This menu item is intended to convert existing NARR GRIB-1 files to the ARL packed format. The data files to process are determined by selecting any file in the GRIB data directory. Subsequent file names will be constructed automatically between the starting and ending day at the hour interval set by the radio-button. Day (DD) and hour (HH) must be embedded the within the GRIB file name according to the following NOMADS archive convention: narr-a_221_{YYYY}{MM}{DD}_{HH}00_000.grb. Year (YYYY) and month (MM) are fixed according to the file name' selected to set the base file name. Time intervals of 12 hours or more should be avoided in transport and dispersion calculations. Only one month of data or less should be processed into one output file.
The GRIB files for the North American Regional Reanalysis (NARR) can be downloaded from the NOMADS web page. When selecting data to download, all variables and cycles should be obtained. The simplest approach is to use an FTP client and go to the directories of the desired data and download all the narr-a_221_{YYYY}{MM}{DD}_{HH}00_000.grb files for the desired period.
However, the NARR GRIB files are bit mapped, meaning some of the corners
do not have data defined due to differences in the internal grid projection
of the model vesus the output grid. HYSPLIT does not support projections
with a bit map and when running the data converter a message will be
generated:
WARNING w3fi63: BMS detected in GRIB file
Insure final grid does not intersect BMS
Full domain grid: 349 277
Bitmap reduction: 309 237
which indicates the the grid has been slightly reduced to insure that
all data points within the domain have valid data. The reduced domain
is shown below with the + indicating every 10th data point.