[ncl-talk] How to make time series plot from satellite swath files of multiple days

[Guido Cioni]

The question is general and involve different steps. There are a lot of examples on the NCL website, you should first try following those.

Specifically,

[1] reading HDF data (https://www.ncl.ucar.edu/Applications/HDF.shtml <https://www.ncl.ucar.edu/Applications/HDF.shtml>) possibly concatenating them (https://www.ncl.ucar.edu/Applications/addfiles.shtml <https://www.ncl.ucar.edu/Applications/addfiles.shtml>) so you already have all the timesteps. Otherwise you'd have to loop over the file and then concatenate the variable afterwards (https://www.ncl.ucar.edu/Document/Functions/Contributed/array_append_record.shtml <https://www.ncl.ucar.edu/Document/Functions/Contributed/array_append_record.shtml>).

[2] extract a lat-lon point from the variable that you're reading. var_point=var({lat_point},{lon_point}) assuming that the variable has coordinate variables attached (https://www.ncl.ucar.edu/Document/Language/subscript_coord.shtml <https://www.ncl.ucar.edu/Document/Language/subscript_coord.shtml>), otherwise you have to find the cell index by yourself (some hint https://www.ncl.ucar.edu/Document/Functions/Built-in/ind.shtml <https://www.ncl.ucar.edu/Document/Functions/Built-in/ind.shtml>). You should also develop an if-condition that checks whether the point is included in the swath: I believe that your satellite data is sparse so maybe the point that you're looking at is not always included in the swath... I  would suggest to assign a _FillValue to the variable if this point is not found so that you can plot the timeseries easily. 

[3] Do a timeseries with gsm_csm_xy, mabye format the x-axis using time_axis_labels (https://www.ncl.ucar.edu/Document/Functions/User_contributed/time_axis_labels.shtml <https://www.ncl.ucar.edu/Document/Functions/User_contributed/time_axis_labels.shtml>).

I believe you have enough to start working now. 

Cheers 




> On 26. Feb 2018, at 15:51, Krishnakumar AP <krishnaap7 at gmail.com> wrote:
> 
> Hello NCL Community,
>  I want to make a time series plot from HDF satellite swaths of multiple days, how to do that? I want to take time series values of Cloud water path from a specific lat and long and make into a time series plot. Could you please guide me? Thanks in advance
> 
> -- 
> 
> Thankfully
> Krishnakumar.AP
>   
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Guido Cioni
http://guidocioni.altervista <http://guidocioni.altervista/>.org

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