[MITgcm-support] Barotropic ocean gyre tutorial

[Jeremy Miller]

P.S. I am attaching the modified python script:

gendata_tut4.1.py

to explain things

Best
Jeremy

On Sun, 4 Apr 2021 at 08:55, Jeremy Miller <jeremysharonmiller at gmail.com>
wrote:

> Dear Dr Rieck,
>
> First of all my apologies for only replying now I was on holiday. And
> thanks for your help.
>
> Unfortunately that didn't solve the problem. After replacing
>
> if sys.byteorder == 'little': tau_2.byteswap(True)
> tau_2.tofile('windx_siny.bin')
>
> with
>
> if sys.byteorder == 'little': tau_2.byteswap(True)
> fid = open('windx_siny.bin', 'wb')
> tau_2.astype('float32').tofile(fid)
>
> as you suggested, the plot still came out blank.
> Regarding Jeffrey Scott's comment that the reason I could not read back
> the bin file was due to a mismatch between float32 and float64, I followed
> his advice and read in the
> bin file using the snippet
>
> tau_2_1 = np.fromfile('windx_siny.bin',dtype='float32')
>
> and I got back an array with every entry being 'inf' except the
> penultimate column, being all '0'.
>
> Is it possible that the snippet
>
> # X=X.astype('float128')
> # Y=Y.astype('float128')
>
> (which is commented) needs to be included but with 'float128' replaced
> with 'float32'?
>
> Best
> Jeremy
>
>
>
>
>
> On Thu, 1 Apr 2021 at 16:47, Jan Klaus Rieck <jan.rieck at mail.mcgill.ca>
> wrote:
>
>> Hello Jeremy Miller,
>>
>> I also use python to to generate input data for the MITgcm. I found that,
>> to generate files that can be read by the MITgcm consistently, I needed to
>> specify the type explicitly.
>> My way of saving the files would look like this in your case:
>>
>> if sys.byteorder == 'little': tau_2.byteswap(True)
>> fid = open(''windx_siny.bin', 'wb')
>> tau_2.astype('float32').tofile(fid)
>>
>> Of course, 'float32' could be replaced by 'float64' if you require double
>> precision.
>>
>> I hope this helps,
>> Jan Rieck
>>
>> On Thu, 2021-04-01 at 10:22 +0300, Jeremy Miller wrote:
>>
>> Dear MITGCM forum,
>>
>> I am Jeremy Miller, I am new to MITgcm and I've been going through the
>> tutorials. I have a question about the "Barotropic Ocean Gyre" tutorial
>> (section 4.1).
>>
>> I managed to compile and run the code, and re-produce the first two plots
>> shown in section 4.1.5 for  wind stress of τ = τ0 cos( πy/Ly), for both the
>> advection and non-advection cases (with the provided input binary files).
>> I ran into problems when trying to produce the third plot, for the case
>> where τ = τ0 sin( πy/Ly). I am a python user, so I translated gendata.m
>> into python to write the input binary files 'windx_cosy.bin'
>> 'windx_siny.bin' (see the file gendata_tut4.1py attached).  As explained in
>> section 3.9 I've included the snippet
>>
>> if sys.byteorder == 'little': tau_2.byteswap(True)
>>
>> where "tau2" is the array to be output. There was no issue in the cosine
>> wind stress, and I managed to reproduce the results that I got with the
>> original 'windx_cosy.bin' provided in the tutorial. However, with the sine
>> wind stress case, the output in 'Eta.0000077760.001.001' is all zeros.
>>
>> When I attempt to read  'windx_siny.bin' with python into a new array
>> called tau2_1. I get absurdly big numbers back, which do not match the
>> original array tau2 that I created. If I Remove the snippet " if
>> sys.byteorder == 'little': tau_2.byteswap(True) ", in the python gendata
>> code, tau2_1 and tau2 match. But, then when I run the code again, the
>> file output.txt contains a long list of NaNs.
>>
>> I have also included the python code used to generate the plots in the
>> file tut_4.1_plots.py
>>
>> Look forward to hearing from you.
>> Yours sincerely
>> Jeremy Miller
>>
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