problem with shortwave radiation and net heat flux

[wiltonwang]

The net heat flux is the sum of sensitive heat, latent heat, shortwave radiation and long wave radiation. But when we enable the SOLAR_SOURCE term, in pre_step3d.F the temperature is calculated using both the net heat flux and the shortwave radiation. It seems that the total heat added to the model is the sum of the net heat flux and the shortwave radiation. So the actual heat is larger than the net heat flux. This problem puzzled me a long time. Could anybody help me out of this end, thanks.

[praveen]

I also have the same question

It seems that the total heat added to the model is the sum of the net heat flux and the shortwave radiation. So the actual heat is larger than the net heat flux.

it seems that the total heat added in to the model becomes high by giving netheat at surface and shortwave radiation in to the interior levels.



Can anyone help us

[nperlin]

Hi,
I'm using ROMS for the coupled ocean-atmosphere simulations (COAMPS model for the atmosphere, and ROMS - for the ocean). The way I handle heat fluxes that are being computed by the atmospheric model and passed to ROMS every ocean model time step, is the following.
As a heat forcing at the surface, ROMS expects you to provide the kinematic heat/temperature flux in units of [deg.C m / s], and pass it to the variable FORCES(ng)%stflx(:,:,itemp) in the model code. THIS surface heat/temperature flux is applied at the topmost ocean layer, readily available to heat the layer, and I assume that it should be comprised of net longwave radiation (positive downward in atm.model) minus sensible heat flux (positive upward in atm. model) minus latent heat flux (positive upward in the atm. model), with the appropriate scaling. In contrary, net shortwave radiation (positive downward in atm. model) is penetrating, and is not directly available to heat the top surface layer, but rather should be passed to a variable FORCES(ng)%srflx.
The results of the coupled simulations using this approach look good.

Please let me know any comments on that!!
Natalie.

[praveen]

hi Natalie.

I assume that it should be comprised of net longwave radiation (positive downward in atm.model) minus sensible heat flux (positive upward in atm. model) minus latent heat flux (positive upward in the atm. model), with the appropriate scaling

So in the model, short wave radiation should remove from the netheat flux ( which already includes shortwave radiation) from the toper layer.

Otherwise we should use a heat flux without shortwave radiation which passes to the variable FORCES(ng)%stflx(:,:,itemp) and shortwave radition separately to FORCES(ng)%srflx as penetrating, as you mentioned above

am I correct ??

another way is by activating BULK_FLUXES. So that the model itself could compute its fluxes.

If I am wrong please correct me

[nperlin]

Hi praveen,

Otherwise we should use a heat flux without shortwave radiation which passes to the variable FORCES(ng)%stflx(:,:,itemp) and shortwave radition separately to FORCES(ng)%srflx as penetrating, as you mentioned above

yes, this is my understanding how surface heat forcing works in ROMS. I use the fluxes computed by the atmospheric model, and so they could combined as needed.

another way is by activating BULK_FLUXES. So that the model itself could compute its fluxes.

Yes, you may also activate BULK_FLUXES. Also note: to enable shortwave radiation you need to activate/"define" some other variables as SHORTWAVE, ANA_SRFLUX, DIURNAL_SRFLUX, ALBEDO, depending on your model application, code modifications, etc. In my case, by choosing to use the fluxes already computed by the atmospheric model, I can make sure that the same amount of heat lost/ transferred downward from the atmosphere is received by the ocean (numerically). And this will be regardless of the way fluxes are computed.

Greetings,
Natalie.

[nperlin]

Hi praveen and others,

I need to modify some of my earlier assupmptions (above), following multiple attempts to figure out the right way to account for surface heat flux in ROMS. The shorwave radiation had to be included in BOTH the net heat flux FORCES(ng)%stflx , and to be given as input in a separate variable, FORCES(ng)%srflx. The temperature is updated in subroutine prestep_3d, based on the amount of heat applied to the layer. The amount of heat applied to the upper water layer is the difference between the incoming total net heat flux at the surface (stflx, including solar) minus the amount of penetrated shorwave radiation at the bottom of the layer (which is also the incoming SW radiation at the top of the next layer down). The penetrated SW radiation is computed from the known srflx, layer depth, and given water type (set WTYPE in ocean.in). Remember also to define SOLAR_SOURCE in cppdefs.h
The failure to include solar radiation into the surface heat flux in our earlier modeling attempts had its major impact on sea surface temperatures that did not change much in offshore ocean during 2-3 days of summertime simulations, even when SW radiation peaked over 900 W/m^2 during the day. After the fix, the reasonable warming of SST took place (approximately 2 deg.C/ 3days) and very slight diurnal cycle was noticeable, which made much more sense, fortunately.
Will appreciate any further comments!!!
Thanks,
Natalie.

[praveen]

hi Natalie.
u r right. netheat flux should comprise shortwave radiation .
Thanks