scholarly journals A-train CALIOP and MLS observations of early winter antarctic polar stratospheric clouds and nitric acid in 2008

2011 ◽  
Vol 11 (10) ◽  
pp. 29283-29356
Author(s):  
A. Lambert ◽  
M. L. Santee ◽  
D. L. Wu ◽  
J. H. Chae
Keyword(s):  
Nitric Acid ◽  
Gas Phase ◽  
Wave Activity ◽  
Equilibrium Curve ◽  
Polar Stratospheric Clouds ◽  
Frost Point ◽  
Time Histories ◽  
Stratospheric Clouds ◽  
The Antarctic ◽  
Temperature Time

Abstract. A-train Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Microwave Limb Sounder (MLS) observations are used to investigate the development of polar stratospheric clouds (PSCs) and the gas phase nitric acid distribution in the early 2008 Antarctic winter. Observational evidence of gravity-wave activity is provided by Atmospheric Infrared Sounder (AIRS) radiances and infrared spectroscopic detection of nitric acid trihydrate (NAT) in PSCs is obtained from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Goddard Earth Observing System Data Assimilation System (GEOS-5 DAS) analyses are used to derive Lagrangian trajectories and to determine temperature-time histories of air parcels. We use CALIOP backscatter and depolarization measurements to classify PSCs and the MLS measurements to determine the corresponding gas phase HNO3 as a function of temperature. For liquid PSCs the uptake of HNO3 follows the theoretical equilibrium curve for supercooled ternary solutions (STS), but at temperatures about 1 K lower as determined from GEOS-5. In the presence of solid phase PSCs, above the ice frost-point, the HNO3 depletion occurs over a wider range of temperatures (+2 to −7 K) distributed about the NAT equilibrium curve. Rapid gas phase HNO3 depletion is first seen by MLS from from 23–25 May 2008, consisting of a decrease in the volume mixing ratio (parts per billion by volume) from 14 ppbv to 7 ppbv on the 46–32 hPa (hectopascal) pressure levels and accompanied by a 2–3 ppbv increase by renitrification at the 68 hPa pressure level. Temperature-time histories of air parcels demonstrate that the depleted HNO3 region is more clearly correlated with prior low temperature exposure of a few kelvin above the frost-point than with either the region bounded by the NAT existence temperature threshold or the region of minimum temperatures. From the combined data we infer the presence of large-size NAT particles with effective radii >5–7 μm and low NAT number densities <1×10−3 cm−3. This denitrification event is observed close to the pole in the Antarctic vortex before synoptic temperatures first fall below the ice frost point and before the widespread occurrence of large-scale NAT PSCs at altitudes 18–26 km in a polar freezing belt. The NAT outbreak is similar to an event previously reported from MIPAS observations in mid-June 2003 and is again linked to NAT formation via ice-seeding following an episode of mountain wave activity detected by AIRS. Subsequent wave-ice formation in the rapid cooling phases over the Antarctic Peninsula and Ellsworth Mountains is detected here by CALIOP and MIPAS. The NAT clouds appear to be composed of relatively small particles with estimated effective radii of around 1 μm and high NAT number densities >0.2 cm−3.

scholarly journals A-train CALIOP and MLS observations of early winter Antarctic polar stratospheric clouds and nitric acid in 2008

2012 ◽  
Vol 12 (6) ◽  
pp. 2899-2931 ◽  
Author(s):  
A. Lambert ◽  
M. L. Santee ◽  
D. L. Wu ◽  
J. H. Chae
Keyword(s):  
Nitric Acid ◽  
Gas Phase ◽  
Wave Activity ◽  
Equilibrium Curve ◽  
Polar Stratospheric Clouds ◽  
Frost Point ◽  
Time Histories ◽  
Stratospheric Clouds ◽  
The Antarctic ◽  
Temperature Time

Abstract. A-train Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Microwave Limb Sounder (MLS) observations are used to investigate the development of polar stratospheric clouds (PSCs) and the gas-phase nitric acid distribution in the early 2008 Antarctic winter. Observational evidence of gravity-wave activity is provided by Atmospheric Infrared Sounder (AIRS) radiances and infrared spectroscopic detection of nitric acid trihydrate (NAT) in PSCs is obtained from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Goddard Earth Observing System Data Assimilation System (GEOS-5 DAS) analyses are used to derive Lagrangian trajectories and to determine temperature-time histories of air parcels. We use CALIOP backscatter and depolarization measurements to classify PSCs and the MLS measurements to determine the corresponding gas-phase HNO3 as a function of temperature. For liquid PSCs the uptake of HNO3 follows the theoretical equilibrium curve for supercooled ternary solutions (STS), but at temperatures about 1 K lower as determined from GEOS-5. In the presence of solid phase PSCs, above the ice frost-point, the HNO3 depletion occurs over a wider range of temperatures (+2 to −7 K) distributed about the NAT equilibrium curve. Rapid gas-phase HNO3 depletion is first seen by MLS from from 23–25 May 2008, consisting of a decrease in the volume mixing ratio from 14 ppbv (parts per billion by volume) to 7 ppbv on the 46–32 hPa (hectopascal) pressure levels and accompanied by a 2–3 ppbv increase by renitrification at the 68 hPa pressure level. The observed region of depleted HNO3 is substantially smaller than the region bounded by the NAT existence temperature threshold. Temperature-time histories of air parcels demonstrate that the depletion is more clearly correlated with prior exposure to temperatures a few kelvin above the frost-point. From the combined data we infer the presence of large-size NAT particles with effective radii >5–7 μm and low NAT number densities <1 × 10−3 cm−3. This denitrification event is observed close to the pole in the Antarctic vortex before synoptic temperatures first fall below the ice frost point and before the widespread occurrence of large-scale NAT PSCs. An episode of mountain wave activity detected by AIRS on 28 May 2008 led to wave-ice formation in the rapid cooling phases over the Antarctic Peninsula and Ellsworth Mountains, seeding an outbreak of NAT PSCs that were detected by CALIOP and MIPAS. The NAT clouds formed at altitudes of 18–26 km in a polar freezing belt and appear to be composed of relatively small particles with estimated effective radii of around 1 μm and high NAT number densities >0.2 cm−3. This NAT outbreak is similar to an event previously reported from MIPAS observations in mid-June 2003.

scholarly journals Accuracy and precision of polar lower stratospheric temperatures from reanalyses evaluated from A-Train CALIOP and MLS, COSMIC GPS RO, and the equilibrium thermodynamics of supercooled ternary solutions and ice clouds

2018 ◽  
Vol 18 (3) ◽  
pp. 1945-1975 ◽  
Author(s):  
Alyn Lambert ◽  
Michelle L. Santee
Keyword(s):  
Pressure Range ◽  
Equilibrium Thermodynamics ◽  
Polar Stratospheric Clouds ◽  
Ice Clouds ◽  
Warm Bias ◽  
Frost Point ◽  
Ternary Solutions ◽  
Accuracy And Precision ◽  
Temperature Reference ◽  
Stratospheric Clouds

Abstract. We investigate the accuracy and precision of polar lower stratospheric temperatures (100–10 hPa during 2008–2013) reported in several contemporary reanalysis datasets comprising two versions of the Modern-Era Retrospective analysis for Research and Applications (MERRA and MERRA-2), the Japanese 55-year Reanalysis (JRA-55), the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-I), and the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (NCEP-CFSR). We also include the Goddard Earth Observing System model version 5.9.1 near-real-time analysis (GEOS-5.9.1). Comparisons of these datasets are made with respect to retrieved temperatures from the Aura Microwave Limb Sounder (MLS), Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) temperatures, and independent absolute temperature references defined by the equilibrium thermodynamics of supercooled ternary solutions (STSs) and ice clouds. Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations of polar stratospheric clouds are used to determine the cloud particle types within the Aura MLS geometric field of view. The thermodynamic calculations for STS and the ice frost point use the colocated MLS gas-phase measurements of HNO3 and H2O. The estimated bias and precision for the STS temperature reference, over the 68 to 21 hPa pressure range, are 0.6–1.5 and 0.3–0.6 K, respectively; for the ice temperature reference, they are 0.4 and 0.3 K, respectively. These uncertainties are smaller than those estimated for the retrieved MLS temperatures and also comparable to GPS RO uncertainties (bias  <  0.2 K, precision  >  0.7 K) in the same pressure range. We examine a case study of the time-varying temperature structure associated with layered ice clouds formed by orographic gravity waves forced by flow over the Palmer Peninsula and compare how the wave amplitudes are reproduced by each reanalysis dataset. We find that the spatial and temporal distribution of temperatures below the ice frost point, and hence the potential to form ice polar stratospheric clouds (PSCs) in model studies driven by the reanalyses, varies significantly because of the underlying differences in the representation of mountain wave activity. High-accuracy COSMIC temperatures are used as a common reference to intercompare the reanalysis temperatures. Over the 68–21 hPa pressure range, the biases of the reanalyses with respect to COSMIC temperatures for both polar regions fall within the narrow range of −0.6 K to +0.5 K. GEOS-5.9.1, MERRA, MERRA-2, and JRA-55 have predominantly cold biases, whereas ERA-I has a predominantly warm bias. NCEP-CFSR has a warm bias in the Arctic but becomes substantially colder in the Antarctic. Reanalysis temperatures are also compared with the PSC reference temperatures. Over the 68–21 hPa pressure range, the reanalysis temperature biases are in the range −1.6 to −0.3 K with standard deviations  ∼  0.6 K for the CALIOP STS reference, and in the range −0.9 to +0.1 K with standard deviations  ∼  0.7 K for the CALIOP ice reference. Comparisons of MLS temperatures with the PSC reference temperatures reveal vertical oscillations in the MLS temperatures and a significant low bias in MLS temperatures of up to 3 K.

scholarly journals Can gravity waves significantly impact PSC occurrence in the Antarctic?

2009 ◽  
Vol 9 (22) ◽  
pp. 8825-8840 ◽  
Author(s):  
A. J. McDonald ◽  
S. E. George ◽  
R. M. Woollands
Keyword(s):  
Antarctic Peninsula ◽  
Gravity Waves ◽  
Clustering Algorithm ◽  
Small Scale ◽  
Temperature Threshold ◽  
Aerosol Extinction ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Stratospheric Clouds ◽  
The Antarctic

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 (TNAT), 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 TNAT 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 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 TNAT 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 TNAT threshold unaided. Additionally, there is a reduction in the magnitude of gravity waves perturbations observed as POAM III samples poleward of the peninsula.

scholarly journals Nucleation of nitric acid hydrates in Polar Stratospheric Clouds by meteoric material

2017 ◽  
Author(s):  
Alexander D. James ◽  
James S. A. Brooke ◽  
Thomas P. Mangan ◽  
Thomas F. Whale ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Heterogeneous Nucleation ◽  
Ozone Depletion ◽  
Mode Of Action ◽  
Polar Stratospheric Clouds ◽  
Water Ice ◽  
Meteoric Smoke ◽  
Polar Stratosphere ◽  
Stratospheric Clouds ◽  
Meteoric Material

Abstract. Heterogeneous nucleation of crystalline nitric acid hydrates in Polar Stratospheric Clouds (PSCs) enhances ozone depletion. However, the identity and mode of action of the particles responsible for nucleation remains unknown. It has been suggested that meteoric material may trigger nucleation of nitric acid trihydrate (NAT), but this has never been directly demonstrated in the laboratory. Meteoric material is present in two forms in the stratosphere, smoke which results from the ablation and re-condensation of vapours, and fragments which result from the disruption of meteoroids entering the atmosphere. Here we show that analogues of both materials have a capacity to nucleate nitric acid hydrates. In combination with estimates from a global model of the amount of meteoric smoke and fragments in the polar stratosphere we show that meteoric material probably accounts for NAT observations in early season polar stratospheric clouds in the absence of water ice.

scholarly journals A closer look at Arctic ozone loss and polar stratospheric clouds

2010 ◽  
Vol 10 (17) ◽  
pp. 8499-8510 ◽  
Author(s):  
N. R. P. Harris ◽  
R. Lehmann ◽  
M. Rex ◽  
P. von der Gathen
Keyword(s):  
Nitric Acid ◽  
Climate Models ◽  
Empirical Relationship ◽  
Early Spring ◽  
Aerosol Formation ◽  
Polar Stratospheric Clouds ◽  
Ozone Loss ◽  
Relationship Analysis ◽  
Near Ultraviolet ◽  
Stratospheric Clouds

Abstract. The empirical relationship found between column-integrated Arctic ozone loss and the potential volume of polar stratospheric clouds inferred from meteorological analyses is recalculated in a self-consistent manner using the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature dependent cold aerosol formation makes little difference to the original, empirical relationship. Analysis of the photochemistry leading to the ozone loss shows that activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate-limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer in the near ultraviolet. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result of these compensating effects, the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as denitrification and renitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss. These results indicate that relatively simple parameterisations of Arctic ozone loss could be developed for use in coupled chemistry climate models.

Coexistence of metastable nitric acid dihydrates: A molecular level contribution to understanding the formation of polar stratospheric clouds crystals

2006 ◽  
Vol 426 (1-3) ◽  
pp. 20-25 ◽  
Author(s):  
Anas Al Natsheh ◽  
Alexey B. Nadykto ◽  
Kurt V. Mikkelsen ◽  
Fangqun Yu ◽  
Juhani Ruuskanen
Keyword(s):  
Nitric Acid ◽  
Molecular Level ◽  
Polar Stratospheric Clouds ◽  
Stratospheric Clouds

scholarly journals Nucleation of nitric acid hydrates in polar stratospheric clouds by meteoric material

2018 ◽  
Vol 18 (7) ◽  
pp. 4519-4531 ◽  
Author(s):  
Alexander D. James ◽  
James S. A. Brooke ◽  
Thomas P. Mangan ◽  
Thomas F. Whale ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Heterogeneous Nucleation ◽  
Ozone Depletion ◽  
Mode Of Action ◽  
Polar Stratospheric Clouds ◽  
Water Ice ◽  
Meteoric Smoke ◽  
Polar Stratosphere ◽  
Stratospheric Clouds ◽  
Meteoric Material

Abstract. Heterogeneous nucleation of crystalline nitric acid hydrates in polar stratospheric clouds (PSCs) enhances ozone depletion. However, the identity and mode of action of the particles responsible for nucleation remains unknown. It has been suggested that meteoric material may trigger nucleation of nitric acid trihydrate (NAT, or other nitric acid phases), but this has never been quantitatively demonstrated in the laboratory. Meteoric material is present in two forms in the stratosphere: smoke that results from the ablation and re-condensation of vapours, and fragments that result from the break-up of meteoroids entering the atmosphere. Here we show that analogues of both materials have a capacity to nucleate nitric acid hydrates. In combination with estimates from a global model of the amount of meteoric smoke and fragments in the polar stratosphere we show that meteoric material probably accounts for NAT observations in early season polar stratospheric clouds in the absence of water ice.

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