Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Thomason, L. W.; Poole, L. R.

doi:10.1029/93jd02461

Cited by 79 publications

(62 citation statements)

References 40 publications

(21 reference statements)

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“…The AEC distinctly decreased from mid-August through earlySeptember; this decrease can be attributed to "cleansing" caused by sedimentation of PSCs that occurred earlier in that altitude region. Once "cleansing" occurs, aerosol concentration in the atmosphere cannot increase at high altitudes without aerosol loading from low latitudes coupled with the breakup of the polar vortex (Thomason and Poole 1993). The above results indicate that PSC formation would be inhibited because of a shortage of background aerosol particles in the atmosphere even when ambient temperatures were sufficiently colder than TNAT.…”

Section: Discussionmentioning

confidence: 75%

“…The decrease in AEC could have been caused both by strong descent motion of upper air with low aerosol concentration inside the polar vortex and "cleansing effect" due to sedimentation of PSCs that had formed previously (e.g., Thomason and Poole 1993). Atmospheric subsidence inside the polar vortex was evident in ILAS-II N2O and CH4 data ; Fig.…”

Section: Discussionmentioning

confidence: 96%

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Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

Saitoh

Hayashida

Sugita

et al. 2006

SOLA

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The Improved Limb Atmospheric Spectrometer (ILAS)-II frequently observed polar stratospheric clouds (PSCs) in the Southern Hemisphere (SH) throughout the winter of 2003. Simultaneous observations of the aerosol extinction coefficient (AEC) at 780 nm, nitric acid, and water vapor data were analyzed to investigate the ambient thermodynamic conditions associated with observed PSCs. PSCs were first observed with ILAS-II at the end of May, and observed most frequently in August/September as temperatures cooled. At approximately 20 km late in the PSC season, however, PSCs were less likely to occur, despite cold temperatures, because of the lower concentration of nitric acid due to denitrification caused by sedimentation of previously occurring PSCs. The probability of PSC occurrence and the probability of ambient temperatures colder than nitric acid trihydrate (NAT) saturation temperature (TNAT ) were well correlated below 20 km throughout the winter. In contrast, PSC frequency at 22 km from late August to early September was low even when temperatures were sufficiently colder than TNAT; this is, at least, partly because of the decrease in background aerosol particles in the atmosphere. IntroductionPolar stratospheric clouds (PSCs) consist mainly of nitric acid and water/ice and form in winter and early spring in the lower stratosphere over both polar regions (e.g., Solomon 1999). PSCs play a crucial role in ozone depletion processes; they provide surfaces for heterogeneous reactions that convert inactive chlorine into active chorine (e.g., Solomon 1999) and cause denitrification (e.g., Fahey et al. 1990) and nitrification (e.g., H ubler et al. 1990). Activated chlorine causes severe ozone depletion, especially in the Southern Hemisphere (SH), which is known as the "ozone hole". The climatology of PSC frequency in the SH was examined using aerosol data from the Stratospheric Aerosol Measurement (SAM) II from 1978to 1989(Poole and Pitts 1994, data from the Polar Ozone and Aerosol Measurement (POAM) II from 1994 to 1996 (Fromm et al. 1997), and data from multiple solar occultation sensors from 1978 to 2000 .Poole and Pitts (1994) examined the relationship between PSC frequency and temperature and showed that PSC formation in the SH is less likely later in PSC season than earlier. Other studies (e.g., Watterson and Tuck 1989;Hervig et al. 1997;Mergenthaler et al. 1997) have suggested that PSC formation late in PSC season in the SH is strongly affected by preceding denitrification and dehydration. However, there have been few studies on the variability of the relationship between PSC frequency and temperature over the course of a PSC season that are based on extensive observations of aerosols, nitric acid, and water vapor in the SH.Against this background, we used data obtained by the PSC identification and TNAT calculationPSCs were identified from ILAS-II AEC data over the SH using methods similar to those for ILAS data in the NH (Hayashida et al. 2000). First, averages and standard deviations for ILAS-II AEC data at te...

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 96%

Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

Saitoh

Hayashida

Sugita

et al. 2006

SOLA

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“…Crutzen (1976) first stated the essential role of OCS for stratospheric aerosol. Chin and Davis (1995), Thomason and Peter (2006), Brühl et al (2012), and Sheng et al (2015) agree on a major contribution of OCS to the formation of stratospheric sulfate aerosol. However, the magnitude with which OCS contributes to the stratospheric aerosol loading during background conditions is still under discussion.…”

Section: Introductionmentioning

confidence: 99%

“…While zero initial guess profiles have been used for the aerosol volume densities, results from the IMK routine processing are taken for the trace gases (von . As the atmospheric parameters are represented at denser altitude levels (1 km) than the vertical field of view (∼ 3 km) and the vertical tangent point spacing (1.5 km) of MIPAS, constraints on the smoothness of the profile shape are introduced by regularisation (Tikhonov, 1963;Steck, 2002). The retrieval of aerosol volume density is restricted to altitudes of up to 33 km, and the regularisation strength has been adjusted such that its resulting vertical resolution is around 3 to 4 km.…”

Section: Chemical Transport Modelmentioning

confidence: 99%

“…In the stratosphere, aerosol particles are mainly composed of sulfuric acid (H 2 SO 4 ) and water (H 2 O) (Kremser et al, 2016;Thomason and Peter, 2006), though organic material has been shown to also play a significant role in the upper troposphere and lower stratosphere (Yu et al, 2016;Murphy et al, 2013). Stratospheric sulfate aerosol has the potential to directly lower surface temperatures by backscattering parts of the incoming solar radiation.…”

Section: Introductionmentioning

confidence: 99%

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MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

et al. 2018

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Abstract. Volcanic eruptions can increase the stratospheric sulfur loading by orders of magnitude above the background level and are the most important source of variability in stratospheric sulfur. We present a set of vertical profiles of sulfate aerosol volume densities and derived liquidphase H 2 SO 4 (sulfuric acid) mole fractions for 2005-2012, retrieved from infrared limb emission measurements performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board of the Environmental Satellite (Envisat). Relative to balloon-borne in situ measurements of aerosol at Laramie, Wyoming, the MIPAS aerosol data have a positive bias that has been corrected, based on the observed differences to the in situ data. We investigate the production of stratospheric sulfate aerosol from volcanically emitted SO 2 for two case studies: the eruptions of Kasatochi in 2008 and Sarychev in 2009, which both occurred in the Northern Hemisphere midlatitudes during boreal summer. With the help of chemical transport model (CTM) simulations for the two volcanic eruptions we show that the MIPAS sulfate aerosol and SO 2 data are qualitatively and quantitatively consistent with each other. Further, we demonstrate that the lifetime of SO 2 is explained well by its oxidation by hydroxyl radicals (OH). While the sedimentation of sulfate aerosol plays a role, we find that the long-term decay of stratospheric sulfur after these volcanic eruptions in midlatitudes is mainly controlled by transport via the BrewerDobson circulation. Sulfur emitted by the two midlatitude volcanoes resides mostly north of 30 • N at altitudes of ∼ 10-16 km, while at higher altitudes (∼ 18-22 km) part of the volcanic sulfur is transported towards the Equator where it is lifted into the stratospheric "overworld" and can further be transported into both hemispheres.

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Stratospheric aerosol-Observations, processes, and impact on climate

et al. 2016

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Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes.

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Use of stratospheric aerosol properties as diagnostics of Antarctic vortex processes

Cited by 79 publications

References 40 publications

Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

Variation in PSC Occurrence Observed with ILAS-II over the Antarctic in 2003

MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

Stratospheric aerosol-Observations, processes, and impact on climate

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