The example programs and HYSPLIT calculations shown in the other sections of this site all use meteorological data fields that have been interpolated to a regular latitude-longitude grid or projected on a conformal map, compressed and formatted in a standard format. This page contains links to source code and PC executable programs that can be used to convert meteorological data in various formats to a HYSPLIT compatible format (ARL packed). Source code is provided for many of the routines so that customized applications can be developed.

• ARL Packed Data Format Overview
• The Gridded Binary Data Format (GRIB)
• Meteorological Data Sources

Briefly, an ARL packed data file consists of a series of fixed length records, one for each meteorological variable. The records are arranged in time series, with surface fields followed by upper air fields. Each record contains a 50 byte ascii header that provides information about the date, time, variable, and packing constants. This is followed by the packed binary data, one byte per grid point. Each byte represents the difference in value between that point and the previous grid point. A group of records at the same time is preceeded by an index record that describes all the variables, levels, and grid information for that time period.

Meteorological data may be obtained from other sources, but it must first be converted to ARL format. Many meteorological centers archive data in GRIdded Binary (GRIB) format. Although conversion software from GRIB to ARL is provided for some of the most common sources, many of these Fortran programs may still require additional customization, depending upon the contents of the data files. Although it may appear simpler to use GRIB data directly for air quality modeling applications, each meteorological center's GRIB file structure is different. The GRIB standard only defines the content of the individual GRIB record and not the organization of the records that are contained in each file. The ARL formatted data are of constant record length, permitting direct access applications using standard IO statements. The ARL data format is also platform independent.

The links below provide resources for converting meteorological data to HYSPLIT-compatible format (most are also available in the data2arl directory of PC HYSPLIT). There is no documentation on how to run these programs, however examination of the source code should be sufficient in most situations. With a few exceptions, almost all of the programs only convert one time period of data per execution. To build a multi-time period file it is necessary to append the results of each execution to a single file. The Unix "cat >>" or DOS "type >>" commands may be used for this process.

Global GRIB files on a regular latitude-longititude grid from either NOAA's GFS model or the ECMWF model. NOAA model output must be on pressure surfaces, ECMWF output may be pressure or their hybrid coordinate.

Bare-bones program to decode NetCDF LAPS output files available on an AWIPS workstation.

Converts MM5 Version 3 DOMAIN files.

GRIB files from NOAA's NAM on pressure surfaces from the post processor after interpolation to the 212 grid, which is at 40 km resolution.

GRIB files from NOAA's NAM on pressure surfaces from the post processor after interpolation to the 218 grid, which is at 12 km resolution.

NetCDF files from NOAA's NAM on pressure surfaces as available on an AWIPS workstation after interpolation to the 218 grid.

Reads history files from the RAMS model version 5.

Reads history files from the RAMS model version 6. Requires the installation of version 5 software.

Converts NCAR-NCEP NetCDF 2.5 deg global reanalysis files as archived by NOAA's CDC.

Converts WRF-ARW NetCDF output files.

Converts WRF-NMM GRIB output files (NOAA's egrd3d) on the native coordinate system (horizontal and verical).