[MITgcm-support] discontinuous flt data

[钱钰坤]

Hi all,


I'm recently using flt pkg to simulate a large number (~4 million) of Lagrangian particles in an idealized
flow.  The MITgcm outputs a series of float_trajectories.*.data files, which contain records with IDs, times,
3D-positions and tracer values.


Since I need to analyze the Lagrangian behavior, I group these records into different Lagrangian particles:
one particle should have the same ID and continuous time records (e.g., for the daily outputs, time records
should be day 1, 2, 3..., N).


However, after grouping all the records, I find that for my 1441-day long simulation, I get
different lengths of particles as:
    total file size: 31437640780 bytes, total FLT Records: 604567757, total particles: 419549
    group of T-count (1440) has       2334 particles
    group of T-count (1441) has   417206 particles
    group of T-count (1439) has              9 particles
    finish reading 419549 FLT Particles

The total number of particles equals to that I deployed into the flow (perfect).  However, not all the particles
have exactly 1441 time records as expected.  For particles with T-records less than 1441, I find that there may
be occasionally a missing record so that the time records are day 1, 2, 4..., N, where the record at day 3 (randomly)
is lost.    I also found many records with time (and other information) is exactly 0, which are all dropped before
grouping into particles.


The idealized flow is in a closed boundary domain and no topographic problem (so that particles will not drift to
lands).  Since there are only 0.5% of total particles have missing records, I could just remove them.  However,
this is a quite large dataset that I am thinking of reading the records step by step.  That is, read all records
at day 1 only and do some analysis, then delete them and read records at day 2 only...  In this case, if there were
missing records, they are very likely to cause some problems.


Does anyone have a similar cases?  Is this a problem with the flt pkg or there are some bugs in my grouping codes?


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