ASPEN Versions

The changes that are visible to users are given below. The many changes that are made for software maintenance and obscure bug fixes are not listed here.

For Aspen version 3.4.0 and up, download the appropriate installer for your operating system below.

Please contact us if you need older Aspen versions or information about previous version history.

For Aspen help or questions, please contact our mailing list at eol-aspen[at]ucar[dot]edu.

  • Add user settable option for whether to discard sonde frames with the wrong sonde ID in ACS files
  • Flag lines with the wrong sonde ID (ACS files only) in the Raw tab, and collect stats on number of bad lines

4.0.1 — May 10, 2024

CentOS 8 Alma 9 MacOS 14 (Sonoma) - Apple Intel MacOS 14 (Sonoma) - Apple M1 Windows 10
  • Add trajectory plot option for Lat-Lon XY Graph tab: added Lat as default Y axis for this plot
  • Add ability to select entire columns in the Raw tab by clicking the column headers
  • Add Ctrl+E keyboard shortcut (Cmd+E on Mac) to jump to the end of the data tables in the Raw and QC tabs
  • Add warning popup about sonde size not matching config set when opening ACS netCDF files
  • Add clearer error text when attempting to read in an Aspen output netCDF
  • Add command line option to set end of drop time in Aspen-QC
  • Update logos for Aspen V4
  • Use GPS altitude in second altitude column in FRD output files; update column header accordingly
  • Fix bug in calculating time of synthetic surface observation that led to coding lowest winds instead of surface winds in TEMPDROP
  • Update mixing ratio equation to be more precise
  • Assorted static code analysis fixes and improvements

4.0.0 — Feb 21, 2024

CentOS 8 MacOS 14 (Sonoma) - Apple Intel MacOS 14 (Sonoma) - Apple Silicon Windows 10
  • Support for ingesting netCDF ACS files
    • Add input option to read data from ACS format netCDFs
    • Select aircraft observation from continuous series after possible launch time corrections (if entire aircraft data set is included)
    • Use WMO sonde types for RD41 and NRD41 (in BUFR only) now that input files contain enough metadata to tell them apart
    • Add sonde model metadata to netcdf and csv output as well
    • Remove times from input file that are not monotonically increasing, rather than rejecting the entire file
  • Turn off XY graph autoscale for wind direction by default
  • Fix bug in calculating MB110 group for upsondes
  • Fix bug where launch PTH didn’t get correctly removed when ignored if there was no aircraft geopotential altitude
  • Fix bug where overriding and then clearing launch altitude would result in an altitude of -999 if original launch altitude was missing
  • Miscellaneous compilation warning fixes and code cleanup

3.4.9 — May 26, 2023

CentOS 7 Alma Linux 9 MacOS 12 (Monterey) - Apple Intel MacOS 13 (Ventura) - Apple M1 Windows 10
  • Fix crash when autosaving skew-T plots on Windows
  • Fix bug causing blank skew-T plots when manually saved


3.4.8 — May 9, 2023

CentOS 7 Alma Linux 9 MacOS 12 (Monterey) - Apple Intel MacOS 13 (Ventura) - Apple M1 Windows 10
  • Fix bug in setting flight level attribute in altitudes calculation
  • Fix crash when calculating altitudes with an empty rh or pressure series
  • Fix bug in reading in lat/lon from FRD files
  • Add columns for wind speed in knots and dew point depression to Levels tab
  • Add button to Options > Synoptic map to clear sondes from the synoptic map database
  • Put fast fall message at top of the errors popup, so it’s more noticeable
  • Update launch detect algorithm to work with changing cabin pressure over time
  • Add prompt to change config sets when:
    • Opening large sonde files while using the mini-dropsonde config set
    • Opening minisonde files while not using the mini-dropsonde config set
  • Fixes and improvements based on static code analysis results
  • Add builds on MacOS Ventura (Apple M1) and Alma Linux 9

3.4.7 — May 6, 2022

CentOS 7 MacOS 12 (Monterey) MacOS 11 (Big Sur) Windows 10
  • Pair latitude & longitude when setting keep and ignore attributes
  • Fix crash when autosaving BUFR with launch latitude and longitude ignored
  • Fix flipped Mission Storm System and Mission ID labels in Comm tab
  • Update rounding function in levels creation to be consistent between operating systems
  • Add operator comments to netCDF and CSV global attributes

3.4.6 — May 1, 2021

CentOS 7 OSX 10.15 (Catalina) Windows 10
  • Update and streamline build scripts
  • Fix bug in launch detect that caused false late launch detects
  • Fix crash when input file had badly formatted time string
  • Fix crash when failing to autosave netCDF files
  • Fix crash when bad launch override value entered
  • Derived parameter updates:
  •    Use 273.15 for Celsius to Kelvin conversion
  •    Correct vapor pressure term in virtual temperature equation
  • GPS thresholds update:
  •    Change default number of satellites threshold to 6 for all dropsonde config sets
  •    Loosen wind error check thresholds for RD41 sondes
  •    Use more permissive of wind error check thresholds for sonde data below 100m
  • Updates for ignoring aircraft data:
  •    Make ignore launch parameters 'sticky' to preserve state of checkboxes between sondes
  •    Add option to use ignored launch parameter values in equilibration time and geopotential altitude calculations
  •    Use highest good dropsonde location in TEMP and BUFR if aircraft location is missing

3.4.5 — Jan 7, 2021

CentOS 7 OSX 10.15 (Catalina) Windows 10
  • Fix end of drop time not showing up in main tab when set from raw tab
  • Switch default save file format to netCDF in graphical interface
  • Read in sonde serial number from COM line of AVAPS files if it is not present on LAU line
  • Fix bug where if surface thermo/winds levels were not present, other levels would be coded with level number 00
  • Add missing libraries to linux installer
  • Format error messages to be more readable in graphical interface
  • Update equations for potential temperature and virtual temperature
  • Apply number of satellites check to GPS position and GPS altitude in addition to winds
  • Enforce paired lat/lon series: when a point is flagged in one, it should be removed from both
  • Add vertical winds to QC and XY graph tabs

3.4.4 — May 1, 2020

CentOS 7 OSX 10.14 (Mojave) Windows 10
  • Fix missing libraries in CentOS installer
  • Fix bug in setting OB number from commandline Aspen
  • Add config parameter to disable calculation of vertical winds
  • Set config items for autosave and fixed data directory to take effect immediately, rather than after restarting Aspen
  • Add check that produces a warning popup when Aspen identifies a floating sonde
  • Visually identify post-splash data in raw tab
  • Add ability to set post-splash data from raw tab

3.4.3 — Jan 6, 2020

CentOS 7 OSX 10.14 (Mojave) Windows 10
  •  Correct order of flag bits in BUFR output
  • Set time in BUFR section 1 to launch time rather than processing time
  • Add hundredths of seconds to time column in FRD output
  • Read in EOL and FRD files in pass-through mode so processing cannot be applied twice
  • Correct text for NW option of eyewall azimuth menu in the Comm tab
  • Add 'no to all' option when prompted to save configuration changes upon closing Aspen
  • Add autosave options for levels CSV and summary text'
  • Automatically include newest Aspen user manual in installation packages
  • Fix pixelation in graphical interface on Retina displays
  • Fix infinite loop on startup when specified dbpath is incorrect
  • Fix a bug where saving a file from the QC tab would also save any config set changes
  • Fix bug in setting ObsNum from command line Aspen
  • Add maximum altitude interpolation gap as a configurable parameter
  • Only include dry bias correction metadata for RD94 sondes
  • Add ability to add or override sonde context metadata (agency, platform type and ID, project, flight) while processing and saving to output
  • Add ability to add dataset DOI to netCDF and CSV output
  • Add vertical winds to netCDF output
  • Only include config set items that directly influence processing in netCDF and CSV output metadata
  • Add sonde serial number to netCDF and CSV output metadata
  • Add equilibration times for temperature, RH, and pressure to netCDF and CSV output metadata

3.4.2 — Jul 24, 2019

CentOS 7
  • Add a missing dependency to the Linux version

3.4.1 — Jul 3, 2019

CentOS 7 OSX 10.14 (Mojave) Windows 10
  • Fixed bug where ignoring lat/lon wouldn't remove them from QC data

3.4.0 — May 20, 2019

CentOS 7 OSX 10.14 (Mojave) Windows 10
  • Threshold RH values of up to 110% to 100% before removing invalid RH
  • Add wind error check, which removes wind speed and direction if error value for GPS winds is too high
  • Build Aspen on Windows 10 and OSX Mojave
  • Update Qt graphics library to version 5
  • Switch Aspen release numbering and AEV coding to semantic versioning
  • Set monotonic pressure check off by default in dropsonde config sets
  • Set buddy check wind speed threshold to 10m/s^2 in dropsonde config sets
  • Add ability to automatically correct early launch detects
  • Update attribute icons


Derived from the HRD Editsonde program (1998). Initially developed for AFRES 53rd Hurricane Hunters real-time operations. Later expanded for general upsonde and dropsonde application.

Operating System

Visualization and quality control of upsonde and dropsonde radiosonde soundings. Command line, batch and GUI based interfaces are available. For support questions, email eol-aspen(at)

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