site map - email us - search  
 

MM5 Model V2

V2 Timing Results

Pre & Post Processing V2
    Releases
    New in V2
    Terrain
    Regrid
    Little_r

V2 Source Code

V2 Tutorial Notes

 


 

New Program: REGRID


Motivation

The current Datagrid program is hardwired to access a few global datasets from NCAR's archive, and then interpolate the global lat/long data to mesoscale grid as defined in program Terrain. As the number of users outside academic community and abroad increases, and as more datasets become available at NCAR (such as NCEP/NCAR reanalysis), the need to have a program that is more flexible to adapt different datasets and be able to run on different platforms is clear.

This new program, REGRID, is designed to overcome these problems by separating data acquisition, which is often variable and may require user effort, from the simple task of interpolation.

To find out more about REGRID, please see Manning and Gill (1998) published in the 1998 MM5 Users' Workshop preprint.

Program Function

The REGRID program is comprised of two sub-programs called pregrid and regridder. The pregrid program reads a global 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.

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

Input Data Format to regridder

The files are written as unformatted FORTRAN 32-bit IEEE records. Four records are used for every horizontal slab.

 

Record 1:

IFV

 

Record 2:

HDATE, XFCST, FIELD, UNITS, DESC, XLVL, NX, NY, IPROJ
 

if (IPROJ == 0) (Cylindrical equidistant grid)

 

Record 3:

STARTLAT, STARTLON, DELTALAT, DELTALON

if (IPROJ == 3) (Lambert conformal grid)

 

Record 3:

STARTLAT, STARTLON, DX, DY, XLONC, TRUELAT1, TRUELAT2

if (IPROJ == 5) (Polar-stereographic grid)

 

Record 3:

STARTLAT, STARTLON, DX, DY, XLONC, TRUELAT1
 

 

Record 4:

SLAB


 

Where:

 

 

 

 

integer

::

IFV

!

The PREGRID format version number, currently 2

character*24

::

HDATE

!

The time, in format "YYYY-MM-DD_HH:mm:ss "
(only the first 19 characters are used)

real

::

XFCST

!

Forecast time (in hours) of the data in the slab

character*8

::

FIELD

!

A field name. Names with special meaning are described in section 4.

character*16

::

UNITS

!

Units describing the field in the slab

character*56

::

DESC

!

Text description of the field.

real

::

XLVL

!

Pressure-level (Pa) of the data.
   200100 Pa indicates surface data;
   201300 Pa indicates sea-level pressure

integer

::

NX

!

Slab dimension in the X direction

integer

::

NY

!

Slab dimension in the Y direction

integer

::

IPROJ

!

Flag denoting the projection. Recognized values are:
  0: Cylindrical Equidistant (Lat/lon) grid.
  3: Lambert-conformal projection
  5: Polar-stereographic projection

real

::

STARTLAT

!

Starting latitude (degrees)

real

::

STARTLON

!

Starting longitude (degrees)

real

::

DELTALAT

!

Latitude increment (degrees) for lat/lon grid

real

::

DELTALON

!

Longitude increment (degrees) for lat/lon grid

real

::

DX

!

Grid-spacing in x (km at TRUELAT1 (and TRUELAT2))

real

::

DY

!

Grid-spacing in y (km at TRUELAT1 (and TRUELAT2))

real

::

XLONC

!

Center longitude of the projection.

real

::

TRUELAT1

!

Extra latitude used for defining Polar Stereographic and Lambert conformal projections

real

::

TRUELAT2

!

A second extra latitude used for defining Lambert conformal projection

real

::

SLAB(NX,NY)

!

Two-dimensional array of data.

 

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);

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

An overview for program pregrid.

A README file from program regridder.

Source tar file

 ftp://ftp.ucar.edu/mesouser/MM5v2/Regrid/regrid.tar.gz 

Major Bug Fixes

  • Updated July 29, 1999

    A correction is put in REGRID/pregrid for processing NCEP GDAS temperature data in ON84 format. The temperature in the dataset is virtual temperature, but the previous releases of REGRID assumed it to be temperature This affects the data obtained from NCAR DSS082.0 or mesouser/catalog.nmc for the period up to March 1997.

UCAR Privacy Policy - Terms of Use - ©2003UCAR