Quasi-biennial oscillation of the tropical stratospheric aerosol layer

Hommel, R.; Timmreck, Claudia; Giorgetta, Marco; Graf, Hans F.

doi:10.5194/acp-15-5557-2015

Cited by 32 publications

(39 citation statements)

References 77 publications

(138 reference statements)

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“…6) a volcanic signature is hardly apparent in the latitudinally resolved time series and the main variability component at low latitudes has a period characteristic of the Quasi-Biennial Oscillation (QBO, reviewed by Baldwin et al, 2001). The enhanced tropical aerosol extinction values at 30 km altitude occur during easterly shear conditions of the QBO (Trepte and Hitchman, 1992;Hommel et al, 2015). The bottom right panel of Fig.…”

Section: Sample Resultsmentioning

confidence: 99%

“…The results demonstrate that enhancements in aerosol extinction at 30 km altitude are linked to strong easterlies at the 10 hPa pressure level. These enhancements in aerosol extinction are caused by an upward motion, which is a manifestation of the QBO secondary oscillation induced by meridional temperature gradients caused by the wave-driven vertical wind shear (Trepte and Hitchman, 1992;Baldwin et al, 2001;Hommel et al, 2015). Brinkhoff et al (2015) recently discussed the underlying physical mechanisms, also based on SCIAMACHY stratospheric aerosol measurements, in more detail.…”

Section: Sample Resultsmentioning

confidence: 99%

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Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results

et al. 2015

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Abstract. Stratospheric aerosol extinction profiles have been retrieved from SCIAMACHY/Envisat measurements of limb-scattered solar radiation. The retrieval is an improved version of an algorithm presented earlier. The retrieved aerosol extinction profiles are compared to co-located aerosol profile measurements from the SAGE II solar occultation instrument at a wavelength of 525 nm. Comparisons were carried out with two versions of the SAGE II data set (version 6.2 and the new version 7.0). In a global average sense the SCIAMACHY and the SAGE II version 7.0 extinction profiles agree to within about 10 % for altitudes above 15 km. Larger relative differences (up to 40 %) are observed at specific latitudes and altitudes. We also find differences between the two SAGE II data versions of up to 40 % for specific latitudes and altitudes, consistent with earlier reports. Sample results on the latitudinal and temporal variability of stratospheric aerosol extinction and optical depth during the SCIAMACHY mission period are presented. The results confirm earlier reports that a series of volcanic eruptions is responsible for the increase in stratospheric aerosol optical depth from 2002 to 2012. Above about an altitude of 28 km, volcanic eruptions are found to have negligible impact in the period 2002-2012.

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Section: Sample Resultsmentioning

confidence: 99%

Section: Sample Resultsmentioning

confidence: 99%

Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results

et al. 2015

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“…Based on satellite observations, Trepte and Hitchman (1992) have shown that transport from the tropics to the midlatitudes is favored during westerly shear phases of the quasi-biennial oscillation (QBO) rather than during the easterly shear phases. More recently, through the use of satellite observations and climate models, Hommel et al (2015) revealed that the vertical and latitudinal extent of the stratospheric aerosol layer (between 16 and 31 km) in the tropics is modulated by the QBO. Pitari et al (2016b) analyzed the radiative perturbations in the stratosphere induced by the last five major volcanic eruptions after 1960 (i.e, Agung, Mount St. Helens, El Chichón, Nevado del Ruiz, and Pinatubo) using a climate model that included an aerosol microphysics module for aerosol formation and growth.…”

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confidence: 99%

Long-range transport of stratospheric aerosols in the Southern Hemisphere following the 2015 Calbuco eruption

et al. 2017

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Abstract. After 43 years of inactivity, the Calbuco volcano, which is located in the southern part of Chile, erupted on 22 April 2015. The space-time evolutions (distribution and transport) of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS), in situ aerosol counting (LOAC OPC) and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21 • S, 55.5 • E), the aerosol signal was unambiguously enhanced in comparison with "background" conditions, with a volcanic aerosol layer extending from 18 to 21 km during the May-July period. All the data reveal an increase by a factor of ∼ 2 in the SAOD (stratospheric aerosol optical depth) with respect to values observed before the eruption. The aerosol mass e-folding time is approximately 90 days, which is rather close to the value (∼ 80 days) reported for the Sarychev eruption. Microphysical measurements obtained before, during, and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over the Reunion Island site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.16 ± 0.02 µm with a unimodal size distribution for particles above 0.2 µm in diameter. Particle concentrations for sizes larger than 1 µm are too low to be properly detected by the LOAC OPC. The aerosol number concentration was ∼ 20 times higher that observed before and 1 year after the eruption. According to OMPS and lidar observations, a tendency toward conditions before the eruption was observed by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island between May and July 2015 reflects an inhomogeneous spatio-temporal distribution of the plume, which is controlled by the localization of these dynamical barriers.

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“…On the other hand, the modulation the QBO itself may introduce on the stratospheric aerosol lifetime (and deposition) has not been explored in 5 depth in case of a geoengineering constant tropical injection of sulfur. This effect, however, was studied for the time evolution of the unperturbed stratospheric aerosol layer by Hommel et al (2015). They found that the aerosol burden non-linearly correlate with the QBO phase because of a wide range of reasons, amongst those the rather wide differences in the size range of the aerosols.…”

Section: Qbo Impact On Stratospheric Sulfatementioning

confidence: 99%

Quantification of sulfur deposition changes under sulfate geoengineering conditions

Visioni¹,

Pitari²,

Tuccella³

et al. 2017

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Abstract.Sustained injection of sulfur dioxide (SO 2 ) in the tropical lower stratosphere has been proposed as a climate engineering technique with the purpose of temporarily mitigating the surface warming predicted for the coming decades. Among several possible environmental side effects, the increase of sulfur deposition at the ground surface still needs to be thoroughly investigated. In this study we present results from a composition-climate coupled model (ULAQ-CCM) and a chemistry-transport 5 model (GEOS-Chem), assuming a sustained lower stratospheric equatorial injection of 8 Tg-SO 2 /yr. Total S-deposition is found to globally increase by 5.2% when sulfate geoengineering is deployed, with a clear interhemispheric asymmetry (3.8% and 10.3% in NH and SH, respectively). The latter is mostly due to the combination of a quasi-homogeneous tropospheric influx of sulfate from the stratosphere, and the highly inhomogeneous amount of anthropogenic sulfur emissions in the boundary layer (mostly located in the Northern Hemisphere). The two models show good consistency in their sulfur species behavior under 10 background and geoengineering conditions, not only for global and hemispheric budgets but also for regional S-deposition values (except over Arctic and Africa). The consistency between models is not limited to time averaged values, but it extends to monthly and inter-annual deposition changes. The latter is driven essentially by the variability of stratospheric large-scale transport associated to the quasi-biennial oscillation (QBO). According to model-mean values, geoengineering S-deposition percent changes on polar regions range between 7.7±0.7% over Antarctica and 8.5±1.3% over the Arctic, where the uncer-15 tainty reflects the model-averaged interannual variability. Similar S-deposition changes are found over quasi-clean continental regions of the Southern Hemisphere, and smaller values are calculated over polluted continental regions of the Northern Hemisphere (2÷4%). The largest difference between the two models is found over Africa and the Arctic (11% and 2%, respectively, for GEOS-Chem, against 2% and 15%, respectively, for ULAQ-CCM).

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Quasi-biennial oscillation of the tropical stratospheric aerosol layer

Cited by 32 publications

References 77 publications

Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results

Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results

Long-range transport of stratospheric aerosols in the Southern Hemisphere following the 2015 Calbuco eruption

Quantification of sulfur deposition changes under sulfate geoengineering conditions

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