[ferret_users] Re: [ferret_users] Re: [ferret_users] computation of MLD using Jean-Baptiste Sallée 2021, Nature

[saurabh rathore <rohitsrb2020@xxxxxxxxx>]

Dear Ansley

G'day

Thank you very much your reply was indeed very helpful and I have learned new things which are very useful. 

I am attaching the code also based on the Nature paper I mentioned earlier. I check both @LOC and @WEQ and they give the same output.

use /projets/nemo-rd/SOCHIC/saurabh/n42tm21-ex/potential-density_991_1000_M.nc

let thres = potden[z=10] + 0.03
let thres0 = potden - thres
let mldz = thres0[z=@loc:0]
let mldf = thres0[z=@weq:0]

let zed = z[gz=potden] + 0*potden
let mldw1 = zed*mldf
let mldw = mldw1[z=@sum]

let mldloc = mldz 
let mldweq = mldw 

set var/title="Mixed Layer Depth (Density Criteria@LOC)"/units="meters" mldloc
set var/title="Mixed Layer Depth (Density Criteria@WEQ)"/units="meters" mldweq

repeat/l=1:120:1 (save/append/file=mld-dens-loc.nc mldloc;can mem/all;set mem/size=6000)
repeat/l=1:120:1 (save/append/file=mld-dens-weq.nc mldweq;can mem/all;set mem/size=6000)

exit

On Tue, May 31, 2022 at 9:12 PM Ansley Manke <a.c.manke@xxxxxxxxx> wrote:

Hi,

There are a couple of transformations that may help you: @LOC and @WEQ.  Besides their documentation for those transformations, here are examples from the list archives and an FAQ about using those functions

This, about mixed-layer depth, using @LOC.  This is from a knowledgeable contributor:
https://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2004/msg00523.html
The same contributor offered the script "mld_temp.jnl" which is included in the scripts with your installation of Ferret or PyFerret.

yes? go/help mld_temp.jnl

(I have not compared in detail whether these match the equation you want to work with.)

And there is also this FAQ, how to define a variable containing the data at the deepest depth
https://ferret.pmel.noaa.gov/Ferret/faq/how-can-i-show-the-value-of-my-variable-at-its-deepest-depth

Ansley

On 5/30/2022 6:59 AM, saurabh rathore wrote:

Dear Ferreters

G'day

I am performing a computation of MLD using the potential density criterion i.e. potential density referenced to the surface, σ0, exceeds by a threshold of 0.03 kg m−3 the density of the water at 10 m, 

σ0(z = −H) = σ0(z = −10 m) + 0.03 kg m−3, with H the mixed-layer depth.

I masked the potential density as

let dens_10m = density[z=10]

let threshold = dens_10m + 0.03

let mask = if density le threshold then density

now I want to take the deepest level of the valid density .i.e mask variable as the MLD. So how to extract this level as a variable of MLD?

let zed = z[gz=density] + 0*density

let zp = zed*mask

mld = zp[z=@max]

I like to know if this is the correct way to compute the MLD?

Cheers, Saurabh

--

REGARDS

Saurabh Rathore

Research Scholar (PhD.)

Centre For Oceans, Rivers, Atmosphere & Land Science Technology

Indian Institute Of Technology, Kharagpur

contact :- 91- 8345984434

--

REGARDS

Saurabh Rathore

Research Scholar (PhD.)

Centre For Oceans, Rivers, Atmosphere & Land Science Technology

Indian Institute Of Technology, Kharagpur

contact :- 91- 8345984434