## NCL Scripts to Regrid NCEP/NCAR Reanalysis Data for Comparison with CCR GCM Output

These scripts allow the user to regrid (interpolate) NCEP/NCAR Reanalysis Data to the CCM1 (R15), CCM3 (T42), Genesis (T31, 2x2), and FOAM (R15) grids so that GCM output may be compared with NCEP/NCAR Reanalysis Data.

There are several versions of these scripts because the NCEP/NCAR Data
is on two grids: a ** fixed**
grid (2.5x2.5 degrees with 73x144 points) and a

**grid (T62 with 94x192 points). You will need to check your data (do a "ncdump -h") for its dimensions so that you know what type of grid it is on.**

*gaussian*#### Contents

- Regrid Data from the NCEP FIXED Grid to a GAUSSIAN Grid
- Scripts to Regrid Data from the NCEP GAUSSIAN Grid to a GAUSSIAN Grid
- Scripts to Regrid Data from the NCEP FIXED Grid to a FIXED Grid
- Description of NCL functions used to perform interpolations
- Links to NCEP/NCAR Reanalysis Data Sites

### Regrid Data from the NCEP FIXED Grid to a GAUSSIAN Grid

**Use function f2gsh(grid : numeric, outdims[2] : integer, twave[1] : integer)**

- grid: input array of 2 or more dimensions (last two dimensions must be nlata x nlona, values must be in ascending latitude order)
- outdims: indicates dimensions of rightmost two dimensions of output grid (outdims[0] = nlatb, outdims[1] = nlonb)
- wave: scalar integer indicating the optional wave truncation:
- twave = 0 => exact interpolation
- twave > 0 => exact interpolation and triangular truncation at twave
- twave < 0 => exact interpolation, triangular truncation at twave and spectral coefficient tapering (the effect is to smooth the data)

#### Scripts

- ncep_fixed_to_CCM1.ncl
- ncep_fixed_to_CCM3.ncl (sfc air temp example)
- CCM3 data file used in script
- NCEP data file used in script
- ncep_fixed_to_genagcm.ncl
- ncep_fixed_to_foam.ncl (sfc air temp example)
- FOAM data file used in script
- NCEP data file used in script

### Scripts to Regrid Data from a GAUSSIAN Grid to a GAUSSIAN Grid

**Use function g2gsh(grid : numeric, outdims[2] : integer, twave[1] : integer)**

- grid: input array of 2 or more dimensions (last two dimensions must be nlata x nlona, values must be in ascending latitude order)
- outdims: indicates dimensions of rightmost two dimensions of output grid (outdims[0] = nlatb, outdims[1] = nlonb)
- wave: scalar integer indicating the optional wave truncation:
- twave = 0 => exact interpolation
- twave > 0 => exact interpolation and triangular truncation at twave
- twave < 0 => exact interpolation, triangular truncation at twave and spectral coefficient tapering (the effect is to smooth the data)

#### Scripts

- ncep_gaussian_to_CCM1.ncl
- ncep_gaussian_to_CCM3.ncl
- ncep_gaussian_to_genagcm.ncl
- ncep_gaussian_to_foam.ncl (latent heat flux example)
- FOAM data file used in script
- NCEP data file used in script

### Scripts to Regrid Data from a FIXED Grid to a FIXED Grid

- ncep_fixed_to_genlsx.ncl