Retrieval of ozone profiles from OMPS limb scattering observations

Abstract

Abstract. This study describes a retrieval algorithm developed at the University of Bremen to obtain vertical profiles of ozone from limb observations performed by the Ozone Mapper and Profiler Suite (OMPS). This algorithm is based on the technique originally developed for use with data from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument. As both instruments make limb measurements of the scattered solar radiation in the ultraviolet (UV) and visible (Vis) spectral ranges, an underlying objective of the study is to obtain consolidated and consistent ozone profiles from the two satellites and to produce a combined data set. The retrieval algorithm uses radiances in the UV and Vis wavelength ranges normalized to the radiance at an upper tangent height to obtain ozone concentrations in the altitude range of 12–60 km. Measurements at altitudes contaminated by clouds in the instrument field of view are identified and filtered out. An independent aerosol retrieval is performed beforehand and its results are used to account for the stratospheric aerosol load in the ozone inversion. The typical vertical resolution of the retrieved profiles varies from ∼ 2.5 km at lower altitudes ( < 30 km) to ∼ 1.5 km (about 45 km) and becomes coarser at upper altitudes. The retrieval errors resulting from the measurement noise are estimated to be 1–4 % above 25 km, increasing to 10–30 % in the upper troposphere. OMPS data are processed for the whole of 2016. The results are compared with the NASA product and validated against profiles derived from passive satellite observations or measured in situ by balloon-borne sondes. Between 20 and 60 km, OMPS ozone profiles typically agree with data from the Microwave Limb Sounder (MLS) v4.2 within 5–10 %, whereas in the lower altitude range the bias becomes larger, especially in the tropics. The comparison of OMPS profiles with ozonesonde measurements shows differences within ±5 % between 13 and 30 km at northern middle and high latitudes. At southern middle and high latitudes, an agreement within 5–7 % is also achieved in the same altitude range. An unexpected bias of approximately 10–20 % is detected in the lower tropical stratosphere. The processing of the 2013 data set using the same retrieval settings and its validation against ozonesondes reveals a much smaller bias; a possible reason for this behaviour is discussed.

Merging of ozone profiles from SCIAMACHY, OMPS and SAGE II observations to study stratospheric ozone changes

“…The QBO is a quasi-periodic variation of the tropical wind direction in the tropical stratosphere: easterly and westerly wind regimes propagate downward with a variable period of approximately 28 months at a given altitude level. Even though it is a tropical phenomenon, the effects of this variable wind pattern on ozone are not confined to the tropical region: they extend to mid and high latitudes and are associated with the secondary meridional circulation (Baldwin et al, 2001). illustrated the effects of the QBO on ozone profiles as a function of altitude with two peaks in ozone changes found at 20-27 km and at 30-38 km, showing opposite phases in the tropics and being in phase at mid latitudes.…”

“…For more details about the University of Bremen OMPS-LP retrieval algorithm implementation and validation, readers are referred to Arosio et al (2018), and for a description of SCIAMACHY retrieval and the validation of the ozone profiles, to Jia et al (2015). Briefly, in Arosio et al (2018) it has been shown that the retrieved OMPS-LP profiles averaged on a yearly basis agree with MLS within 5 %-10 % between 20 and 50 km, while below 20 km discrepancies are larger, especially in the tropical upper troposphere and lower stratosphere. Also, the validation with ozonesondes showed an agreement within ±7 % between 20 and 30 km in five chosen latitude bands, with a larger overestimation of the retrieved profiles in the tropics below 22 km.…”

Stratospheric aerosol characteristics from space-borne observations: extinction coefficient and Ångström exponent

“…The atmospheric modelling community is particularly interested in this type of information because climate models require information about stratospheric aerosol to define the initial conditions and/or to assess the accuracy of their performance (Solomon et al, 2011;Fyfe et al, 2013;Brühl et al, 2015;Bingen et al, 2017). Other important applications of stratospheric aerosol data are the investigation of the effects of geoengineering (IPCC, 2013;Kremser et al, 2016) and use of stratospheric aerosol information to improve the retrieval of stratospheric trace gases, e.g., water vapour (Rozanov et al, 2011) and ozone (Arosio et al, 2018;Zawada et al, 2018), from remote-sensing instruments. Most commonly, stratospheric aerosols are characterized by either their extinction coefficient (Ext) or one or several particle size distribution (PSD) parameters (e.g., median (r med ), effective (r eff ) or mode (R mod ) radius, distribution width parameter (σ ), aerosol particle number density (N)).…”

Estimating and Reporting Uncertainties in Remotely Sensed Atmospheric Composition and Temperature

“…Within linear theory and the assumption in force that the better resolved data set contains no sizeable amount of a priori information, the Connor et al approach indeed solves the problem that the original datasets are not directly comparable due to different vertical resolutions. The problem of interpolability of averaging kernels is discussed in Arosio et al (2018). 30 Problems occur when linear theory is no longer adequate to describe the problem.…”