[ncl-talk] rho_mwjf

Mon Jan 17 02:26:35 MST 2022

Dear Will and Dennis,

Many many thanks for you. I am using Max Planck Earth System model (MPI-ESM). The thetao is the potential temperature and salinity unit is psu. 

Thanks again and best regards,

Chathu

-----Original Messages-----
From:"Dennis Shea" <shea at ucar.edu>
Sent Time:2022-01-17 11:38:07 (Monday)
To: "Will Hobbs" <will.hobbs at utas.edu.au>
Cc: Chathurika <chatu at scsio.ac.cn>, ncl-talk <ncl-talk at ucar.edu>
Subject: Re: [ncl-talk] rho_mwjf

THX, Will
============

Two ocean functions: potmp_insitu_ocn , depth_to_pres

-----------------------------------------------------------------------

Assorted ocean functions in contributed.ncl :. These are NOT SUPPORTED; documented in functions

gravity_ocn         : Gravity as a function of latitude
depth_ocn           : Depth(pressure, depth, correction_term) [ UNESCO: 1983 ]
salinity_un83_ocn   : Salinity calculation (pss) from conductivity
atg_ocn             : Computes the adiabatic temperature gradient
potentmp_ocn        : Potential temperature from in-situ measurements
vsnd_un95_ocn       : speed of sound in seawater as a function of s, t & p
vsnd_teos10_ocn     : speed of sound in seawater as a function of s, t & p (van T Hoff eqn)
densatp_ocn         : Calculate the density of seawater at a given s, t AND p [Millero & Poisson (1981)]
aou_ocn             : Oxygen concentration at saturation

%> less $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
~                                                                

On Sun, Jan 16, 2022 at 2:43 PM Will Hobbs via ncl-talk <ncl-talk at mailman.ucar.edu> wrote:

Chathu

The function rho_mwjf() should really be deprecated, it’s only applicable to the Equation of State for the CESM3 version of POP and NOT for observations (I would guess that POP has moved on now as well).

If you’re working with observational data that you should really be using TEOS-10 (https://www.teos-10.org) and if you’re working with a model then strictly speaking you should track down the EoS for that model (which is likely a simplified version of TEOS-19).

If you’re really wedded to using rho_mwjf(), then double-check that you have the correct salinity units. Also, you have to accept that the EoS probably doesn’t work that for extreme conditions (for example supercooled water near ice shelves), which may explain the erroneous density.

I did start a few years ago with Dennis on implementing NCL wrappers for the fortran TEOS-10 library, but life/work got in the way, and with the deprecation of NCL it became a low priority. I’ve attached an NCL library of some of the (now obsolete) UNESCO EoS functions – you’re welcome to use but AT YOUR OWN RISK.

Will

From: ncl-talk <ncl-talk-bounces at mailman.ucar.edu> on behalf of Chathurika via ncl-talk <ncl-talk at mailman.ucar.edu>
Reply to: Chathurika <chatu at scsio.ac.cn>
Date: Sunday, 16 January 2022 at 12:52 am
To: ncl-talk <ncl-talk at ucar.edu>
Subject: [ncl-talk] rho_mwjf

Dear NCL users,

I am really appreciate if you can show me what I is wrong with my script. As you know the southern ocean density is around 26-27 as follows at each depth level.

(0) 26.34497

(1) 26.3656

(2) 26.40527

(3) 26.45532

(4) 26.5199

(5) 26.58557

(6) 26.65369

(7) 26.71924

(8) 26.77869

(9) 26.83704

(10) 26.89197

(11) 26.94214

(12) 26.99036

(13) 27.0343

(14) 27.0769

(15) 27.11511

(16) 27.15247

(17) 27.18738

(18) 27.22571

(19) 27.26978

(20) 27.32153

(21) 27.39014

(22) 27.46655

(23) 27.52747

(24) 27.57336

(25) 27.61084

(26) 27.65247

(27) 27.6958

(28) 27.73132

(29) 27.75598

(30) 27.77417

(31) 27.78784

(32) 27.79846

(33) 27.80762

(34) 27.81592

(35) 27.82202

(36) 27.82605

(37) 27.82739

(38) 27.82776

(39) 27.8324

However, when I calculate the density at each depth levels using rho_mwjf (script is attached below), It calculate density which is not reasonable, shows;

(0) 26.3907

(1) 26.4604

(2) 26.54432

(3) 26.6379

(4) 26.74557

(5) 26.85472

(6) 26.97386

(7) 27.10243

(8) 27.24155

(9) 27.40277

(10) 27.58386

(11) 27.78384

(12) 28.00518

(13) 28.24571

(14) 28.5084

(15) 28.79022

(16) 29.09488

(17) 29.43268

(18) 29.82106

(19) 30.26328

(20) 30.76077

(21) 31.32516

(22) 31.94666

(23) 32.59835

(24) 33.27908

(25) 33.99501

(26) 34.78358

(27) 35.64154

(28) 36.53573

(29) 37.46336

(30) 38.45152

(31) 39.54657

(32) 40.74771

(33) 42.0564

(34) 43.53943

(35) 45.23687

(36) 47.14139

(37) 49.24323

(38) 51.43494

(39) 53.81633

depth from 6 m to 5720 m, 40 levels

Could please anyone say what am I doing here wrong? if this is not the right way to calculate density using temperature and salinity what will be the other way? Many many thanks. Please be kind to reply me.

The script: 

diri=".../salinity/hist/"
sfile = "salinity.nc" 

f = addfile(diri+sfile,"r")
vname=getfilevarnames(f)
print(vname)

  salt           = f->so(:,:,{-25:-70},:)
  printVarSummary(salt)
  printMinMax(salt, False)

 s_range = dim_avg_n_Wrap(salt, 0)
 printVarSummary(s_range)

 delete(salt)

diri=".../temperature/hist/"
sfile = "temperature.nc" 

f = addfile(diri+sfile,"r")
vname=getfilevarnames(f)
print(vname)

  temp           = f->thetao(:,:,{-25:-70},:)
  printVarSummary(temp)
  printMinMax(temp, False)

 t_range = dim_avg_n_Wrap(temp, 0)
 printVarSummary(t_range)

 delete(temp)

depth = (/6, 17,27,37,47,57,68.5,82.5,100,122.5,150,182.5,220\
   ,262.5,310,362.5,420,485,560,645,740,845,960,1085,1220,1365\
   ,1525,1700,1885,2080,2290,2525,2785,3070,3395,3770,4195,4670,5170,5720/) 

ndim = dimsizes(t_range)

nlev = ndim(0)
nlat = ndim(1)
nlon = ndim(2)

rho = new((/nlev,nlat,nlon/), typeof(t_range))

do i = 0, nlev-1
    rho(i,:,:) = rho_mwjf(t_range(i,:,:),s_range(i,:,:),depth(i))

end do

copy_VarCoords(t_range, rho)
rho = 1000.*(rho-1.) 

printVarSummary(rho)
printMinMax(rho, True)

abc = dim_avg_n_Wrap(rho, (/1,2/))
printVarSummary(abc)

print(abc)

Thank you and best regards,

Chathu

Wickramage Chathurika Hemamali

Msc in Physical Oceanography

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Wickramage Chathurika Hemamali
Msc in Physical Oceanography

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