Seasonal and QBO variations in the OH nightglow emission observed by TIMED/SABER

Abstract

[1] Using TIMED/SABER observations, we present global distribution of the semiannual oscillation (SAO), annual oscillation (AO), and quasi-biennial oscillation (QBO) in the OH nightglow peak emission rate and height as well as the intensity. The latitudinal variations of the SAO, AO, and QBO in the peak emission rate are similar to those in the intensity. For the peak emission rate and the intensity, the SAO and QBO amplitudes have three peaks (one at the equator and others at about 35°S and 35°N). The AO amplitude peaks at about 20°S and 20°N, respectively. The SAO phase is delayed poleward from the equinoxes at the equator to the solstices at 50°S/N; in addition, the phases of the AO are delayed poleward from 30°S. For the peak height, the SAO and QBO amplitudes have three peaks (around the equator, 40°S, and 40°N). Its AO amplitudes at 50°S and 50°N are larger than those at other latitudes; the phase of the SAO shifts from the solstice at the equator to near the equinoxes at 50°S/N. The airglow QBO is stronger in tropics than midlatitude and is likely the real QBO oscillation at the equator. In addition, the emission in the Southern Hemisphere is weaker than that in the Northern Hemisphere. The SAO and QBO are hemispherically symmetrical, and the AO is hemispherically antisymmetrical at some latitudes. The peak emission rate and peak height SAOs are generally in antiphase. The peak emission rate and intensity SAOs are generally in phase.Citation: Gao, H., J. Xu, and Q. Wu (2010), Seasonal and QBO variations in the OH nightglow emission observed by TIMED/ SABER,

Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

“…An apparent SAO seems to dominate the OH * emission pattern, especially at the equatorial and midlatitudes, and a strong phase propagation of the oscillation towards the poles can be observed. It can also be seen that the OH * emission does not show a constant SAO phase as a function of latitude (see also Gao et al, 2010), similar to the analyzed VLF data. We examined the OH * data (1 • width) at the latitudes that match the middle of the two transmitterreceiver GCPs, during the same time period as the VLF data (2005-2010 for DN-NWC, and 2009-2012 for MH-NSY), by using Eq.…”

“…The OH * airglow layer peaks around 87 km (Baker and Stair Jr., 1988), in the altitude vicinity of the VLF nighttime reflection height. We used the 2.0 µm data as they are a direct measure of the chemical reaction which creates the OH * (Mlynczak, 1999;Mlynczak et al, 2013) and are tightly linked to atomic oxygen abundance as well as MLT dynamics (Gao et al, 2010;Marsh et al, 2006). A 60-day running-mean of the data was created, in order to obtain good local time coverage (Marsh et al, 2006).…”

“…One of these oscillations is the semi-annual oscillation (SAO). Among different parameters, the SAO can be detected in neutral atmospheric measures, e.g., the wind regime in the mesosphere-lower thermosphere (MLT) (e.g., Groves, 1972;Gregory and Manson, 1975;Lysenko et al, 1994); MLT temperatures (e.g., Groves, 1972;Takahashi et al, 1995;Taylor et al, 2005;Huang et al, 2006;Shepherd et al, 2006); and concentrations of atmospheric species, such as atomic oxygen at 80-115 km altitudes (e.g, Russell et al, 2004) and excited hydroxyl (OH * ) molecules around 87 km (e.g., Takahashi et al, 1995;Marsh et al, 2006;Shepherd et al, 2006;Gao et al, 2010). In addition, the charged part of the atmosphere (i.e., the ionosphere), experiences the SAO, which was observed and derived in and from measurements of several parameters, e.g., the ionospheric lower transition height at ∼ 180-260 km (a level where atomic and molecular ion concentrations become equal) (e.g., Lei et al, 2004); the electron and plasma density within the daytime D, E, and F regions of the ionosphere (e.g., Lauter and Nitzsche, 1967;Bremer and Singer, 1977;Forbes et al, 2000;Peters and Entzian, 2015); and also ionospheric total electron content (TEC) (e.g., Zhao et al, 2007;Opio et al, 2015).…”

Optimizing hydroxyl airglow retrievals from long-slit astronomical spectroscopic observations

“…Even though the absolute peak altitudes are known to vary with season (Gao et al, 2010), they can be taken as constant on the timescales of a few minutes over which this experiment was executed. With a steady-state OH model driven using a neutral atmosphere from the Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar Empirical model (NRLMSISE) (Picone et al, 2002), the altitude of the (9,7) transition was fixed.…”

Mesospheric OH layer altitude at midlatitudes: variability over the Sierra Nevada Observatory in Granada, Spain (37° N, 3° W)

“…In addition, sudden stratospheric warmings alter the OH altitude, producing up to 10 km vertical shifts during the descent phase (Shepherd et al, 2010b). On a medium timescale, the seasonal variation in the emission altitudes exhibits semiannual, annual and quasi-biennial oscillations with up to 1.0, 1.5 and 0.5 km amplitudes, respectively (Winick et al, 2009;Gao et al, 2010;Sheese et al, 2014;von Savigny, 2015;Reid et al, 2017). Ghodpage et al (2016) and Sivakandan et al (2016) reported a year-to-year monthly mean OH altitude variation of 2-3 km and attributed it to the effect of the El Niño-Southern Oscillation (ENSO).…”