Reading 3-dimensional netcdf data

I downloaded precipitation data from SIM2RAIN. It is 3 dimensional and temporal resolution is 1 day. For example for year 2005, my file size is 365(days)*1440(long)*720(lat). I want to show precipitation data for each day in matrix (1440,720). So, It means ı will have 365 files. My file name is CCI_SM2RAIN_2005_BC.nc. I can do it by using Arcmap but it is very time consuming. How can I do this in matlab ? Thanks for help.

Answer 1

[KSSV]

You can read your nc file like shown below....Change the variables in the below to your variables naming converntion in your file.

ncfile='CCI_SM2RAIN_2005_BC.nc'
lon = ncread(ncfile,'Longitude') ; nx = length(lon) ; 
lat = ncread(ncfile,'Latitude') ; ny = length(lat) ; 
time = ncread(ncfile,'Time') ;
for i = 1:length(time)
    z = ncread(ncfile,'Rainfall',[i 1 1 ],[1, nx ny]) ;
    z = squeeze(z) ; 
    pcolor(lon,lat,z') ; 
    title(sprintf("Time step = %d",i)) ; 
    shading interp 
    drawnow
end

[Gokhan Kayan]

Thanks for the comment KSSV. But the file does not accept longitude latitude and time as variables. It gives error when ı try to run it. My only variable is rainfall here.

[KSSV]

I already mentioned that you have to change the variable names as according to your file variable names.

[Gokhan Kayan]

I run it again by changing variable names. My new code is like this:

ncfile='CCI_SM2RAIN_2005_BC.nc'
lon = ncread(ncfile,'Longitude') ; nx = length(lon) ; 
lat = ncread(ncfile,'Latitude') ; ny = length(lat) ; 
time = ncread(ncfile,'Time') ;
for i = 1:length(time)
    z = ncread(ncfile,'z',[1 1 i],[nx ny 1]) ;
    pcolor(lon,lat,z') ; 
    shading interp 
    drawnow
end

And it gives me this errors.

Error using internal.matlab.imagesci.nc/getGroupAndVarid (line 2096)
Could not find variable or group 'z' in file.

Error in internal.matlab.imagesci.nc/read (line 593)
            [gid, varid] = getGroupAndVarid(this, location);

Error in ncread (line 66)
vardata = ncObj.read(varName, varargin{:});

Error in nc (line 6)
    z = ncread(ncfile,'z',[1 1 i],[nx ny 1]) ;

[KSSV]

What is 3D variable? You need to change it from 'z' to what it is in the file.

[Gokhan Kayan]

My 3D variable is 'Rainfall'. I think we should arrange this

z = ncread(ncfile,'Rainfall',[1 1 i],[nx ny 1]) ;

as

z = ncread(ncfile,'Rainfall',[i 1 1],[ 1 nx ny]) ;

because Time is first place for rainfall. 2nd one is longitude and 3rd variable is latitude.

Then I run code

ncfile='CCI_SM2RAIN_2005_BC.nc'
lon = ncread(ncfile,'Longitude') ; nx = length(lon) ; 
lat = ncread(ncfile,'Latitude') ; ny = length(lat) ; 
time = ncread(ncfile,'Time') ;
for i = 1:length(time)
    z = ncread(ncfile,'Rainfall',[i 1 1],[ 1 nx ny]) ;
    pcolor(lon,lat,'Rainfall') ; 
    shading interp 
    drawnow
end

Now it gives me this error

Error using pcolor (line 58)
Color data input must be a matrix.

Error in nc (line 7)
    pcolor(lon,lat,'Rainfall') ;

[KSSV]

ncfile='CCI_SM2RAIN_2005_BC.nc'
lon = ncread(ncfile,'Longitude') ; nx = length(lon) ; 
lat = ncread(ncfile,'Latitude') ; ny = length(lat) ; 
time = ncread(ncfile,'Time') ;
for i = 1:length(time)
    z = ncread(ncfile,'Rainfall',[i 1 1],[ 1 nx ny]) ;
    pcolor(lon,lat,z') ; 
    shading interp 
    drawnow
end

[KSSV]

Edited the answer.

[KSSV]

Also you can read the entire data into MATLAB workspace using:

z = ncread(ncfile.'Rainfall') ; 
for i = 1:length(time)
    R = squeeze(z(i,:,:)) ;
    pcolor(lon,lat,R')
    shading interp 
    drawnow
end

I have edited the original answer again.....now it will work..check it.

[Gokhan Kayan]

Thanks. You are great, It worked perfectly :)