Retrieving the vertical distribution of stratospheric OClO from Odin/OSIRIS limb-scattered sunlight measurements

Abstract. The major volcanic eruption of Mount Pinatubo in 1991 has been shown to have significant effects on stratospheric chemistry and ozone depletion even at midlatitudes. Since then, only "moderate" but recurrent volcanic eruptions have modulated the stratospheric aerosol loading and are assumed to be one cause for the reported increase in the global aerosol content over the past 15 years. This particularly enhanced aerosol context raises questions about the effects on stratospheric chemistry which depend on the latitude, altitude and season of injection. In this study, we focus on the midlatitude Sarychev volcano eruption in June 2009, which injected 0.9 Tg of sulfur dioxide (about 20 times less than Pinatubo) into a lower stratosphere mainly governed by high-stratospheric temperatures. Together with in situ measurements of aerosol amounts, we analyse high-resolution in situ and/or remote-sensing observations of NO 2 , HNO 3 and BrO from balloon-borne infrared and UV-visible spectrometers launched in Sweden in August-September 2009. It is shown that differences between observations and threedimensional (3-D) chemistry-transport model (CTM) outputs are not due to transport calculation issues but rather reflect the chemical impact of the volcanic plume below 19 km altitude. Good measurement-model agreement is obtained when the CTM is driven by volcanic aerosol loadings derived from in situ or space-borne data. As a result of enhanced N 2 O 5 hydrolysis in the Sarychev volcanic aerosol conditions, the model calculates reductions of ∼ 45 % and increases of ∼ 11 % in NO 2 and HNO 3 amounts respectively over the August-September 2009 period. The decrease in NO x abundances is limited due to the expected saturation effect for high aerosol loadings. The links between the various chemical catalytic cycles involving chlorine, bromine, nitrogen and HO x compounds in the lower stratosphere are discussed. The increased BrO amounts (∼ 22 %) compare rather well with the balloon-borne observations when volcanic aerosol levels are accounted for in the CTM and appear to be mainly controlled by the coupling with nitrogen chemistry rather than by enhanced BrONO 2 hydrolysis. We show Published by Copernicus Publications on behalf of the European Geosciences Union. 2230G. Berthet et al.: Impact of a moderate volcanic eruption on chemistry in the lower stratosphere that the chlorine partitioning is significantly controlled by enhanced BrONO 2 hydrolysis. However, simulated effects of the Sarychev eruption on chlorine activation are very limited in the high-temperature conditions in the stratosphere in the period considered, inhibiting the effect of ClONO 2 hydrolysis. As a consequence, the simulated chemical ozone loss due to the Sarychev aerosols is low with a reduction of −22 ppbv (−1.5 %) of the ozone budget around 16 km. This is at least 10 times lower than the maximum ozone depletion from chemical processes (up to −20 %) reported in the Northern Hemisphere lower stratosphere over the first year following the Pinatubo erupti...

show abstract

“…Krecl et al, 2006;Berthet et al, 2005;Brohede et al, 2007). It is designed to perform annual simulations as well as detailed process studies.…”

Section: Model Calculationsmentioning

confidence: 99%

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

et al. 2017

View full text Add to dashboard Cite

show abstract

“…This is due to the fact that the broadband shape of the atmospheric transmission and the convolution with the instrument function do not commute (Wenig et al, 2005). The tilt effect was previously described and is explicitly corrected for by Sioris et al (2003Sioris et al ( , 2006, Haley et al (2004), Krecl et al (2006), McLinden and Haley (2008), McLinden et al (2010), and Rozanov et al (2011) by including one additional tilt-effect pseudo absorber in the spectral analyses, the magnitude of which was determined from the spectral fit. In their pioneering work, Sioris et al (2003) named this effect the "tilt effect" and corrected its impact by including a correction spectrum calculated using a radiative transfer model in the spectral analysis.…”

Section: Introductionmentioning

confidence: 99%

The tilt effect in DOAS observations

et al. 2017

View full text Add to dashboard Cite

Abstract. Experience of differential atmospheric absorption spectroscopy (DOAS) shows that a spectral shift between measurement spectra and reference spectra is frequently required in order to achieve optimal fit results, while the straightforward calculation of the optical density proves inferior. The shift is often attributed to temporal instabilities of the instrument but implicitly solved the problem of the tilt effect discussed/explained in this paper.Spectral positions of Fraunhofer and molecular absorption lines are systematically shifted for different measurement geometries due to an overall slope -or tilt -of the intensity spectrum. The phenomenon has become known as the tilt effect for limb satellite observations, where it is corrected for in a first-order approximation, whereas the remaining community is less aware of its cause and consequences.It is caused by the measurement process, because atmospheric absorption and convolution in the spectrometer do not commute. Highly resolved spectral structures in the spectrum will first be modified by absorption and scattering processes in the atmosphere before they are recorded with a spectrometer, which convolves them with a specific instrument function. In the DOAS spectral evaluation process, however, the polynomial (or other function used for this purpose) accounting for broadband absorption is applied after the convolution is performed.In this paper, we derive that changing the order of the two modifications of the spectra leads to different results. Assuming typical geometries for the observations of scattered sunlight and a spectral resolution of 0.6 nm, this effect can be interpreted as a spectral shift of up to 1.5 pm, which is confirmed in the actual analysis of the ground-based measurements of scattered sunlight as well as in numerical radiative transfer simulations. If no spectral shift is allowed by the fitting routine, residual structures of up to 2.5 × 10 −3 peak-topeak are observed. Thus, this effect needs to be considered for DOAS applications aiming at an rms of the residual of 10 −3 and below.

show abstract

“…Following other authors, e.g., Haley et al, 2004;Sofieva et al, 2004;Krecl et al, 2006, we employ the Backus and Gilbert approach (Backus and Gilbert, 1970) that suggests the so-called spread function to define the averaging kernel width:…”

Section: General Characterization Of the Retrievalmentioning

confidence: 99%

Retrieval of water vapor vertical distributions in the upper troposphere and the lower stratosphere from SCIAMACHY limb measurements

et al. 2011

View full text Add to dashboard Cite

Abstract. This study describes the retrieval of water vapor vertical distributions in the upper troposphere and lower stratosphere (UTLS) altitude range from space-borne observations of the scattered solar light made in limb viewing geometry. First results using measurements from SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) aboard ENVISAT (Environmental Satellite) are presented here. In previous publications, the retrieval of water vapor vertical distributions has been achieved exploiting either the emitted radiance leaving the atmosphere or the transmitted solar radiation. In this study, the scattered solar radiation is used as a new source of information on the water vapor content in the UTLS region. A recently developed retrieval algorithm utilizes the differential absorption structure of the water vapor in 1353-1410 nm spectral range and yields the water vapor content in the 11-25 km altitude range. In this study, the retrieval algorithm is successfully applied to SCIAMACHY limb measurements and the resulting water vapor profiles are compared to in situ balloon-borne observations. The results from both satellite and balloon-borne instruments are found to agree typically within 10 %.

show abstract

Retrieving the vertical distribution of stratospheric OClO from Odin/OSIRIS limb-scattered sunlight measurements

Cited by 32 publications

References 56 publications

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

The tilt effect in DOAS observations

Retrieval of water vapor vertical distributions in the upper troposphere and the lower stratosphere from SCIAMACHY limb measurements

Contact Info

Product

Resources

About