Large nitric acid trihydrate particles and denitrification caused by mountain waves in the Arctic stratosphere

Mann, Graham

doi:10.1029/2004jd005271

Cited by 36 publications

(40 citation statements)

References 41 publications

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“…Further, our results are in agreement with Pitts et al (2011) who found an increase in ice PSC observations and coincident decrease in NAT mixture observations and suggested that this indicates heterogeneous nucleation of ice on NAT particles may be an important mechanism for the formation of synopticscale ice PSCs. In contrast, for the denitrification that was observed between 9-15 January sedimenting NAT particles that formed on mountain wave ice PSCs as has been discussed by Fueglistaler et al (2002), Dhaniyala et al (2002) and Mann et al (2005) could be a possible mechanism.…”

Section: Discussionmentioning

confidence: 61%

“…In contrast, for the denitrification that was observed between 9-15 January sedimenting NAT particles that formed on mountain wave ice PSCs as has been discussed by Fueglistaler et al (2002), Dhaniyala et al (2002) and Mann et al (2005) could be a possible mechanism.…”

Section: Psc Formation and Denitrificationmentioning

confidence: 61%

“…Fahey et al (2001) suggested that Arctic denitrification could be caused by a selective, but yet unknown, nucleation mechanism responsible for the formation of a small number of large solid particles as was first observed in the 1999/2000 Arctic winter stratosphere. In connection with mountain waves it was suggested that NAT clouds could form on mountain wave ice clouds and that these NAT clouds could serve as "mother clouds" producing a small number of large NAT particles that could sediment out and cause denitrification (Fueglistaler et al, 2002;Dhaniyala et al, 2002;Mann et al, 2005). During cold Arctic winters dehydration has been observed in the Arctic (e.g.…”

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confidence: 99%

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Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

et al. 2011

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Abstract. The sedimentation of HNO 3 containing Polar Stratospheric Cloud (PSC) particles leads to a permanent removal of HNO 3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion. The polar vortex in the Arctic winter 2009/2010 was very cold and stable between end of December and end of January. Strong denitrification between 475 to 525 K was observed in the Arctic in mid of January by the Odin Sub Millimetre Radiometer (Odin/SMR). This was the strongest denitrification that had been observed in the entire Odin/SMR measuring period (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010). Lidar measurements of PSCs were performed in the area of Kiruna, Northern Sweden with the IRF (Institutet för Rymdfysik) lidar and with the Esrange lidar in January 2010. The measurements show that PSCs were present over the area of Kiruna during the entire period of observations. The formation of PSCs during the Arctic winter 2009/2010 is investigated using a microphysical box model. Box model simulations are performed along air parcel trajectories calculated six days backward according to the PSC measurements with the ground-based lidar in the Kiruna area. From the temperature history of the backward trajectories and the box model simulations we find two PSC regions, one over Kiruna according to the measurements made in Kiruna and one north of Scandinavia which is much colder, reaching also temperatures below T ice . Using the box model simulations along backward Correspondence to: F. Khosrawi (farah@misu.su.se) trajectories together with the observations of Odin/SMR, Aura/MLS (Microwave Limb Sounder), CALIPSO (CloudAerosol Lidar and Infrared Pathfinder Satellite Observations) and the ground-based lidar we investigate how and by which type of PSC particles the denitrification that was observed during the Arctic winter 2009/2010 was caused. From our analysis we find that due to an unusually strong synoptic cooling event in mid January, ice particle formation on NAT may be a possible formation mechanism during that particular winter that may have caused the denitrification observed in mid January. In contrast, the denitrification that was observed in the beginning of January could have been caused by the sedimentation of NAT particles that formed on mountain wave ice clouds.

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Section: Discussionmentioning

confidence: 61%

Section: Psc Formation and Denitrificationmentioning

confidence: 61%

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confidence: 99%

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Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

et al. 2011

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“…As a result, our understanding of gravity waves on a global-scale is considerably poorer than of the larger-scale stratospheric dynamics (Fritts and Alexander, 2003). Since gravity wave dynamics drive important aspects of the global stratospheric circulation, climate and chemical state (e.g., Alexander and Rosenlof, 2003;Mann et al, 2005), this lack of data represents an important gap in our knowledge.…”

Section: Introductionmentioning

confidence: 83%

Imaging gravity waves in lower stratospheric AMSU-A radiances, Part 1: Simple forward model

Eckermann

2006

Atmos. Chem. Phys.

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Abstract. Using a simplified model of in-orbit radiance acquisition by the Advanced Microwave Sounding Unit (AMSU-A), we derive three-dimensional temperature weighting functions for Channel 9 measurements (peaking at ∼60-90 hPa) at all 30 cross-track beam positions and use them to investigate the sensitivity of these radiances to gravity waves. The vertical widths of the weighting functions limit detection to waves with vertical wavelengths of 10 km, with slightly better vertical wavelength sensitivity at the outermost scan angles due to the limb effect. Fourier Transforms of two-dimensional cross-track weighting functions reveal optimal sensitivity to cross-track wavelengths at the near-nadir scan angles, where horizontal measurement footprints are smallest. This sensitivity is greater for the AMSU-A on the Aqua satellite than for the identical instruments on the NOAA meteorological satellites, due to a lower orbit altitude and thus smaller horizontal footprints from antenna spreading. Small cross-track asymmetries in the radiance response to gravity waves are found that peak at the mid-range scan angles, with more symmetric responses at near-nadir and far off-nadir scan angles. Three-dimensional simulations show gravity wave oscillations imaged in horizontal AMSU-A radiance maps swept out by the scan pattern and satellite motion. A distorting curvature is added to imaged wave phase lines due to vertical variations in weighting function peaks with cross-track scan angle. This wave distortion is analogous to the well-known "limb darkening" and "limb brightening" of microwave radiances acquired from purely vertical background temperature profiles by crosstrack scanners. Waves propagating along track are more visible in these images at the outermost scan angles than those propagating cross track, due to oversampling and narrower widths of the horizontal measurement footprints in the along track direction. Based on nominal noise floors and repreCorrespondence to: S. D. Eckermann (stephen.eckermann@nrl.navy.mil) sentative lower stratospheric wave temperature amplitudes, our modeling indicates that Channel 9 AMSU-A radiances can resolve and horizontally image gravity waves with horizontal wavelengths of 150 km and vertical wavelengths of 10 km.

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“…However, modelling studies by Dhaniyala et al (2002) and Fueglistaler et al (2002) have shown that the dense NAT clouds produced downwind of mountain wave ice PSCs may subsequently act as sources for large NAT particles at low number concentrations throughout cold regions of the vortex by gradual sedimentation into the underlying NATsupersaturated air. Mann et al (2005) have explored the vortex-wide influence of such a mechanism and suggest that it may play a significant role in large NAT particle production and denitrification in the Arctic. However, methods of including such processes in largescale models have not yet been developed.…”

Section: Introductionmentioning

confidence: 99%

3-D microphysical model studies of Arctic denitrification: comparison with observations

et al. 2005

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Abstract. Simulations of Arctic denitrification using a 3-D chemistry-microphysics transport model are compared with observations for the winters 1994/95, 1996/97 and 1999/2000. The model of Denitrification by Lagrangian Particle Sedimentation (DLAPSE) couples the full chemical scheme of the 3-D chemical transport model, SLIMCAT, with a nitric acid trihydrate (NAT) growth and sedimentation scheme. We use observations from the Microwave Limb Sounder (MLS) and Improved Limb Atmospheric Sounder (ILAS) satellite instruments, the balloon-borne Michelsen Interferometer for Passive Atmospheric Sounding (MIPAS-B), and the in situ NO y instrument on-board the ER-2. As well as directly comparing model results with observations, we also assess the extent to which these observations are able to validate the modelling approach taken. For instance, in 1999/2000 the model captures the temporal development of denitrification observed by the ER-2 from late January into March. However, in this winter the vortex was already highly denitrified by late January so the observations do not provide a strong constraint on the modelled rate of denitrification. The model also reproduces the MLS observations of denitrification in early February 2000. In 1996/97 the model captures the timing and magnitude of denitrification as observed by ILAS, although the lack of observations north of ∼67 • N in the beginning of February make it difficult to constrain the actual timing of onset. The comparison for this winter does not support previous conclusions that denitrification must be caused by an ice-mediated process. In 1994/95 the model notably underestimates the magnitude of denitrification observed during a single balloon flight of the MIPAS-B instruCorrespondence to: S. Davies (stewart@env.leeds.ac.uk) ment. Agreement between model and MLS HNO 3 at 68 hPa in mid-February 1995 is significantly better. Sensitivity tests show that a 1.5 K overall decrease in vortex temperatures, or a factor 4 increase in assumed NAT nucleation rates, produce the best statistical fit to MLS observations. Both adjustments would be required to bring the model into agreement with the MIPAS-B observations. The agreement between the model and observations suggests that a NAT-only denitrification scheme (without ice), which was discounted by previous studies, must now be considered as one mechanism for the observed Arctic denitrification. The timing of onset and the rate of denitrification remain poorly constrained by the available observations.

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Large nitric acid trihydrate particles and denitrification caused by mountain waves in the Arctic stratosphere

Cited by 36 publications

References 41 publications

Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

Imaging gravity waves in lower stratospheric AMSU-A radiances, Part 1: Simple forward model

3-D microphysical model studies of Arctic denitrification: comparison with observations

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