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- ItemQuasi‐10‐Day Wave and Semidiurnal Tide Nonlinear Interactions During the Southern Hemispheric SSW 2019 Observed in the Northern Hemispheric Mesosphere(Hoboken, NJ : Wiley, 2020) He, Maosheng; Chau, Jorge L.; Forbes, Jeffrey M.; Thorsen, Denise; Li, Guozhu; Siddiqui, Tarique Adnan; Yamazaki, Yosuke; Hocking, Wayne K.Mesospheric winds from three longitudinal sectors at 65°N and 54°N latitude are combined to diagnose the zonal wave numbers (m) of spectral wave signatures during the Southern Hemisphere sudden stratospheric warming (SSW) 2019. Diagnosed are quasi-10- and 6-day planetary waves (Q10DW and Q6DW, m = 1), solar semidiurnal tides with m = 1, 2, 3 (SW1, SW2, and SW3), lunar semidiurnal tide, and the upper and lower sidebands (USB and LSB, m = 1 and 3) of Q10DW-SW2 nonlinear interactions. We further present 7-year composite analyses to distinguish SSW effects from climatological features. Before (after) the SSW onset, LSB (USB) enhances, accompanied by the enhancing (fading) Q10DW, and a weakening of climatological SW2 maximum. These behaviors are explained in terms of Manley-Rowe relation, that is, the energy goes first from SW2 to Q10DW and LSB, and then from SW2 and Q10DW to USB. Our results illustrate that the interactions can explain most wind variabilities associated with the SSW. © 2020. The Authors.
- ItemFour-Dimensional Quantification of Kelvin-Helmholtz Instabilities in the Polar SummerMesosphere Using Volumetric Radar Imaging(Hoboken, NJ : Wiley, 2020) Chau, J.L.; Urco, J.M.; Avsarkisov, V.; Vierinen, J.P.; Latteck, R.; Hall, C.M.; Tsutsumi, M.We present and characterize in time and three spatial dimensions a Kelvin-Helmholtz Instability (KHI) event from polar mesospheric summer echoes (PMSE) observed with the Middle Atmosphere Alomar Radar System. We use a newly developed radar imaging mode, which observed PMSE intensity and line of sight velocity with high temporal and angular resolution. The identified KHI event occurs in a narrow layer of 2.4 km thickness centered at 85 km altitude, is elongated along north-south direction, presents separation between billows of ~ 8 km in the east-west direction, and its billow width is ~ 3 km. The accompanying vertical gradients of the horizontal wind are between 35 and 45 m/s/km and vertical velocities inside the billows are ± 12 m/s. Based on the estimated Richardson (< 0.25), horizontal Froude ( ~ 0.8), and buoyancy Reynolds ( ~ 2.5 × 10 4) numbers, the observed event is a KHI that occurs under weak stratification and generates strong turbulence. © 2019. The Authors.
- 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.
- ItemHigh-Order Solar Migrating Tides Quench at SSW Onsets(Hoboken, NJ : Wiley, 2020) He, Maosheng; Forbes, Jeffrey M.; Chau, Jorge L.; Li, Guozhu; Wan, Weixing; Korotyshkin, Dmitry V.Sudden stratospheric warming events (SSWs) are the most spectacular atmospheric vertical coupling processes, well-known for being associated with diverse wave activities in the upper atmosphere and ionosphere. The first four solar tidal harmonics have been reported as being engaged. Here, combining mesospheric winds detected by three midlatitude radars, we demonstrate at least the first six harmonics that occurred during SSW 2018. Wave number diagnosis demonstrates that all six harmonics are dominated by migrating components. Wavelet analyses reveal that the fourth, fifth, and sixth harmonics quench after the SSW onset. The six harmonics and the quenching appear also in a statistical analysis based on near-12-year observations from one of the radars. We attribute the quenching to reversal of the background eastward wind. ©2020. The Authors.
- ItemThe Meteoric Ni Layer in the Upper Atmosphere(Hoboken, NJ : Wiley, 2020) Daly, Shane M.; Feng, Wuhu; Mangan, Thomas P.; Gerding, Michael; Plane, John M.C.The first global atmospheric model of Ni (WACCM-Ni) has been developed to understand recent observations of the mesospheric Ni layer by ground-based resonance lidars. The three components of the model are: the Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neutral, ion-molecule, and photochemical reactions pertinent to the chemistry of Ni in the upper atmosphere. In order to achieve closure on the chemistry, the reaction kinetics of three important reactions were first studied using a fast flow tube with pulsed laser ablation of a Ni target, yielding k(NiO + O) = (4.6 ± 1.4) × 10−11, k(NiO + CO) = (3.0 ± 0.5) × 10−11, and k(NiO2 + O) = (2.5 ± 1.2) × 10−11 cm3 molecule−1 s−1 at 294 K. The photodissociation rate of NiOH was computed to be J(NiOH) = 0.02 s−1. WACCM-Ni simulates satisfactorily the observed neutral Ni layer peak height and width, and Ni+ measurements from rocket-borne mass spectrometry. The Ni layer is predicted to have a similar seasonal and latitudinal variation as the Fe layer, and its unusually broad bottom-side compared with Fe is caused by the relatively fast NiO + CO reaction. The quantum yield for photon emission from the Ni + O3 reaction, observed in the nightglow, is estimated to be between 6% and 40%. ©2020. The Authors.