The Detection of Large HNO
            <sub>3</sub>
            -Containing Particles in the Winter Arctic Stratosphere

Fahey, D. W.; Gao, R. S.; Carslaw, K. S.; Kettleborough, J.; Popp, Peter; Northway, M. J.; Holecek, J. C.; Ciciora, S. C.; McLaughlin, Richard J.; Thompson, Thomas L.; Winkler, R.; Baumgardner, Darrel; Gandrud, B. W.; Wennberg, P. O.; Dhaniyala, Suresh; McKinney, K. A.; Peter, Thomas; Salawitch, R. J.; Bui, T. P.; Elkins, James W.; Webster, Christopher R.; Atlas, Elliot L.; Jost, H.; Wilson, J. C.; Herman, R. L.; Kleinböhl, A.; König, M.

doi:10.1126/science.1057265

Cited by 309 publications

(506 citation statements)

References 35 publications

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“…(in the range 10 −5 to 10 −3 cm −3 ) in the Arctic lower stratosphere (Fahey et al, 2001). Subsequent modelling studies have indicated that the sedimentation of these large NAT particles was capable of causing denitrification comparable to that observed Drdla et al, 2002).…”

Section: S Davies Et Al: Model and Mipas-observed Arctic Denitrificmentioning

confidence: 87%

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

et al. 2006

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Abstract. Observations of gas-phase HNO 3 and N 2 O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E) were made during the cold Arctic winter of 2002/2003. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation) microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NO y and N 2 O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in midDecember 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.

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Section: S Davies Et Al: Model and Mipas-observed Arctic Denitrificmentioning

confidence: 87%

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

et al. 2006

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“…The main intention was to find some additional information to better discriminate STS and NAT clouds. This is non-trivial because the optical properties become very similar between both types if the NAT particles have a large radius, like the so-called NAT rocks (Fahey et al, 2001). Taylor et al (1994) exploited the different gradients in the extinction spectrum of sulfate and NAT in the 1400 and 1200 cm −1 region for aerosol and PSC measurements of the Improved Stratospheric and Mesospheric Sounder (ISAMS) on the Upper Atmospheric Research Satellite (UARS).…”

Section: -D Btd Classification Methodsmentioning

confidence: 99%

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

et al. 2016

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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument on board the ESA Envisat satellite operated from July 2002 until April 2012. The infrared limb emission measurements represent a unique dataset of daytime and night-time observations of polar stratospheric clouds (PSCs) up to both poles. Cloud detection sensitivity is comparable to space-borne lidars, and it is possible to classify different cloud types from the spectral measurements in different atmospheric windows regions.Here we present a new infrared PSC classification scheme based on the combination of a well-established two-colour ratio method and multiple 2-D brightness temperature difference probability density functions. The method is a simple probabilistic classifier based on Bayes' theorem with a strong independence assumption. The method has been tested in conjunction with a database of radiative transfer model calculations of realistic PSC particle size distributions, geometries, and composition. The Bayesian classifier distinguishes between solid particles of ice and nitric acid trihydrate (NAT), as well as liquid droplets of super-cooled ternary solution (STS).The classification results are compared to coincident measurements from the space-borne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument over the temporal overlap of both satellite missions (June 2006-March 2012. Both datasets show a good agreement for the specific PSC classes, although the viewing geometries and the vertical and horizontal resolution are quite different. Discrepancies are observed between the CALIOP and the MI-PAS ice class. The Bayesian classifier for MIPAS identifies substantially more ice clouds in the Southern Hemisphere polar vortex than CALIOP. This disagreement is attributed in part to the difference in the sensitivity on mixed-type clouds. Ice seems to dominate the spectral behaviour in the limb infrared spectra and may cause an overestimation in ice occurrence compared to the real fraction of ice within the PSC area in the polar vortex.The entire MIPAS measurement period was processed with the new classification approach. Examples like the detection of the Antarctic NAT belt during early winter, and its possible link to mountain wave events over the Antarctic Peninsula, which are observed by the Atmospheric Infrared Sounder (AIRS) instrument, highlight the importance of a climatology of 9 Southern Hemisphere and 10 Northern Hemisphere winters in total. The new dataset is valuable both for detailed process studies, and for comparisons with and improvements of the PSC parameterizations used in chemistry transport and climate models.

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“…Likewise, the initial value assumed for HNO 3 implies that denitrification through the sedimentation of large NAT (nitric acid trihydrate) particles (e.g. Fahey et al, 2001;Molleker et al, 2014;Grooß et al, 2014) had occurred by this time. This assumption likely constitutes a slightly too early onset of denitrification, but the impact of this assumption is minimal during polar night.…”

Section: Model Descriptionmentioning

confidence: 99%

“…In the case of STS particles the reduction of gas-phase HNO 3 lasts only as long as temperatures are low enough for the particles to exist, because the particles are too small to sediment significantly. Nitric acid trihydrate particles, however, can grow to large sizes allowing substantial sedimentation rates, so that HNO 3 is removed from stratospheric air masses permanently (a process referred to as "denitrification"; Fahey et al, 2001;Molleker et al, 2014). Denitrification is observed regularly in the lower stratosphere in Antarctica and in cold winters in the Arctic (e.g.…”

Section: A2 Denitrificationmentioning

confidence: 99%

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

Müller¹,

Grooß²,

Zafar

et al. 2018

Atmos. Chem. Phys.

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Abstract. The Antarctic ozone hole arises from ozone destruction driven by elevated levels of ozone destroying ("active") chlorine in Antarctic spring. These elevated levels of active chlorine have to be formed first and then maintained throughout the period of ozone destruction. It is a matter of debate how this maintenance of active chlorine is brought about in Antarctic spring, when the rate of formation of HCl (considered to be the main chlorine deactivation mechanism in Antarctica) is extremely high. Here we show that in the heart of the ozone hole (16-18 km or 85-55 hPa, in the core of the vortex), high levels of active chlorine are maintained by effective chemical cycles (referred to as HCl null cycles hereafter). In these cycles, the formation of HCl is balanced by immediate reactivation, i.e. by immediate reformation of active chlorine. Under these conditions, polar stratospheric clouds sequester HNO 3 and thereby cause NO 2 concentrations to be low. These HCl null cycles allow active chlorine levels to be maintained in the Antarctic lower stratosphere and thus rapid ozone destruction to occur. For the observed almost complete activation of stratospheric chlorine in the lower stratosphere, the heterogeneous reaction HCl + HOCl is essential; the production of HOCl occurs via HO 2 + ClO, with the HO 2 resulting from CH 2 O photolysis. These results are important for assessing the impact of changes of the future stratospheric composition on the recovery of the ozone hole. Our simulations indicate that, in the lower stratosphere, future increased methane concentrations will not lead to enhanced chlorine deactivation (through the reaction CH 4 + Cl −→ HCl+CH 3 ) and that extreme ozone destruction to levels below ≈ 0.1 ppm will occur until mid-century.

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The Detection of Large HNO ₃ -Containing Particles in the Winter Arctic Stratosphere

Cited by 309 publications

References 35 publications

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

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The Detection of Large HNO 3 -Containing Particles in the Winter Arctic Stratosphere

Cited by 309 publications

References 35 publications

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

Contact Info

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Resources

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The Detection of Large HNO ₃ -Containing Particles in the Winter Arctic Stratosphere