DOI: 10.5281/zenodo.14891291
title: Nocturnal means of OH(3-1) airglow rotational temperatures from the mesopause region obtained during Sudden Stratospheric Warmings (SSW) at different sites in Europe between 2009 and 2023

description: The temperatures are derived from the rotational vibrational transition of the OH molecule originating from a thin layer in approximately 86-87 km centroid height. The spectra have been obtained with largely the Ground-based Infrared P-branch Spectrometers (GRIPS) located at the Arctic Lidar Observatory for Middle Atmosphere Research, ALOMAR (ALR, 69.28°N, 16.01°E; GRIPS 9), at the University of Wuppertal (WUP, 51.25°N, 7.15°E; GRIPS 17), at the Observatoire de Haute-Provence (OHP, 43.93°N, 5.71°E; GRIPS 12), at the Environmental Research Station “Schneefernerhaus” (UFS: 47.42°N, 10.98°E, GRIPS 7 and GRIPS 8) and at Catania (CAT, 37.51°N, 15.04°E, GRIPS 11). The instruments are operated by the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) in close cooperation with representatives from the above-mentioned observatories. All sites are part of the international Network for the Detection of Mesospheric Change (NDMC). The data set covers the time period 40 nights prior and after the onsets of the Sudden Stratospheric Warmings (SSW) in 2010 (9th Feb), 2013 (7th Jan), 2018 (12th Feb), 2019 (2nd Jan), 2021 (5th Jan) and 2023 (16th Feb). It is used in a study of SSW by Harvey et al. ("Signatures of Polar Vortex Weakening in the MLTI: A Review", Surveys in Geophysics, 2025, https://doi.org/10.1007/s10712-025-09899-3).

The wavelength range covered by the instruments allows the observation of the OH(3-1) Q- and P-branches as well as of the OH(4-2) R- and Q-branches. Rotational temperatures are calculated using OH(3-1) P-branch emissions between 1520 nm and 1550 nm. During routine operation one spectrum is obtained every 15s, originating from a field of view of approximately 15° x 15°, which corresponds to ca. 560 km² in 87 km height (2° x 2° in case of GRIPS 11 and GRIPS 17, corresponding to ca. 20 km² in 87 km height).

All GRIPS are equipped with a Czerny-Turner spectrograph and a thermoelectrically cooled InGaAs array. Only the P1(2), P1(3) and P1(4) rotational lines of the (3-1) vibrational transition are used for the derivation of temperatures. Intensities are only read out at the line centers of the smoothed spectra due to residual overlapping of the lines at their wings. Important physical constants applied during the processing are taken from Mies (1974) (Einstein coefficients) and Krassovsky et al. (1962) (rotational term values).

For the estimation of a nocturnal mean (individual time series) value all samples of the nightly temperature time series are weighted according to their individual precision. Thus, mean temperatures are between 1 and 2 K lower compared to the unweighted arithmetic mean (cloud covered periods are excluded from analysis; insufficient removal however will result in low precision values with a warm bias due to spectral characteristics of water / ice droplets). Data from an instrument are regarded only if its effective observation amounts to at least 2 h. Other dates are flagged with “NaN”, i.e. missing value.

Further details concerning the derivation of rotational temperatures from the airglow are presented in Schmidt, C., Höppner, K. and Bittner, M. (2013): A ground-based spectrometer equipped with an InGaAs array for routine observations of OH(3-1) rotational temperatures in the mesopause region. Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) 102 (2013) 125–139. https://dx.doi.org/10.1016/j.jastp.2013.05.001. Exemplary information on the long-term performance for the NDMC reference site UFS are given in Schmidt, C., Küchelbacher, L., Wüst, S. and Bittner, M. (2023): OH airglow observations with two identical spectrometers: benefits of increased data homogeneity in the identification of variations induced by the 11-year solar cycle, the QBO, and other factors. Atmospheric Measurement Techniques (AMT), Vol. 16, 19, 4331-4356. https://doi.org/10.5194/amt-16-4331-2023.

The following table describes the content of the ASCII-file containing the data (separator between two columns is “two blanks” aka “  ” aka ”2X”).






Column



parameter



unit



Format



description



Site





1



date



Days



I3



±40 nights around SSW onset



n.a.





2



temperature



Kelvin



F5.1



2009/2010



ALR





3



temperature



Kelvin



F5.1



2012/2013



ALR





4



temperature



Kelvin



F5.1



2017/2018



ALR





5



temperature



Kelvin



F5.1



2018/2019



ALR





6



temperature



Kelvin



F5.1



2020/2021



ALR





7



temperature



Kelvin



F5.1



2022/2023



ALR





8



temperature



Kelvin



F5.1



mean of all seasons



ALR





9



temperature



Kelvin



F5.1



smoothed mean of all seasons



ALR





10



temperature



Kelvin



F5.1



2009/2010



WUP





11



temperature



Kelvin



F5.1



2012/2013



WUP





12



temperature



Kelvin



F5.1



2017/2018



WUP





13



temperature



Kelvin



F5.1



2018/2019



WUP





14



temperature



Kelvin



F5.1



2020/2021



WUP





15



temperature



Kelvin



F5.1



2022/2023



WUP





16



temperature



Kelvin



F5.1



mean of all seasons



WUP





17



temperature



Kelvin



F5.1



smoothed mean of all seasons



WUP





18



temperature



Kelvin



F5.1



2009/2010



UFS





19



temperature



Kelvin



F5.1



2012/2013



UFS





20



temperature



Kelvin



F5.1



2017/2018



UFS





21



temperature



Kelvin



F5.1



2018/2019



UFS





22



temperature



Kelvin



F5.1



2020/2021



UFS





23



temperature



Kelvin



F5.1



2022/2023



UFS





24



temperature



Kelvin



F5.1



mean of all seasons



UFS





25



temperature



Kelvin



F5.1



smoothed mean of all seasons



UFS





26



temperature



Kelvin



F5.1



2009/2010



OHP





27



temperature



Kelvin



F5.1



2012/2013



OHP





28



temperature



Kelvin



F5.1



2017/2018



OHP





29



temperature



Kelvin



F5.1



2018/2019



OHP





30



temperature



Kelvin



F5.1



2020/2021



OHP





31



temperature



Kelvin



F5.1



2022/2023



OHP





32



temperature



Kelvin



F5.1



mean of all seasons



OHP





33



temperature



Kelvin



F5.1



smoothed mean of all seasons



OHP





34



temperature



Kelvin



F5.1



2009/2010



CAT





35



temperature



Kelvin



F5.1



2012/2013



CAT





36



temperature



Kelvin



F5.1



2017/2018



CAT





37



temperature



Kelvin



F5.1



2018/2019



CAT





38



temperature



Kelvin



F5.1



2020/2021



CAT





39



temperature



Kelvin



F5.1



2022/2023



CAT





40



temperature



Kelvin



F5.1



mean of all seasons



CAT





41



temperature



Kelvin



F5.1



smoothed mean of all seasons



CAT