Note that the file formats are not complete; i.e one format will contain information that another format does not support. Thus, the CSV and netCDF formats can document the configuration parameters used in the processing, whereas the CLASS format does not support inclusion of this information.
| Data product | File output formats |
|---|---|
| Raw data | CLASS EOL CSV netCDF |
| QC data | CLASS EOL FRD CSV netCDF BUFR (subset of levels data merged in) |
| XY graph image | PNG JPG PDF |
| Skew-T image | PNG JPG SVG |
| Levels data | CSV |
| WMO TEMP message | ASCII text |
| Summary information |
NCAR CLASS upsonde files
The CLASS file starts with a 15 line header section, followed by a variable number of data lines. The data lines are arranged in fixed width columns. A mandatory set of 21 data parameters is reported, though a number of these (specifically the “quality” values) are always marked with a missing value indicator.
The data is reported in the sequence of decreasing pressure, i.e. from the surface upward, regardless of the direction of the sounding.
NCAR EOL dropsonde files
The EOL file starts with a 15 line header section, followed by a variable number of data lines. The data lines are arranged in fixed width columns. A fixed set of 17 data parameters is reported. The data is reported in the sequence of decreasing pressure, i.e. from the surface upward, regardless of the direction of the sounding.
More information about the EOL format is available on the EOL website.
NOAA HRD FRD dropsonde files
The FRD file starts with a 21 line header section, followed by a variable number of data lines. The data lines are arranged in fixed width columns. A fixed set of 18 parameters is reported, though a number of these are always set to zeros. More information on FRD file format can be found in the HRD README.
The data is reported in the sequence of increasing time for both up and drop soundings.
Comma Separated Values (CSV)
The “Comma Separated Value” file format is used for data interchange between Aspen and other software. It is a free form structure, with one data record per line, and the fields in a record separated by commas. A CSV file can be read directly into Microsoft Excel, and the data will be correctly organized in the spreadsheet. See the Input File Formats section for more information on how Aspen CSV file are formatted.
Levels data is also provided in CSV format, where the file contains the data from the table in the Levels tab.
NetCDF files
Network Common Data Form (netCDF) is a binary, array-based, self-describing data format that is commonly used for earth science data. Sounding data is stored in a series for each variable, indexed by time. Metadata is stored as attributes of either specific variables or the entire file. When possible, Aspen netCDF output is compliant with the Climate and Forecast (CF) Conventions for file structure and metadata.
In-depth documentation of Aspen netCDF output is available on the EOL website for radiosondes and dropsondes.
WMO BUFR files
BUFR messages report both one-second averages of the entire quality controlled sounding profile and the contents of the calculated levels. BUFR files use a binary format specified by the World Meteorological Organization’s Manual on Codes (no. 306). Aspen codes sounding data as B/C25 (binary equivalent of TEMP, TEMP SHIP, or TEMP MOBIL) or B/C26 (binary equivalent of TEMP DROP), depending on the sounding file.
Averaging for BUFR output
Since B/C25 and B/C26 formats are currently limited to 1-second resolution, full resolution dropsonde data must be averaged down to 1Hz. The averaging algorithm calculates the mean of all valid data points in each one-second bin, using U and V component averaging for winds before converting back to speed and direction.
WMO TEMP files
TEMP messages report specially encoded levels data in ASCII text. The contents and formatting of TEMP messages is determined by the World Meteorological Organization’s Manual on Codes (no. 306). Aspen codes sounding data as TEMP (FM35), TEMP SHIP (FM36), TEMP DROP (FM 37), or TEMP MOBIL (FM 38) depending on the sounding file.
Graphics files
Aspen can save graphics products in several file formats. SVG and PNG format are higher resolution than JPG and therefore preferred.
NASA ICARTT files
The ICARTT data format is used by NASA for dropsonde and other airborne atmospheric data. It is an ASCII format with a metadata header followed by data.
Aspen does not produce ICARTT files natively, however, Sean Freeman at CSU has written a Python converter from Aspen netCDF to ICARTT. Please contact the aspen mailing list if you would like a copy of the conversion code.
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