[ncl-talk] rho_mwjf

Sun Jan 16 14:42:39 MST 2022

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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