have been trying to understand the meridional heat redistribution simply due to a larger solar forcing, and how the zonal mean surface temperature and precipitation are affected.

From literature, I find that the atmosphere meridional heat transport can be represented by the moist static energy (MSE) which is the sum of the latent heat and the dry static energy (DSE = potential energy g*z + sensible heat c*T, where g is the gravity constant, z is the geopotential height, c is the dry air heat capacity and T is the temperature). The meridional heat flux (VM) is the meridional wind times the MSE.

The closest output variable I can find from CAM6 Masterfield list is VT (meridional heat transport, unit: k m/s).

Despite that the units of VM and VT are different (W/m2 vs K m/s), from the source code it seems to be a product of temperature and meridional wind, which makes me wonder if it is just "meridional sensible heat transport".

Thanks for help!

 

[nusbaume]

Hi Binghan Liu,

I sadly think you’ll need to calculate the full MSE equation in order to get what you are looking for. I believe this can be done by doing the following:

MSE = Q*Lv + T*Cp + Z3*g

With the output CAM variables being:

Q = specific humidity

T = air temperature

Z3 = geopotential height

And the relevant constants being:

Lv = 2500840 J/kg (latent heat of vaporization of water)

Cp = 1005 J/kg/K (specific heat capacity of dry air)

G = 9.81 m/s2 (acceleration due to gravity)

Then you can calculate the meridional flux of MSE by simply doing:

VM = V*MSE

Otherwise I am not aware of an MSE variable that is output by the model directly. However, we are hoping that the next version of CAM (CAM7) will provide at least some of these energy variables without the need to calculate them offline.

Anyways, I hope that helps, and have a great day!

Jesse

 

[pybl]

Thank you, Jesse.

This truly helps!