Retrieval of O<sub>2</sub>(<sup>1</sup>Σ) and O<sub>2</sub>(<sup>1</sup>Δ) volume emission rates in the mesosphere and lower thermosphere using SCIAMACHY MLT limb scans

Abstract

Abstract. We present the retrieved volume emission rates (VERs) from the airglow of both the daytime and twilight O 2 ( 1 ) band and O 2 ( 1 ) band emissions in the mesosphere and lower thermosphere (MLT). The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard the European Space Agency Envisat satellite observes upwelling radiances in limb-viewing geometry during its special MLT mode over the range 50-150 km. In this study we use the limb observations in the visible (595-811 nm) and near-infrared (1200-1360 nm) bands.We have investigated the daily mean latitudinal distributions and the time series of the retrieved VER in the altitude range from 53 to 149 km. The maximal observed VERs of O 2 ( 1 ) during daytime are typically 1 to 2 orders of magnitude larger than those of O 2 ( 1 ). The latter peaks at around 90 km, whereas the O 2 ( 1 ) emissivity decreases with altitude, with the largest values at the lower edge of the observations (about 53 km). The VER values in the upper mesosphere (above 80 km) are found to depend on the position of the sun, with pronounced high values occurring during summer for O 2 ( 1 ). O 2 ( 1 ) emissions show additional high values at polar latitudes during winter and spring. These additional high values are presumably related to the downwelling of atomic oxygen after large sudden stratospheric warmings (SSWs). Accurate measurements of the O 2 ( 1 ) and O 2 ( 1 ) airglow, provided that the mechanism of their production is understood, yield valuable information about both the chemistry and dynamics in the MLT. For example, they can be used to infer the amounts and distribution of ozone, solar heating rates, and temperature in the MLT.

Reevaluating the Use of O2 a1Δg Band in Spaceborne Remote Sensing of Greenhouse Gases

“…These VER profile shapes are very similar. The weak dependencies of VER and O 2 ( a 1 Δ g ) number density on the solar zenith angle are consistent with previous studies (Wiensz, ; Zarboo et al, ), because the ozone photolysis is optically thin at the airglow altitudes. The insignificant variations of VER and O 2 ( a 1 Δ g ) also indicate that the gravity waves do not have a strong impact on the overall intensity of O 2 ( a 1 Δ g ) airglow.…”

“…However, OSIRIS only has two channels in the O 2 a 1 Δ g band and therefore provides little constraint on the spectral shape of airglow. Zarboo et al () retrieved mesosphere/thermosphere (50–150 km) airglow emission spectra using SCIAMACHY limb observations assuming no self‐absorption, whereas O 2 ( a 1 Δ g ) airglow is also present in the stratosphere with significant self‐absorption. As such, we propose a physics‐based method to model high‐resolution airglow emission spectrum using available spectroscopic parameters from the HIgh‐resolution TRANsmission molecular absorption database 2016 (HITRAN2016; Gordon et al, ).…”

The use of O2 1.27 µm absorption band revisited for GHG monitoring from space and application to MicroCarb

“…In a recent study to retrieve the volume emission rates of O 2 ( 1 Δ) and O 2 ( 1 Σ) in the mesosphere and lower thermosphere, Zarboo et al (2018) have used a special mode of SCIAMACHY: the MLT limb scan mode, dedicated to the study of the mesosphere and lower thermosphere in the region 50-150 km. This mode was used only twice a month from July 2008 until April 2012.…”

“…are respectively for the foreground segment and the background segment the optical thickness of O 2 absorption from the segment to the observer, along the LOS. 10 Zarboo et al (2018) have also used the SCIAMACHY limb scans in order to retrieve the vertical profile of the O 2 * emissivity. However, their technique is quite different.…”

“…We list below a few commonly used absorption bands and their potential contamination by airglow. Zarboo et al (2018) have retrieved form SCIAMACHY limb observations the VER of the emission by the O 2 20 molecule excited in the 1 Σ state when it decays to the fundamental in the O 2 band A at 0.76 µm (their figure 5).…”