Program: REGRID

• Motivation

• Program Function

• Input Data Format to regridder

• Supported Datasets

• Program Document

• Source Tar File

Motivation

The Version 3 REGRID program was based on the initial development of the program in Version 2, and it has gone through five significant updates since then. The purpose of developing this program is to separte external data ingest from internal data processing. As many of our users have access to their own unique datasets, this program allows a user to relatively easily ingest those data.

To find out more about REGRID, please read Chapter 5 of our online tutorial notes.

Program Function

The REGRID program is comprised of two sub-programs called pregrid and regridder. The pregrid program reads one or more external gridded pressure dataset and rewrites it to a specified simple format. The regridder program then reads in this reformatted data and interpolates it to mesoscale grid.

If an user wants to input a different dataset than those supported (see the list below), all the user needs to do is to read the dataset and write it to the simple format, and then run regridder.

Some enhancements in V3:

pregrid

• Allow simple interpolation of missing-level data in the vertical.

• Able to handle 'thinned' grid (a form of GRIB data).

regridder

• Allows constant fields, such as SST and snow cover (since these fields can be kept constant in a model simulation).

• Missing soil temps over islands can be estimated.

• Allow choice of linear or quadratic horizontal interpolation of fields.

• The snow cover field can be estimated from SNODEPTH field.

• Able to generate surface data if they are not in the input.

• Able to process intermediate files generated by INTERPB.

• A simple tropical cyclone bogussing scheme is available.

The program is written in Fortran 90 and can be run on various workstations, Linux, and Cray.

Input Data Format to regridder

Read about the intermediate format.

Supported Datasets

Several datasets are currently supported by the pregrid program:

• NCEP GDAS analysis (in ON84 format, discontinued in April 1997);

• NCEP GDAS analysis (in GRIB format, beginning in April 1997);

• TOGA basic level-III anlaysis (GRIB);

• NCEP/NCAR reanalysis archived at NCAR (GRIB);

• NCEP ETA 212 forecast, available on OSO server (GRIB);

• ECMWF reanalysis (GRIB);

• Final Analysis (FNL) (GRIB);

For a description of GRIB format, you may find NCEP Office Note 388 useful. You can download it from this site: ftp://ftp.ncep.noaa.gov/pub/nws/nmc/docs/gribed1.

Program Documents

pregrid.

Chapter 5 of our online Tutorial Notes for regridder.

Source tar file

ftp://ftp.ucar.edu/mesouser/MM5v3/REGRID.TAR.gz