How to cite: Zhou, X.: Quiet‐Time Day‐to‐Day Variability of Equatorial Vertical E × B Drift From Atmosphere Perturbations at Dawn, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3361, https://doi.org/10.5194/egusphere-egu22-3361, 2022.

The ionosphere exhibits enhanced semi-diurnal lunitidal (M2) perturbations during sudden stratospheric warming (SSW) events, of which the manifestation and mechanism are not well documented and understood. We studied the latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW with total electron content (TEC) data in the American and eastern Asia-Australia sectors. Results show that the M2 perturbations in the two sectors all enhanced during the SSW. The largest M2 amplitudes in the Northern and Southern Hemispheres appear at about 15°N and 20°S geomagnetic latitudes, respectively, with stronger magnitude in the Northern Hemisphere. Also, M2 perturbations in the two sectors all extend to middle latitudes only in the Southern Hemisphere and show local maxima around 35~40°S geomagnetic latitudes. The similar latitudinal and interhemispheric variations of the low-latitude M2 perturbtations in the two sectors indicate that such variations may be mainly caused by the meridional wind modulation on the equatorial plasma fountain. Meanwhile, the longitudinal differences are also noticeable. The TEC M2 amplitude in the American sector is obviously larger than that in the eastern Asia-Australia sector, especially in the southern middle latitude. The M2 perturbations in the American southern middle latitude may be influenced by the combined effect of the zonal wind and local positive magnetic declination in the Weddell Sea Anomaly region.

How to cite: Liu, J., Zhang, D., Hao, Y., and Xiao, Z.: The latitudinal and interhemispheric variations of the ionospheric M2 perturbations during the 2009 SSW in the American and eastern Asia-Australia sectors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8318, https://doi.org/10.5194/egusphere-egu22-8318, 2022.

The coupled response of the atmosphere-ionosphere system to planetary waves propagating from below has been observed through MF and Meteor radars at different longitudes along with the ground geomagnetic data from 23 stations of Northern (NH) and Southern Hemisphere (SH) during northern winter months of January, 2015 and 2017. The focus is on delineating the quasi-2-day (Q2DW) and quasi-6-day wave signatures in the mesosphere-lower thermosphere (MLT) and in ionospheric Sq currents besides deciphering their effects on the overall neutral dynamics at low latitudes. Analysis extended to longitudinally separated stations confirms the penetration of these planetary waves into the ionosphere either directly or indirectly through interaction with other wave modes in the MLT region.

How to cite: Jadhav, A., Subramanian, G., and Patil, P.: Planetary wave activity observed in atmosphere-ionosphere system over low latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9390, https://doi.org/10.5194/egusphere-egu22-9390, 2022.

In this study, the variability of migrating solar diurnal (DW1) tide in the mesosphere-lower thermosphere (MLT) region during Northern and Southern Hemisphere (NH & SH) Sudden Stratospheric Warmings (SSWs) is investigated using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature  observations and reanalysis-driven Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) simulations. The periods examined include four major NH SSWs that occurred during January in 2006, 2009, 2010 and 2013 and two SH SSWs that were recorded in September in 2002 and 2019. Our analysis shows that the observed DW1 tide displays a marked decline in the equatorial region after the onset of NH and SH SSWs. As WACCM-X simulations qualitatively reproduce this feature of DW1 tidal variability common to both NH and SH SSWs, they have been used to examine the possible mechanism that could explain these observations in DW1 tide. It is known that changes in the latitudinal shear of zonal winds at low-latitudes strongly affect the seasonal variation of DW1 tide in the MLT. We explore this mechanism to show that SSW-associated changes in the latitudinal shear in the MLT could be used to explain the observed variability of DW1 tide during NH and SH SSWs.

How to cite: Siddiqui, T. A., Stolle, C., and Yamazaki, Y.: Migrating solar diurnal tidal variability during Northern and Southern Hemisphere Sudden Stratospheric Warmings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11327, https://doi.org/10.5194/egusphere-egu22-11327, 2022.

For a better understanding of atmospheric dynamics, it is very important to know the general condition (dynamics and chemistry) in the atmosphere. Aeolus wind measurements provide wind measurements from satellite instrument. ERA 5 can produce very detailed information about dynamics without gaps in time series in high resolution (0.25°). Planetary waves (PWs) are global scale waves, which are well-known as main drivers of the large-scale weather patterns in mid-latitudes on time scales from several days up to weeks in the troposphere. When PWs break, they often cut pressure cells off the jet stream. A specific example are so-called streamer events, which occur predominantly in the mid- and high-latitudes of the lower stratosphere. Streamers are characterized by ozone-poor airmasses occuring mainly in the Northern Atlantic / European section and leading to various consequences due to a strong increase of UV radiation. We compare ERA5 reanalysis with Aeolus measurements. This comparison can bring us an answer if we can use ERA5 instead of Aeolus measurements in case of time gaps. We also use homogeneity test for ERA5 time series. Moreover, we also analyze characteristics of gravity waves (GW) in the ionosphere using continuous Doppler sounding and in the troposphere using large aperture array of microbarometers. Similarly, ground based infrasound monitoring is performed. We investigate, if there are any changes of GW or infrasound characteristics related to stratospheric processes, e.g., streamer events.

How to cite: Kozubek, M., Lastovicka, J., Chum, J., Sindelarova, T., Podolska, K., Kuechelbacher, L., Wuest, S., and Bittner, M.:  First results from comparison ERA5 and Aeolus measurements: Lidar measurements to Identify Streamers and analyze Atmospheric waves (LISA) (Aeolus+Innovation), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-880, https://doi.org/10.5194/egusphere-egu22-880, 2022.

In the mesosphere and lower-thermosphere, quasi-2-day waves are spectacular planetary-scale oscillations. Almost all relevant observational studies are based on ground-based single-station or single-satellite methods and, therefore, cannot determine the zonal wavenumber unambiguously. We employ a series of multi-station methods on winds measured by four longitudinally separated low-latitude ground-based radars in the current work. These methods help us to determine two dominant zonal wavenumbers at 80–100 km altitude. These results are used to complement satellite measurements. The agreement between datasets is extraordinary, allowing us to extend the characteristics of the waves to higher altitudes using satellite measurements.

The current work was published in He et al. (2021, https://doi.org/10.1029/93jd00380), which was extended into a broad altitude range up to the topside F-region in Forbes et al. (2021, https://doi.org/10.1029/2021JA029961).

How to cite: He, M., Chau, J. L., Forbes, J. M., Zhang, X., Englert, C. R., Harding, B. J., Immel, T. J., Lima, L. M., Rao, S. V. B., Ratnam, M. V., Li, G., Harlander, J. M., Marr, K. D., and Makela, J. J.: Quasi-2-Day Wave in Low-Latitude Atmospheric Winds as Viewed From the Ground and Space During January–March, 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2763, https://doi.org/10.5194/egusphere-egu22-2763, 2022.

Multi-step vertical coupling (MSVC) describes a paradigm shift regarding the role of gravity waves (GWs) in the winter middle and upper atmosphere. It is well known that primary GWs propagate into the winter stratosphere and lower mesosphere, where they dissipate. However, since this process is localized in space and intermittent, secondary GWs are generated. These propagate into the lower thermosphere, dissipate, and generate tertiary GWs and so forth. Recent modeling and observational studies showed that secondary and tertiary GWs from MSVC are the predominant GWs in the upper mesosphere and in the thermosphere during wintertime. MSVC cannot be simulated with GW parameterizations as used in conventional whole atmosphere models.

In this presentation, we describe the HIgh Altitude Mechanistic general Circulation Model (HIAMCM), which resolves medium-scale GWs from the surface up to z~450 km, including MSVC induced by primary GWs from jets, fronts, and orography. This is made possible by combining a sufficiently high spatial resolution with advanced methods for turbulent and molecular diffusion. Furthermore, the HIAMCM can be nudged to MERRA-2 reanalysis in the troposphere and stratosphere. The nudging is performed in spectral space and restricted to horizontal wavelenghs larger than ~1500-2000 km. As a result, the generation, propagation, and dissipation of resolved GWs is not affected by the nudging and simulated like in the free-running model. We present recent applications of the HIAMCM regarding 1) the role of secondary GWs in the winter polar mesopause region, 2) the wintertime thermospheric GW hotspot over the Southern Andes/Antarctic Peninsula, and 3) the southward propagation of thermospheric GWs during daytime (as a driver for corresponding traveling ionospheric disturbances). Furthermore, we contrast the MSVC during the strong polar vortex period in December 2016 to the MSVC during the sudden stratospheric warming in January/February 2017.

How to cite: Becker, E., Vadas, S. L., Goncharenko, L., and Harvey, V. L.: Multi-step vertical coupling from the troposphere to the thermosphere due to gravity waves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10900, https://doi.org/10.5194/egusphere-egu22-10900, 2022.

The polar vortices play a central role in vertically coupling the Sun-Earth system by facilitating the descent of reactive odd nitrogen (NO_x = NO + NO₂) produced in the atmosphere by energetic particle precipitation (EPP-NO_x). Downward transport of EPP-NO_x from the mesosphere-lower thermosphere (MLT) to the stratosphere inside the winter polar vortex is particularly impactful in the wake of prolonged sudden stratospheric warming (SSW) events. This work is motivated by the fact that state-of-the-art global climate models severely underestimate EPP-NO_x abundances in the polar MLT. It is not clear whether this deficiency is due to a missing NO_x source or to inadequate transport processes. As a step toward understanding the transport pathways by which MLT air enters the top of the polar vortex, we explore the extent to which planetary waves impact the geographic distribution of NO near the polar winter mesopause in the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension combined with data assimilation using the Data Assimilation Research Testbed (WACCMX+DART). We present planetary wave-driven NO patterns near the polar winter mesopause during 16 case studies from the Arctic winters of 2005/2006 through 2018/2019. During all cases the model is in reasonable agreement with Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) derived zonal winds and Solar Occultation For Ice Experiment (SOFIE) and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) NO measurements. Superposed Epoch Analysis is employed to diagnose typical mesopause planetary wave behavior and vertical transport characteristics during 10 minor and 6 major SSW events. Results show that descent of NO into the top of the polar vortex is enhanced by about a factor of 4 in traveling planetary wave troughs vs. in ridges and that this planetary wave-driven enhanced NO descent occurs during both minor and major SSW events. These results present a new conceptual model of zonally varying, vs. zonally uniform, polar descent in the MLT.

How to cite: Harvey, V. L., Pedatella, N., Datta-Barua, S., Randall, C., Siskind, D., Greer, K., and Goncharenko, L.: Planetary wave-driven enhanced NO descent into the top of the Arctic polar vortex during major and minor sudden stratospheric warmings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1136, https://doi.org/10.5194/egusphere-egu22-1136, 2022.

The importance of the realistic predictions of the climate variability in the whole atmosphere system, vertical and horizontal teleconnections between the stratospheric QBO and SAO and ITM dynamics are now well recognized. The paper presents a brief summary of the QBO impact on the MLT neutral dynamics seen from the last decade of ITM observations and predictions by two whole atmosphere models constrained in the lower atmosphere by GEOS meteorology of NASA/GMAO. We present the initial modeling and observational evidences that the QBO-related variations in the MLT thermal tides can modulate the equatorial ionospheric anomaly wave-4 and wave-3 longitudinal structure affecting the ITM system on regional scales. Several hypotheses about the influence of the stratospheric QBO on the ionosphere due to the combined influences of migrating and non-migrating tides will be suggested based on the preliminary multi-year observational analysis of TEC data.   

How to cite: Yudin, V., Goncharenko, L., Karol, S., Lieberman, R., Liu, H., McInerney, J., and Pedatella, N.: Global Teleconnections between QBO Dynamics and ITM Anomalies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3552, https://doi.org/10.5194/egusphere-egu22-3552, 2022.