[MITgcm-support] UV_VEL_Z
Jean-Michel Campin
jmc at ocean.mit.edu
Wed Feb 1 23:17:34 EST 2012
Hi Angela,
I put few comments below.
On Wed, Feb 01, 2012 at 12:36:58PM -0700, Angela Zalucha wrote:
> Hi,
>
> I am interested in the diagnostic UV_VEL_Z (#40, Meridional
> Transport of Zonal Momentum), which I understand is the time average
> of u*v.
>
> But I am confused because available_diagnostics.log (see below) says
> its "mate" is itself. What does that mean? Is there another
> quantity I should be outputting with it (like uvel and vvel must be
> output together)?
You don't have to worry, it's just that it's not invariant, depends
on the local orientation of the grid, and therefore needs to be
interpreted carefully. Just basic things (sorry if this is obvious
to you):
uVel,vVel = model horiz. velocity (oriented along model grid)
uE,vN = eastward & northward velocity comp. ;
CS,SN = cos & sin of model grid orientation vs geographic orient.
uE = CS * uVel - SN * vVel
vN = SN * uVel + CS * vVel
UV_VEL_Z = uVel * vVel
but uE * vN = (CS*uVel - SN*vVel)*(SN*uVel + CS*vVel)
= (CS^2-SN^2)*uVel*vVel + CS*SN*(uVel^2 -vVel^2)
Now, there is an other diagnostics, UV_VEL_C, which is precisely
uE*vN, that might fit better what you are looking for.
> How do I convert this in matlab to a lat lon grid?
> Like this?
>
> uvcube2latlon(x,y,uv_vel_z,uv_vel_z,xi,yi)
>
> or this?
>
> cube2latlon(x,y,uv_vel_z,xi,yi)
You should use this 2nd transformation. Just keep in mind that
UV_VEL_Z is located at the grid-cell corner, so that the x,y
arguments should be xG & yG ; whereas UV_VEL_C is located
at the grid-cell center, so that x,y arguments should be xC,yC.
Cheers,
Jean-Michel
PS: David told me he saw you at the meeting. Hope everything is going well.
> or...?
>
> Thanks,
> Angela
>
>
> available_diagnostics.log:
> Total Nb of available Diagnostics: ndiagt= 179
> ------------------------------------------------------------------------------------
> Num |<-Name->|Levs| mate |<- code ->|<-- Units -->|<- Tile (max=80c)
> ------------------------------------------------------------------------------------
> 1 |SDIAG1 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #1
> 2 |SDIAG2 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #2
> 3 |SDIAG3 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #3
> 4 |SDIAG4 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #4
> 5 |SDIAG5 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #5
> 6 |SDIAG6 | 1 | |SM L1|user-defined |User-Defined Surface Diagnostic #6
> 7 |SDIAG7 | 1 | |SU L1|user-defined |User-Defined U.pt Surface Diagnostic #7
> 8 |SDIAG8 | 1 | |SV L1|user-defined |User-Defined V.pt Surface Diagnostic #8
> 9 |SDIAG9 | 1 | 10 |UU L1|user-defined |User-Defined U.vector Surface Diag. #9
> 10 |SDIAG10 | 1 | 9 |VV L1|user-defined |User-Defined V.vector Surface Diag. #10
> 11 |UDIAG1 | 30 | |SM MR|user-defined |User-Defined Model-Level Diagnostic #1
> 12 |UDIAG2 | 30 | |SM MR|user-defined |User-Defined Model-Level Diagnostic #2
> 13 |UDIAG3 | 30 | |SMR MR|user-defined |User-Defined Model-Level Diagnostic #3
> 14 |UDIAG4 | 30 | |SMR MR|user-defined |User-Defined Model-Level Diagnostic #4
> 15 |UDIAG5 | 30 | |SU MR|user-defined |User-Defined U.pt Model-Level Diag. #5
> 16 |UDIAG6 | 30 | |SV MR|user-defined |User-Defined V.pt Model-Level Diag. #6
> 17 |UDIAG7 | 30 | 18 |UUR MR|user-defined |User-Defined U.vector Model-Lev Diag.#7
> 18 |UDIAG8 | 30 | 17 |VVR MR|user-defined |User-Defined V.vector Model-Lev Diag.#8
> 19 |UDIAG9 | 30 | |SM ML|user-defined |User-Defined Phys-Level Diagnostic #9
> 20 |UDIAG10 | 30 | |SM ML|user-defined |User-Defined Phys-Level Diagnostic #10
> 21 |SDIAGC | 1 | 22 |SM C L1|user-defined |User-Defined Counted Surface Diagnostic
> 22 |SDIAGCC | 1 | |SM L1|count |User-Defined Surface Diagnostic Counter
> 23 |ETAN | 1 | |SM M1|Pa |Surface Pressre Anomaly
> 24 |ETANSQ | 1 | |SM P M1|Pa^2 |Square of Surface Pressure Anomaly
> 25 |DETADT2 | 1 | |SM M1|Pa^2/s^2 |Square of Surface Pressure Anomaly Tendency
> 26 |THETA | 30 | |SMR MR|K |Potential Temperature
> 27 |SALT | 30 | |SMR MR|g/kg |Specific Humidity
> 28 |RELHUM | 30 | |SMR MR|percent |Relative Humidity
> 29 |UVEL | 30 | 30 |UUR MR|m/s |Zonal Component of Velocity (m/s)
> 30 |VVEL | 30 | 29 |VVR MR|m/s |Meridional Component of Velocity (m/s)
> 31 |WVEL | 30 | |WM LR|Pa/s |Vertical Component of Velocity (r_units/s)
> 32 |THETASQ | 30 | |SMRP MR|K^2 |Square of Potential Temperature
> 33 |SALTSQ | 30 | |SMRP MR|(g/kg)^2 |Square of Specific Humidity
> 34 |UVELSQ | 30 | 35 |UURP MR|m^2/s^2 |Square of Zonal Comp of Velocity (m^2/s^2)
> 35 |VVELSQ | 30 | 34 |VVRP MR|m^2/s^2 |Square of Meridional Comp of Velocity (m^2/s^2)
> 36 |WVELSQ | 30 | |WM P LR|Pa^2/s^2 |Square of Vertical Comp of Velocity
> 37 |UE_VEL_C| 30 | 38 |UMR MR|m/s |Eastward Velocity (m/s) (cell center)
> 38 |VN_VEL_C| 30 | 37 |VMR MR|m/s |Northward Velocity (m/s) (cell center)
> 39 |UV_VEL_C| 30 | 39 |UMR MR|m^2/s^2 |Product of horizontal Comp of velocity (cell center)
> 40 |UV_VEL_Z| 30 | 40 |UZR MR|m^2/s^2 |Meridional Transport of Zonal Momentum (m^2/s^2)
>
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