[ferret_users] Fwd: dynamic height calculations

Hi Ferret users,

might be my query is not posted in ferret mail group. hence i am forwarding it again.

regards, saurabh

---------- Forwarded message ----------
From: saurabh rathore <rohitsrb2020@xxxxxxxxx>
Date: Fri, Dec 16, 2016 at 12:50 PM
Subject: dynamic height calculations
To: ferret users <ferret_users@xxxxxxxx>

hi ferreters,

i am trying to compute dynamic height by using potential temperature (deg. Celsius) and salinity (psu).

1) i used the go dynamic_height.jnl. after using this go script i got the plot but i am confused about the units mentioned by the plot. For dynamic height it is showing dyn-cm instead for dyn-m. i checked the script and found that there is no unit conversion. it is straight forward taking the depth mentioned by the data which is specified for depth i.e. Z[G=Temp] (argo temperature data) in meters. please tell me about the units used in this go script.

2) Moreover in the go dynamic_hight script it is defined as SVanom = SV - SV(35,0,0) [ in SV(35,0,0) the depth is zero instead of SV(35,0,z[g=temp]), why the depth is mentioned as zero instead fo variable according to the depth in data ?]

you the see the script by the command go/help dynamic_height.jnl

these are the commands i issued in the calculation.

use ptemp_argo.nc                  ! potential temp
use "/media/salt_argo.nc"        ! salinity

let dyn_S=salt[d=2]
let dyn_T=ptemp[d=1]
let dyn_P=z[gz=ptemp[d=1]]

set region/z=0:2000                ! for dynamic height at z=0 and reference depth is 2000 m

go dynamic_height

fill dyn_ht[l=@ave]

go fland

frame/file=1.png

3) but if i do my own calculation for this computation but using the following steps

use ptemp_argo.nc
use "/media/salt_argo.nc"

let tm=ptemp[d=1]
let sa=salt[d=2]

let ro0=rho_un(35,0,z[g=tt])-1000                   !! potential density at T=0, S=35, P
let al0=1/ro0                                                    !! specific volume i.e. alpha0

let ro=rho_un(sa,pot,z[g=tt])-1000                  !! potential density
let al=1/ro                                                        !! specific volume i.e. alpha

let dif=al-al0                                                    !! alpha - alpha0
let ro_ref=ro[z=2000]                                      !! reference potential density i.e. density at reference level of no motion

let h1=dif*ro_ref
let h=h1[z=0:2000@din]                                 !! dynamic height at surface z=0 with reference to z=2000 m

fill h[l=@ave]                                                  !! units in m
go fland

frame/file=2.png

but the plot is different from the go dynamic_height script. the dynamic height is more from the script as compare to my script. i am attaching both the plot and the reference document for the computation.

regards, saurabh

REGARDS

Saurabh Rathore

Research Scholar (PhD.)

Centre For Oceans, Rivers, Atmosphere & Land Science Technology

Indian Institute Of Technology, Kharagpur