Recent progress in mesospheric gravity wave studies using nigthglow imaging system

Abstract

ABSTRACT.A variety of optical remote sensing techniques have now revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicities ranging from ∼5 min to many hours and horizontal scales of a few tens of km to several thousands km, are due to freely propagating atmospheric gravity waves and forced tidal oscillations. Passive optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region (∼80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art groundbased CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180 • ) image measurements are used to illustrate the characteristics of small-scale, short period (<1 hour) waves and to investigate their seasonal propagation and momentum impact on the MLT region. These results are then contrasted with measurements of mesospheric temperature made using a new temperature mapping imaging system capable of determining induced temperature amplitudes of a large range of wave motions and investigating night-to-night and seasonal variability in mesospheric temperature.Keywords: gravity waves, mesospheric dynamics, airglow imaging, seasonal variability. RESUMO.O espectro de ondas na alta atmosfera tem sido revelado por uma variedade de técnicas de sensoriamento remotoótico. Muitas destas perturbações apresentam períodos variando de 5 minutos a algumas horas e escalas horizontais que variam de dezenas a milhares de quilômetros e são devidas a livre propagação de ondas de gravidade e marés atmosféricas. Observaçõesóticas das características espacial e temporal destas ondas na região (∼80-100 km) da mesosfera e baixa termosfera (MLT) utilizam a variação da aeroluminescência atmosférica. Este trabalho descreve o estado da arte das técnicas que utilizam o imageamento via CCD para detectar estas ondas através das variações provocadas na intensidade e temperatura. Medidas de um imageador de céu todo (All-sky, 180 • ) são usadas parar determinar as características de ondas de pequena escala e curto período (<1 hora) e investigar a sazonalidade da direção propagação destas ondas, como também o depósito de momento na região da MLT. Estes resultados são comparados com medidas da temperatura atmosférica realizadas usando um novo sistema de imageamento de mapeamento da temperatura mesosférica capaz de determinar variações nas amplitudes da temperatura provocadas pelas ondas de gravidade através da investigação da variabilidade noturna da temperatura mesosférica.

Simultaneous observations of storm‐generated sprite and gravity wave over Bangladesh

“…The generated gravity waves can propagate upward and can modulate the airglow layers in the 80-100 km height range [Taylor and Hapgood, 1988;Taylor et al, 2007;Snively and Pasko, 2008]. Using the imaging nighttime airglow from ground observation sites [Taylor and Hapgood, 1988;Swenson and Mende, 1994;Chung et al, 2003;Sentman et al, 2003;Taylor et al, 2007;Suzuki et al, 2013;Xu et al, 2015] or spaceborne observation [Dewan et al, 1998;Mende et al, 1998;Yue et al, 2013;Akiya et al, 2014;Xu et al, 2015], gravity waves can be easily identified and observed. In addition, storm-generated gravity waves have also been confirmed by GPS data [Horinouchi and Tsuda, 2009;Lay et al, 2015].…”

Airglow Derived Measurements of Q-Branch Transition Probabilities for Several Hydroxyl Meinel Bands

“…Most frequently the filters J, H, and K are used to isolate the wavelength regions 1.165-1.328 µm, 1.484-1.780 µm, and 2.083-2.363 µm, respectively. The J-band filter spans two OH Meinel transitions, the (7,4) and (8,5), while the H-band filter contains the (3,1), (4,2), (5,3) and (6,4) transitions and the K-band filter spans the (9,7) transition.…”

“…Radiative relaxation of this excited OH in the Meinel system results in the bright near-infrared (NIR) radiation known as OH nightglow or airglow. The OH Meinel emission occurs over an approximately 8 km thick layer [1], and spectroscopic observations of the nightglow have been used to infer the atmospheric conditions at the peak of the layer near 87 km altitude [2][3][4][5][6][7][8].…”

“…Here, we present measurements of the Q-branch Einstein coefficients, relative to the P-or R-branch, for seven vibrational transitions, (3,1), (4,2), (5,3), (6,4), (7,4), (8,5) and (9,7) using two different methods. We show that many of the measured Einstein coefficients are significantly lower than those tabulated in HITRAN [14], suggesting that the angular momentum uncoupling is a general feature that varies with vibrational level.…”

Observation of Quasiperiodic Structures in the Hydroxyl Airglow on Scales Below 100 m

“…The hydroxyl (OH) airglow near 90 km (Meinel, , ) is one of the more intense emissions, and observations of the OH airglow are often employed to measure gravity waves and breaking features in the MLT region (Diettrich et al, ; Fritts et al, ; Li et al, ). Responding to a wide range of vertical wavelengths (Liu & Swenson, ; Swenson & Gardner, ), measurements of the horizontal wavelength of gravity waves have been made with OH airglow imagers (Sedlak et al, ; Taylor et al, ). Studies such as these typically detected atmospheric gravity waves in the OH airglow layer on scales of the order ~1 to hundreds of kilometers.…”