Preprints
https://doi.org/10.5194/amt-2024-93
https://doi.org/10.5194/amt-2024-93
27 Jun 2024
 | 27 Jun 2024
Status: this preprint is currently under review for the journal AMT.

Digitization and calibration of historical solar absorption infrared spectra from the Jungfraujoch site

Jamal Makkor, Mathias Palm, Matthias Buschmann, Emmanuel Mahieu, Martyn P. Chipperfield, and Justus Notholt

Abstract. This study describes the digitization and calibration of historically significant solar absorption spectra recorded at the Jungfraujoch International Scientific Station in the 1950s. Using a homemade Pfund-type grating spectrometer, these spectra were recorded on paper rolls to study the solar spectrum which was then used to compile a solar atlas between 2.8 and 23.7 microns (~421 to 3571 cm−1) that later contributed to the development of the HITRAN database. We now digitized these old spectra to make them available for atmospheric studies. Our approach involves image processing techniques, including colour masking for digitization and peak detection for accurate wavenumber calibration against a synthetic spectrum.

We also developed a validation method by re-digitizing degraded FTIR spectra to the same resolution as the old spectra to evaluate the digitization accuracy. Furthermore, we studied the influence of line thickness on the digitization error.

The number of spectra transformed into a machine-readable format is 108 (freely available for download), with an average digitization error of 1.55 % and a wavenumber shift standard diviation of 0.075 cm−1. These digitized and calibrated spectra now offer a valuable resource for atmospheric studies, providing essential historical data for atmospheric research. This work not only helps to preserve scientific heritage but also enhances the utility of historical data in contemporary research.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Jamal Makkor, Mathias Palm, Matthias Buschmann, Emmanuel Mahieu, Martyn P. Chipperfield, and Justus Notholt

Status: open (until 22 Aug 2024)

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Jamal Makkor, Mathias Palm, Matthias Buschmann, Emmanuel Mahieu, Martyn P. Chipperfield, and Justus Notholt
Jamal Makkor, Mathias Palm, Matthias Buschmann, Emmanuel Mahieu, Martyn P. Chipperfield, and Justus Notholt

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Short summary
During the years 1950 and 1951, Marcel Migeotte took regular solar measurements in form of paper rolls at the Jungfraujoch site. These historical spectra proved valuable for atmospheric research and needed to be saved for posterity. Therefore, a digitization method which used image processing techniques was developed to extract them from the historical paper rolls. This allowed them to be saved in a machine-readable format that is easily accessible to the scientific community.