Why don't you use CDO for this task? You can regrid your data easily by that...

Regridding is a technique to change the spatial resolution using statistical interpolation. There are several methods, but the following commands used conservative remapping. You may explore others like remapbil remapbic remapnn remapdis remapycon remapcon remapcon2 using the CDO

Here are the commands you need to invoke.

cdo -f nc -sellonlatbox,lon1,lon2,lat1,lat2 -random,r1440x720 template.nc

Where  lon1,lon2,lat1,lat2 are your desired domain. The above command creates template of your desired resolution. This template is for 0.25 degree resolution. If you want to change the resolution, you have change those 1440 and 720 accordingly (Hope it is easily understood). Check with ncdump -c template.nc

Next regrid using the following command ...

cdo -remapcon,template.nc input.nc output.nc

Hope this helps !

Why don't you use CDO for this task? You can regrid your data easily by that...

Regridding is a technique to change the spatial resolution using statistical interpolation. There are several methods, but the following commands used conservative remapping. You may explore others like remapbil remapbic remapnn remapdis remapycon remapcon remapcon2 using the CDO

Here are the commands you need to invoke.

cdo -f nc -sellonlatbox,lon1,lon2,lat1,lat2 -random,r1440x720 template.nc

Where  lon1,lon2,lat1,lat2 are your desired domain. The above command creates template of your desired resolution. This template is for 0.25 degree resolution. If you want to change the resolution, you have change those 1440 and 720 accordingly (Hope it is easily understood). Check with ncdump -c template.nc

Next regrid using the following command ...

cdo -remapcon,template.nc input.nc output.nc

Hope this helps !

The following is by Dennis Shea (NCAR):

Regridding is the process of interpolating from one grid resolution to a different grid resolution. This could involve temporal, vertical or spatial ('horizontal') interpolations. However, most commonly, regridding refers to spatial interpolation. There are numerous grid interpolation methods and users should choose the method appropriate for the intended task. Using an inappropriate interpolation scheme may lead to misleading results. Further, most climate grids are georeferenced on a sphere where pole singularities and the convergence of the longitude meridions can be issues that need to be addressed.

Source:

https://climatedataguide.ucar.edu/climate-data-tools-and-analysis/regridding-overview

I also think cdo is a better option

You follow the link below if you still prefer to use grads;

http://opengrads.org/doc/udxt/re/re.html

Thank you guys Kishore B. Ragi Peter Nunekpeku

regridding data is a techinic which allow a conversion from one resolution to another. try using this link there is tools allowing conversion

https://www.cpc.ncep.noaa.gov/products/wesley/

Kishore B. Ragi How to get the resolution (r) equivalent of different degrees (e.g. 0.25, 0.5, 1, 1.5, 2, 2.5 deg)?

Dear Bappa Das

Here the commands you need to invoke.

cdo -f nc -sellonlatbox,lon1,lon2,lat1,lat2 -random,r1440x720 template.nc

Where  lon1,lon2,lat1,lat2 are your desired domain. The above command creates a template of a 0.25-degree resolution. If you want to change the resolution, you have to change those 1440 and 720 accordingly. For example, 1-degree resolution, it will be r360x180.

Next regrid using the following command ...

cdo -remapcon,template.nc input.nc output.nc

This should create a regridded netcdf file. Check if you got the required resolution.

I hope this helps and solves your purpose.

PS: Here you can have several regridding techniques such as remapcon, remapcon2, remapbic, remapnn, etc. Please explore these techniques before applying to regridding your present data. You have to see how sensitive your data is and how these regridding techniques will make the data worse.

Regards,

Kishore

Kishore B. Ragi How to regrid in CDO that I got it. I want to have a ready reckoner like

Degree r

0.25 1440x720

0.5 720x360

1 360x180

1.5 ??

2 180x60

2.5 ??

Yes.

1.5 240x120

2.5 144x72

You can check the lon/lat values in your template.nc before regridding your data using the following command. If you find a little change, you can tweak your r values one more or less and check again to see what you wanted.

ncdump -c output.nc

Regards,

Kishore