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- ItemClimatologies and long-term changes in mesospheric wind and wave measurements based on radar observations at high and mid latitudes(Göttingen : Copernicus GmbH, 2019) Wilhelm, S.; Stober, G.; Brown, P.We report on long-term observations of atmospheric parameters in the mesosphere and lower thermosphere (MLT) made over the last 2 decades. Within this study, we show, based on meteor wind measurement, the long-term variability of winds, tides, and kinetic energy of planetary and gravity waves. These measurements were done between the years 2002 and 2018 for the high-latitude location of Andenes (69.3°N, 16°E) and the mid-latitude locations of Juliusruh (54.6°N, 13.4°E) and Tavistock (43.3°N, 80.8°W). While the climatologies for each location show a similar pattern, the locations differ strongly with respect to the altitude and season of several parameters. Our results show annual wind tendencies for Andenes which are toward the south and to the west, with changes of up to 3°m s-1 per decade, while the mid-latitude locations show smaller opposite tendencies to negligible changes. The diurnal tides show nearly no significant long-term changes, while changes for the semidiurnal tides differ regarding altitude. Andenes shows only during winter a tidal weakening above 90°km, while for the Canadian Meteor Orbit Radar (CMOR) an enhancement of the semidiurnal tides during the winter and a weakening during fall occur. Furthermore, the kinetic energy for planetary waves showed strong peak values during winters which also featured the occurrence of sudden stratospheric warming. The influence of the 11-year solar cycle on the winds and tides is presented. The amplitudes of the mean winds exhibit a significant amplitude response for the zonal component below 82°km during summer and from November to December between 84 and 95°km at Andenes and CMOR. The semidiurnal tides (SDTs) show a clear 11-year response at all locations, from October to November. © 2019 by ASME.
- ItemOzone–gravity wave interaction in the upper stratosphere/lower mesosphere(Katlenburg-Lindau : EGU, 2022) Gabriel, AxelThe increase in amplitudes of upward propagating gravity waves (GWs) with height due to decreasing density is usually described by exponential growth. Recent measurements show some evidence that the upper stratospheric/lower mesospheric gravity wave potential energy density (GWPED) increases more strongly during the daytime than during the nighttime. This paper suggests that ozone-gravity wave interaction can principally produce such a phenomenon. The coupling between ozone-photochemistry and temperature is particularly strong in the upper stratosphere where the time-mean ozone mixing ratio decreases with height. Therefore, an initial ascent (or descent) of an air parcel must lead to an increase (or decrease) in ozone and in the heating rate compared to the environment, and, hence, to an amplification of the initial wave perturbation. Standard solutions of upward propagating GWs with linear ozone-temperature coupling are formulated, suggesting amplitude amplifications at a specific level during daytime of 5ĝ€¯% to 15ĝ€¯% for low-frequency GWs (periods ≥4ĝ€¯h), as a function of the intrinsic frequency which decreases if ozone-temperature coupling is included. Subsequently, the cumulative amplification during the upward level-by-level propagation leads to much stronger GW amplitudes at upper mesospheric altitudes, i.e., for single low-frequency GWs, up to a factor of 1.5 to 3 in the temperature perturbations and 3 to 9 in the GWPED increasing from summer low to polar latitudes. Consequently, the mean GWPED of a representative range of mesoscale GWs (horizontal wavelengths between 200 and 1100ĝ€¯km, vertical wavelengths between 3 and 9ĝ€¯km) is stronger by a factor of 1.7 to 3.4 (2 to 50ĝ€¯Jĝ€¯kg-1, or 2ĝ€¯% to 50ĝ€¯% in relation to the observed order of 100ĝ€¯Jĝ€¯kg-1, assuming initial GW perturbations of 1 to 2ĝ€¯K in the middle stratosphere). Conclusively, the identified process might be an important component in the middle atmospheric circulation, which has not been considered up to now.
- ItemGlobal observations of 2 day wave coupling to the diurnal tide in a high‐altitude forecast‐assimilation system(Hoboken, NJ : Wiley, 2017-4-18) Lieberman, R.S.; Riggin, D.M.; Nguyen, V.; Palo, S.E.; Siskind, D.E.; Mitchell, N.J.; Stober, G.; Wilhelm, S.; Livesey, N.J.We examine wave components in a high-altitude forecast-assimilation system that arise from nonlinear interaction between the diurnal tide and the westward traveling quasi 2 day wave. The process yields a westward traveling “sum” wave with zonal wave number 4 and a period of 16 h, and an eastward traveling “difference” wave with zonal wave number 2 and a period of 2 days. While the eastward 2 day wave has been reported in satellite temperatures, the westward 16 h wave lies outside the Nyquist limits of resolution of twice daily local time satellite sampling. Hourly output from a high-altitude forecast-assimilation model is used to diagnose the nonlinear quadriad. A steady state primitive equation model forced by tide-2 day wave advection is used to intepret the nonlinear wave products. The westward 16 h wave maximizes in the midlatitude winter mesosphere and behaves like an inertia-gravity wave. The nonlinearly generated component of the eastward 2 day wave maximizes at high latitudes in the lower thermosphere, and only weakly penetrates to low latitudes. The 16 h and the eastward 2 day waves are of comparable amplitude and alias to the same apparent frequency when viewed from a satellite perspective.
- ItemInfluence of tides and gravity waves on layering processes in the polar summer mesopause region(Göttingen : Copernicus, 2008) Hoffmann, P.; Rapp, M.; Fiedler, J.; Latteck, R.Polar Mesosphere Summer Echoes (PMSE) have been studied at Andenes (69° N, 16° E), Norway, using VHF radar observations since 1994. One remarkable feature of these observations is the fact that {during 50% of the time,} the radar echoes occur in the form of two or more distinct layers. In the case of multiple PMSE layers, statistical analysis shows that the lower layer occurs at a mean height of ∼83.4 km, which is almost identical to the mean height of noctilucent clouds (NLC) derived from observation with the ALOMAR Rayleigh/Mie/Raman lidar at the same site. To investigate the layering processes microphysical model simulations under the influence of tidal and gravity waves were performed. In the presence of long period gravity waves, these model investigations predict an enhanced formation of multiple PMSE layer structures, where the lower layer is a consequence of the occurrence of the largest particles at the bottom of the ice cloud. This explains the coincidence of the lowermost PMSE layers and NLC. During periods with enhanced amplitudes of the semidiurnal tide, the observed NLC and PMSE show pronounced tidal structures comparable to the results of corresponding microphysical simulations. At periods with short period gravity waves there is a tendency for a decreasing occurrence of NLC and for variable weak PMSE structures.
- ItemRetrieving horizontally resolved wind fields using multi-static meteor radar observations(Göttingen : Copernicus GmbH, 2018) Stober, G.; Chau, J.L.; Vierinen, J.; Jacobi, C.; Wilhelm, S.Recently, the MMARIA (Multi-static, Multi-frequency Agile Radar for Investigations of the Atmosphere) concept of a multi-static VHF meteor radar network to derive horizontally resolved wind fields in the mesosphere-lower thermosphere was introduced. Here we present preliminary results of the MMARIA network above Eastern Germany using two transmitters located at Juliusruh and Collm, and five receiving links: two monostatic and three multi-static. The observations are complemented during a one-week campaign, with a couple of addition continuous-wave coded transmitters, making a total of seven multi-static links. In order to access the kinematic properties of non-homogenous wind fields, we developed a wind retrieval algorithm that applies regularization to determine the non-linear wind field in the altitude range of 82-98 km. The potential of such observations and the new retrieval to investigate gravity waves with horizontal scales between 50-200 km is presented and discussed. In particular, it is demonstrated that horizonal wavelength spectra of gravity waves can be obtained from the new data set. © Author(s) 2018.
- ItemSimultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during the WADIS sounding rocket project(Göttingen : Copernicus GmbH, 2019) Strelnikov, B.; Eberhart, M.; Friedrich, M.; Hedin, J.; Khaplanov, M.; Baumgarten, G.; Williams, B.P.; Staszak, T.; Asmus, H.; Strelnikova, I.; Latteck, R.; Grygalashvyly, M.; Lübken, F.-J.; Höffner, J.; Wörl, R.; Gumbel, J.; Löhle, S.; Fasoulas, S.; Rapp, M.; Barjatya, A.; Taylor, M.J.; Pautet, P.-D.In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere-lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties. © 2019 Author(s).
- ItemDerivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer(Katlenburg-Lindau : Copernicus, 2018-5-18) Wüst, Sabine; Offenwanger, Thomas; Schmidt, Carsten; Bittner, Michael; Jacobi, Christoph; Stober, Gunter; Yee, Jeng-Hwa; Mlynczak, Martin G.; Russell III, James M.For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09∘ N, 11.28∘ E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30∘ N, 13.02∘ E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar. In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.