MATLAB: How to regrid/interpolate netCDF data (2.5×2.5 degree) to higher resolution (e.g. 0.25×0.25 degree)

meshgridnetcdfpermutesqueeze

I am trying to use the script below by Hongxiao Jin in her Master thesis to regrid my netCDF NCEP Reanalysis II data to higher resolution at 0.25×0.25 degree. However, there are some errors in the script occurred. I installed mexcdf package to analyze netCDF data. Some errors occurred include: 1) Undefined function 'netcdf' for input arguments of type 'char'; 2) The expression to the left of the equals sign is not a valid target for an assignment in line 6. Thanks for your help.
 %Extracting Air relative humidity Example 2004 
  nc = netcdf('rhum.mon.mean.nc', 'nowrite'); %matlab function
  description = nc.description(:);    % Global attribute.
  variables = var(nc);    % Get variable data.
  Rhum2004=squeeze(variables{6}(301:312,1,:,:));%variables{6} 360X17X73X144 
  Rhum2004(find(Rhum2004==32766|Rhum2004==-32767)=nan; 
  nc = close(nc); 
  Rhum2004=permute(Rhum2004,[3 1 2]);%144X12X73 0->360
  Rhum2004=[Rhum2004(73:144,:,:);Rhum2004(1:72,:,:)];%-180->180 
  Rhum2004=permute(Rhum2004,[2 3 1]);%12X73X144
  Rhum2004=Rhum2004.*0.01+302.65; 
  [OX,OY]=meshgrid(-180:2.5:177.5,90:-2.5:-90); 
  [NX,NY]=meshgrid(-179.875:0.25:179.875,89.875:-0.25:-89.875); 
  RH2004=nan(12,720,1440); 
  for i=1:12 
  RH2004(i,:,:) = single(interp2(OX,OY,squeeze(Rhum2004(i,:,:)),NX,NY,'bilinear')); 
  end
  save RH2004 RH2004

Best Answer

%Regrid Air relative humidity Example 2004 
rhum = ncread('rhum.mon.mean.nc','rhum');
Rhum2004 = squeeze(rhum(:,:,:,301:312));
size(Rhum2004)
Rhum2004(find(Rhum2004==32766|Rhum2004==-32767))=nan; 
Rhum2004=[Rhum2004(73:144,:,:);Rhum2004(1:72,:,:)];%-180->180 
[OY,OX]=meshgrid(90:-2.5:-90, -180:2.5:177.5); 
[NY,NX]=meshgrid(89.875:-0.25:-89.875,-179.875:0.25:179.875); 
RH2004=nan(1440,720,12); 
for i=1:12 
RH2004(:,:,i) = ...
single(interp2(OY,OX,Rhum2004(:,:,i),NY,NX,'bilinear')); 
end
save RH2004 RH2004
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