[MITgcm-support] Flt package -- T, S interpolation and pressure output

[Ewa Katarzyna Karczewska]

Hi all,

I'm using the flt package for 3-D advection of floats.

I am new to the package and to understand it better I wanted to compare 
the flt output with the interpolation carried out in matlab.

More specifically, I'm trying to compare the salinity and temperature 
flt output values (from float_trajectories.data files) for a particular 
float, with the salinity and temperature values manually interpolated in 
matlab using: interpn() function, 5-day averaged offline fields, float 
location from flt output (longitude, latitude, depth) and x,y,z (grid).

I expected both interpolations (flt and matlab) to be the same, but they 
are very different. I'm trying to understand why. Both methods use 
trilinear Interpolation and have the same fields, lon, lat and depth as 
an input.
Is there something I'm missing? Does the Flt package not simply extract 
and interpolates the salinity and temperature values from a specific 
5-day averaged T,S fields (specified by the timestep) once it has 
float's location (lon, lat, depth)?

I'm advecting floats in a 4 year simulation which recycles one year of 
the 5-day averaged offline fields (T,S,U,V,W) (73 files recycled 4 times).

The timestep for the offline fields is set to 5 days 
(deltaToffline=432000.,) :

  &OFFLINE_PARM02
   offlineIter0=0,
   deltaToffline=432000.,
   offlineForcingPeriod=432000.,
   offlineForcingCycle=31104000.,
  &

The float_trajectory data files are outputted every 5 days

  &FLT_NML
  FLT_Iter0 =  0,
  flt_noise    = 0.0,
  flt_int_traj =  432000.,
  flt_int_prof = 432000.,
  flt_file     = 'flt_ini_pos.bin',



Also, is there a way of getting the pressure output in the flt 
float_trajectories.data file?

At the moment, in the flt_traj.F the pressure is set to the surface 
height anomaly (ETAN)
CALL FLT_BILINEAR2D(ix,jy,pp,etaN,     0,bi,bj,myThid)

and it gives output of '0'

I've tried using PHIHYD but it didn't work.



I will appreciate any suggestions.

Thanks,
Ewa



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