Articles | Volume 8, issue 3
Atmos. Meas. Tech., 8, 1021–1041, 2015

Special issue: Limb observations of the middle atmosphere by space- and airborne...

Atmos. Meas. Tech., 8, 1021–1041, 2015

Research article 04 Mar 2015

Research article | 04 Mar 2015

Atomic oxygen retrievals in the MLT region from SCIAMACHY nightglow limb measurements

O. Lednyts'kyy1, C. von Savigny1, K.-U. Eichmann2, and M. G. Mlynczak3 O. Lednyts'kyy et al.
  • 1Institute of Physics, Ernst-Moritz-Arndt-University of Greifswald, Greifswald, Germany
  • 2Institute of Environmental Physics, University of Bremen, Bremen, Germany
  • 3NASA Langley Research Center, Hampton, VA, USA

Abstract. Vertical distributions of atomic oxygen concentration ([O]) in the mesosphere and lower thermosphere (MLT) region were retrieved from sun-synchronous SCIAMACHY/Envisat (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY on board the Environmental Satellite) limb measurements of the oxygen 557.7 nm green line emission in the terrestrial nightglow. A band pass filter was applied to eliminate contributions from other emissions, the impact of measurement noise and auroral activity. Vertical volume emission rate profiles were retrieved from integrated limb-emission rate profiles under the assumption that each atmospheric layer is horizontally homogeneous and absorption and scattering can be neglected. The radiative transfer problem was solved using regularized total least squares minimization in the inversion procedure. Atomic oxygen concentration profiles were retrieved from data collected for altitudes in the range 85–105 km with approximately 4 km vertical resolution during the time period from August 2002 to April 2012 at approximately 22:00 local time. The retrieval of [O] profiles was based on the generally accepted two-step Barth transfer scheme including consideration of quenching processes and the use of different available sources of temperature and atmospheric density profiles. A sensitivity analysis was performed for the retrieved [O] profiles to estimate maximum uncertainties assuming independent contributions of uncertainty components. Errors in photochemical model parameters depending on temperature uncertainties and random errors of model parameters contribute less than 50% to the overall [O] retrieval error. The retrieved [O] profiles were compared with reference [O] profiles provided by SABER/TIMED (Sounding of the Atmosphere using Broadband Emission Radiometry instrument on board the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite) or by the NRLMSISE-00 (Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar Extended model, year: 2000) and SD-WACCM4 (Whole Atmosphere Community Climate Model with Specified Dynamics, version 4). A comparison of the retrieved [O] profiles with the reference [O] profiles led to the conclusion that the photochemical model taking into account quenching of O(1S) by O2, O(3P), and N2 and the SABER/TIMED model as a source of temperature and density profiles are the most appropriate choices for our case. The retrieved [O] profile time series exhibits characteristic seasonal variations in agreement with satellite observations based on analysis of OH Meinel band emissions and atmospheric models. A pronounced 11-year solar cycle variation can also be identified in the retrieved atomic oxygen concentration time series.

Short summary
This paper deals with the retrieval of atomic oxygen concentration profiles in the Earth's upper mesosphere/lower thermosphere region from SCIAMACHY observations of oxygen green line airglow emissions. Atomic oxygen is one of the most important chemical constituents of this atmospheric region, and long-term satellite data sets are rare. The paper includes a detailed description of the retrieval algorithm, an error budget, validation results and some first scientific analyses.