In particular, global and regional infrasound station networks have proven highly effective in detecting and locating a wide range of natural and anthropogenic phenomena. Recent studies have shown that multi-technology analyses provide foundations for addressing geophysical inverse problems, enabling novel probing of both global-scale and small-scale structures in the middle atmosphere for enhanced weather prediction and climate modeling.
In addition to data-driven contributions, this session invites model-based papers dealing with the dynamics of the middle atmosphere across scales and altitudes, as well as its predictability. We welcome contributions on the characterization of atmospheric phenomena (gravity or planetary waves for example), using complementary observational methods across both local and global scales. Contributions addressing advances in wave propagation modeling, signal processing, and machine learning applications are also of great interest. Additional areas of focus include the development of derived data products and services for scientific and civilian use, as well as innovative instrumentation, including sensors deployed on mobile or elevated platforms such as balloons on Earth or other planets. Seismo-acoustic studies investigating the coupled Earth–ocean–atmosphere system, particularly focusing on ionospheric responses to processes originating from the ocean and solid Earth, are also encouraged.
PICO: Fri, 8 May, 08:30–12:30 | PICO spot 5
Since more than sixty years, rockets have transported tens of thousands of satellites to space. More and more rocket stages and other space debris are returning to Earth, sometimes intentionally, sometimes unexpected. Such descending objects move supersonically through the atmosphere, disintegrate, and can even explode. During these processes, they can produce shock and sound waves which can be monitored using pressure sensors at the Earth’s surface. The infrasound component of the International Monitoring System (IMS) for monitoring compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), as well as additional national infrasound arrays, are therefore well suited for detecting and characterizing such events. Additionally, the infrasound waves can couple to the subsurface as seismic waves.
On 19 February 2025, the upper stage of a SpaceX Falcon 9 rocket reentered Earth’s atmosphere approximately over Ireland and produced a bright fireball along its trajectory over the United Kingdom, the Netherlands, northern Germany and western Poland, where fragments of the rocket were eventually recovered. This highlight case of a reentry of space material was not only visually observed, but also recorded by various scientific instruments, including infrasound arrays in the Netherlands, Germany, Sweden and Norway and the dense seismic borehole network in the northern part of the Netherlands. This case study investigates the potential of infrasound to monitor space rockets during their reentry. We characterize the Falcon 9 reentry event and reconstruct its trajectory based on infrasound and seismoacoustic recordings.
How to cite: Hupe, P., Pilger, C., Assink, J., Schneider, S., Grumer, J., Naesholm, S. P., and Baumgarten, G.: Seismoacoustic analysis of a Falcon-9 rocket stage reentry on 19 February 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6974, https://doi.org/10.5194/egusphere-egu26-6974, 2026.
Hungary's first and only infrasound station has been operating in Piszkéstető since 2017. During its eight years of operation, it has recorded numerous events, including quarry blasts, which are published annually in the Hungarian Seismoacoustic Bulletin (HSAB).
Our research aims to model the effect of azimuth deviation due to cross-winds and to investigate its impact on the location of mine explosions in Hungary and neighbouring countries, using data from the Piszkéstető infrasound station (PSZI).
Using seismic data to determine the dates and locations of the mine explosions, we modeled the resulting infrasound waves using ray tracing. The resulting ground intercepts were used to determine the azimuths of the rays closest to PSZI. With the modeled azimuths of these events, we re-determined their locations using the iLoc single-event location algorithm, which were then compared with the detected azimuths and locations determined without an infrasound phase.
The difference between the detected and modeled azimuth values is less than 5º in most cases, but there were also larger values of around 10º. The differences between locations with and without an infrasound phase were the largest in these cases, and in many instances, the calculation using modeled azimuths was more accurate than the detected ones.
Overall, our research provides a basis for incorporating ray tracing into seismo-acoustic positioning to improve the accuracy of HSAB’s event locations. The method still has some shortcomings, especially when the proximity of the mines to PSZI means no suitable ground intersection point is calculated.
How to cite: Cziráki, K. and Pásztor, M.: Revisiting the Hungarian Seismoacoustic Bulletins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11429, https://doi.org/10.5194/egusphere-egu26-11429, 2026.
Strong storms in the North Atlantic are a significant natural source of low-frequency seismic and acoustic signals (microseisms and microbaroms), commonly detected by monitoring stations in Romania. Storm Éowyn was an intense extratropical cyclone that impacted Ireland and the United Kingdom on 24 January 2025, driven by an exceptionally strong jet stream. The storm produced maximum wind gusts of 183 km/h and sustained winds of 135 km/h in western Ireland, breaking national records dating back to 1945.
This study presents a joint seismo-acoustic analysis of Storm Éowyn as an intense source of oceanic ambient noise, using simultaneous seismic and infrasonic observations from the Romanian arrays BURAR, BURARI, and IPLOR. Infrasonic and seismic data were processed using the PMCC correlation-based method to characterize the temporal variability of microbarom and microseism signals between 21 and 27 January 2025. Seismo-acoustic detections in the 0.1–0.6 Hz frequency range were analyzed with DTK-PMCC and DTK-DIVA software packaged into CTBTO NDC-in-a-Box.
The storm trajectory was computed using CyTRACK, an open-source Python toolbox for cyclone detection and tracking. ERA5 hourly reanalysis data from the Copernicus Climate Data Store provided mean sea level pressure, 10-m wind speed, and relative vorticity fields. Seismo-acoustic detections were compared with ARROW products from IFREMER describing microseism and microbarom source models. To assess detection performance and backazimuth discrepancies, we calculated the effective sound speed ratio (Ceff) at 50 km altitude using temperature and wind profiles from ECMWF operational analyses obtained via CAMS.
During the storm's peak impact on 24 January, power spectral density analysis revealed microbarometric peaks at 0.23 Hz (BURARI) and 0.22 Hz (IPLOR), while the microseismic peak at BURAR reached 0.29 Hz. Results demonstrate good agreement between observed signals and modeled source locations.
This study confirms the capability of Romanian infrasound and seismic arrays to monitor microbaroms and microseisms generated by intense North Atlantic storms. These findings provide a foundation for investigating other seismo-acoustic low-frequency signals from North Atlantic cyclones, which dominate winter detections at Romanian stations.
How to cite: Ghica, D., Ene, D., and Antonescu, B.: Seismo-acoustic observation of the Éowyn impactful storm at Romanian infrasound and seismic arrays, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9780, https://doi.org/10.5194/egusphere-egu26-9780, 2026.
Weak, sustained infrasound waves associated with natural and environmental sources (e.g., waterfalls, avalanches, dams, and debris flows) can be detected by remote infrasound arrays. Large-volume water flows at waterfalls and dams convert the mechanical energy of flowing water into various forms of energy, including acoustic energy in the infrasound range. Under certain circumstances, infrasound observations of sudden and otherwise unexpected large-scale water flow events can be used for early disaster warning, thereby contributing to disaster mitigation. Beyond early warning, this study investigates whether remote infrasound observations can be used to quantify the intensity of water release (discharge rates) at dams. To establish a relationship between infrasound energy and water discharge at a reference distance of 1 km, data were obtained from controlled water-release events at a dam in South Korea. Since water-release signals observed at regional distances are generally noise-like and exhibit low signal-to-noise ratios, two infrasound detection algorithms, based on the correlation (PMCC) and the maximum likelihood (MCML), were applied, and their detection results were compared to evaluate the performance of each method. Based on the detected infrasound signals at a distance of 15 km from the dam, discharge rates were estimated using the derived empirical relationship. The estimated discharge rates show promising agreement with the actual discharge rates, demonstrating the feasibility of this approach. Overall, our results indicate that infrasound monitoring has practical potential not only for early warning but also for quantifying hazardous water discharge, thereby enhancing disaster monitoring and response capabilities.
How to cite: Che, I.-Y., Won, M., Park, J., Hayward, C., Le Pichon, A., and Kim, K.: Estimation of Dam Water Discharge Rate Using Observations of Low-Frequency Acoustic Waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4679, https://doi.org/10.5194/egusphere-egu26-4679, 2026.
Human activity can create acoustic emissions capable of traveling many kilometers. Narrow band, “tonal” signatures are particularly distinct, as there are few processes in nature that produce them (e.g., volcanic tremor). Although stratospheric balloon flights over cities commonly record these signals, the plethora of emitters makes any single source difficult to distinguish. Acoustic sensors aboard the TRANSAT balloon flight from Sweden to Canada captured a multi-hour narrowband signal while crossing northern Norway. This distinct, isolated recording indicates a singular emitter capable of projecting sound nearly 40 km in the air and at least 100 km laterally. We describe the signal properties, calculate the detection range of the floating sensor, and constrain possible locations of the emission source. This is a first step towards the detection, characterization, and geolocation of narrowband acoustic signals from the stratosphere using a single free flying sensor. This has implications for characterizing anthropogenic activity on Earth as well as evaluating volcanic activity during proposed balloon missions to Venus.
How to cite: Näsholm, S. P., Bowman, D. C., Lees, J. M., Anderson, J. F., Froment, M., and Kero, J.: Acoustic emissions from an industrial facility recorded during the TRANSAT stratospheric balloon flight, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9638, https://doi.org/10.5194/egusphere-egu26-9638, 2026.
We investigate explosive yield estimation from infrasound signals generated by controlled ground explosions at the Hukkakero ammunition disposal site in northern Finland. Since 1988, highly repeatable blasts with yields of approximately 20 tons TNT equivalent have been conducted annually, providing a valuable reference dataset.
Explosive yield is estimated using a Bayesian framework that explicitly accounts for uncertainties in source characteristics and transmission loss statistics. Spectral characteristics of the signals are extracted using the multichannel maximum-likelihood (MCML) method, providing robust inputs for yield estimation. Propagation effects are represented through an updated statistical transmission loss law derived from extensive full-wave simulations under realistic atmospheric conditions. Rather than relying on deterministic scaling relations, transmission loss is incorporated as a probability distribution within the Bayesian formulation as a function of frequency and effective sound speed ratio.
Applying this approach to historical infrasound observations from the IMS array IS37 (northern Norway, ~320 km from Hukkakero) yields probabilistic explosive energy estimates with physically meaningful uncertainty bounds. The results demonstrate improved robustness and reduced bias compared with traditional methods, particularly for regional-distance observations where atmospheric effects strongly influence signal amplitudes.
How to cite: Le Pichon, A., Kristoffersen, S., Vergoz, J., and Näsholm, S. P.: A Bayesian framework for explosive yield estimation using statistical signal characterization and attenuation modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12366, https://doi.org/10.5194/egusphere-egu26-12366, 2026.
This poster is devoted to analysis of polar vortex state in the stratosphere. We use the ERA-5 data of daily averages of zonal wind poleward of 60° N at the selected layers from 250 hPa up to 1 hPa in the winter period 1979/80 (October-March). We compute the latitudinal average of longitudinal averages U. Thus we obtain one value per day. It is a very important, because its negative value is one of signs of sudden stratospheric warmings. In each day we made a map of geographical distribution of geopotential height, geographical distribution of grids with easterly wind. For each grid point we compute the vertical difference of zonal wind between adjacent layers: lower layer –upper layer and we consider the following types of differences: Type 1: in both layers the west wind is present, but in the type +1 the west wind is stronger in the lower layer, so this grid increases U, type -1 has weaker wind in lower layer, so it decreases U. Type 2: in both layers the east wind is present, but in the type +2 the east wind is weaker in the lower layer, so this grid increases U. Type -2 has stronger east wind in lower layer, so it decreases U. Type 3 has opposite wind direction at adjacent layers in the case of +3 we observe east wind in upper layer and west wind in lower layers –increases U. The opposite is true for -3 type with decreases U. We divided the total difference in zonal wind between adjacent layers into 6 parts. In each part we compute the total sum. We also computed the number of grids in each part and we made a maps of geographical distribution of these points. We compare these sums and we found the largest one for each layer and day and we compare the results between days with positive and negative U
How to cite: Krizan, P.: Analysis of state of polar vortex in the stratosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4947, https://doi.org/10.5194/egusphere-egu26-4947, 2026.
We analysed more than 30 years of OH*(3,1) rotational temperatures that have been observed
from Wuppertal, Germany, since 1988 with respect to periodic fluctuations (2 to 60 d) using the
Lomb-Scargle periodogram. The main type of fluctuation observed in the last decades shows
a period of about 28 d. Other periods which are frequently detected in the observations lie in
the period ranges around 2 d, from 5 to 6 d, from 8 to 12 d, and around 15 d and can likely
be assigned to the quasi-2-day, the quasi-5-day, the quasi-10-day , and the quasi-16-day wave,
respectively.
The wave activity is typically larger in winter time than in summer time because of the different
wave filtering in summer and winter. This winter to summer difference holds for waves with
longer periods, but it breaks off in the case of shorter periods below about 20 d. The occurrence
frequency of these waves (< 20 d) exhibit two smaller maxima around the equinoxes. Thereby
the waves with periods below 10 d account for the majority of observations in the months from
April to September, whereby the waves with periods between 10 d and 20 d were more equally
observed in the whole year except for the late spring and summer, where almost no events were
observed.
The long-term behaviour of the wave activity indicates a quasi-bidecadal oscillation, which is
seen in different proxies for the wave activity. A further comparison of these proxies indicates
that this long-term oscillation is likely driven by the amplitude of the waves, i.e. the strength
of the events and not the duration of the events.
How to cite: Kalicinsky, C., Reisch, R., and Knieling, P.: Ground-based observations of periodic temperaturefluctuations in the mesopause region with periods larger than 2 days, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18017, https://doi.org/10.5194/egusphere-egu26-18017, 2026.
Ground-based lidar measurements with the CORAL instrument at the southern tip of South America (53.8S, 67.8E) provide vertical temperature measurements and gravity wave characteristics at a resolution of 15 min throughout the middle atmosphere, up to the OH emission layer. Of this layer, the AWE instruments onboard the International Space Station provides global imaging of OH brightness and temperature at 2 km x 2 km resolution. We identified coincident and common-volume observations during winter 2024 and analyze these for gravity wave and instability dynamics. The geographic region is known for strong orographic wave forcing and deep propagation of gravity waves into the middle atmosphere during winter, including mountain wave breaking, secondary wave generation, and the generation of vortex rings and Kelvin-Helmholtz instabilities in the upper mesosphere. Gravity waves identified by lidar are typically 2-3 hours in period and 10-15 km in vertical wavelength in the upper stratosphere, lower mesosphere. In the upper mesosphere, smaller scales prevail. By wavelet analysis, we find that periods down to 40 min sporadically occur in thin, confined altitude layers. These observations are combined with AWE measurements showing varied local responses including mesospheric bores, small-scale mountain waves and large- and small-scale vortex rings and ring clusters related to the breaking of the gravity waves propagating from below.
How to cite: Kaifler, N., Kaifler, B., Reichert, R., Pautet, D., Fritts, D. C., and Stockwell, R.: Coincident measurements of ground-based lidar and the AWE OH imager onboard the ISS above the Southern Andes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16888, https://doi.org/10.5194/egusphere-egu26-16888, 2026.
Gravity waves transport momentum and energy vertically and horizontally and play a key role for the circulation in the upper mesosphere and lower thermosphere (UMLT). They can experience convective or dynamic instabilities or undergo nonlinear interactions with the background flow. The UMLT is of particular importance, as gravity waves frequently reach their breaking levels in this region, often referred to as the turbopause.
This altitude range is observed using two FAIM cameras measuring the OH-airglow emission centered at approximately 86 km altitude, with a full width at half maximum of about 7–8 km, from different locations. By applying a newly developed tomographic reconstruction technique to coordinated dual-camera OH-airglow observations of the same air volume, the three-dimensional structure of gravity waves in the UMLT can be recovered. The resulting volumetric data provide detailed information about horizontal and vertical gravity-wave features, representing a middle-atmosphere sounding technique complementary to established methods such as lidar or radar observations.
To characterize these waves, vertical wavelengths are extracted in a dedicated post-processing step by applying a two-dimensional FFT to selected altitude layers of the tomographically reconstructed volume. This approach provides access to vertical phase progression and vertical wavelength information that is fundamentally unattainable with a single OH airglow imager. By analyzing the phase differences of the wave signals in the FFT spectra between different altitude layers, the vertical propagation angle can be derived. In combination with the horizontal wavelength, this enables the determination of the vertical wavelength and thus a full three-dimensional gravity-wave characterization.
First results from this dual-FAIM tomographic approach are presented, demonstrating both the feasibility and the performance of the method. The analysis is based on coordinated OH-airglow observations from FAIM installations at Oberpfaffenhofen (lon = 11.28, lat = 48.09) and Otlica (lon = 13.91, lat = 45.94) over a one-year period. These data are used to assess retrieval quality, identify sensitivity limits for vertical wavelength derivations, and demonstrate the enhanced scientific value of three-dimensional gravity-wave characterization for multi-instrument analyses of middle-atmosphere dynamics.
Within the project GIGAWATT, a collaboration of the German Aerospace Center, the University of Augsburg and the University of Bern, we are currently advancing this work by incorporating new measurements and combining complementary observational techniques, including radiometric temperature and wind observations in the stratosphere and lower mesosphere and multi-static OH airglow tomography, to establish a high-resolution gravity-wave observatory for the Alpine region. This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under the project number 540878795.
How to cite: Winkler-Zurlinden, R., Hannawald, P., Stober, G., Wüst, S., and Bittner, M.: Three-dimensional reconstruction of gravity waves in the UMLT derived from dual OH airglow observations using a tomographic retrieval, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11372, https://doi.org/10.5194/egusphere-egu26-11372, 2026.
Remote sensing from satellites provides a powerful means of observing the Earth’s atmosphere with global coverage and high vertical resolution. Among these techniques, Global Navigation Satellite System radio occultation (GNSS-RO) offers a low-cost approach that delivers large volumes of high-quality atmospheric temperature profiles. While several tens of thousands of GNSS-RO observations are assimilated daily into numerical weather prediction systems from multiple satellite missions, only a subset of these are made available for community research. Here we explore the Radio Occultation Meteorology and Climate Experiment (ROMEX) dataset: a unique, community-available collection of high-density GNSS-RO observations, combining measurements from multiple satellite missions to provide approximately 30,000-40,000 profiles per day during September-November 2022, resulting in an unprecedented sampling density for scientific applications.
In this study, we investigate the ROMEX dataset to assess the additional insight enabled by such exceptionally dense spatial and temporal sampling, with a focus on fast-moving equatorial waves in the tropical atmosphere. The high sampling density of ROMEX is particularly suited to resolving planetary-scale equatorial wave modes with short periods, which are difficult to capture using conventional measurements such as those by radiosondes or sun-synchronous satellites. ROMEX’s strongest performance in the upper troposphere and lower stratosphere further provides access to a key region of equatorial wave activity. Using temperature perturbations derived from the GNSS-RO profiles, we separate symmetric and antisymmetric wave components and examine their distribution in frequency-wavenumber space to identify distinct equatorial wave modes and recover their characteristic horizontal structures. We show that multiple equatorial wave modes, including Kelvin waves, mixed Rossby-gravity waves, equatorial Rossby waves, and both eastward and westward inertia-gravity waves, can be exceptionally clearly identified and studied using ROMEX observations. Among these, Kelvin waves with periods of approximately 10-13 days are observed, with maximum amplitudes near 18 km. In addition to the large-scale planetary waves themselves, we also investigate their modulation of the small-scale gravity wave flux in the tropics, and vice versa, revealing new insights into wave-wave interaction and momentum driving reaching the mid stratosphere.
Our results demonstrate that dense GNSS-RO datasets such as ROMEX offer substantial potential for atmospheric science beyond their established role in numerical weather prediction. In particular, the unique coverage and vertical resolution of ROMEX open new opportunities to study tropical wave dynamics and their impact on the structure of the tropical and extratropical atmosphere.
How to cite: Lucas, L., Hindley, N., Wright, C., Noble, P., and Randel, W.: Investigating equatorial waves with high-density ROMEX GNSS-RO observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20004, https://doi.org/10.5194/egusphere-egu26-20004, 2026.
Gravity waves are a significant driver of middle atmosphere dynamics with various excitation sources, e.g. the jet stream, convection zones, flow over orography and natural hazards such as tsunamis. OH-airglow measurements allow continuous night-time observations of gravity waves and various other wave types including singular events like bores and wall events at an altitude of about 86 km.
Their respective signals are subject to the measurement system “Observations of Airglow with Spectrometer and Imager Systems” (OASIS). Imager systems allow the derivation of wave parameters such as the horizontal wavelength and the propagation direction. Data from spectrometers complement this information with wave amplitudes derived in temperature and absolute OH radiance.
Since November 2022, the measurement system OASIS started routine observations at the Very Large Telescope (VLT) in the Atacama Desert at Cerro Paranal, Chile (24.6°S, 70.4°W) in cooperation with the European Southern Observatory (ESO). It is composed of two Fast Airglow Imagers (FAIM) and one Ground-based infrared P-branch Spectrometer (GRIPS) with high temporal resolution (1 image every 1/2 seconds, 1 spectrum every 15 seconds). Currently, over three years of data with nearly 100% night-time data coverage have been acquired. One of the goals of the observation site beside the general investigation of atmospheric dynamics is the investigation of tsunami-induced signals in OH airglow.
Monitoring the OH airglow provides a unique opportunity to make continuous night-time observations of the middle atmosphere with high temporal and spatial resolution. However, the OH airglow causes noise in ground-based astronomical observations in the short-wave infrared like performed with the VLT due to its emissions in this spectral range. The project AirMon-VLT (“Airglow Monitor at the VLT”) brings together the interests of atmospheric scientists to understand middle atmosphere dynamics even better and astronomers who want to precisely know about the OH airglow variability and radiance. With this detailed knowledge an improved scheduling of deep sky observations for example at times with low OH airglow variability and radiance could be achieved. Also, precise and highly temporally resolved information about the change of OH airglow radiance can help to improve the correction of astronomical spectra.
Within AirMon-VLT, the short and medium-term variability of OH airglow is investigated with statistical methods answering questions like which changes in airglow radiance could typically be expected within minutes/hours/days/etc., e.g. due to infrasound, gravity waves, tides, planetary waves, and by singular events like bore or wall events. With methods from the field of artificial intelligence predictions of the airglow variability will be made into the near and medium future (nowcasting and forecasting) to allow for a better scheduling of the astronomical targets. Also, additional data like ERA5 reanalysis data will be investigated for a more comprehensive understanding of causes of the variability from lower atmospheric layers.
We present the project AirMon-VLT and the measurement system OASIS. We show first results of statistical evaluations about typical changes of airglow radiances related to various wave phenomena, including singular events like a potential wall event with an exceptional high radiance change of 60% within only one hour.
How to cite: Hannawald, P., Lienhart, R., Smette, A., Stephan, J., Olbing, L., Schmidt, C., Wüst, S., and Bittner, M.: Investigation of the short- and medium-term variability of OH airglow at Cerro Paranal, Chile within the project AirMon-VLT, using statistical and artificial intelligence methods, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11703, https://doi.org/10.5194/egusphere-egu26-11703, 2026.
Gravity waves influence atmospheric dynamics through transport of momentum and energy, and their understanding is thus essential for improving their parametrisations in atmospheric models. In this work, we study gravity waves using data from a global ICON simulation with a horizontal resolution of approximately 2.5 km. The data are divided into triangular subdomains defined by a low-resolution ICON model grid, which has a horizontal resolution of about 160 km. We evaluate 3D spatiotemporal spectra within these subdomains and subsequently filter the spectra using linear gravity wave theory, yielding the global distribution of local gravity wave spectra. Analysis of the spectra reveals latitudinal dependence, with the zonal wind direction shaping the spectral form. Notably, spectra simplify dramatically using tens to hundreds of principal components, capturing variance efficiently. This approach enhances gravity wave parametrizations by providing low-dimensional spectral representations, enabling more accurate and computationally efficient global modeling.
How to cite: Procházková, Z., Mahmoudi, E., Chew, R., Dolaptchiev, S., Stephan, C. C., Völker, G. S., and Achatz, U.: Variability of local gravity wave spectra, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2721, https://doi.org/10.5194/egusphere-egu26-2721, 2026.
Turbulence is a significant contributor to weather-related aviation incidents, with profound economic and safety implications. Clear-air turbulence (CAT) refers to turbulence occurring in the atmosphere, typically near the tropopause, without the observable convective cloud features. CAT is particularly hazardous as it remains invisible to pilots and many onboard instruments. With its occurrence expected to increase due to anthropogenic climate change, improved CAT detection is essential.
This study examines the infrasonic signature of CAT as a means for remote detection. Turbulence is a well-established source of sound, and infrasound has proven effective in detecting a range of geophysical events as the long-wavelength acoustic information can travel long distances with minimal attenuation. Using the Weather Research and Forecasting (WRF) model and observed meteorological data, high-resolution simulations were performed to reproduce representative case studies of CAT, including a documented event over Trout Peak in Wyoming, USA. These simulations provide the inputs for the acoustic model, with the dominant acoustic sources arising from turbulence and vorticity.
Acoustic pressure was computed at various far-field observation locations for two subdomains, one containing the CAT region and another representing the background flow with only minor fluctuations, to isolate the acoustic contributions from CAT specifically. The acoustic propagation is assumed to occur in a static and homogeneous medium, neglecting the effects of refraction and convection. Results reveal a significant increase in acoustic power associated with the CAT, with distinct and directionally dependent spectral peaks. These findings support the feasibility of using infrasound as a tool for real-time remote CAT detection.
How to cite: Drapeau, C., Shaygani, A., Mohammadifar, M., Hickey, J.-P., and Waite, M.: Numerical modeling of infrasonic emissions from clear-air turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-568, https://doi.org/10.5194/egusphere-egu26-568, 2026.
Gravity waves (GWs) are a fundamental driver of circulation, tracer transport, and mixing in the middle and upper atmosphere, but their treatment in global circulation models remains incomplete. In particular, standard parameterizations typically restrict propagation to the vertical and treat GW–turbulence interactions in only a rudimentary manner, potentially leading to systematic biases in simulated dynamics and transport. This manuscript uses the Multi-Scale Gravity-Wave Model (MS-GWaM) implemented in Community Climate Icosahedral Nonhydrostatic Model UA-ICON, together with a novel theoretical framework to quantify the impact of (i) oblique GW propagation and (ii) explicit bidirectional coupling between GWs and turbulence. The Ensemble simulations for non-orographic GWs reveal that allowing for oblique propagation lowers and cools the summer mesopause by shifting the deposition of momentum and heat to lower altitudes, reduces GW-induced vertical shear in the middle and lower atmosphere, and enhances turbulent kinetic energy (TKE) in the upper mesosphere and lower thermosphere. In contrast, coupling GWs to turbulence produces a nearly opposite mesopause response, lifting and warming the mesopause, while maintaining a reduction in wave-induced shear and further enhancing turbulence. Tracer experiments additionally show that turbulent coupling significantly increases mixing in regions of enhanced TKE with implications for chemical redistribution. These results demonstrate that both oblique GW propagation and GW–turbulence interactions exert leading-order controls on mesosphere–lower thermosphere circulation, temperature structure, and tracer transport. Neglecting these processes in global models likely contributes to biases in the Brewer–Dobson circulation, energy balance, and constituent distributions, underscoring the need for next-generation GW parameterizations that capture these effects.
How to cite: Banerjee, T., Kim, Y.-H., Voelker, G. S., Borchert, S., Kosareva, A., Kunkel, D., Masur, G.-T., Procházková, Z., Schmidli, J., and Achatz, U.: The Impact of Non-Orographic Gravity Waves on Transport and Mixing: Effects of Oblique Propagation and Coupling to Turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13511, https://doi.org/10.5194/egusphere-egu26-13511, 2026.
Mostly for reasons of efficiency, the standard approach to parameterizing gravity wave leaves out various effects. Among others, two of those are oblique wave propagation and horizontal flux convergences, summarized as 3D effects. Another aspect is deviations of wave-mean-flow interaction that arise if the mean flow is not balanced, so that pseudo-momentum (Eliassen-Palm) fluxes do not suffice for the quantification of the wave impact on the resolved flow (Wei et al 2019). The comparative importance of these effects for zonal-mean winds and temperatures, residual-mean transport, and solar tides has been investigated, using the Lagrangian gravity-wave parameterization MS-GWaM (Bölöni et al 2021, Kim et al 2021, 2024, Voelker et al 2024) in the global circulation model ICON. Comparisons between ensembles of boreal-winter simulations show that 3D dynamics leads to a statistically significant relative circulation that lowers and cools the summer mesopause but also cools/heats the summer/winter stratopause region and cools the mid-latitude winter stratosphere. Replacing pseudo-momentum forcing by a more general approach mainly affects in December the summer mesopause in manner opposite to 3D, and in February also reduces significantly the polar-night jet in the stratosphere. Gravity waves seem to be responsible for most of the differences, but modified Rossby-wave fluxes partly compensate for their effects, in a manner similar as observed by Cohen et al (2013). Solar tides show a related response, where non-balanced dynamics mostly affects the summer mesosphere / lower thermosphere, but 3D has significant effects on tides in both hemispheres and down into the stratosphere.
How to cite: Achatz, U., Banerjee, T., Kim, Y.-H., Kühner, T., Masur, G. T., Prochazkova, Z., and Voelker, G. S.: Effects of Non-Classical Gravity-Wave Dynamics on Middle-Atmosphere Circulation and Solar Tides, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5411, https://doi.org/10.5194/egusphere-egu26-5411, 2026.
Infrasound technology is used to monitor the atmosphere and to verify compliance with the Comprehensive Nuclear Test-Ban-Treaty. Acoustic signals recorded by the International Monitoring System allow to characterize sources of interest.
Fine-scale atmospheric perturbations of the order of a few kilometers to a few hundred meters in vertical wavelength are necessary to explain the duration and amplitude of acoustic signals. Such internal gravity wave (GW) perturbations must be added to atmospheric specifications for propagation simulations. Indeed, operational meteorological products underestimate or miss that part of the GW spectrum. The GW universal spectrum approach provides a convenient framework to quickly derive vertical perturbation profiles of GW using inverse Fourier transform along the atmospheric column.
Using radiosonde and lidar measurements from the Observatoire De Haute-Provence in South of France (43° 55′ 51″ N, 5° 42′ 48″ E) and from La Réunion Island (21° 04′ 47″ S, 55° 22′ 59″ E) across many years, we characterize monthly GW vertical wavenumber spectra in different altitude layers. We fit those spectra using the modified Desaubies analytical model in order to retrieve relevant parameters (namely the maximum amplitude of the spectrum and the characteristic wavenumber m*). We also compare the observed spectra and their related parameters and quantities, notably kinetic and potential energies, to those derived from ERA5 products.
Using the calibrated parameters of the GW spectra, we derive the associated ensemble perturbation profiles in a stochastic approach using bootstrap techniques. The goal is to be representative of the observed vertical distribution of the spectra. The ensembles of perturbation profiles are then used as input to infrasound propagation simulations. We discuss how waveform simulations used in operational monitoring can benefit from these better-constrained atmospheric fine-scale uncertainties.
How to cite: Listowski, C., Jaulgey, M., Chane-Ming, F., Hauchecorne, A., Sochala, P., Vergoz, J., and Le Pichon, A.: Investigating vertical gravity wave spectra to calibrate a gravity wave perturbation model: comparison with ERA5 reanalysis products and application to infrasound propagation simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5982, https://doi.org/10.5194/egusphere-egu26-5982, 2026.
Infrasound signals are generated by various anthropogenic and natural sources, and are one of the technologies used in monitoring compliance with the Comprehensive Nuclear-Test Ban Treaty (CTBT). It is, therefore, of interest to study and better understand the impacts of atmospheric parameters, notably gravity waves (GW), on infrasound propagation. Middle-atmosphere dynamics, up to the lower thermosphere, must be simulated to account for the different acoustic waveguides that allow the long-range propagation and infrasound detections by the CTBT’s International Monitoring System.
Since infrasound propagates up to the lower thermosphere, an upper atmospheric model like the upper-atmosphere extension of the ICON model (UA-ICON) is necessary to properly understand and predict infrasound propagation. Toward this goal, we will present studies of UA-ICON using two different GW parameterizations: the operational one also used for the operational ICON forecasts issued by DWD, and a 3D gravity wave parameterization scheme (MS-GWaM) that includes improved GW propagation. We also propose a method to derive stochastic predictions of realistic GW perturbation profiles using MS-GWaM. These results are compared to lidar observations, showing the importance of correctly tuned GW parameterizations on temperature profiles, from tropical to high latitudes. In addition, we will present case studies of infrasound propagation to highlight the importance of mesospheric wind and temperature, as well as GWs, on infrasound propagation and source localization. Notably, infrasound allows us to investigate equatorial latitudes where lidar measurements are missing.
How to cite: Kristoffersen, S., Listowski, C., Achatz, U., Völker, G.-S., Wing, R., Khaykin, S., Baumgarten, G., Hauchecorne, A., Le Pichon, A., and Vergoz, J.: The impact of gravity wave parameterizations on the upper atmosphere ICON model and infrasound propagation., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8082, https://doi.org/10.5194/egusphere-egu26-8082, 2026.
Since the deployment of the Hungarian infrasound array (PSZI) in May 2017, a large number of PMCC (Progressive Multichannel Correlation) detections have been collected and manually categorized using ground-truth information from independent sources. This dataset enabled the training and evaluation of machine learning (ML) models for infrasound signal classification.
The final ensemble model consists of a Random Forest model trained on PMCC-related features and a Convolutional Neural Network trained on spectrograms. To automate infrasound signal processing, these were trained to distinguish detections originating from known sources from those of unknown origin.
Based on the ensemble ML model, we designed a monitoring system to help with daily routine processing. We aimed to remove noise, such as detections associated with industrial activity from the daily list of detections and highlight those that are from signals of interest, for instance quarry blasts, thunderstorms and activity of the Etna. During the one-year-long test phase, the system achieved high accuracy in classifying quarry blast signals and successfully identified multiple eruptions of Mount Etna, highlighting its capability for automated infrasound signal source classification.
How to cite: Pásztor, M. and Bondár, I.: Lessons learned from a one-year-long deployment of a machine learning-based infrasound monitoring system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11707, https://doi.org/10.5194/egusphere-egu26-11707, 2026.
Infrasound is a key component of the geophysical monitoring network that detects large-scale artificial and natural events such as nuclear tests, earthquakes, volcanic eruptions, and fireballs. In this context, full waveform propagation modeling at regional and local distances enables more sophisticated identification of source properties. However, infrasound propagation modeling often suffers from heavy computation due to the dense grid nodes to avoid the numerical dispersion. This study proposes a hybrid dispersion relation preserving (DRP) finite difference to efficiently implement modeling on staggered grid. DRP offers a trade-off between numerical dispersion and accuracy by optimizing finite difference coefficients through least squares fitting within a given wavenumber range. We modify the previous staggered grid DRP schemes to ensure that dispersion error is evenly distributed within the designated wavenumber domain. Then, this is applied to the collocated grid as well, so that advection terms in infrasound governing equations can be handled accordingly. We establish the relationship between the cutoff wavenumber in DRP and minimum points per wavelength (PPW) for modeling, so this relationship suggests minimum PPW required for each finite difference order. Numerical simulations demonstrate that the proposed hybrid DRP outperforms the traditional finite difference method of the same order, particularly in suppressing numerical dispersion. Our modeling is 2D modeling in Cartesian coordinates and is associated with a line source. Therefore, attenuation by geometrical spreading is smaller than that of point source observations. To address this, a line-source to point-source transformation filter is applied to compensate for the attenuation difference, allowing for a direct comparison with observed infrasound signals. The processed synthetic signal shows good agreement with acoustic explosion models, such as Kinney and Graham (1985) model. Lastly, 155 mm artillery acoustic signals are experimentally acquired at distances of 200 m, 1, 3, 5, 10 km, and the source time function was estimated from the recording at 200 m. The synthetic results show a good match with observations from 1 to 10 km, proving that proposed modeling is capable of identifying source properties.
How to cite: Won, M. and Che, I.-Y.: Hybrid dispersion relation preserving finite difference approach to infrasound propagation modeling on staggered grids , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3246, https://doi.org/10.5194/egusphere-egu26-3246, 2026.
Infrasound, and more generally acoustic waves, are omnipresent in the atmosphere due to their intrinsic characteristics and a wide variety of sources. The propagation of these waves is strongly influenced by the properties of the propagation environment, such as the speed of sound and wind. Therefore, observing and studying these waves can reveal important details about the state of the atmosphere.
The concept of using infrasound to improve atmospheric modeling by exploiting the sensitivity of waveforms is illustrated in a preliminary investigation (Gerier et al., 2025). From a data assimilation technique perspective, our goal here is to investigate and extend further their work by adapting the sensitivity kernel of infrasound full waveform to the sensitivity kernel of infrasound arrival times.
Sensitivity of arrival times to a specific model corresponds to the Fréchet derivative of the difference between the arrival time of the observation and that of the synthetic infrasound. First, the synthetic infrasound is computed by solving the linearized Euler equation using finite differences discretization. Then, the Fréchet derivative is obtained by using the adjoint method, which requires solving an adjoint wavefield problem and cross-correlating the adjoint wavefield with the synthetic direct wavefield.
The validation of the arrival time sensitivity kernels is discussed, along with the effects and implication of source frequency. The explosion at the Hukkakero site in Finland is chosen as a case study. A comparison between the sensitivity of waveforms and travel times is also performed.
How to cite: Gerier, S., Martin, R., and Garcia, R. F.: Sensitivity kernels of infrasound travel times to atmospheric parameters: numerical developments, validation and tests cases, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18408, https://doi.org/10.5194/egusphere-egu26-18408, 2026.
The amplitude of infrasonic arrivals at ground level depends on both atmospheric propagation conditions and the three-dimensional geometry of the source. Temperature and wind speed gradients, as well as the source's directivity, can create shadow zones where the geometric acoustic approximation incorrectly predicts no arrival. For instance, during the 2007 Carancas meteorite entry, the I08BO infrasound station was located at the boundary between the geometric arrival zone and the shadow zone. In such configuration, conventional ray-tracing models were unable to simulate the recorded signals while a full wave code, such as Flhoward3D, can simulate arrivals in both zones. However, a small variation in the trajectory azimuth or elevation, or in the sound speed profile, can sharply change the dynamics of the arrivals at the station. To invert the trajectory, we rely on a surrogate model capable of reproducing the discontinuities in the numerical signal predictions.
To address this challenge, our surrogate construction approach proceeds in three steps. First, the parametric domain is partitioned using clustering techniques applied to numerical signals. Each cluster is then associated with a physical behavior, such as a shadow or light zone. Second, a principal component analysis (PCA) is performed for each cluster. Third, the relationship between the PCA coordinates and the input parameters is approximated using least-squares regression.
We compare the method's performance to that of a global surrogate model. Next, the method is applied to invert the Carancas trajectory angles using only arrivals at a single infrasonic station. This work paves the way for inferring wind or gravity wave profiles when infrasound propagation is highly sensitive to small atmospheric variations.
How to cite: Verdier, A., Gainville, O., Marchiano, R., and Sochala, P.: Cluster-based waveform surrogate model for three-dimensional propagation of the sonic boom : an application to Carancas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10899, https://doi.org/10.5194/egusphere-egu26-10899, 2026.
State-of-the-art Earth system models (ESMs) cannot explicitly resolve many small-scale atmospheric processes such as atmospheric gravity waves, and thus must represent, or parameterize, them based on the resolved state. Machine learning (ML) has the potential to address this. In our study, we train neural networks on ERA5 reanalysis data to predict momentum fluxes of orographic gravity waves as function of the lower resolution state variables as would be represented by a coarse ESM. Employing a full year of ERA5 data, we filter inertia-gravity waves by normal-mode function decomposition using the software MODES, and train ML models, more precisely: U-Nets, on data coarse-grained to the ESM's target resolution. We consider four different cases: the full spectrum of resolved inertia-gravity waves or just its subgrid-scale part, both over all land or just over mountainous terrain. Our neural networks successfully predict momentum fluxes, with a global coefficient of determination (R2) ranging from 0.72 to 0.56, depending on the case, when evaluated offline with unseen data. An analysis of our models using SHAP values, an explainable AI technique, shows that the networks are learning physically meaningful relationships. In addition, we give a comparison with the physics-based parameterization scheme by Lott and Miller. These results offer the opportunity for the development of operational ML-based parameterizations to improve the representation of gravity waves and their effects in climate models.
How to cite: Haslauer, E., Schwabe, M., Dörnbrack, A., Gerber, E. P., Rapp, M., Žagar, N., and Eyring, V.: Interpretable Neural Networks to Estimate Momentum Fluxes of Orographic Gravity Waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19244, https://doi.org/10.5194/egusphere-egu26-19244, 2026.
NASA’s Atmospheric Waves Experiment (AWE), installed on the International Space Station in November 2023, provides high-resolution nighttime imaging of mesospheric hydroxyl (OH) airglow emissions near 87 km altitude, enabling detailed observation of atmospheric gravity waves (AGWs) on regional to global scales. With ~2 km horizontal resolution, ~1.1s cadence, and repeated mid-latitude coverage from the ISS orbit, AWE offers new opportunities to investigate the generation and vertical propagation of gravity waves associated with tropospheric weather systems. This study examines European cases of deep convection observed during the current AWE mission lifetime (2023–present), focusing on the identification and characterization of convectively generated AGWs and their vertical coupling through the stratosphere, mesosphere, and ionosphere. Convective activity is identified using publicly available European precipitation radar products, while stratospheric temperature perturbations are analyzed using observations from the Atmospheric Infrared Sounder (AIRS). Mesospheric wave signatures are characterized using AWE airglow imagery, and ionospheric responses are examined using GNSS-derived total electron content (TEC) data from European ground-based GNSS networks. A unified analysis framework incorporating keogram construction and Fourier- and wavelet-based spectral methods is applied to quantify horizontal wavelengths, phase speeds, and propagation characteristics of observed wave fields across atmospheric layers. Similar studies in the CONUS region have indicated coherent AGW signatures spanning multiple altitudes, with mesospheric horizontal wavelengths on the order of tens of kilometers and higher-altitude ionospheric disturbances consistent with medium-scale traveling ionospheric disturbances. The coordinated use of satellite- and ground-based observations is intended to improve identification of gravity wave sources, constrain vertical coupling processes, and assess their role in middle-atmosphere dynamics over Europe. These results highlight the capability of coordinated, multi-instrument observations to resolve gravity wave generation and propagation in the middle atmosphere. The study contributes to improved understanding of middle-atmosphere dynamics, vertical coupling processes, and their implications for atmospheric predictability and modeling.
How to cite: Aguilar Guerrero, J., Bergsson, B., Snively, J., Scherliess, L., Zhao, Y., and Pautet, P.-D.: Multi-instrument Characterization of Convectively Generated Gravity Waves Over Europe Using AWE, AIRS, and GNSS Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22136, https://doi.org/10.5194/egusphere-egu26-22136, 2026.
