Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78° N, 16° E)

Abstract

Abstract. Measurements of hydroxyl nightglow emissions over Longyearbyen (78 • N, 16 • E) recorded simultaneously by the SABER instrument onboard the TIMED satellite and a ground-based Ebert-Fastie spectrometer have been used to derive an empirical formula for the height of the OH layer as a function of the integrated emission rate (IER). Altitude profiles of the OH volume emission rate (VER) derived from SABER observations over a period of more than six years provided a relation between the height of the OH layer peak and the integrated emission rate following the procedure described by Liu and Shepherd (2006). An extended period of overlap of SABER and ground-based spectrometer measurements of OH(6-2) IER during the 2003-2004 winter season allowed us to express ground-based IER values in terms of their satellite equivalents. The combination of these two formulae provided a method for inferring an altitude of the OH emission layer over Longyearbyen from ground-based measurements alone. Such a method is required when SABER is in a southward looking yaw cycle. In the SABER data for the period 2002-2008, the peak altitude of the OH layer ranged from a minimum near 76 km to a maximum near 90 km. The uncertainty in the inferred altitude of the peak emission, which includes a contribution for atmospheric extinction, was estimated to be ±2.7 km and is comparable with the ±2.6 km value quoted for the nominal altitude (87 km) of the OH layer. Longer periods of overlap of satellite and ground-based measurements together with simultaneous onsite measurements of atmospheric extinction could reduce the uncertainty to approximately 2 km.

Hydroxyl layer: trend of number density and intra-annual variability

“…The peak height decreases with increasing latitude. Qualitatively similar results were presented by Liu and Shepherd (2006) for data collected by WINDII on 29 August 1992, who showed an anticorrelation between the layer altitude and the integrated emission rates of the OH * emission profiles for the latitudinal band between 32.5 and 37.5 • N. Also, Mulligan et al (2009) found an inverse behavior between layer height and OH * intensity in high latitude (78 • N) inferred from SABER measurements on the TIMED satellite. For an essentially larger time and latitudinal interval, von Savigny (2015) Grygalashvyly et al (2014): the concentration of OH * is directly proportional to pressure and, consequently, inversely proportional to altitude.…”

“…1995a, 1995b, 1997), Yee et al (1997), She and Lowe (1998), Reisin (2000, 2010), Bittner et al (2000Bittner et al ( , 2002, Yamada et al (2001), Liu and Shepherd (2006), Reisin and Scheer (2004), Espy et al (2007, Mulligan et al (2009), Xu et al (2010, and von Savigny et al (2012Savigny et al ( , 2015. In an earlier paper, Yee et al (1997) stated that the quantitative comparison between theoretical and experimental brightness is rather poor.…”

Several notes on the OH* layer

“…Then, they subdivided latitudinal band into five bins and derived coefficients for each one. In a later study, the coefficients for the given empirical formula were derived for 78 ± 5 • N (Mulligan et al, 2009). This is evident from analytical Eq.…”

“…This subject was empirically investigated in a number of works (Yee et al, 1997;Liu and Shepherd, 2006;Mulligan et al, 2009). Liu and Shepherd (2006), based on WINDII measurements for the latitude band 40 • S-40 • N and the period from November 1991 to August 1997, derived an empirical formula for the dependence of the height of the layer on integrated intensity (that is equivalent to number density), day of year, and local time.…”

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

“…One possibility is to use observations with more than one instrument and determine whether to triangulate OH observations at separated locations (Kubota et al, 1999;Ejiri et al, 2002;Kataoka et al, 2013) or to correlate them with simultaneous ground-based wind measurements (Yu et al, 2017). Another possibility is to employ the OH intensities measured from the ground to infer the OH emission altitude, relying on the fact that the latter depends quasi-linearly on the former (Yee et al, 1997;Melo et al, 1999;Liu and Shepherd, 2006;Mulligan et al, 2009;von Savigny, 2015). In this context, Liu and Shepherd (2006) proposed a method to predict the altitude of the OH layer from ground-based instrument measurements of intensities by using an empirical function derived from space-based instrument measurements.…”