Changelog

7.3

Version 7.3 introduces a new stratospheric temperature data product. Details of the temperature retrieval can be found in Zawada et al [1]. No algorithmic changes have been made to the aerosol, O₃, and NO₂

[1]

Zawada, D., et al. “A multi-decadal time series of upper stratospheric temperature profiles from Odin-OSIRIS limb scattered spectra.” EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-2264, 2023.

7.2

Changes to the retrieval algorithm:

• Implemented a point spread function correction, which reduces the effects of temperature-dependent blurring in the spectrograph optics

• Updated O₃ cross sections to the Daumont, Brion, and Malicet [2] dataset

• Adjusted Tikhonov scale factor in the NO₂ retrieval for a less strict regularization

Changes to the format of the data files:

• In the aerosol data files, changed the units of pressure from Pa to hPa to be consistent with the ozone and nitrogen products

• Added a vertical resolution data field to the aerosol files, computed as the FWHM of the averaging kernel. This field was already included in version 7.1 of the ozone and nitrogen files

• For profiles where the tropopause altitude could not be determined, changed the fill value from 99 km to NaN

[2]

Daumont, D., et al. “Ozone UV spectroscopy I: Absorption cross-sections at room temperature.” Journal of Atmospheric Chemistry 15.2 (1992): 145-155.

7.1

Version 7.1 brings the improvements from the v7.0 algorithm to the O₃ and NO₂ processing, including the Levenberg-Marquardt retrieval and satellite pointing correction. From this version forwards, all three products are processed at the same time and share the same version number. Version 7.1 replaces the v5.10 O₃ and v6.03 NO₂ products.

Additionally, several improvements have been made to the retrieval algorithm, including:

• MERRA 2 pressure/temperature profiles are used instead of ERA interim

• Retrieval iterative procedure is optimized to improve the number of scans which converge

• Automatic determination of the lower bound is improved

• Updated spectral resolution in NO₂ absorption band by fitting to solar Fraunhofer lines on a scan-by-scan basis

In addition, small changes have been made to the formatting and naming of some data fields. In particular, information about detected clouds is reported as the cloud top altitude for each scan, as opposed to the two-dimensional cloud mask seen in v7.0. See Data Fields for a description of all data fields included in the product.

7.0

Where’s version 6?

Version 6 was a particle size research product. Due to measurement saturation it had limitations at low altitudes and in volcanic plumes that caused complications for extinction climatologies. However it has been used in particle size studies and can be downloaded from here.

Version 7.0 replaces version 5.07/5.10 of the OSIRIS aerosol products. Ozone and NO₂ were not included in this version. Several updates were made to the algorithm in version 7.0, which include:

• Moved to Levenberg-Marquardt retrieval algorithm

• Multi-wavelength measurement vector for improved UTLS sensitivity and reduced dependence on assumed particle size

• Improved cloud flagging

• Updated lower bounds

• Updated satellite pointing that corrects long-term drifts