Daytime ozone loss term in the mesopause region

Abstract

Abstract. For the retrieval of atomic oxygen via ozone observations in the extended mesopause region under sunlight conditions, two assumptions are used: first, the photochemical equilibrium of ozone and, second, that the ozone losses are dominated by ozone's dissociation from solar UV radiation, silently ignoring the O 3 destruction by atomic hydrogen. We verify both by 3-D modeling. We found that ozone approaches photochemical equilibrium at 75-100 km for daytime conditions. Hence, the first assumption is valid. However, the reaction of ozone with atomic hydrogen was found to be an important loss process and should not be omitted in retrieving atomic oxygen.

Atomic Oxygen Retrieved From the SABER 2.0‐ and 1.6‐μm Radiances Using New First‐Principles Nighttime OH(v) Model

“…The new retrieval approach improves upon the commonly used method for retrieving atomic oxygen (see Mlynczak et al, 2013;Smith et al, 2010, and references therein) by eliminating its corner stone assumptions about main processes of ozone quenching entering into the chemical balance equation and about the validity of the ozone chemical equilibrium, which are not always true in the mesopause region (see Belikovich et al, 2018;Kulikov et al, 2017Kulikov et al, , 2018.…”

Technical note: Evaluation of the simultaneous measurements of mesospheric OH, HO<sub>2</sub>, and O<sub>3</sub> under a photochemical equilibrium assumption – a statistical approach

“…We used the latest version (v4.2) of the MLS "standard" product (Livesey et al, 2017) for trace gas concentrations and temperature T within the 1-0.046 mbar pressure interval, where all data are suitable for scientific applications (Wang et al, 2015a, b;Schwartz et al, 2015). We took the daytime data when the solar zenith angle χ < 80 • for January, May, and September 2005.…”

“…"Pressure", "estimated precision", "status flag", "quality", "convergence", and "clouds" fields were taken into account. HO 2 data were seen as the day-minus-night difference as prescribed by the MLS data guidelines (Livesey et al, 2017). Following Pickett et al (2008), each daytime profile of this component measured on a given day at a latitude Lat, a profile resulting from averaging the nighttime profiles of HO 2 , measured on the same day in the latitude range of Lat ± 5 • , was subtracted.…”

“…Almost everywhere in the mesosphere and lower thermosphere (with the exception of 85-95 km, see Kulikov et al, 2017) the photodissociation is the main ozone sink, i.e., k 52 + k 53 k 21 · H. Therefore, in the zero order approximation, Eq. (3) can be simplified and the concentration of atomic oxygen can be defined in terms of ozone concentration:…”

Results of Russian studies of the middle atmosphere (2015–2018)

“…В работе [32] для восстановления атомарного кислорода по наблюдениям озона в протяженной области мезопаузы при солнечном освещении используются допущения фотохимического равновесия озона и потеря озона при фотодиссоциации (без учета разрушения атомарным водородом). Допущения проверены 3D-моделированием.…”