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- ItemA global atmospheric model of meteoric iron(Hoboken, NJ : Wiley, 2013) Feng, Wuhu; Marsh, Daniel R.; Chipperfield, Martyn P.; Janches, Diego; Höffner, Josef; Yi, Fan; Plane, John M.C.The first global model of meteoric iron in the atmosphere (WACCM-Fe) has been developed by combining three components: the Whole Atmosphere Community Climate Model (WACCM), a description of the neutral and ion-molecule chemistry of iron in the mesosphere and lower thermosphere (MLT), and a treatment of the injection of meteoric constituents into the atmosphere. The iron chemistry treats seven neutral and four ionized iron containing species with 30 neutral and ion-molecule reactions. The meteoric input function (MIF), which describes the injection of Fe as a function of height, latitude, and day, is precalculated from an astronomical model coupled to a chemical meteoric ablation model (CABMOD). This newly developed WACCM-Fe model has been evaluated against a number of available ground-based lidar observations and performs well in simulating the mesospheric atomic Fe layer. The model reproduces the strong positive correlation of temperature and Fe density around the Fe layer peak and the large anticorrelation around 100 km. The diurnal tide has a significant effect in the middle of the layer, and the model also captures well the observed seasonal variations. However, the model overestimates the peak Fe+concentration compared with the limited rocket-borne mass spectrometer data available, although good agreement on the ion layer underside can be obtained by adjusting the rate coefficients for dissociative recombination of Fe-molecular ions with electrons. Sensitivity experiments with the same chemistry in a 1-D model are used to highlight significant remaining uncertainties in reaction rate coefficients, and to explore the dependence of the total Fe abundance on the MIF and rate of vertical transport.
- ItemLong‐Term Changes in the Northern Midwinter Middle Atmosphere in Relation to the Quasi‐Biennial Oscillation(Hoboken, NJ : Wiley, 2019) Gabriel, A.Long-term changes in the middle atmosphere due to anthropogenic greenhouse gas emissions are examined in relation to the effect of the equatorial Quasi-Biennial Oscillation (QBO) on the northern midwinter circulation. The examinations are based on the Coupled Model Intercomparison Project Phase 5 simulations for 1979–2100 with the Earth-System-Model MPI-ESM-MR that generates the QBO internally. In particular, the three-dimensional residual circulation is used as proxy for the Brewer-Dobson circulation, revealing an increasing downwelling in the center of the polar low over Northern Europe/Siberia (~5% per decade). The changes in northern midwinter temperature, zonal wind, and residual circulation are much stronger during westerly (QBO-W) than easterly (QBO-E) phase of QBO (e.g., for a moderate increase in greenhouse gases, we find maximum decreases in the zonal mean westerly jet at 60°N and 3 hPa of about −14.8 ± 5.4 m/s for QBO-W but only −4.7 ± 5.2 m/s for QBO-E). This is due to a change of the extratropical QBO-W signature toward QBO-E signature while the equatorial QBO remains nearly unchanged (i.e., a change toward disappearance of the so-called Holton-Tan relationship). Similar to the current change from QBO-W to QBO-E signature, the changes during QBO-W include an increase in amplitude and eastward shift in phase of stratospheric stationary Wave 1 at the cost of Wave 2, with decreasing westerlies over North America and increasing downwelling over Siberia. The eastward shift in phase of stationary Wave 1 is related to the associated increase in meridional transport of planetary vorticity. © 2019. The Authors.
- ItemCharacteristics of the Quiet-Time Hot Spot GravityWaves Observed by GOCE Over the Southern Andes on 5 July 2010(Hoboken, NJ : Wiley, 2019) Vadas, Sharon L.; Xu, Shuang; Yue, Jia; Bossert, Katrina; Becker, Erich; Baumgarten, GerdWe analyze quiet-time data from the Gravity Field and Ocean Circulation Explorer satellite as it overpassed the Southern Andes at z≃275 km on 5 July 2010 at 23 UT. We extract the 20 largest traveling atmospheric disturbances from the density perturbations and cross-track winds using Fourier analysis. Using gravity wave (GW) dissipative theory that includes realistic molecular viscosity, we search parameter space to determine which hot spot traveling atmospheric disturbances are GWs. This results in the identification of 17 GWs having horizontal wavelengths λH = 170–1,850 km, intrinsic periods τIr = 11–54 min, intrinsic horizontal phase speeds cIH = 245–630 m/s, and density perturbations (Formula presented.) 0.03–7%. We unambiguously determine the propagation direction for 11 of these GWs and find that most had large meridional components to their propagation directions. Using reverse ray tracing, we find that 10 of these GWs must have been created in the mesosphere or thermosphere. We show that mountain waves (MWs) were observed in the stratosphere earlier that day and that these MWs saturated at z∼ 70–75 km from convective instability. We suggest that these 10 Gravity Field and Ocean Circulation Explorer hot spot GWs are likely tertiary (or higher-order) GWs created from the dissipation of secondary GWs excited by the local body forces created from MW breaking. We suggest that the other GW is likely a secondary or tertiary (or higher-order) GW. This study strongly suggests that the hot spot GWs over the Southern Andes in the quiet-time middle winter thermosphere cannot be successfully modeled by conventional global circulation models where GWs are parameterized and launched in the troposphere or stratosphere. ©2019. The Authors.
- ItemPMC Turbo : Studying Gravity Wave and Instability Dynamics in the Summer Mesosphere Using Polar Mesospheric Cloud Imaging and Profiling From a Stratospheric Balloon(Hoboken, NJ : Wiley, 2019) Fritts, David C.; Miller, Amber D.; Kjellstrand, C. Bjorn; Geach, Christopher; Williams, Bifford P.; Kaifler, Bernd; Kaifler, Natalie; Jones, Glenn; Rapp, Markus; Limon, Michele; Reimuller, Jason; Wang, Ling; Hanany, Shaul; Gisinger, Sonja; Zhao, Yucheng; Stober, Gunter; Randall, Cora E.The Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment was designed to observe and quantify the dynamics of small-scale gravity waves (GWs) and instabilities leading to turbulence in the upper mesosphere during polar summer using instruments aboard a stratospheric balloon. The PMC Turbo scientific payload comprised seven high-resolution cameras and a Rayleigh lidar. Overlapping wide and narrow camera field of views from the balloon altitude of ~38 km enabled resolution of features extending from ~20 m to ~100 km at the PMC layer altitude of ~82 km. The Rayleigh lidar provided profiles of temperature below the PMC altitudes and of the PMCs throughout the flight. PMCs were imaged during an ~5.9-day flight from Esrange, Sweden, to Northern Canada in July 2018. These data reveal sensitivity of the PMCs and the dynamics driving their structure and variability to tropospheric weather and larger-scale GWs and tides at the PMC altitudes. Initial results reveal strong modulation of PMC presence and brightness by larger-scale waves, significant variability in the occurrence of GWs and instability dynamics on time scales of hours, and a diversity of small-scale dynamics leading to instabilities and turbulence at smaller scales. At multiple times, the overall field of view was dominated by extensive and nearly continuous GWs and instabilities at horizontal scales from ~2 to 100 km, suggesting sustained turbulence generation and persistence. At other times, GWs were less pronounced and instabilities were localized and/or weaker, but not absent. An overview of the PMC Turbo experiment motivations, scientific goals, and initial results is presented here. © 2019. The Authors.
- ItemSolar cycle response and long-term trends in the mesospheric metal layers(Hoboken, NJ : Wiley, 2016) Dawkins, E.C.M.; Plane, J.M.C.; Chipperfield, M.P.; Feng, W.; Marsh, D.R.; Höffner, J.; Janches, D.The meteoric metal layers (Na, Fe, and K)—which form as a result of the ablation of incoming meteors—act as unique tracers for chemical and dynamical processes that occur within the upper mesosphere/lower thermosphere region. In this work, we examine whether these metal layers are sensitive indicators of decadal long-term changes within the upper atmosphere. Output from a whole-atmosphere climate model is used to assess the response of the Na, K, and Fe layers across a 50 year period (1955–2005). At short timescales, the K layer has previously been shown to exhibit a very different seasonal behavior compared to the other metals. Here we show that this unusual behavior is also exhibited at longer timescales (both the ~11 year solar cycle and 50 year periods), where K displays a much more pronounced response to atmospheric temperature changes than either Na or Fe. The contrasting solar cycle behavior of the K and Na layers predicted by the model is confirmed using satellite and lidar observations for the period 2004–2013.
- ItemZonalWave Number Diagnosis of RossbyWave-Like Oscillations Using Paired Ground-Based Radars(Hoboken, NJ : Wiley, 2020) He, Maosheng; Yamazaki, Yosuke; Hoffmann, Peter; Hall, Chris M.; Tsutsumi, Masaki; Li, Guozhu; Chau, Jorge LuisFree traveling Rossby wave normal modes (RNMs) are often investigated through large-scale space-time spectral analyses, which therefore is subject to observational availability, especially in the mesosphere. Ground-based mesospheric observations were broadly used to identify RNMs mostly according to the periods of RNMs without resolving their horizontal scales. The current study diagnoses zonal wave numbers of RNM-like oscillations occurring in mesospheric winds observed by two meteor radars at about 79°N. We explore four winters comprising the major stratospheric sudden warming events (SSWs) 2009, 2010, and 2013. Diagnosed are predominant oscillations at the periods of 10 and 16 days lasting mostly for three to five whole cycles. All dominant oscillations are associated with westward zonal wave number m=1, excepting one 16-day oscillation associated with m=2. We discuss the m=1 oscillations as transient RNMs and the m=2 oscillation as a secondary wave of nonlinear interaction between an RNM and a stationary Rossby wave. All the oscillations occur around onsets of the three SSWs, suggesting associations between RNMs and SSWs. For comparison, we also explore the wind collected by a similar network at 54°N during 2012–2016. Explored is a manifestation of 5-day wave, namely, an oscillation at 5–7 days with m=1), around the onset of SSW 2013, supporting the associations between RNMs and SSWs. ©2020. The Authors.
- ItemLidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations(Hoboken, NJ : Wiley, 2018-8-6) Chu, Xinzhao; Zhao, Jian; Lu, Xian; Harvey, V. Lynn; Jones, R. Michael; Becker, Erich; Chen, Cao; Fong, Weichun; Yu, Zhibin; Roberts, Brendan R.; Dörnbrack, AndreasFive years of Fe Boltzmann lidar's Rayleigh temperature data from 2011 to 2015 at McMurdo are used to characterize gravity wave potential energy mass density (Epm), potential energy volume density (Epv), vertical wave number spectra, and static stability N² in the stratosphere 30–50 km. Epm (Epv) profiles increase (decrease) with altitude, and the scale heights of Epv indicate stronger wave dissipation in winter than in summer. Altitude mean (Formula presented.) and (Formula presented.) obey lognormal distributions and possess narrowly clustered small values in summer but widely spread large values in winter. (Formula presented.) and (Formula presented.) vary significantly from observation to observation but exhibit repeated seasonal patterns with summer minima and winter maxima. The winter maxima in 2012 and 2015 are higher than in other years, indicating interannual variations. Altitude mean (Formula presented.) varies by ~30–40% from the midwinter maxima to minima around October and exhibits a nearly bimodal distribution. Monthly mean vertical wave number power spectral density for vertical wavelengths of 5–20 km increases from summer to winter. Using Modern Era Retrospective Analysis for Research and Applications version 2 data, we find that large values of (Formula presented.) during wintertime occur when McMurdo is well inside the polar vortex. Monthly mean (Formula presented.) are anticorrelated with wind rotation angles but positively correlated with wind speeds at 3 and 30 km. Corresponding correlation coefficients are −0.62, +0.87, and +0.80, respectively. Results indicate that the summer-winter asymmetry of (Formula presented.) is mainly caused by critical level filtering that dissipates most gravity waves in summer. (Formula presented.) variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.
- ItemEvidence for the In‐Situ Generation of Plasma Depletion Structures Over the Transition Region of Geomagnetic Low‐Mid Latitude(Hoboken, NJ : Wiley, 2021) Sivakandan, M.; Mondal, S.; Sarkhel, S.; Chakrabarty, D.; Sunil Krishna, M.V.; Upadhayaya, A.K.; Shinbori, A.; Sori, T.; Kannaujiya, S.; Champati Ray, P.K.On a geomagnetic quiet night of October 29, 2018, we captured an observational evidence of the onset of dark band structures within the field-of-view of an all-sky airglow imager operating at 630.0 nm over a geomagnetic low-mid latitude transition region, Hanle, Leh Ladakh. Simultaneous ionosonde observations over New Delhi shows the occurrence of spread-F in the ionograms. Additionally, virtual and peak height indicate vertical upliftment in the F layer altitude and reduction in the ionospheric peak frequency were also observed when the dark band pass through the ionosonde location. All these results confirmed that the observed depletions are indeed associated with ionospheric F region plasma irregularities. The rate of total electron content index (ROTI) indicates the absence of plasma bubble activities over the equatorial/low latitude region which confirms that the observed event is a mid-latitude plasma depletion. Our calculations reveal that the growth time of the plasma depletion is ∼2 h if one considers only the Perkins instability mechanism. This is not consistent with the present observations as the plasma depletion developed within ∼25 min. By invoking possible Es layer instabilities and associated E-F region coupling, we show that the growth rate increases roughly by an order of magnitude. This strongly suggests that the Cosgrove and Tsunoda mechanism may be simultaneously operational in this case. Furthermore, it is also suggested that reduced F region flux-tube integrated conductivity in the southern part of onset region created conducive background conditions for the growth of the plasma depletion on this night.
- ItemObservations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming(Hoboken, NJ : Wiley, 2018-12-11) Triplett, Colin C.; Li, Jintai; Collins, Richard L.; Lehmacher, Gerald A.; Barjatya, Aroh; Fritts, David C.; Strelnikov, Boris; Lübken, Franz‐Josef; Thurairajah, Brentha; Harvey, V. Lynn; Hampton, Donald L.; Varney, Roger H.Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters.
- ItemMulti‐Point Measurements of the Plasma Properties Inside an Aurora From the SPIDER Sounding Rocket(Hoboken, NJ : Wiley, 2021) Giono, Gabriel; Ivchenko, Nickolay; Sergienko, Tima; Brändström, UrbanThe Small Payloads for Investigation of Disturbances in Electrojet by Rockets (SPIDER) sounding rocket was launched on February 2nd, 2016 (21:09 UT), deploying 10 free falling units (FFUs) inside a westward traveling auroral surge. Each FFUs deployed spherical electric field and Langmuir probes on wire-booms, providing in situ multi-point recordings of the electric field and plasma properties. The analytical retrieval of the plasma parameters, namely the electron density, electron temperature and plasma potential, from the Langmuir probe measurements was non-trivial due to sheath effects and detailed explanation are discussed in this article. An empirical assumption on the sheath thickness was required, which was confirmed by simulating the plasma environment around the FFU using the Spacecraft Plasma Interaction Software (SPIS). In addition, the retrieved electron density and temperature are also in agreement with the simultaneous incoherent scatter radar measurements from the EISCAT facility. These two independent confirmations provided a good level of confidence in the plasma parameters obtained from the FFUs, and events observed during the flight are discussed in more details. Hints of drift-wave instabilities and increased currents inside a region of enhanced density were observed by the FFUs.
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