Convert sveral netCDF files to ASCII or CSV

Question

Majid Mohamod 2017-6-1

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回答： javeed hamad 2022-3-27

HI all, I have 2000 files of netCDF (.nc). These files are for precipitation of my study area. I have the script which included below. I want to make this script to call all netCDF and output them as ASCII. Some netCDF files have attached too.. I really appreciate your help and time.

Thanks, Majid

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Majid Mohamod 2017-6-5

Yes, GDAL is Geospatial Data Abstraction Library.

The script is suppose to work with my files. The way how I run the script as the following: 1- I combined the two files " NetCDFreader + NetCDF2ASCII" as on script. 2- I changed the fpath to the folder path wher the netcdf files are located. 3. I run the script.

The result, the script didn't work!

I am worry that the way which I wrote the fpath is not correct. I don't know if there is a specific method to write the fpath?

As I understood from your comment, you wrote that the script didn't work with you too? Please, any suggestion to solve this problem?

Thanks, Majid

per isakson 2017-6-5

编辑：per isakson 2017-6-5

What makes you think that this FEX-submission can read and convert your files?
"ArcSWAT" &nbsp is that The Soil and Water Assessment Tool (SWAT)?
What makes you think that the FEX-submission will write a csv-file that is appropriate for ArcSWAT ?
NetCDFreader requires that the extension is .nc. Yours is .nc4.

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Answer 1

KSSV 2017-6-5

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https://ww2.mathworks.cn/matlabcentral/answers/342924-convert-sveral-netcdf-files-to-ascii-or-csv#answer_269554

在 MATLAB Online 中打开

Dear Majid

Reading nc files is not a deal in MATLAB. It is pretty straight forward and easy. If you would have tried to read the documentation, by this time you could have solved your problem. No files is required to read the ncfiles. Just you need to know only few functions: ncdisp, ncreaad and ncreadatt.

In the below code, I am reading the precipitation data of the six ncfiles which you gave in the attachment. I am reading the begin, end date and time also. The output is taken into cells.

files = dir('*.nc4') ;
nfiles = length(files) ;
P = cell(nfiles,1) ; % precipitation of all files
date = cell(nfiles,2) ;
time = cell(nfiles,2) ;
for i = 1:nfiles
    %%Read dat
    date{i,1} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.BeginDate')  ;
    date{i,2} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.EndDate')  ;
    %%Read time 
    time{i,1} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.BeginTime')  ;
    time{i,2} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.EndTime')  ;
    %%REad precipitation 
    P{i} = ncread(files(i).name,'precipitation') ;
end

Now you can write the above data into what ever format you want.

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KSSV 2017-6-5

在 MATLAB Online 中打开

I prefer to work with netCDF. See the below code, which reads all the above six ncfiles and writes them into single nc file.

files = dir('*.nc4') ;
nfiles = length(files) ;
P = cell(nfiles,1) ; % precipitation of all files
date = cell(nfiles,2) ;
time = cell(nfiles,2) ;
for i = 1:nfiles
    %%Read dat
    date{i,1} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.BeginDate')  ;
    date{i,2} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.EndDate')  ;
    %%Read time
    time{i,1} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.BeginTime')  ;
    time{i,2} = ncreadatt(files(i).name,'/','HDF5_GLOBAL.EndTime')  ;
    %%REad precipitation
    P{i} = ncread(files(i).name,'precipitation') ;
end
%%Write all the above data into nc-file
ncfile = 'merged.nc' ;
[nx,ny] = size(P{1}) ;
%
nccreate(ncfile,'time','Dimensions',{'time',1,Inf},'DeflateLevel',8) ;
%
nccreate(ncfile,'precipitation','Dimensions',{'lat',nx,'lon',ny,'time'},'DeflateLevel',8) ;
ncwriteatt(ncfile,'precipitation','units','mm');
ncwriteatt(ncfile,'precipitation','long_name','Daily accumulated precipitation (combined microwave-IR) estimate with gauge calibration over land');
ncwriteatt(ncfile,'precipitation','coordinates','lat lon');
ncwriteatt(ncfile,'precipitation','FillValue','-9999.9004');
ncwriteatt(ncfile,'precipitation','origname','precipitation');
ncwriteatt(ncfile,'precipitation','fullnamepath','/precipitation');
for i = 1:nfiles
    ncwrite(ncfile,'precipitation',P{i},[1,1,i]) ;
end
ncwriteatt(ncfile,'/','HDF5_GLOBAL.BeginDate',date{1,1}) ;
ncwriteatt(ncfile,'/','HDF5_GLOBAL.BeginTime',time{1,1}) ;
ncwriteatt(ncfile,'/','HDF5_GLOBAL.EndDate',date{nfiles,2}) ;
ncwriteatt(ncfile,'/','HDF5_GLOBAL.EndTime',time{1,2}) ;
ncwriteatt(ncfile,'/','creation_date',datestr(now));
ncdisp(ncfile)

KSSV 2017-6-6

I have answered this in your new question. I was about to answer here..:)

Majid Mohamod 2017-6-6

I am going to check it now. Thanks :)

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Answer 2

shobhit pipil 2018-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/342924-convert-sveral-netcdf-files-to-ascii-or-csv#answer_352775

编辑：shobhit pipil 2018-12-17

data = [];

Files=dir('*.nc');

for k=1:length(Files)

FileNames=Files(k).name

pr=ncread(FileNames,'rainfall_amount');%name of netCDF file; 'pr' is the precip variable in the netCDF file

long=ncread(FileNames,'x'); %'longitude' is the longitude variable in the netCDF file

lat=ncread(FileNames,'y'); %'latitude' is the latitude variable in the netCDF file

for j= 716:746(lat); %1:length(lat);

for i= 328:368(long); %1:length(long);

v=pr(i,j,:); %read through all lat,longs in netCDF

outfile=sprintf('%d_%d_PCP.txt',lat(j),long(i));%name of outputfile; format is 'LATITUDE_LONGITUDE_PCP.txt'

fid=fopen(outfile,'w+');

data2=(v);

data2(isnan(data2)) = -99.0 ; %cleanup in case the data is a NaN

data = {data;data2};

end

%fprintf(fid, '18900101\n');%#write the climate data starting date to header of outfile. Change '20200101' to the starting date of your dataset. For example, Jan. 1, 1950 is 19500101

fprintf(fid,'%5.1f\n',data); %formatting the data for SWAT specifications

fclose(fid);

disp([outfile 'created'])%display created file

fclose all

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shobhit pipil 2018-12-17

Would anybody please reply to me. I am trying to extract the NetCDF pricipitation data into SWAT format. The current script is not able to write data from NetCDF to txt file from each iteration. Please help.

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Answer 3

javeed hamad 2022-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/342924-convert-sveral-netcdf-files-to-ascii-or-csv#answer_927934

HI every one!

I want to extract GHI (Global horizontal irradiation) data from NC file which include almost 3500 files for my study area, can someone please guide which script should use to extract multiple files simultaneously.

Thanks a lot, Javeed