Articles | Volume 42, issue 1
https://doi.org/10.5194/angeo-42-29-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-42-29-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
20 Feb 2024
Regular paper |
| 20 Feb 2024
| 20 Feb 2024
Observations of polar mesospheric summer echoes resembling kilometer-scale varicose-mode flows
Leibniz Institute of Atmospheric Physics, Schlossstraße 6, 18225 Kühlungsborn, Germany
Jorge L. Chau
Leibniz Institute of Atmospheric Physics, Schlossstraße 6, 18225 Kühlungsborn, Germany
Ralph Latteck
Leibniz Institute of Atmospheric Physics, Schlossstraße 6, 18225 Kühlungsborn, Germany
Toralf Renkwitz
Leibniz Institute of Atmospheric Physics, Schlossstraße 6, 18225 Kühlungsborn, Germany
Marius Zecha
Leibniz Institute of Atmospheric Physics, Schlossstraße 6, 18225 Kühlungsborn, Germany
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Yadu Krishnan Krishnakumar, Toralf Renkwitz, and Andreas Ahrens
Atmos. Chem. Phys., 26, 9571–9587, https://doi.org/10.5194/acp-26-9571-2026, https://doi.org/10.5194/acp-26-9571-2026, 2026
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We report on the observations of radar echoes at the lower HF range from the lower part of the ionosphere, below 60 km altitude. The observed echoes are actually seen below and isolated to the generally accepted lowermost ionospheric D region. For the detection of these echoes we employed machine learning techniques for the inspection of 4 years of radar raw data. We derived statistical parameters of their occurrence and hypothesised a connection for galactic cosmic rays as an ionisation source.
Christoph Jacobi, Ales Kuchar, Manfred Ern, Toralf Renkwitz, Ralph Latteck, and Jorge L. Chau
Adv. Radio Sci., 24, 15–28, https://doi.org/10.5194/ars-24-15-2026, https://doi.org/10.5194/ars-24-15-2026, 2026
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Analyses of more than four decades (1979–2024) of mean horizontal winds in the mesopause region at about 90 km altitude show long-term trends and an influence of the 11-year solar cycle. After the 1990s, both linear trends and the solar cycle effect change and strongly weaken, indicating a change in dynamics or solar forcing. Gravity wave proxies also show a solar cycle effect, which decreases after the 1990s.
Devin Huyghebaert, Juha Vierinen, Björn Gustavsson, Ralph Latteck, Toralf Renkwitz, Marius Zecha, Claudia C. Stephan, J. Federico Conte, Daniel Kastinen, Johan Kero, and Jorge L. Chau
Atmos. Meas. Tech., 19, 4277–4292, https://doi.org/10.5194/amt-19-4277-2026, https://doi.org/10.5194/amt-19-4277-2026, 2026
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The phenomena of meteors occurs at altitudes of 60–120 km and can be used to measure the neutral atmosphere. We use a large high power radar system in Norway (Middle Atmosphere Alomar Radar System (MAARSY)) to measure the meteors and determine changes to the atmospheric density between the years of 2016–2023 at altitudes of 85–115 km. The same time period between years are compared, minimizing changes to the measurements due to factors other than the atmosphere.
Juha Vierinen, Dabrowka Knach, Jorge Luis Chau, Gerd Baumgarten, Devin Huyghebaert, Matthias Clahsen, Nico Pfeffer, Toralf Renkwitz, Robin Wing, Kenneth Obenberger, Björn Gustavsson, and Daniel Kastinen
EGUsphere, https://doi.org/10.5194/egusphere-2026-2857, https://doi.org/10.5194/egusphere-2026-2857, 2026
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We observed the re-entry of a Falcon 9 rocket upper stage over Europe using a network of cameras and radars normally used to study meteors. The measurements showed how hot ionized gas formed around the debris during hypervelocity entry, producing strong radio echoes high in the atmosphere. As the number of satellites and rocket launches increases, these observations can help improve monitoring of space waste re-entering the atmosphere and its possible environmental effects.
Ralph Latteck and Franz-Josef Lübken
Adv. Radio Sci., 24, 1–13, https://doi.org/10.5194/ars-24-1-2026, https://doi.org/10.5194/ars-24-1-2026, 2026
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Using 30 years of radar observations at Andøya, this study presents the world’s longest record of a rare summer phenomenon high above the Arctic. The season lasts about 104 days and is gradually starting earlier and ending later. Even after accounting for solar and geomagnetic effects, a small but steady rise remains. The strongest signals occur about 84 km up and show no long-term change, offering new insight into ongoing shifts in the upper atmosphere.
Alex Timothy Chartier, Ryan Poffenbarger, Rafael Mesquita, Diego Janches, Jorge Chau, Toralf Renkwitz, Ralph Latteck, and William Bristow
EGUsphere, https://doi.org/10.5194/egusphere-2026-1634, https://doi.org/10.5194/egusphere-2026-1634, 2026
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We created a new long-term record of upper atmosphere winds using data from a global network of radars spanning more than 30 years. Because these measurements do not directly show altitude, we developed a method to estimate where the signals come from and tested it against other observations and models. The results show good agreement, meaning these data can now be used with greater confidence to study atmospheric motion and its effects on communication and space systems.
Toralf Renkwitz, Matthias Clahsen, and Ralph Latteck
Atmos. Meas. Tech., 19, 1825–1835, https://doi.org/10.5194/amt-19-1825-2026, https://doi.org/10.5194/amt-19-1825-2026, 2026
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We describe the use of a nearby drifting stratospheric balloon to calibrate three different radar systems. While for radars in the VHF range different calibration options exist, it is much more complicate to do this in the lower HF range. The main complication is the required distance and size of the target, which is especially challenging for vertical pointing radars. We also present the validation of proper phase calibration and the general radiation pattern.
Daniel J. Emmons, Cornelius Csar Jude H. Salinas, Dong L. Wu, Nimalan Swarnalingam, Eugene V. Dao, Jorge L. Chau, Yosuke Yamazaki, Kyle E. Fitch, and Victoriya V. Forsythe
Ann. Geophys., 44, 17–34, https://doi.org/10.5194/angeo-44-17-2026, https://doi.org/10.5194/angeo-44-17-2026, 2026
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The E-region of the Earth’s ionosphere plays an important role in atmospheric energy balance and High Frequency radio propagation. In this paper, we compare predictions from two recently developed ionospheric models to observations by ionospheric sounders (ionosondes). Overall, the models show reasonable agreement with the observations. However, there are several areas for improvement in the models as well as questions about the accuracy of the automatically processed ionosonde dataset.
J. Federico Conte, Jorge L. Chau, Toralf Renkwitz, Ralph Latteck, Masaki Tsutsumi, Christoph Jacobi, Njål Gulbrandsen, and Satonori Nozawa
Ann. Geophys., 43, 603–619, https://doi.org/10.5194/angeo-43-603-2025, https://doi.org/10.5194/angeo-43-603-2025, 2025
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Analysis of 10 years of continuous measurements provided MMARIA/SIMONe Norway and MMARIA/SIMONe Germany reveals that the divergent and vortical motions in the mesosphere and lower thermosphere exchange the dominant role depending on the height and the time of the year. At summer mesopause altitudes over middle latitudes, the horizontal divergence and the relative vorticity contribute approximately the same, indicating an energetic balance between mesoscale divergent and vortical motions.
Christoph Jacobi, Khalil Karami, Ales Kuchar, Manfred Ern, Toralf Renkwitz, Ralph Latteck, and Jorge L. Chau
Adv. Radio Sci., 23, 21–31, https://doi.org/10.5194/ars-23-21-2025, https://doi.org/10.5194/ars-23-21-2025, 2025
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Half-hourly mean winds have been obtained using ground-based low-frequency and very high frequency radio observations of the mesopause region at Collm, Germany, since 1984. Long-term changes of wind variances, which are proxies for short-period atmospheric gravity waves, have been analysed. Gravity wave amplitudes increase with time in winter, but mainly decrease in summer. The trends are consistent with mean wind changes according to wave theory.
Ralph Latteck and Damian J. Murphy
Ann. Geophys., 42, 55–68, https://doi.org/10.5194/angeo-42-55-2024, https://doi.org/10.5194/angeo-42-55-2024, 2024
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This paper gives an overview of continuous measurements of polar mesophere summer echoes (PMSE) by VHF radars at Andøya (69° N) and Davis (69° S). PMSE signal strengths are of the same order of magnitude; significantly fewer PMSE were observed in the Southern than the Northern Hemisphere. Compared to Andøya, the PMSE season over Davis starts ~7 d later and ends 9 d earlier; PMSE occur less frequently but with greater seasonal/diurnal occurrence variability, reaching higher peak altitudes.
Juliana Jaen, Toralf Renkwitz, Huixin Liu, Christoph Jacobi, Robin Wing, Aleš Kuchař, Masaki Tsutsumi, Njål Gulbrandsen, and Jorge L. Chau
Atmos. Chem. Phys., 23, 14871–14887, https://doi.org/10.5194/acp-23-14871-2023, https://doi.org/10.5194/acp-23-14871-2023, 2023
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Investigation of winds is important to understand atmospheric dynamics. In the summer mesosphere and lower thermosphere, there are three main wind flows: the mesospheric westward, the mesopause southward (equatorward), and the lower-thermospheric eastward wind. Combining almost 2 decades of measurements from different radars, we study the trend, their interannual oscillations, and the effects of the geomagnetic activity over these wind maxima.
Christoph Jacobi, Ales Kuchar, Toralf Renkwitz, and Juliana Jaen
Adv. Radio Sci., 21, 111–121, https://doi.org/10.5194/ars-21-111-2023, https://doi.org/10.5194/ars-21-111-2023, 2023
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Middle atmosphere long-term changes show the signature of climate change. We analyse 43 years of mesopause region horizontal winds obtained at two sites in Germany. We observe mainly positive trends of the zonal prevailing wind throughout the year, while the meridional winds tend to decrease in magnitude in both summer and winter. Furthermore, there is a change in long-term trends around the late 1990s, which is most clearly visible in summer winds.
Toralf Renkwitz, Mani Sivakandan, Juliana Jaen, and Werner Singer
Atmos. Chem. Phys., 23, 10823–10834, https://doi.org/10.5194/acp-23-10823-2023, https://doi.org/10.5194/acp-23-10823-2023, 2023
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The paper focuses on remote sensing of the lowermost part of the ionosphere (D region) between ca. 50 and 90 km altitude, which overlaps widely with the mesosphere. We present a climatology of electron density over northern Norway, covering solar-maximum and solar-minimum conditions (2014–2022). Excluding detected energetic particle precipitation events, we derived a quiet-profile climatology. We also found a spring–fall asymmetry, while a symmetric solar zenith angle dependence was expected.
Sumanta Sarkhel, Gunter Stober, Jorge L. Chau, Steven M. Smith, Christoph Jacobi, Subarna Mondal, Martin G. Mlynczak, and James M. Russell III
Ann. Geophys., 40, 179–190, https://doi.org/10.5194/angeo-40-179-2022, https://doi.org/10.5194/angeo-40-179-2022, 2022
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A rare gravity wave event was observed on the night of 25 April 2017 over northern Germany. An all-sky airglow imager recorded an upward-propagating wave at different altitudes in mesosphere with a prominent wave front above 91 km and faintly observed below. Based on wind and satellite-borne temperature profiles close to the event location, we have found the presence of a leaky thermal duct layer in 85–91 km. The appearance of this duct layer caused the wave amplitudes to diminish below 91 km.
Juliana Jaen, Toralf Renkwitz, Jorge L. Chau, Maosheng He, Peter Hoffmann, Yosuke Yamazaki, Christoph Jacobi, Masaki Tsutsumi, Vivien Matthias, and Chris Hall
Ann. Geophys., 40, 23–35, https://doi.org/10.5194/angeo-40-23-2022, https://doi.org/10.5194/angeo-40-23-2022, 2022
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To study long-term trends in the mesosphere and lower thermosphere (70–100 km), we established two summer length definitions and analyzed the variability over the years (2004–2020). After the analysis, we found significant trends in the summer beginning of one definition. Furthermore, we were able to extend one of the time series up to 31 years and obtained evidence of non-uniform trends and periodicities similar to those known for the quasi-biennial oscillation and El Niño–Southern Oscillation.
Ryan Volz, Jorge L. Chau, Philip J. Erickson, Juha P. Vierinen, J. Miguel Urco, and Matthias Clahsen
Atmos. Meas. Tech., 14, 7199–7219, https://doi.org/10.5194/amt-14-7199-2021, https://doi.org/10.5194/amt-14-7199-2021, 2021
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We introduce a new way of estimating winds in the upper atmosphere (about 80 to 100 km in altitude) from the observed Doppler shift of meteor trails using a statistical method called Gaussian process regression. Wind estimates and, critically, the uncertainty of those estimates can be evaluated smoothly (i.e., not gridded) in space and time. The effective resolution is set by provided parameters, which are limited in practice by the number density of the observed meteors.
Fabio Vargas, Jorge L. Chau, Harikrishnan Charuvil Asokan, and Michael Gerding
Atmos. Chem. Phys., 21, 13631–13654, https://doi.org/10.5194/acp-21-13631-2021, https://doi.org/10.5194/acp-21-13631-2021, 2021
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We study large- and small-scale gravity wave cases observed in both airglow imagery and meteor radar data obtained during the SIMONe campaign carried out in early November 2018. We calculate the intrinsic features of several waves and estimate their impact in the mesosphere and lower thermosphere region via transferring energy and momentum to the atmosphere. We also associate cases of large-scale waves with secondary wave generation in the stratosphere.
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Short summary
Scientists are studying the mesosphere and lower thermosphere using radar in northern Norway. They found peculiar events with strong upward and downward air movements, happening frequently (up to 2.5 % per month) from 2015 to 2021. Over 700 such events were noted, lasting around 20 min and expanding the studied layer. A total of 17 % of these events had extreme vertical speeds, showing their unique nature.
Scientists are studying the mesosphere and lower thermosphere using radar in northern Norway....
