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The frequency range of infrasound embedded between the gravity wave and the audible range. It corresponds to periods of 0.05 s up to 5 min.
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Many geo-hazards such as earthquakes, tsunamis, volcanic eruptions, severe weather, etc., produce acoustic waves with sub-audible frequency, so called infrasound. This sound propagates from the surface to the middle and upper atmosphere causing pressure and temperature perturbations. Temperature fluctuations connected with the above mentioned event...
Contexts in source publication
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... Eqs. (2), (3), and (5) the particle velocity u is proportional to the inverse square root of distance and pressure and the inverse scaled attenuation over 20. Therefore, if both, the distance and the attenuation increases, the particle velocity decreases. If the pressure decreases, the particle velocity increases. Due to the fact that the background air pressure decreases exponentially with height (Eq. 4), the increase of the square of particle velocity is also exponential and it exceeds the decrease due to the other effects until attenuation becomes dominant. Following Eq. (1), the temperature fluctuation T increases in the same way as the particle velocity u . Figure 6 shows an example of a temperature fluctuation development with height and range. It has been calculated using HARPA/DLR (for more details see Pilger and Bittner, 2009). With increasing height the decreasing air density leads to an exponential increase of the fluctuation. The temperature fluctuations in the OH layer (ca. 87 ± 4 km) are largest directly above a source. Shown is an example case using strong sound amplitude of 100 Pa (at 1 km initial distance from the source) and weak attenuation for a low frequency of 0.01 Hz. The expected temperature fluctuation amounts ∼ 5 K in the OH layer for this signal. A pattern recognition algorithm is needed in order to reli- ably identify and classify infrasound signals in the OH temperature fluctuations originating from different sources. The source characteristics, which can be used to distinguish different signals, are sound frequency, sound amplitude and sound waveform. While infrasonic frequencies range from 0.003 Hz to 16 Hz (corresponding to periods of 5 min to 0.05 s, see Fig. 1), each source has its own characteristic frequency range. Only a few infrasonic signals have one constant main frequency (e.g. microbaroms: 0.2 Hz), while most ...
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... N ν and Q ν , T rot denote the population number and the state sum of the initial vibrational state ν . A and F ν ,J ,i denote the Einstein coefficient of spontaneous emission and the term value of the rotational level with respect to the vibrational level ν and the doublet branch i . J is the quantum number of angular momentum and k B the Boltzmann constant. The temperature retrieval is based on the transition coefficients from Mies (1974) and the rotational energy values from Krassovsky (1962). The GRIPS spectrometers have been deployed for the observation of OH airglow for nearly 30 years (see e.g. Bittner et al., 2002; Höppner and Bittner, 2007). The first instruments were designed and built during the early 1980s at the University of Wuppertal, Germany (51.3 ◦ N, 7.2 ◦ E). More than two decades of experience and data have been gathered with this instrument series making it a prominent instrument in the history of airglow spectroscopy. At the end of this development line, GRIPS 6 – installed at DLR-DFD in Oberpfaffenhofen, Germany (48.1 ◦ N, 11.3 ◦ E) in 2009 – and the identically equipped GRIPS 5 – located at the Environmental Research Station Schneefernerhaus at Mt. Zugspitze, Germany (47.4 ◦ N, 11.0 ◦ E) – repre- sent advanced scanning spectrometers for near infrared airglow observations. Both instruments routinely and automatically measure the OH temperatures night by night (data are available from the World Data Center for Remote Sensing of the Atmosphere, WDC-RSAT, and can be accessed via Originally, the GRIPS system is used to monitor climate signals and observe long-term trends in the mesopause region (e.g. Bittner et al., 2000; Höppner and Bittner, 2007), to better understand the impact of atmospheric dynamics on larger-scale circulation, to validate satellite-based measurements and to evaluate climate and atmospheric models. In addition, high temporal resolution data obtained with the new spectrometers GRIPS 5/6 reveal temperature oscillations with periods below the Brunt-Väisälä period. Key features of these spectrometers are a thermoelectri- cally cooled 512 pixel InGaAs-array and a high aperture polychromator. This new spectrometer design offers a temporal resolution of 15 s, well within the infrasound regime (see Fig. 1). The overall dimension of the system is com- paratively small with only 600 × 500 × 400 mm 3 (see Fig. 9). The field of view of GRIPS 5/6 is 7.9 ◦ × 7.9 ◦ . While the GRIPS 6 is looking into zenith direction, the GRIPS 5 instrument is looking at a zenith angle of 45 ◦ into southward direction, so its field of view is located over Northern Italy (see Fig. 12). In order to gain reliable estimates of the uncertainty of the derived temperature values, the signal-to-noise ratio of each individual spectrum is derived by applying a low pass filter. The filtered spectrum gives a reliable estimate of the peak intensities, while the residuals are taken as their respective uncertainties. This approach has proven to yield feasi- ble results in gaining the instrument’s precision. A conve- nient side effect of this approach is the fact that precision increases on longer time scales. As a consequence the uncertainty is typically of the order of 7.5 K for a 15 s exposure, while decreasing to values below 2 K at time scales of 1 min. Since the signal-to-noise ratio is a function of source intensity, atmospheric opacity and all possible influences caused by the instrument, the uncertainty of the derived temperatures strongly depends on the measurement conditions. During the nights discussed in Sect. 4, temperature values range from 200 K to 240 K for the night of 2 to 3 November 2008 and from 180 K to 220 K for 5 to 6 November 2008, while the respective uncertainties of the 15 s values range between 7 K and 12 K for both nights (see Figs. 10, 11, 13, and 14). Thus the precision of the GRIPS instrument cannot explain the variability in our data and atmospheric waves are the likely explanation as is further confirmed by the results of the wavelet analysis. A field campaign SCARAMANGA at the Environmental Research Station Schneefernerhaus in the German Alps (UFS, 47.4 ◦ N, 11.0 ◦ E) was conducted during October- December 2008. The GRIPS 5 spectrometer was deployed for this campaign to demonstrate the capability of this instrumentation to detect low frequency infrasonic ...
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... waves are sound waves with frequencies below 16 Hz, which is in the sub-audible range. Infrasound is on the other hand limited by the acoustic cut-off frequency at about 0.003 Hz, which separates sound from gravity waves. This frequency range corresponds to signal periods of 0.05 s up to 5 min (see Fig. 1). Sound waves are longitudinal waves because wave disturbances travel parallel to the direction of wave propagation. They occur in the atmosphere when a periodic vibra- tion causes alternating adiabatic compression and expansion of air. In each wave induced compression cycle of the gas there will be a temperature increase T (see Liszka, ...
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... and is the subject of this paper. Infrasonic waves are sound waves with frequencies below 16 Hz, which is in the sub-audible range. Infrasound is on the other hand limited by the acoustic cut-off frequency at about 0.003 Hz, which separates sound from gravity waves. This frequency range corresponds to signal periods of 0.05 s up to 5 min (see Fig. ...
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... infrasonic frequencies range from 0.003 Hz to 16 Hz (corresponding to periods of 5 min to 0.05 s, see Fig. 1), each source has its own characteristic frequency range. Only a few infrasonic signals have one constant main frequency (e.g. microbaroms: 0.2 Hz), while most signal frequencies can vary by one or two orders of magnitude. For example, explosion frequencies are yield-dependent: the stronger an explosion, the longer its period. Other ...
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... features of these spectrometers are a thermoelectri- cally cooled 512 pixel InGaAs-array and a high aperture polychromator. This new spectrometer design offers a tem- poral resolution of 15 s, well within the infrasound regime (see Fig. 1). The overall dimension of the system is com- paratively small with only 600×500×400 mm 3 (see Fig. 9). The field of view of GRIPS 5/6 is 7.9 • ×7.9 • . While the GRIPS 6 is looking into zenith direction, the GRIPS 5 in- strument is looking at a zenith angle of 45 • into southward direction, so its field of view is located over ...
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... The overall dimension of the system is com- paratively small with only 600×500×400 mm 3 (see Fig. 9). The field of view of GRIPS 5/6 is 7.9 • ×7.9 • . While the GRIPS 6 is looking into zenith direction, the GRIPS 5 in- strument is looking at a zenith angle of 45 • into southward direction, so its field of view is located over Northern Italy (see Fig. ...
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... derived tempera- tures strongly depends on the measurement conditions. Dur- ing the nights discussed in Sect. 4, temperature values range from 200 K to 240 K for the night of 2 to 3 November 2008 and from 180 K to 220 K for 5 to 6 November 2008, while the respective uncertainties of the 15 s values range between 7 K and 12 K for both nights (see Figs. 10, 11, 13, and 14). Thus the precision of the GRIPS instrument cannot explain the variability in our data and atmospheric waves are the likely explanation as is further confirmed by the results of the wavelet ...
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... 10 to 15 show typical examples of nights with sig- nificant wave activity in the above mentioned period ranges indicating the impact of short period (infrasonic) signals on mesopause temperature time series. Figure 10 shows the time series of OH(3-1) rotational temperatures obtained with the GRIPS 5 instrument during the night of 5 to 6 November 2008. A large data gap be- tween 01:15 UTC and 02:30 UTC is due to dense cloudi- Fig. 14. ...
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... above mentioned period ranges indicating the impact of short period (infrasonic) signals on mesopause temperature time series. Figure 10 shows the time series of OH(3-1) rotational temperatures obtained with the GRIPS 5 instrument during the night of 5 to 6 November 2008. A large data gap be- tween 01:15 UTC and 02:30 UTC is due to dense cloudi- Fig. 14. The same as in Fig. 11, but for the night of 2 to 3 Novem- ber 2008. A noticeable amount of wave activity is located around 04:00 UTC in a period range of 0.5 to 1.5 min (see also Fig. ...
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... ranges indicating the impact of short period (infrasonic) signals on mesopause temperature time series. Figure 10 shows the time series of OH(3-1) rotational temperatures obtained with the GRIPS 5 instrument during the night of 5 to 6 November 2008. A large data gap be- tween 01:15 UTC and 02:30 UTC is due to dense cloudi- Fig. 14. The same as in Fig. 11, but for the night of 2 to 3 Novem- ber 2008. A noticeable amount of wave activity is located around 04:00 UTC in a period range of 0.5 to 1.5 min (see also Fig. ...
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... obtained with the GRIPS 5 instrument during the night of 5 to 6 November 2008. A large data gap be- tween 01:15 UTC and 02:30 UTC is due to dense cloudi- Fig. 14. The same as in Fig. 11, but for the night of 2 to 3 Novem- ber 2008. A noticeable amount of wave activity is located around 04:00 UTC in a period range of 0.5 to 1.5 min (see also Fig. ...
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... less, a total of 2466 spectra, equivalent to more than 10 h of observation, were obtained during this night. Figure 11 shows the corresponding wavelet spectrogram of this time series in the period range of 0.5 to 10 min; signals exceed- ing a 95% significance level have been identified during the time spans between 19:30 UTC and 21:00 UTC, 23:00 UTC and 01:15 UTC and between 02:30 UTC and 05:00 UTC, re- spectively. Wave activity is observed in both, the short pe- riod gravity wave range with periods around 6 to 8 min (not discussed here) and the infrasonic period range with periods around 3 to 4 min. ...
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... is indeed in agreement with the fact that some thun- derstorm activity was recorded in Northern Italy through- out the whole night. Figure 12 shows the associated con- vective available potential energy (CAPE) for central Europe quantified by ECMWF operational analysis. A region of in- creased CAPE and therewith strong thunderstorm potential is centered at about 45 • N and 12 • E, which is located 300 km southward of the instrument and approximately 150 km from the center of the instrument's field of view in the mesopause region. ...
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... 45 • N and 12 • E, which is located 300 km southward of the instrument and approximately 150 km from the center of the instrument's field of view in the mesopause region. Infrasonic waves generated of the described thunder- storm source reach the field of view in a 150 km distance as seen in Fig. 6 and could therefore be detected by GRIPS 5 (see Fig. 11). Figure 13 shows the temperature time series for the sec- ond half of the night from 2 to 3 November 2008, based on 1691 spectra in 15 s intervals. Especially the time frame near 04:00 UTC indicates short period wave activity between 30 and 90 s over at least 15 min of continuous duration (see Figs. 14 and 15). Orographical sources ...
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... waves generated of the described thunder- storm source reach the field of view in a 150 km distance as seen in Fig. 6 and could therefore be detected by GRIPS 5 (see Fig. 11). Figure 13 shows the temperature time series for the sec- ond half of the night from 2 to 3 November 2008, based on 1691 spectra in 15 s intervals. Especially the time frame near 04:00 UTC indicates short period wave activity between 30 and 90 s over at least 15 min of continuous duration (see Figs. 14 and 15). ...
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... could therefore be detected by GRIPS 5 (see Fig. 11). Figure 13 shows the temperature time series for the sec- ond half of the night from 2 to 3 November 2008, based on 1691 spectra in 15 s intervals. Especially the time frame near 04:00 UTC indicates short period wave activity between 30 and 90 s over at least 15 min of continuous duration (see Figs. 14 and 15). Orographical sources are a potential ex- planation for these signals. The so-called "mountain asso- ciated waves (MAWs)" are orographically generated infra- sonic waves in a typical period range of 20 to 60 s (e.g. Wilson and Olson, 2003). These lee waves occur when air is forced over a mountain ridge and is redirected vertically ...
Citations
... Shortly thereafter, the prototype of a new instrument was put into operation at the environmental research station "Schneefernerhaus" (UFS) in central Europe (47.42 • N,10.98 • E) in 2008 (see Schmidt et al., 2013;Bittner et al., 2010). Based on the previous experience of other research groups in the NDMC, routine observations were planned with two identical instruments (each as a backup for the other) from the very beginning. ...
Hydroxyl (OH) radical airglow observations have been performed at the environmental research station “Schneefernerhaus” (UFS; 47.42∘ N, 10.98∘ E) since October 2008, with continuous operation since July 2009. The instrumental setup relies on the parallel operation of two identical instruments, each a GRIPS (GRound-based Infrared P-branch Spectrometer), in order to achieve maximum completeness and homogeneity. After the first decade of observations the acquired time series are evaluated with respect to the main influences on data quality and comparability to those at other sites. Data quality is essentially limited by gaps impacting the completeness. While technical failures are largely excluded by the setup, gaps caused by adverse meteorological conditions can systematically influence estimates of the annual mean. The overall sampling density is high, with nightly mean temperatures obtained for 3382 of 4018 nights of observation (84 %), but the average coverage changes throughout the year. This can bias the annual mean up to 0.8 K if not properly accounted for. Sensitivity studies performed with the two identical instruments and their retrievals show that the comparability between the observations is influenced by the annual and semiannual cycle as well as the choice of Einstein-A coefficients, which influence the estimate of the annual cycle's amplitude. A strong 11-year solar signal of 5.9±0.6 K per 100 sfu is identified in the data. The OH temperatures follow the F10.7 cm value with a time lag of 90±65 d. However, the precise value depends on details of the analysis. The highest correlation (R2=0.91) is achieved for yearly mean OH temperatures averaged around 4 February and the F10.7 cm solar flux leading ahead with 110 d. A prominent 2-year oscillation is identified between 2011 and 2015. This signal is linked to the quasi-biennial oscillation (QBO), leading to a temperature reduction of approximately 1 K during QBO westward phases in 2011, 2013, and 2015 and a respective 1 K increase in 2012 and 2014 during QBO eastward phases. The amplitude of the semiannual cycle shows a similar behavior with the decade's minimum amplitudes (∼ 2.5–3 K) retrieved for 2011, 2013, and 2015 and maximum amplitudes observed in 2012 and 2014 (∼4 K). The signal appears to disappear after 2016 when the solar flux approaches its next minimum. Although it appears as a rather strict 24-month periodicity between 2011 and 2015, spectral analyses show a more or less continuous oscillation with a period of approximately 21 months over the entire time span, which can be interpreted as the result of a nonlinear interaction of the QBO (28 months) with the annual cycle (12 months).
... N,10.98° E) in 2008 (see Schmidt et al. (2013), Bittner et al. (2010)). ...
Hydroxyl (OH) radical airglow observations have been performed at the environmental research station ‘Schneefernerhaus’ (UFS, 47.42° N, 10.98° E) since October 2008, and with continuous operation since July 2009. The instrumental setup relies on the parallel operation of two identical GRIPS (Ground-based Infrared P-branch Spectrometer) in order to achieve maximum completeness and homogeneity. After the first decade of observations the acquired time series are evaluated with respect to the main influences on data quality and comparability to those on other sites. Data quality is essentially limited by gaps impacting the completeness. While technical failures are largely excluded by the setup, gaps caused by adverse meteorological conditions can systematically influence estimates of the annual mean. The overall sampling density is high, with nightly mean temperatures obtained for 3382 of 4018 nights of observation (84 %), but the average coverage changes throughout the year. This can bias the annual mean up to 0.8 K if not properly accounted for. Sensitivity studies performed with the two identical instruments and their retrieval show that the comparability between the observations is influenced by the annual and semi-annual cycle as well as the choice of Einstein-A-coefficients, which influence the estimate of the annual cycle’s amplitude. A strong 11-year solar signal of 5.9 ± 0.6 K / 100 sfu is identified in the data. The OH temperatures follow the F10.7cm value with a time lag of 90 ± 65 days. However, the precise value depends on details of the analysis. The highest correlation (R2=0.91) is achieved for yearly mean OH temperatures averaged around 4th February and the F10.7cm solar flux leading ahead with 110 days. A prominent two-year oscillation is identified between 2011 and 2015. This signal is linked to the quasi-biennial oscillation (QBO) leading to a temperature reduction of approximately 1 K during QBO westward phases in 2011, 2013, 2015 and a respective 1 K increase in 2012 and 2014 during QBO eastward phases. The amplitude of the semi-annual cycle shows a similar behavior with the decade’s minimum amplitudes (~2.5–3 K) retrieved for 2011, 2013 and 2015 and maximum amplitudes observed in 2012 and 2014 (~4 K). The signal appears to disappear after 2016 when the solar flux approaches its next minimum. Although it appears as a rather strict 24-month periodicity between 2011 and 2015, spectral analyses show a more or less continuous oscillation with a period of approximately 21 months over the entire time span, which can be interpreted as the result of a non-linear interaction of the QBO (28 months) with the annual cycle (12 months).
... Using an in-house built grating spectrograph (Singh and Pallamraju, 2017a) we have previously brought out several new results by simultaneous measurements of the OH(6-2) Meinel band at around 840 nm and O 2 (0-1) atmospheric band at around 866 nm (Singh and Pallamraju, 2016. Measurements of the OH(3-1) band airglow brightness and corresponding rotational temperature are being carried out since last three decades (e.g., Scheer et al., 1994;Suzuki et al., 2008;Azeem and Sivjee, 2009;Bittner et al., 2010;Schmidt et al., 2013;Pautet et al., 2014;Takanori et al., 2021). In this work, we present a grating based spectrograph PRL Airglow InfraRed Spectrograph (PAIRS)) for the measurement of the OH(3-1) band brightness and corresponding rotational temperatures. ...
... The observation of infrasound with the help of OH * airglow measurements is currently still quite difficult. Especially in the context of observing and learning more about natural hazards (Bittner et al., 2010), the detection of infrasound is of interest as Inchin et al. (2020) modelled. Here, OH * airglow intensity measurements are better suited than temperature observations. ...
Measurements of hydroxyl (OH*) airglow intensity are a straightforward and cost-efficient method which allows the derivation of information about the climate and dynamics of the upper mesosphere/lower thermosphere (UMLT) on different spatiotemporal scales during darkness. Today, instrument components can be bought “off-the-shelf” and developments in detector technology allows operation without cooling, or at least without liquid nitrogen cooling, which is difficult to automate. This makes instruments compact and suitable for automated operation. Here, we briefly summarize why an OH* airglow layer exists, how atmospheric dynamics influence it and how temperature can be derived from OH* airglow measurements. Then, we provide an overview of the scientific results regarding atmospheric dynamics (mainly gravity waves (GWs) but also planetary waves (PWs) and infrasound) achieved with OH* airglow measurements. We focus on long-term ground-based OH* airglow measurements or airglow measurements using a network of ground-based instruments. The paper includes further results from global or near-global satellite-based OH* airglow measurements, which are of special importance for characterizing the OH* airglow layer. Additionally, the results from the very few available airborne case studies using OH* airglow instruments are summarized. Scientific and technical challenges for the next few years are described.
... The observation of infrasound with the help of OH* airglow measurements is currently still quite difficult. Especially in the context of observing and learning more about natural hazards (Bittner et al., 2010), the detection of infrasound is of interest as Inchin et al. (2020) modelled. Here, OH* airglow intensity measurements are better suited than temperature observations. ...
Measurements of hydroxyl (OH*) airglow intensity are a straightforward and cost-efficient method which allows information to be derived about the climate and dynamics of the upper mesosphere / lower thermosphere (UMLT) on different spatiotemporal scales during darkness. Today, instrument components can be bought “off-the-shelf” and developments in detector technology allows operation without cooling or at least without liquid nitrogen cooling, which is difficult to automate. This makes instruments compact and suitable for automated operation. Here, we provide an overview of the scientific results regarding atmospheric dynamics and relying on long-term ground-based OH*-airglow measurements or airglow measurements using a network of ground-based instruments. It includes further results from global or nearly-global satellite-based OH*-airglow measurements. Additionally, the results from the very few available airborne case studies using OH*-airglow instruments are summarised. Scientific and technical challenges for the next few years are described.
... Questions remain as to the circumstances under which TAGWs can be sufficiently strong and coherent at mesopause altitudes (∼75-95 km) to induce detectable MA fluctuations. Although limited modeling studies have addressed TAGW-induced MA fluctuations (Bittner et al., 2010;Hickey et al., 2010), they suggest promise to discern signatures for typical wave characteristics. ...
Numerical simulations of mesopause airglow (MA) fluctuations induced by tsunami‐generated acoustic and gravity waves (TAGWs) are performed. Simulated tsunamis over realistic bathymetry are used to excite atmospheric waves at the surface level of a three‐dimensional nonlinear and compressible neutral atmospheric model. The model incorporates the dynamics and chemistry of hydroxyl OH(3,1) MA under nighttime assumptions. We report case study results of eight recent large tsunami events and demonstrate that TAGW‐induced MA fluctuations are readily detectable with modern ground‐ and space‐based imagers, and may provide quantitative insight. The amplitudes of MA fluctuations reflect the evolution of ocean surface displacements, enhancing or decreasing accordingly, and revealing the tsunami's lobes and local wave focusing. The results suggest that MA observations have potential to supplement early‐warning systems, providing information on spatial and temporal evolution of tsunami waves of ∼10 cm and higher for the cases shown. They may find applications in tsunami tracking over large open ocean areas, as well as in the investigation or reconstruction of tsunami source characteristics.
... Among the three nights of observation, December 12th was the only cloudfree night, which is necessary for the observation of OH radiation. Other studies have analyzed the OH temperature modulations caused by the propagation of infrasound with periods of several minutes using the GRIPS (GRound-based Infrared Pbranch Spectrometer) measurement system (Bittner et al., 2010;Pilger and Bittner, 2009) but the present study is about the perturbation of OH radiation caused by the propagation of infrasound with periods of a few seconds using a short-wave infrared camera. ...
La haute atmosphère, et plus précisément la région appelée MLT (Mesosphere Lower Thermosphere) qui se situeentre 60 et 110 km d'altitude, est le siège de processus divers (chimiques, radiatifs, dynamiques) dont l'étudeest cruciale pour la compréhension du climat et le développement des futurs modèles climatiques. Cette régionse caractérise entre autres par l'émission nocturne du rayonnement provenant d'atomes et de molécules (rayonnementnightglow) et permettant, grâce à l'observation au niveau du sol ou à partir de plateformes satellitaires,d'obtenir des informations sur ces processus. Il apparaît donc un grand intérêt à l'étude du rayonnement nightglow : l'observation des phénomènesimpactant le rayonnement dans la MLT avec pour finalité la compréhension du climat.L’objet de la thèse consiste à étudier les divers phénomènes dynamiques impliqués dans la variabilitédu rayonnement émis dans la MLT par l'espèce OH, qui est un des traceurs de la dynamique locale.Une campagne de mesure a été réalisé en collaboration avec le Latmos (Laboratoire atmosphères, milieux, observationsspatiales) et l’IMCCE (Institut de Mécanique Céleste et de Calcul des Ephémérides) à l’Observatoirede Haute-Provence durant la nuit du 12 au 13 décembre 2017 concordant avec le pic d’activité des Géminides(chute de météores). Une caméra InGaAs SWIR (Short-Wave InfraRed) a imagé le rayonnement émis par lamolécule OH à 87 km d’altitude. Un lidar Rayleigh a permis de mesurer le profil de température en fonction de l'altitude et du temps et un réseau de microbaromètres a mesuré les fluctuations de pressions au sol.Le travail réalisé est concentré sur la détection et la propagation des infrasons dans la basse thermosphère produit à la surface et la propagation des ondes de gravité à travers la mésosphère perturbée lors d’une inversion mésosphérique.Le travail entrepris a permis de montrer l'impact important de l'inversion sur la propagation verticale des ondes de gravité et sur l'activité infrasonique.
... These are found to be in good agreement with the kinetic mesospheric temperatures (see e.g. Bittner et al., 2010;Noll et al., 2016) and can be derived from the line intensities of the OH* airglow radiation, which are measured with spectrometers (Mulligan et al., 1995;Espy and Stegman, 2002;Espy et al., 2003;French and Burns, 2004;Schmidt et al., 2013Schmidt et al., , 2018. ...
The period range between 6 and 480 min is known to represent
the major part of the gravity wave spectrum driving mesospheric dynamics. We
present a method using wavelet analysis to calculate gravity wave activity
with a high period resolution and apply it to temperature data acquired with
the OH* airglow spectrometers called GRIPS (GRound-based Infrared P-branch
Spectrometer) within the framework of the NDMC (Network for the Detection of
Mesospheric Change; https://ndmc.dlr.de, last access: 22 September 2020). We analyse data measured at the
NDMC sites Abastumani in Georgia (ABA; 41.75∘ N,
42.82∘ E), ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) in Norway (ALR; 69.28∘ N,
16.01∘ E), Neumayer Station III in the Antarctic (NEU;
70.67∘ S, 8.27∘ W), Observatoire de Haute-Provence in France (OHP;
43.93∘ N, 5.71∘ E), Oberpfaffenhofen in Germany (OPN;
48.09∘ N, 11.28∘ E), Sonnblick in Austria (SBO;
47.05∘ N, 12.95∘ E), Tel Aviv in Israel (TAV;
32.11∘ N, 34.80∘ E), and the Environmental Research
Station Schneefernerhaus on top of Zugspitze mountain in Germany (UFS;
47.42∘ N, 10.98∘ E). All eight instruments are
identical in construction and deliver consistent and comparable data sets.
For periods shorter than 60 min, gravity wave activity is found to be
relatively low and hardly shows any seasonal variability on the timescale
of months. We find a semi-annual cycle with maxima during winter and summer
for gravity waves with periods longer than 60 min, which gradually develops
into an annual cycle with a winter maximum for longer periods. The
transition from a semi-annual pattern to a primarily annual pattern starts
around a gravity wave period of 200 min. Although there are indications of
enhanced gravity wave sources above mountainous terrain, the overall pattern
of gravity wave activity does not differ significantly for the
abovementioned observation sites. Thus, large-scale mechanisms such as
stratospheric wind filtering seem to dominate the evolution of mesospheric
gravity wave activity.
... Pilger and Bittner (2009) numerically investigated possible mesopause airglow (MA) perturbations of AWs from tropospheric sources. Bittner et al. (2010) reported mesopause temperature perturbations up to ∼5 K from tsunami-excited ...
... To the best of our knowledge, this report presents the first simulations of MA emission perturbations driven by nonlinear AW shocks generated at the near-field region of an earthquake. Results support the hypotheses of Bittner et al. (2010) as to the potential value of airglow data for sensing hazard-generated AWs and also demonstrate the importance of nonlinearity, where signatures may persist following the passage of initial AWs. No equivalent airglow data for such events have been reported to date, and we are not aware of any data sets that would have captured the nonlinear phenomena predicted here for prior earthquakes. ...
Plain Language Summary
Large earthquakes can produce substantial Earth's surface deformation. For earthquakes that occur offshore, sea floor deformation may also result in ocean surface displacements that generate tsunamis. At the interface with the atmosphere, these displacements can serve as a source of very low frequency acoustic waves. Reaching the upper atmosphere (∼70 km and higher), these waves can be strong enough to form shock waves and generate observable disturbances. This paper reports the results of numerical simulations of ∼80–90‐km altitude airglow disturbances driven by strong acoustic waves excited during a hypothetical nighttime equivalent of the 2011 Tohoku‐Oki earthquake (magnitude 9.1). Modeling results show that, for such large earthquakes if occurring at nighttime, airglow disturbances could be readily detected with specialized ground‐ and space‐based imagers. The possibility to detect airglow disturbances earlier than the arrival of the tsunami at the shore points to the potential applicability of such observations for tsunami early‐warning systems. Also, the results suggest that such observations can be a useful tool for the characterization of earthquake processes and the propagation of seismic waves.
... These are found to be in good agreement with the kinetic mesospheric temperatures (see e.g. Bittner et al., 2010;Noll et al., 2016) and can be derived from the line intensities of the OH* airglow radiation, which are measured with spectrometers (Mulligan et al., 1995;Espy & Stegman, 2002;Espy et al., 2003;French & Burns, 2004;Schmidt et al., 2013Schmidt et al., , 2018. ...
Abstract. The period range between 6 min and 480 min is known to represent the major part of the gravity wave spectrum driving mesospheric dynamics. We present a method using wavelet analysis to calculate gravity wave activity with a high period-resolution and apply it to temperature data acquired with the OH* airglow spectrometers GRIPS (GRound-based Infrared P-branch Spectrometer) within the framework of the NDMC (Network for the Detection of Mesospheric Change; https://ndmc.dlr.de ). We analyse data measured at the NDMC sites Abastumani in Georgia (ABA, 41.75° N, 42.82° E), ALOMAR in Norway (ALR, 69.28° N, 16.01° E), Neumayer III in the Antarctic (NEU, 70.67° S, 8.27° W), Observatoire de Haute-Provence in France (OHP, 43.93° N, 5.71° E), Oberpfaffenhofen in Germany (OPN, 48.09° N, 11.28° E), Sonnblick in Austria (SBO, 47.05° N, 12.95° E), Tel Aviv in Israel (TAV, 32.11° N, 34.80° E), and the Environmental Research Station Schneefernerhaus on top of Mt. Zugspitze, Germany (UFS, 47.42° N, 10.98° E). All eight instruments are identical in construction and deliver consistent and comparable data sets.
For periods shorter than 60 min, gravity wave activity is found to be relatively low and hardly shows any seasonal variability on the time scale of months. We find a semi-annual cycle with maxima during winter and summer for gravity waves with periods longer than 60 min, which gradually develops into an annual cycle with a winter maximum for longer periods. The transition from a semi-annual pattern to a primarily annual pattern occurs around a gravity wave period of 200 min. Although there are indications of enhanced gravity wave sources above mountainous terrain, the overall pattern of gravity wave activity does not differ significantly for the abovementioned observation sites. Thus, large-scale mechanisms such as stratospheric wind filtering seem to dominate the temporal course of mesospheric gravity wave activity.
