Analysis of 2D airglow imager data with respect to dynamics using machine learning

We demonstrate how machine learning can be easily applied to support the analysis of large quantities of excited hydroxyl (OH*) airglow imager data. We use a TCN (temporal convolutional network) classification algorithm to automatically pre-sort images into the three categories “dynamic” (images where small-scale motions like turbulence are likely to be found), “calm” (clear-sky images with weak airglow variations) and “cloudy” (cloudy images where no airglow analyses can be performed). The proposed approach is demonstrated using image data of FAIM 3 (Fast Airglow IMager), acquired at Oberpfaffenhofen, Germany, between 11 June 2019 and 25 February 2020, achieving a mean average precision of 0.82 in image classification. The attached video sequence demonstrates the classification abilities of the learned TCN. Within the dynamic category, we find a subset of 13 episodes of image series showing turbulence. As FAIM 3 exhibits a high spatial (23 m per pixel) and temporal (2.8 s per image) resolution, turbulence parameters can be derived to estimate the energy diffusion rate. Similarly to the results the authors found for another FAIM station (Sedlak et al., 2021), the values of the energy dissipation rate range from 0.03 to 3.18 W kg−1

Wave signatures of the Hunga Tonga-Hunga Ha'apai eruption in 86km height

Nocturnal observations of the OH airglow (originating at ca. 86 km height) are performed with the infrared spectrometer GRIPS (GRound-based Infrared P-branch Spectrometer) from the Sonnblick Observatory (SBO) since mid-2015. The measurements are embedded in the Virtual Alpine Observatory (VAO). The shock wave generated by the eruption of the Hunga Tongo-Hunga Ha'apai (HTHH; 20.5°S, 175.4°W) volcano is a special event in the context of atmospheric wave dynamics

Mesopausen-Temperaturen über Europa 2010-2022 und der Einfluss der Sonne

Since 2009 the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been observing the OH airglow region from the environmental research station "Schneefernerhaus" (UFS) without any interruption. This faint luminosity originates in the Mesosphere-Lower-Thermosphere (MLT) region at approximately 86-87 km height. More sites were put into operation during the following years. It is now evident that solar radiation exerts a strong forcing on OH temperatures. However, this relation to the solar cycle varies in intensity between the individual sites

Strahlungsenergieflussdichten des OH-Nachthimmelleuchtens

Since 2009 the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been observing the OH airglow region from the environmental research station "Schneefernerhaus" (UFS). This faint luminosity originates in the Meso-sphere Lower Thermosphere (MLT) region at approximately 86-87 km height. After complex calibration and quality assurance, first results concerning the long-term development of the OH airglow radiance are obtained. This will be used in future studies to infer the concentrations of atomic oxygen, which is not only required for the production of OH but also an important energy reservoir in the middle atmosphere

Spuren der durch die Eruption des Hunga Tonga-Hunga Ha'apai ausgelösten Druckwelle auch in der Mittleren Atmosphäre über Europa

On January 15th 2022 the Hunga Tonga – Hunga Ha'apai volcano erupted and generated strong atmospheric pressure waves of which some propagated several times across the globe. At the Environmental Research Station “Schneefernerhaus” (UFS), as well as in whole Europe, signals could be detected even at MLT (Mesosphere-Lower-Thermosphere) heights (80-100 km) using the GRIPS (GRound-based Infrared P-branch Spectrometer) and the BAIER (Bavarian Airglow ImagER) instruments for the observation of the OH and the O2 airglow

Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09∘ N, 11.28∘ E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30∘ N, 13.02∘ E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar. In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength

Flow of bottom water in the northwestern Weddell Sea

The Weddell Sea is known to feed recently formed deep and bottom water into the Antarctic circumpolar water belt, from whence it spreads into the basins of the world ocean. The rates are still a matter of debate. To quantify the flow of bottom water in the northwestern Weddell Sea data obtained during five cruises with R/V Polarstern between October 1989 and May 1998 were used. During the cruises in the Weddell Sea, five hydrographic surveys were carried out to measure water mass properties, and moored instruments were deployed over a time period of 8.5 years to obtain quasi-continuous time series. The average flow in the bottom water plume in the northwestern Weddell Sea deduced from the combined conductivity-temperature-depth and moored observations is 1.3±0.4 Sv. Intensive fluctuations of a wide range of timescales including annual and interannual variations are superimposed. The variations are partly induced by fluctuations in the formation rates and partly by current velocity fluctuations related to the large-scale circulation. Taking into account entrainment of modified Warm Deep Water and Weddell Sea Deep Water during the descent of the plume along the slope, between 0.5 Sv and 1.3 Sv of surface-ventilated water is supplied to the deep sea. This is significantly less than the widely accepted ventilation rates of the deep sea. If there are no other significant sources of newly ventilated water in the Weddell Sea, either the dominant role of Weddell Sea Bottom Water in the Southern Ocean or the global ventilation rates have to be reconsidered