Table of Contents - The Atmospheric Studies Group at TRC

Section 3: READ62 Upper Air Preprocessor
3. READ62 UPPER AIR PREPROCESSOR
READ62 is a preprocessing program that extract and process upper air wind and temperature data from
standard NCDC data formats into a form required by the CALMET meteorological model. READ62
processes data in TD-6201 format or the NCDC FSL rawinsonde data format. Note that the user must
specifically request the TD-6201 format when ordering upper air data from NCDC, if this format is
desired.
User options are specified in a control file. In the control file, the user selects the starting and ending
dates of the data to be extracted, the top pressure level, the type of input data, and the format of the output
file. Also selected are processing options determining how missing data are treated. The programs will
either flag or eliminate sounding levels with missing data.
If the user selects the option to flag (rather than eliminate) levels with missing data, the data field of the
missing variables are flagged with a series of nines. If the option to eliminate levels with missing data is
chosen, only sounding levels with all values valid will be included in the output data file. It is generally
recommended that the levels with missing data be retained in order to avoid eliminating levels that might
have some valid data.
Although CALMET allows missing values of wind speed, wind direction, and temperature at intermediate
levels (i.e., levels other than the surface and model top), the user is cautioned against using soundings
with significant gaps due to missing data. For example, adequate vertical resolution of the morning
temperature structure near the surface is especially important to the model for predicting daytime mixing
heights. It should be kept in mind that the model will fill in missing data by assuming that a straight-line
interpolation between valid levels is appropriate. If this assumption is questionable, the sounding should
not be used with the model.
Two input files are required by the preprocessor: a user input control file and the NCDC upper air data
file. Two output files are produced. A list file summarizes the options selected, provides a summary of
the soundings processed, and contains informational messages indicating problems in the data set. The
second output file contains the processed upper air data in a CALMET-ready format. Table 3-1 contains
a listing of the input and output files for READ62.
The format of the READ62 control input file follows the same rules as those used in the CALMET.INP
file (refer to the CALMET section for details). Only data within the delimiter characters (!) are processed.
The input data consist of a leading delimiter followed by the variable name, equals sign, input value or
values, and a terminating delimiter (e.g., !XX = 12.5!). READ62.INP may be created/edited directly
using a conventional editor, or it may be created/edited indirectly by means of the PC-based, Windowscompatible
Graphical User Interface (GUI) developed for the geophysical preprocessors (CALPRO). A
description of each input variable is shown in Table 3-2. A sample input file is shown in Table 3-3. The
output list file is shown in Table 3-4.
3-1