[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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