Photolysis of sulfuric acid vapor by visible light as a source of the polar stratospheric CN layer

Mills, Michael J.; Toon, O. B.; Vaida, Veronica; Hintze, Paul E.; Kjaergaard, Henrik G.; Schofield, Daniel P.; Robinson, Timothy W.

doi:10.1029/2004jd005519

Cited by 53 publications

(88 citation statements)

References 37 publications

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“…We note however that nucleation can be seen in the middle stratosphere at SH mid-latitudes in the volcanically quiescent C_noPinatubo September 1991 monthly-mean, indicating the occurrence of nucleation in springtime, as seen in the McMurdo OPC record (Campbell and Deshler, 2014). Note that the mechanism here is that particle evaporation and subsequent photolysis of sulfuric acid leads to a reservoir of SO 2 building up during polar winter, which leads to new particle formation in polar spring (Mills et al, 2005). This is the same mechanism that is leading to the layer of elevated N 5 at 25-30 km in the March Laramie profiles (see Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Carslaw and Kärcher, 2006). Also included are photolysis reactions for H 2 SO 4 and SO 3 , which occur above about 30 km and lead to a reservoir of SO 2 building up during polar winter, enabling new particle formation in the polar lower stratosphere during spring (Mills et al, 2005). The chemistry is integrated with the ASAD chemical integration package (Carver et al, 1997) with the Newton-Raphson sparse matrix solver from Wild et al (2000).…”

Section: Stratospheric Chemistry Extended To Include the Sulfur Cyclementioning

confidence: 99%

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Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

et al. 2014

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Abstract. We use a stratosphere-troposphere compositionclimate model with interactive sulfur chemistry and aerosol microphysics, to investigate the effect of the 1991 Mount Pinatubo eruption on stratospheric aerosol properties. Satellite measurements indicate that shortly after the eruption, between 14 and 23 Tg of SO 2 (7 to 11.5 Tg of sulfur) was present in the tropical stratosphere. Best estimates of the peak global stratospheric aerosol burden are in the range 19 to 26 Tg, or 3.7 to 6.7 Tg of sulfur assuming a composition of between 59 and 77 % H 2 SO 4 . In light of this large uncertainty range, we performed two main simulations with 10 and 20 Tg of SO 2 injected into the tropical lower stratosphere. Simulated stratospheric aerosol properties through the 1991 to 1995 period are compared against a range of available satellite and in situ measurements. Stratospheric aerosol optical depth (sAOD) and effective radius from both simulations show good qualitative agreement with the observations, with the timing of peak sAOD and decay timescale matching well with the observations in the tropics and mid-latitudes. However, injecting 20 Tg gives a factor of 2 too high stratospheric aerosol mass burden compared to the satellite data, with consequent strong high biases in simulated sAOD and surface area density, with the 10 Tg injection in much better agreement. Our model cannot explain the large fraction of the injected sulfur that the satellite-derived SO 2 and aerosol burdens indicate was removed within the first few months after the eruption. We suggest that either there is an additional alternative loss pathway for the SO 2 not included in our model (e.g. via accommodation into ash or ice in the volcanic cloud) or that a larger proportion of the injected sulfur was removed via cross-tropopause transport than in our simulations.We also critically evaluate the simulated evolution of the particle size distribution, comparing in detail to balloonborne optical particle counter (OPC) measurements from Laramie, Wyoming, USA (41 • N). Overall, the model captures remarkably well the complex variations in particle concentration profiles across the different OPC size channels. However, for the 19 to 27 km injection height-range used here, both runs have a modest high bias in the lowermost stratosphere for the finest particles (radii less than 250 nm), and the decay timescale is longer in the model for these particles, with a much later return to background conditions. Also, Published by Copernicus Publications on behalf of the European Geosciences Union. S. S. Dhomse et al.: Simulation of Pinatubo aerosol in a CCMwhereas the 10 Tg run compared best to the satellite measurements, a significant low bias is apparent in the coarser size channels in the volcanically perturbed lower stratosphere. Overall, our results suggest that, with appropriate calibration, aerosol microphysics models are capable of capturing the observed variation in particle size distribution in the stratosphere across both volcanically perturbed and quiescen...

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Section: Discussionmentioning

confidence: 99%

Section: Stratospheric Chemistry Extended To Include the Sulfur Cyclementioning

confidence: 99%

Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

et al. 2014

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“…We compare to this data set below. Only a few extratropical data are available for H 2 SO 4 vapour and are discussed in Mills et al (2005) and HOM11.…”

Section: Precursor Gasesmentioning

confidence: 99%

“…Above 50 hPa, the mixing ratio increases due to the oxidation of OCS. Above 10 hPa the photolysis of H 2 SO 4 vapour establishes an upper-stratospheric reservoir of SO 2 , which plays a large role in the triggering of new aerosol formation in the polar spring stratosphere when the sunlight returns (Mills et al, 1999(Mills et al, , 2005Campbell et al, 2014, HOM11). The MI-PAS profile varies much less than the modelled one.…”

Section: Precursor Gasesmentioning

confidence: 99%

Quasi-biennial oscillation of the tropical stratospheric aerosol layer

et al. 2015

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Abstract. This study describes how aerosol in an aerosolcoupled climate model of the middle atmosphere is influenced by the quasi-biennial oscillation (QBO) during times when the stratosphere is largely unperturbed by volcanic material. In accordance with satellite observations, the vertical extent of the stratospheric aerosol layer in the tropics is modulated by the QBO by up to 6 km, or ∼ 35 % of its mean vertical extent between 100-7 hPa (about 16-33 km). Its largest vertical extent lags behind the occurrence of strongest QBO westerlies. The largest reduction lags behind maximum QBO easterlies. Strongest QBO signals in the aerosol surface area (30 %) and number densities (up to 100 % e.g. in the Aitken mode) are found in regions where aerosol evaporates, that is above the 10 hPa pressure level (∼ 31 km). Positive modulations are found in the QBO easterly shear, negative modulations in the westerly shear. Below 10 hPa, in regions where the aerosol mixing ratio is largest (50-20 hPa, or ∼ 20-26 km), in most of the analysed parameters only moderate statistically significant QBO signatures (< 10 %) have been found.QBO signatures in the model prognostic aerosol mixing ratio are significant at the 95 % confidence level throughout the tropical stratosphere where modelled mixing ratios exceed 0.1 ppbm. In some regions of the tropical lower stratosphere the QBO signatures in other analysed parameters are partly not statistically significant. Peak-to-peak amplitudes of the QBO signature in the prognostic mixing ratios are up to twice as large as seasonal variations in the region where aerosols evaporate and between 70-30 hPa. Between the tropical tropopause and 70 hPa the QBO signature is relatively weak and seasonal variations dominate the variability of the simulated Junge layer. QBO effects on the upper lid of the tropical aerosol layer turn the quasi-static balance between processes maintaining the layer's vertical extent into a cyclic balance when considering this dominant mode of atmospheric variability. Global aerosol-interactive models without a QBO are only able to simulate the quasistatic balance state. To assess the global impact of stratospheric aerosols on climate processes, those partly nonlinear relationships between the QBO and stratospheric aerosols have to be taken into account.

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“…MSPs are thought to participate in the nucleation of waterice clouds in the mesosphere (Rapp and Thomas, 2006;Gumbel and Megner, 2009), and also impact on trace vapours such as H 2 SO 4 and HNO 3 throughout the middle atmosphere (Turco et al, 1981;Prather and Rodriguez, 1988;Mills et al, 2005). After MSPs have been transported down from the mesosphere in the winter polar vortex , they are thought to be assimilated in liquid (supercooled) H 2 SO 4 -H 2 O droplets (typically 40-75 Wt % acid composition, radius >100 nm) in the stratospheric aerosol or Junge layer which is located between 15 and 30 km in altitude (Carslaw et al, 1997;Deshler, 2008).…”

Section: Introductionmentioning

confidence: 99%

Interactions of meteoric smoke particles with sulphuric acid in the Earth's stratosphere

et al. 2012

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Abstract. Nano-sized meteoric smoke particles (MSPs) with iron-magnesium silicate compositions, formed in the upper mesosphere as a result of meteoric ablation, may remove sulphuric acid from the gas-phase above 40 km and may also affect the composition and behaviour of supercooled H 2 SO 4 -H 2 O droplets in the global stratospheric aerosol (Junge) layer.This study describes a time-resolved spectroscopic analysis of the evolution of the ferric (Fe 3+ ) ion originating from amorphous ferrous (Fe 2+ )-based silicate powders dissolved in varying Wt % sulphuric acid (30-75 %) solutions over a temperature range of 223-295 K. Complete dissolution of the particles was observed under all conditions. The first-order rate coefficient for dissolution decreases at higher Wt % and lower temperature, which is consistent with the increased solution viscosity limiting diffusion of H 2 SO 4 to the particle surfaces. Dissolution under stratospheric conditions should take less than a week, and is much faster than the dissolution of crystalline Fe 2+ compounds.The chemistry climate model UMSLIMCAT (based on the UKMO Unified Model) was then used to study the transport of MSPs through the middle atmosphere. A series of model experiments were performed with different uptake coefficients. Setting the concentration of 1.5 nm radius MSPs at 80 km to 3000 cm −3 (based on rocket-borne charged particle measurements), the model matches the reported Wt % Fe values of 0.5-1.0 in Junge layer sulphate particles, and the MSP optical extinction between 40 and 75 km measured by a satellite-borne spectrometer, if the global meteoric input rate is about 20 tonnes per day. The model indicates that an uptake coefficient ≥0.01 is required to account for the observed two orders of magnitude depletion of H 2 SO 4 vapour above 40 km.

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Photolysis of sulfuric acid vapor by visible light as a source of the polar stratospheric CN layer

Cited by 53 publications

References 37 publications

Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

Quasi-biennial oscillation of the tropical stratospheric aerosol layer

Interactions of meteoric smoke particles with sulphuric acid in the Earth's stratosphere

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