Aircraft lidar observations of an enhanced type Ia polar stratospheric clouds during APE‐POLECAT

Tsias, A.; Wirth, Martin; Carslaw, K. S.; Biele, Jens; Mehrtens, Hela; Reichardt, Jens; Wedekind, C.; Weiß, Volker; Renger, W.; Neuber, Roland; Zahn, U. von; Stein, B.; Santacesaria, V.; Stefanutti, L.; Fierli, F.; Bacmeister, Julio T.; Peter, Thomas

doi:10.1029/1998jd100055

Cited by 69 publications

(83 citation statements)

References 25 publications

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“…They concluded that during the "PSC season" when the background temperature was close enough to the NAT formation temperature (T NAT ), derived in Hanson and Mauersberger (1988), gravity wave perturbations influence PSC formation approximately 15% of the time. Interestingly, this value is similar to the findings of Felton et al (2007) who concluded Type Ia enhanced PSCs, which are likely to be NAT crystals with unusually large lidar backscattering ratios which appear down wind of mountain wave-induced ice clouds (Tsias et al, 1999), make up 11% of the clouds observed during the SAGE III Ozone Loss and Validation Experiment (SOLVE) campaign in winter 2000 in the Northern Hemisphere. However, the warmer mean temperature in the Arctic means that this is likely to be coincidental.…”

Section: Introductionsupporting

confidence: 76%

Can gravity waves significantly impact PSC occurrence in the Antarctic?

2009

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Abstract.A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs). POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm.A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (T NAT ), shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed.Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses). For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to T NAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically Correspondence to: A. J. McDonald (adrian.mcdonald@canterbury.ac.nz) associated with the Antarctic Peninsula; a known mountain wave "hotspot". The latitudinal variation of POAM III observations means that we only observe this region in June-July, and thus the true pattern of enhanced PSC production may continue operating into later months.The analysis has shown that early in the Antarctic winter stratospheric background temperatures are close to the T NAT threshold (and PSC formation), and are thus sensitive to temperature perturbations associated with mountain wave activity near the Antarctic peninsula (40% of PSC formation). Later in the season, and at latitudes away from the peninsula, temperature perturbations associated with gravity waves contribute to about 15% of the observed PSC (a value which corresponds well to several previous studies). This lower value is likely to be due to colder background temperatures already achieving the T NAT threshold unaided. Additionally, there is a reduction in the magnitude of gravity waves perturbations observed as POAM III samples poleward of the peninsula.

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Section: Introductionsupporting

confidence: 76%

Can gravity waves significantly impact PSC occurrence in the Antarctic?

2009

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“…While this cannot establish a freezing process above (T ice ), since the ice phase may be very short lived compared to a long lived hydrate phase initiated by the ice, it is consistent with a freezing process above T ice which would help explain many observations of solid PSC particles (Drdla et al, 2002a). High number concentrations of small solid particles in equilibrium with the gas phase could be nucleated in mountain wave conditions (Tsias et al, 1999). Other investigations show PSCs to be dominated by liquid particles with only small concentrations of solid particles growing to large sizes; an observation which calls for a selective nucleation mechanism (Drdla et al, 2002b).…”

Section: Introductionmentioning

confidence: 65%

Formation of solid particles in synoptic-scale Arctic PSCs in early winter 2002/2003

et al. 2004

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Abstract. Polar stratospheric clouds (PSC) have been observed in early winter (December 2002) during the SOLVE II/Vintersol campaign, both from balloons carrying comprehensive instrumentation for measurements of chemical composition, size distributions, and optical properties of the particles, as well as from individual backscatter soundings from Esrange and Sodankylä. The observations are unique in the sense that the PSC particles seem to have formed in the early winter under synoptic temperature conditions and not being influenced by mountain lee waves. A sequence of measurements during a 5-days period shows a gradual change between liquid and solid type PSCs with the development of a well-known sandwich structure. It appears that all PSC observations show the presence of a background population of solid particles, occasionally mixed in with more optically dominating liquid particles. The measurements have been compared with results from a detailed microphysical and optical simulation of the formation processes. Calculated extinctions are in good agreement with SAGE-III measurements from the same period. Apparently the solid particles are controlled by the synoptic temperature history while the presence of liquid particles is controlled by the local temperatures at the time of observation. The temperature histories indicate that the solid particles are nucleated above the ice frost point, and a surface freezing mechanism for this is included in the model. Reducing the calculated freezing ratesCorrespondence to: N. Larsen (nl@dmi.dk) by a factor 10-20, the model is able to simulate the observed particle size distributions and reproduce observed HNO 3 gas phase concentrations.

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“…Under quasi-stationary meteorological conditions these mesoscale clouds do not strongly vary their spatial position relative to the ground, and in the air flowing through them particles nucleate, grow, and evaporate continuously over a period of hours. Previously, particle evolution in wave PSCs was successfully studied based on quasi-Lagrangian observations acquired with airborne lidars (Carslaw et al, 1998;Tsias et al, 1999;Wirth et al, 1999;Dörnbrack et al, 2002;Hu et al, 2002;Fueglistaler et al, 2003). A similar study that rests upon data obtained with ground-based lidars has not been published so far, probably mainly due to the fact that they lack the additional dimension that is offered by aircraft observations.…”

Section: Introductionmentioning

confidence: 99%

“…Gobbi et al, 1998;Stein et al, 1999;Toon et al, 2000;Biele et al, 2001). In this case, the interpretation of the PSC data in terms of the two coexisting particle classes can be improved if backscatter coefficients (or backscatter ratios) are studied separately for both states of polarization, since droplet scattering adds to the parallel-polarized lidar signal alone (single scattering assumed) whereas the light backscattered from nonspherical solid particles has both parallel-and perpendicular-polarized components.…”

Section: Polarization-sensitive Backscatter Ratiosmentioning

confidence: 99%

Mountain wave PSC dynamics and microphysics from ground-based lidar measurements and meteorological modeling

Reichardt

Dörnbrack²,

Reichardt

et al. 2004

Atmos. Chem. Phys.

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Abstract. The day-long observation of a polar stratospheric cloud (PSC) by two co-located ground-based lidars at the Swedish research facility Esrange (67.9 • N, 21.1 • E) on 16 January 1997 is analyzed in terms of PSC dynamics and microphysics. Mesoscale modeling is utilized to simulate the meteorological setting of the lidar measurements. Microphysical properties of the PSC particles are retrieved by comparing the measured particle depolarization ratio and the PSC-averaged lidar ratio with theoretical optical data derived for different particle shapes. In the morning, nitric acid trihydrate (NAT) particles and then increasingly coexisting liquid ternary aerosol (LTA) were detected as outflow from a mountain wave-induced ice PSC upwind Esrange. The NAT PSC is in good agreement with simulations for irregularshaped particles with length-to-diameter ratios between 0.75 and 1.25, maximum dimensions from 0.7 to 0.9 µm, and a number density from 8 to 12 cm −3 and the coexisting LTA droplets had diameters from 0.7 to 0.9 µm, a refractive index of 1.39 and a number density from 7 to 11 cm −3 . The total amount of condensed HNO 3 was in the range of 8-12 ppbv. The data provide further observational evidence that NAT forms via deposition nucleation on ice particles as a number of recently published papers suggest. By early afternoon the mountain-wave ice PSC expanded above the lidar site. Its optical data indicate a decrease in minimum particle size from 3 to 1.9 µm with time. Later on, following the weakening of the mountain wave, wave-induced LTA was observed only. Our study demonstrates that ground-based lidar measurements of PSCs can be comprehensively interpreted if combined with mesoscale meteorological data.

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Aircraft lidar observations of an enhanced type Ia polar stratospheric clouds during APE‐POLECAT

Cited by 69 publications

References 25 publications

Can gravity waves significantly impact PSC occurrence in the Antarctic?

Can gravity waves significantly impact PSC occurrence in the Antarctic?

Formation of solid particles in synoptic-scale Arctic PSCs in early winter 2002/2003

Mountain wave PSC dynamics and microphysics from ground-based lidar measurements and meteorological modeling

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