[MITgcm-support] MITgcm Floats Package Depth Interpolation Issue

[钱钰坤]

Hi John,


Not sure if you have modified the code but I always specify the actual vertical positions (not fractal indice) in the flt input files.  I found these in README.flt (https://github.com/MITgcm/MITgcm/blob/master/pkg/flt/README.flt):


c     Each float contains a 9 element double precision record of a  c     direct access file. The records are: c      c     - npart   A unique float identifier (1,2,3,...) c     - tstart  start date of integration of float (in s) c               Note: If tstart=-1 floats are integrated right from the  c               beginning c     - xpart   x position of float (in units of XC) c     - ypart   y position of float (in units of YC) c     - kpart   actual vertical level of float c     - kfloat  target level of float (should be the same as kpart at c               the beginning) c     - iup     flag if the float  c               - should profile   ( >  0 = return cycle (in s) to surface)  c               - remain at depth  ( =  0 ) c               - is a 3D float    ( = -1 ). c               - should be advected WITHOUT additional noise ( = -2 ).  c                 (This implies that the float is non-profiling) c               - is a mooring     ( = -3 ), i.e. the float is not advected c     - itop    time of float the surface (in s) c     - tend    end  date of integration of float (in s) c               Note: If tend=-1 floats are integrated till the end of c               the integration


And if you are a pythoner you may want to check this repo (https://github.com/rabernat/floater/blob/master/floater/generators.py). 

Hope this helps.

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

 Best regards 
 
Yu-Kun Qian (钱钰坤) 
Center for Monsoon and Environment Research 
 Department of Atmospheric Sciences
School of Environmental Science and Engineering 
 Sun Yat-sen University 
No. 135 Xingang West Road, Haizhu District 
Guangzhou, 510275, P.R. China 
Tel; 020-84115227 
Email: qianyk at mail3.sysu.edu.cn      


 
 
 
------------------ Original ------------------
From:  "John Paul Irving"<jpi18 at my.fsu.edu>;
Date:  Tue, Mar 31, 2020 11:37 PM
To:  "MITgcm-support at mitgcm.org"<MITgcm-support at mitgcm.org>; 

Subject:  [MITgcm-support] MITgcm Floats Package Depth Interpolation Issue

 

   Hello All,
  
 
  I am working on a project utilizing the MITgcm flt package. I am running the model on a curvilinear grid with multiple processors. In my flt input files i prescribe the vertical position of the flts in fractal indices, and the FLT_MAP_K2R function in the flt_mapping.F  file converts these fractal indices to a depth in meters. However the floats are not being mapped to their exact positions in the simulation. For particles launched between 50-500 meters, the initial starting positions are less than 1m off the desired depth.  But for particles at 1000m launch depth, they are about 20 meters off. I have 45 vertical levels as follows. the dz between layers is 10m in the upper150m, 25m until 600m, 50m until 1000, and then with larger levels to the bottom.
  
 
  I am having trouble figuring out why it cannot interpolate the exact depth values that i originally used to interpolate to an indice? I also have confusion about why 2 floats launched at the same depth are then read in at slightly different depths?
  
 
  Was wondering if anyone else has tried to do this and seen this issue, thanks!
  
 
    
John Irving
 

 
 
jpi18 at my.fsu.edu
 
Florida State University  
 
Department of Earth, Ocean, & Atmospheric Science
 
 
 
 
 
   
 
   

 
 
John Irving
 

 
 
jpi18 at my.fsu.edu
 
Florida State University  
 
Department of Earth, Ocean, & Atmospheric Science
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