Articles | Volume 12
11 Nov 2014
11 Nov 2014
Extreme ultraviolet (EUV) solar spectral irradiance (SSI) for ionospheric application – history and contemporary state-of-art
G. Schmidtke et al.
Ales Kuchar, Petr Sacha, Roland Eichinger, Christoph Jacobi, Petr Pisoft, and Harald Rieder
We focus on the impact of small-scale orographic gravity waves (OGWs) above the Himalayas. The interaction of GWs with the large-scale circulation in the stratosphere is not still well understood and can have implications on climate projections. We use a chemistry-climate model to show that these strong OGW events are associated with anomalously increased upward planetary-scale waves and in turn affect the circumpolar circulation and have the potential to alter ozone variability as well.
Gunter Stober, Alan Liu, Alexander Kozlovsky, Zishun Qiao, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njal Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, and Nicholas Mitchell
Precise and accurate measurements of vertical winds at the mesosphere and lower thermosphere are rare. Although meteor radars have been used for decades to observe horizontal winds, their ability to derive reliable vertical wind measurements was always questioned. In this article, we provide mathematical concepts to retrieve mathematical and physical consistent solutions, which are compared to the state-of-the-art non-hydrostatic model UA-ICON.
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,Short summary
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,Short summary
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.
Christoph Jacobi, Friederike Lilienthal, Dmitry Korotyshkin, Evgeny Merzlyakov, and Gunter Stober
Adv. Radio Sci., 19, 185–193,Short summary
We compare winds and tidal amplitudes in the upper mesosphere/lower thermosphere region for cases with disturbed and undisturbed geomagnetic conditions. The zonal winds in both the mesosphere and lower thermosphere tend to be weaker during disturbed conditions. The summer equatorward meridional wind jet is weaker for disturbed geomagnetic conditions. The effect of geomagnetic variability on tidal amplitudes, except for the semidiurnal tide, is relatively small.
Gunter Stober, Ales Kuchar, Dimitry Pokhotelov, Huixin Liu, Han-Li Liu, Hauke Schmidt, Christoph Jacobi, Kathrin Baumgarten, Peter Brown, Diego Janches, Damian Murphy, Alexander Kozlovsky, Mark Lester, Evgenia Belova, Johan Kero, and Nicholas Mitchell
Atmos. Chem. Phys., 21, 13855–13902,Short summary
Little is known about the climate change of wind systems in the mesosphere and lower thermosphere at the edge of space at altitudes from 70–110 km. Meteor radars represent a well-accepted remote sensing technique to measure winds at these altitudes. Here we present a state-of-the-art climatological interhemispheric comparison using continuous and long-lasting observations from worldwide distributed meteor radars from the Arctic to the Antarctic and sophisticated general circulation models.
Rajesh Vaishnav, Christoph Jacobi, Jens Berdermann, Mihail Codrescu, and Erik Schmölter
Ann. Geophys., 39, 641–655,Short summary
We investigate the role of eddy diffusion in the delayed ionospheric response against solar flux changes in the solar rotation period using the CTIPe model. The study confirms that eddy diffusion is an important factor affecting the delay of the total electron content. An increase in eddy diffusion leads to faster transport processes and an increased loss rate, resulting in a decrease in the ionospheric delay.
Rajesh Vaishnav, Erik Schmölter, Christoph Jacobi, Jens Berdermann, and Mihail Codrescu
Ann. Geophys., 39, 341–355,Short summary
We investigate the delayed ionospheric response using the observed and CTIPe-model-simulated TEC against the solar EUV flux. The ionospheric delay estimated using model-simulated TEC is in good agreement with the delay estimated for observed TEC. The study confirms the model's capabilities to reproduce the delayed ionospheric response against the solar EUV flux. Results also indicate that the average delay is higher in the Northern Hemisphere as compared to the Southern Hemisphere.
Harikrishnan Charuvil Asokan, Jorge L. Chau, Raffaele Marino, Juha Vierinen, Fabio Vargas, Juan Miguel Urco, Matthias Clahsen, and Christoph Jacobi
Atmos. Chem. Phys. Discuss.,
Preprint withdrawnShort summary
This paper explores the dynamics of gravity waves and turbulence present in the mesosphere and lower thermosphere (MLT) region. We utilized two different techniques on meteor radar observations and simulations to obtain power spectra at different horizontal scales. The techniques are applied to a special campaign conducted in northern Germany in November 2018. The study revealed the dominance of large-scale structures with horizontal scales larger than 500 km during the campaign period.
Ales Kuchar, Petr Sacha, Roland Eichinger, Christoph Jacobi, Petr Pisoft, and Harald E. Rieder
Weather Clim. Dynam., 1, 481–495,Short summary
Our study focuses on the impact of topographic structures such as the Himalayas and Rocky Mountains, so-called orographic gravity-wave hotspots. These hotspots play an important role in the dynamics of the middle atmosphere, in particular in the lower stratosphere. We study intermittency and zonally asymmetric character of these hotspots and their effects on the upper stratosphere and mesosphere using a new detection method in various modeling and observational datasets.
Christoph Geißler, Christoph Jacobi, and Friederike Lilienthal
Ann. Geophys., 38, 527–544,Short summary
This is an extensive model study to analyze the migrating quarterdiurnal solar tide (QDT) and its forcing mechanisms in the middle atmosphere. We first show a climatology of the QDT amplitudes and examine the contribution of the different forcing mechanisms, including direct solar, nonlinear and gravity wave forcing, on the QDT amplitude. We then investigate the destructive interference between the individual forcing mechanisms.
Friederike Lilienthal, Erdal Yiğit, Nadja Samtleben, and Christoph Jacobi
Geosci. Model Dev. Discuss.,
Preprint withdrawnShort summary
Gravity waves are a small-scale but prominent dynamical feature in the Earth's atmosphere. Here, we use a mechanistic nonlinear general circulation model and implement a modern whole atmosphere gravity wave parameterization. We study the response of the atmosphere on several phase speed spectra. We find a large influence of fast travelling waves on the background dynamics in the thermosphere and also a strong dependence of the amplitude of the terdiurnal solar tide, indicating wave interactions.
Erik Schmölter, Jens Berdermann, Norbert Jakowski, and Christoph Jacobi
Ann. Geophys., 38, 149–162,Short summary
This study correlates ionospheric parameters with the integrated solar radiation for an analysis of the delayed ionospheric response in order to confirm previous studies on the delay and to further specify variations of the delay (seasonal and spatial). Results also indicate the dependence on the geomagnetic activity as well as on the 11-year solar cycle. The results are important for the understanding of ionospheric processes and could be used for the validation of ionospheric models.
Nadja Samtleben, Aleš Kuchař, Petr Šácha, Petr Pišoft, and Christoph Jacobi
Ann. Geophys., 38, 95–108,Short summary
The additional transfer of momentum and energy induced by locally breaking gravity wave hotspots in the lower stratosphere may lead to a destabilization of the polar vortex, which is strongly dependent on the position of the hotspot. The simulations with a global circulation model show that hotspots located above Eurasia cause a total decrease in the stationary planetary wave (SPW) activity, while the impact of hotspots located in North America mostly increase the SPW activity.
Rajesh Vaishnav, Christoph Jacobi, and Jens Berdermann
Ann. Geophys., 37, 1141–1159,Short summary
We investigate the ionospheric response to the temporal and spatial dynamics of the solar activity using total electron content (TEC) maps and multiple solar proxies. The maximum correlation at a 16–32-d timescale is observed between the He-II, Mg-II, and F30 with respect to global mean TEC, with an effective time delay of about 1 d. The most suitable proxy to represent the solar activity at the timescales of 16–32 d and 32–64 d is He-II.
Friederike Lilienthal and Christoph Jacobi
Ann. Geophys., 37, 943–953,Short summary
We analyzed the forcing mechanisms of the migrating terdiurnal solar tide in the middle atmosphere, focusing the impact on the zonal mean circulation. We show that the primary solar forcing is the most dominant one but secondary wave–wave interactions also contribute in the lower thermosphere region. We further demonstrate that small-scale gravity waves can strongly and irregularly influence the amplitude of the terdiurnal tide as well as the background circulation in the thermosphere.
Christoph Jacobi and Christina Arras
Adv. Radio Sci., 17, 213–224,Short summary
We analyze tidal phases and related wind shear in the mesosphere and lower thermosphere as observed by a meteor radar. The wind shear phases are compared with those of sporadic E occurrence rates, which were derived from GPS radio occultation observations. We find good correspondence between radar derived wind shear and sporadic E phases for the semidiurnal, terdiurnal, and quarterdiurnal tidal components, but not for the diurnal tide.
Nadja Samtleben, Christoph Jacobi, Petr Pišoft, Petr Šácha, and Aleš Kuchař
Ann. Geophys., 37, 507–523,Short summary
Simulations of locally breaking gravity wave hot spots in the stratosphere show a suppression of wave propagation at midlatitudes, which is partly compensated for by additional wave propagation through the polar region. This leads to a displacement of the polar vortex towards lower latitudes. The effect is highly dependent on the position of the artificial gravity wave forcing. It is strongest (weakest) for hot spots at lower to middle latitudes (higher latitudes).
Christoph Jacobi, Christina Arras, Christoph Geißler, and Friederike Lilienthal
Ann. Geophys., 37, 273–288,Short summary
Sporadic E (Es) layers in the Earth's ionosphere are produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth's magnetic field. We present analyses of the 6 h tidal signatures in ES occurrence rates derived from GPS radio observations. Times of maxima in ES agree well with those of negative wind shear obtained from radar observation. The global distribution of ES amplitudes agrees with wind shear amplitudes from numerical modeling.
Daniel Mewes and Christoph Jacobi
Atmos. Chem. Phys., 19, 3927–3937,Short summary
Horizontal moist static energy (MSE) transport patterns were extracted from reanalysis data using an artificial neuronal network for the winter months. The results show that during the last 30 years transport pathways that favour MSE transport through the North Atlantic are getting more frequent. This North Atlantic pathway is connected to positive temperature anomalies over the central Arctic, which implies a connection between Arctic amplification and the change in horizontal heat transport.
Sven Wilhelm, Gunter Stober, Vivien Matthias, Christoph Jacobi, and Damian J. Murphy
Ann. Geophys., 37, 1–14,Short summary
This study shows that the mesospheric winds are affected by an expansion–shrinking of the mesosphere and lower thermosphere that takes place due to changes in the intensity of the solar radiation, which affects the density within the atmosphere. On seasonal timescales, an increase in the neutral density occurs together with a decrease in the eastward-directed zonal wind. Further, even after removing the seasonal and the 11-year solar cycle variations, we show a connection between them.
Friederike Lilienthal, Christoph Jacobi, and Christoph Geißler
Atmos. Chem. Phys., 18, 15725–15742,Short summary
The terdiurnal solar tide is an atmospheric wave, owing to the daily variation of solar heating with a period of 8 h. Here, we present model simulations of this tide and investigate the relative importance of possible forcing mechanisms because they are still under debate. These are, besides direct solar heating, nonlinear interactions between other tides and gravity wave–tide interactions. As a result, solar heating is most important and nonlinear effects partly counteract this forcing.
Christoph Jacobi, Christoph Geißler, Friederike Lilienthal, and Amelie Krug
Adv. Radio Sci., 16, 141–147,Short summary
The possible sources of the quarterdiurnal tide (QDT) in the middle atmosphere are still under discussion. Therefore, meteor radar winds were analyzed with respect to non-linear interaction, which probably plays a role in winter, but to a lesser degree in summer. Numerical model experiments lead to the conclusion that, although non-linear tidal interaction is indeed one source of the QDT, the major source is direct solar forcing of the 6-hr tidal components.
Erik Schmölter, Jens Berdermann, Norbert Jakowski, Christoph Jacobi, and Rajesh Vaishnav
Adv. Radio Sci., 16, 149–155,Short summary
Physical and chemical processes in the ionosphere are driven by complex interactions with the solar radiation. The ionospheric plasma is in particular sensitive to solar variations with a time delay between one and two days. Here we present preliminary results of the ionospheric delay based on a comprehensive and reliable database consisting of GNSS TEC Maps and EUV spectral flux data.
Rajesh Vaishnav, Christoph Jacobi, Jens Berdermann, Erik Schmölter, and Mihail Codrescu
Adv. Radio Sci., 16, 157–165,Short summary
We investigate the ionospheric response to solar Extreme Ultraviolet (EUV) variations using different solar proxies and IGS TEC maps. An ionospheric delay in GTEC is observed at the 27 days solar rotation period with the time scale of about ~ 1–2 days. Here we present preliminary results from the CTIPe model simulations which qualitatively reproduce the observed ~1-2 days delay in GTEC, which is might be due to vertical transport processes.
Gunter Stober, Jorge L. Chau, Juha Vierinen, Christoph Jacobi, and Sven Wilhelm
Atmos. Meas. Tech., 11, 4891–4907,
Sabine Wüst, Thomas Offenwanger, Carsten Schmidt, Michael Bittner, Christoph Jacobi, Gunter Stober, Jeng-Hwa Yee, Martin G. Mlynczak, and James M. Russell III
Atmos. Meas. Tech., 11, 2937–2947,Short summary
OH*-spectrometer measurements allow the analysis of gravity wave ground-based periods, but spatial information cannot necessarily be deduced. We combine the approach of Wachter at al. (2015) in order to derive horizontal wavelengths (but based on only one OH* spectrometer) with additional information about wind and temperature and compute vertical wavelengths. Knowledge of these parameters is a precondition for the calculation of further information such as the wave group velocity.
Christoph Jacobi, Tatiana Ermakova, Daniel Mewes, and Alexander I. Pogoreltsev
Adv. Radio Sci., 15, 199–206,Short summary
There is continuous interest in coupling processes between the lower and middle atmosphere. Here we analyse midlatitude winds measured by radar at 82–97 km and find that especially in February they are positively correlated with El Niño. The signal is strong for the upper altitudes accessible to the radar, but weakens below. The observations can be qualitatively reproduced by numerical experiments using a mechanistic global circulation model.
Friederike Lilienthal, Christoph Jacobi, Torsten Schmidt, Alejandro de la Torre, and Peter Alexander
Ann. Geophys., 35, 785–798,Short summary
Gravity waves (GWs) are one of the most important dynamical features of the middle atmosphere that extends from the tropopause to the lower thermosphere. They originate from the troposphere and propagate upward. Here, we show the impact of the horizontal GW distribution in the lower atmosphere on the dynamics of the middle atmosphere using a global circulation model. As a result, we find that non-zonal GW structures can force additional stationary planetary waves.
Gunter Stober, Vivien Matthias, Christoph Jacobi, Sven Wilhelm, Josef Höffner, and Jorge L. Chau
Ann. Geophys., 35, 711–720,
Petr Šácha, Friederike Lilienthal, Christoph Jacobi, and Petr Pišoft
Atmos. Chem. Phys., 16, 15755–15775,Short summary
With a mechanistic model for the middle and upper atmosphere we performed sensitivity simulations to study a possible impact of a localized GW breaking hotspot in the eastern Asia–northern Pacific region and also the possible influence of the spatial distribution of gravity wave activity on the middle atmospheric circulation and transport. We show implications for polar vortex stability, in situ PW generation and longitudinal variability and strength of the Brewer–Dobson circulation.
Ch. Jacobi, N. Samtleben, and G. Stober
Adv. Radio Sci., 14, 169–174,Short summary
VHF meteor radar observations of mesosphere/lower thermosphere daily temperatures have been performed at Collm, Germany. The data have been analyzed with respect to long-period oscillations at time scales of 2 to 30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The results are comparable with analyses from radar wind measurements.
Christoph Jacobi, Norbert Jakowski, Gerhard Schmidtke, and Thomas N. Woods
Adv. Radio Sci., 14, 175–180,Short summary
The ionospheric response to solar extreme ultraviolet variability is shown by simple proxies based on Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment solar spectra. The daily proxies are compared with global mean total electron content. At time scales of the solar rotation up to about 40 days there is a time lag between EUV and TEC variability of about one day, with a tendency to increase for longer time scales.
P. Šácha, A. Kuchař, C. Jacobi, and P. Pišoft
Atmos. Chem. Phys., 15, 13097–13112,Short summary
In this study, we present a discovery of an internal gravity wave activity and breaking hotspot collocated with an area of anomalously low annual cycle amplitude and specific dynamics in the stratosphere over the Northeastern Pacific/Eastern Asia coastal region. The reasons why this particular IGW activity hotspot was not discovered before nor the specific dynamics of this region pointed out are discussed together with possible consequences on the middle atmospheric dynamics and transport.
F. Lilienthal and Ch. Jacobi
Atmos. Chem. Phys., 15, 9917–9927,Short summary
The quasi 2-day wave (QTDW), one of the most striking features in the mesosphere/lower thermosphere, is analyzed using meteor radar measurements at Collm (51°N, 13°E) during 2004-2014. The QTDW has periods lasting between 43 and 52h during strong summer bursts, and weaker enhancements are found during winter. A correlation between QTDW amplitudes and wind shear suggests baroclinic instability to be a likely forcing mechanism.
Adv. Radio Sci., 12, 161–165,
F. Lilienthal and Ch. Jacobi
Adv. Radio Sci., 12, 205–210,
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