Converting Meteorological Data for HYSPLIT

Meteorological data files are available from a variety of sources. However, most will need to be reformatted for use by HYSPLIT. The Meteorology / Convert to ARL menu tab provides several options that will be discussed only briefly below. These data can be in Gridded Binary Format (only GRIB-1 is supported), or Network Common Data Form (NetCDF), CMAQ-IOAPI, or custom binary formats, such as from NCAR's MM5. The HYSPLIT data conversion is necessary because each meteorological model may contain different variable names, data organization, horizontal grid projection, or vertical coordinate systems. Keeping the meteorological pre-processing external to HYSPLIT provides more stability to the base code structure. Note that some of the data conversion programs are only available for UNIX systems.

1. The Convert to ARL tab contains the following sub-menus:


• WRF-ARW: The Advanced Weather Research model output files are in NetCDF (UNIX only).


• NARR archive: The North America Regional Reanalysis is available in GRIB-1 format (PC and UNIX).


• Global lat-lon: Regular latitude-longitude GRIB-1 files from NOAA and ECMWF global models can be processed from this menu (PC and UNIX).


• ERA-40: GRIB-1 files from the ECMWF 40 year global or Interim reanalysis projects can be processed through this menu (PC and UNIX).


• MM5V3: Version 5 of NCAR's mesoscale model can be converted from their binary format (PC and UNIX).


• MCIP IOAPI: Meteorological files for the CMAQ model are available in this format, which is a variation of NetCDF (UNIX only).


• User entered: This menu permits the user to manually enter one observation point but for several time periods to create a spatially homogeneous custom meteorological file (PC and UNIX).


2. Except for the User Entered option, the various data conversion options will not be discussed in any more detail because most require either the download of large data files or running your own meteorological model. Both of which are beyond the scope of this tutorial. However, the user data entry option will create a 3-dimensional gridded file with a uniform wind field (in height and space) that can be used to run HYSPLIT, or combined with another meteorological file to complete a simulation.


3. First select the user entered menu tab to open the menu to set the grid center which should be 40.7N 83.5W. The grid center is set slightly northeast of the release location because of the wind direction. If the stndata.txt file does not already exist (it doesn't), then select Create File.


4. The meteorology enter data menu provides one line for each time period. Enter the information as shown at 6 hour intervals (25 12Z; 25 18Z; 26 00Z; 26 06Z), changing only the time. Set the wind direction and speed to 225 at 6.0 m/s and stability category 3 for all times. Then Save Data to File and Run Convert which will then create the binary meteorological file stndata.bin in the \working directory for use by HYSPLIT.


5. Open the profile menu and select the stndata.bin file. No other changes are necessary to see the sounding at the first time period. The other time periods will all be the same. The wind direction and speed have been converted to vector components at all levels and velocity variances correspond to values that will give plume growth similar to stability category 3 (C) at all levels below the mixed layer depth.

HYSPLIT requires meteorological data on an evenly spaced grid (latitude-longitude or conformal projection) at multiple heights and time periods over the duration of the simulation. These data can be obtained from various sources or converted to the proper format. The manually created data file from this section will be used for a more complex simulation later in the tutorial.