scholarly journals Composition analysis of liquid particles in the Arctic stratosphere

2004 ◽  
Vol 4 (3) ◽  
pp. 2513-2531
Author(s):  
C. Weisser ◽  
K. Mauersberger ◽  
J. Schreiner ◽  
N. Larsen ◽  
F. Cairo ◽  
...  
Keyword(s):  
Equilibrium Temperature ◽  
Solid Particles ◽  
The Arctic ◽  
Composition Analysis ◽  
Synoptic Scale ◽  
Molar Ratios ◽  
Frost Point ◽  
Model Predictions ◽  
Stratospheric Clouds ◽  
First Time

Abstract. Synoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain leewaves were observed in early December 2002 from Kiruna/Sweden using balloon-borne instruments. The physical, chemical, and optical properties of the particles were measured. Within the PSC solid particles existed whenever the temperature was below the equilibrium temperature for nitric acid trihydrate and liquid particles appeared when the temperature fell below an even lower threshold about 3 K above the frost point. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight although the molar ratios H2O/HNO3 were about a factor of 2 higher than model predictions. In addition HCl has been measured for the first time in liquid aerosols. The chlorine isotope signature served as a unique tool to identify unambiguously HCl dissolved in STS particles. Within a narrow temperature range of about three degrees above the frost point, measured HCl molar ratios are below 1 weight%. There is only fair agreement with model predictions.

scholarly journals Composition analysis of liquid particles in the Arctic stratosphere under synoptic conditions

2006 ◽  
Vol 6 (3) ◽  
pp. 689-696 ◽  
Author(s):  
C. Weisser ◽  
K. Mauersberger ◽  
J. Schreiner ◽  
N. Larsen ◽  
F. Cairo ◽  
...  
Keyword(s):  
Equilibrium Temperature ◽  
Solid Particles ◽  
The Arctic ◽  
Composition Analysis ◽  
Molar Ratios ◽  
Frost Point ◽  
Synoptic Conditions ◽  
Lee Waves ◽  
Stratospheric Clouds ◽  
First Time

Abstract. Synoptic scale polar stratospheric clouds (PSCs) that formed without the presence of mountain lee waves were observed in early December 2002 from Kiruna/Sweden using balloon-borne instruments. The physical, chemical, and optical properties of the particles were measured. Within the PSC solid particles existed whenever the temperature was below the equilibrium temperature for nitric acid trihydrate and liquid particles appeared when the temperature fell below an even lower threshold about 3 K above the frost point with solid particles still present. The correlation of liquid supercooled ternary solution aerosols with local temperatures is a pronounced feature observed during this flight; average molar ratios H2O/HNO3 were somewhat higher than predicted by models. In addition HCl has been measured for the first time in liquid aerosols. The chlorine isotope signature served as a unique tool to identify unambiguously HCl dissolved in STS particles. Within a narrow temperature range of about three degrees above the frost point, the measured average amount of HCl in liquid particles is below 1 weight%.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT)

2013 ◽  
Vol 13 (3) ◽  
pp. 7979-8021 ◽  
Author(s):  
C. R. Hoyle ◽  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Companion Paper ◽  
Solid Particles ◽  
The Arctic ◽  
Formation Pathway ◽  
Constant Rate ◽  
Immersion Freezing ◽  
Heterogeneous Formation ◽  
Stratospheric Clouds ◽  
First Time

Abstract. Satellite based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarisation (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled the thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed PSCs very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

scholarly journals Polar Stratospheric Cloud evolution and chlorine activation measured by CALIPSO and MLS, and modelled by ATLAS

2015 ◽  
Vol 15 (16) ◽  
pp. 22141-22182
Author(s):  
H. Nakajima ◽  
I. Wohltmann ◽  
T. Wegner ◽  
M. Takeda ◽  
M. C. Pitts ◽  
...  
Keyword(s):  
The Arctic ◽  
Temperature History ◽  
Threshold Temperature ◽  
Limiting Factor ◽  
Temperature Decrease ◽  
Air Mass ◽  
Frost Point ◽  
Rapid Temperature ◽  
Cloud Evolution ◽  
Stratospheric Clouds

Abstract. We examined observations of polar stratospheric clouds (PSCs) by CALIPSO and of HCl, ClO and HNO3 by MLS along air mass trajectories to investigate the dependence of the inferred PSC composition on the temperature history of the air parcels, and the dependence of the level of chlorine activation on PSC composition. Several case studies based on individual trajectories from the Arctic winter 2009/10 were conducted, with the trajectories chosen such that the first processing of the air mass by PSCs in this winter occurred on the trajectory. Transitions of PSC composition classes were observed to be highly dependent on the temperature history. In cases of a gradual temperature decrease, nitric acid trihydrate (NAT) and super-cooled ternary solution (STS) mixture clouds were observed. In cases of rapid temperature decrease, STS clouds were first observed, followed by NAT/STS mixture clouds. When temperatures dropped below the frost point, ice clouds formed, and then transformed into NAT/STS mixture clouds when temperature increased above the frost point. The threshold temperature for rapid chlorine activation on PSCs is approximately 4 K below the NAT existence temperature, TNAT. Furthermore, simulations of the ATLAS chemistry and transport box model along the trajectories were used to corroborate the measurements and show good agreement with the observations. Rapid chlorine activation was observed when an airmass encountered PSCs. The observed and modelled dependence of the rate of chlorine activation on the PSC composition class was small. Usually, chlorine activation was limited by the amount of available ClONO2. Where ClONO2 was not the limiting factor, a large dependence on temperature was evident.

scholarly journals Polar stratospheric cloud evolution and chlorine activation measured by CALIPSO and MLS, and modeled by ATLAS

2016 ◽  
Vol 16 (5) ◽  
pp. 3311-3325 ◽  
Author(s):  
Hideaki Nakajima ◽  
Ingo Wohltmann ◽  
Tobias Wegner ◽  
Masanori Takeda ◽  
Michael C. Pitts ◽  
...  
Keyword(s):  
The Arctic ◽  
Temperature History ◽  
Threshold Temperature ◽  
Limiting Factor ◽  
Temperature Decrease ◽  
Air Mass ◽  
Frost Point ◽  
Rapid Temperature ◽  
Cloud Evolution ◽  
Stratospheric Clouds

Abstract. We examined observations of polar stratospheric clouds (PSCs) by CALIPSO, and of HCl and ClO by MLS along air mass trajectories, to investigate the dependence of the inferred PSC composition on the temperature history of the air parcels and the dependence of the level of chlorine activation on PSC composition. Several case studies based on individual trajectories from the Arctic winter 2009/2010 were conducted, with the trajectories chosen such that the first processing of the air mass by PSCs in this winter occurred on the trajectory. Transitions of PSC composition classes were observed to be highly dependent on the temperature history. In cases of a gradual temperature decrease, nitric acid trihydrate (NAT) and super-cooled ternary solution (STS) mixture clouds were observed. In cases of rapid temperature decrease, STS clouds were first observed, followed by NAT/STS mixture clouds. When temperatures dropped below the frost point, ice clouds formed and then transformed into NAT/STS mixture clouds when temperature increased above the frost point. The threshold temperature for rapid chlorine activation on PSCs is approximately 4 K below the NAT existence temperature, TNAT. Furthermore, simulations of the ATLAS chemistry and transport box model along the trajectories were used to corroborate the measurements and show good agreement with the observations. Rapid chlorine activation was observed when an air mass encountered PSCs. Usually, chlorine activation was limited by the amount of available ClONO2. Where ClONO2 was not the limiting factor, a large dependence on temperature was evident.

scholarly journals Nitric Acid Trihydrate (NAT) formation at low NAT supersaturation in Polar Stratospheric Clouds (PSCs)

2005 ◽  
Vol 5 (5) ◽  
pp. 1371-1380 ◽  
Author(s):  
C. Voigt ◽  
H. Schlager ◽  
B. P. Luo ◽  
A. Dörnbrack ◽  
A. Roiger ◽  
...  
Keyword(s):  
Nitric Acid ◽  
High Altitude ◽  
Equilibrium Temperature ◽  
In Situ Measurements ◽  
The Arctic ◽  
Polar Stratospheric Clouds ◽  
Research Aircraft ◽  
Stratospheric Clouds ◽  
Polar Ozone

Abstract. A PSC was detected on 6 February 2003 in the Arctic stratosphere by in-situ measurements onboard the high-altitude research aircraft Geophysica. Low number densities (~10-4cm-3) of small nitric acid (HNO3) containing particles (d<6µm) were observed at altitudes between 18 and 20km. Provided the temperatures remain below the NAT equilibrium temperature TNAT, these NAT particles have the potential to grow further and to remove HNO3 from the stratosphere, thereby enhancing polar ozone loss. Interestingly, the NAT particles formed in less than a day at temperatures just slightly below TNAT (T>TNAT-3.1K). This unique measurement of PSC formation at extremely low NAT saturation ratios (SNAT≤10) constrains current NAT nucleation theories. We suggest, that the NAT particles have formed heterogeneously, but for certain not on ice. Conversely, meteoritic particles may be favorable candidates for triggering NAT nucleation at the observed low number densities.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 2: Nucleation of ice on synoptic scales

2013 ◽  
Vol 13 (21) ◽  
pp. 10769-10785 ◽  
Author(s):  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Temperature Fluctuations ◽  
Ice Nucleation ◽  
Solid Particles ◽  
Small Scale ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Ice Nuclei ◽  
Scale Temperature ◽  
Stratospheric Clouds

Abstract. This paper provides compelling evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (polar stratospheric clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~1000 km dimension). CALIPSO observations also showed widespread PSCs containing NAT (nitric acid trihydrate) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the entire Arctic winter 2009/2010.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 2: Nucleation of ice on synoptic scales

2013 ◽  
Vol 13 (4) ◽  
pp. 8831-8872 ◽  
Author(s):  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Temperature Fluctuations ◽  
Ice Nucleation ◽  
Solid Particles ◽  
Small Scale ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Ice Nuclei ◽  
Scale Temperature ◽  
Stratospheric Clouds

Abstract. This paper provides unprecedented evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (Polar Stratospheric Clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~ 1000 km dimension). CALIPSO observations also showed widespread PSCs containing nitric acid trihydrate (NAT) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the entire Arctic winter 2009/2010.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT)

2013 ◽  
Vol 13 (18) ◽  
pp. 9577-9595 ◽  
Author(s):  
C. R. Hoyle ◽  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Companion Paper ◽  
Solid Particles ◽  
The Arctic ◽  
Orthogonal Polarization ◽  
Polar Stratospheric Clouds ◽  
Formation Pathway ◽  
Immersion Freezing ◽  
Heterogeneous Formation ◽  
Stratospheric Clouds

Abstract. Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

scholarly journals Stratospheric water vapour as tracer for Vortex filamentation in the Arctic winter 2002/2003

2003 ◽  
Vol 3 (6) ◽  
pp. 1991-1997 ◽  
Author(s):  
M. Müller ◽  
R. Neuber ◽  
F. Fierli ◽  
A. Hauchecorne ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapour ◽  
Large Scale ◽  
Polar Vortex ◽  
The Arctic ◽  
Edge Region ◽  
Particle Sedimentation ◽  
Frost Point ◽  
Lagrangian Advection ◽  
Stratospheric Clouds ◽  
Stratospheric Water Vapour

Abstract. Balloon-borne frost point hygrometers measured three high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen during winter 2002/2003. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. The water vapour sounding on 11 February 2003 was obtained within the vortex edge region of the lower stratosphere. Here, a significant reduction of water vapour mixing ratio was observed between 16 and 19 km. The stratospheric temperatures indicate that this dehydration was not caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. Ozone observations on this day indicate a large scale movement of the polar vortex and show laminae in the same altitude range as the water vapour profile. The link between the observed water vapour reduction and filaments in the vortex edge region is indicated in the results of the semi-lagrangian advection model MIMOSA, which show that adjacent filaments of polar and mid latitude air can be identified above the Spitsbergen region. A vertical cross-section produced by the MIMOSA model reveals that the water vapour sonde flew through polar air in the lowest part of the stratosphere below 425 K, then passed through filaments of mid latitude air with lower water vapour concentrations, before it finally entered the polar vortex above 450 K. These results indicate that on 11 February 2003 the frost point hygrometer measured different water vapour concentrations as the sonde detected air with different origins. Instead of being linked to dehydration due to PSC particle sedimentation, the local reduction in the stratospheric water vapour profile was in this case caused by dynamical processes in the polar stratosphere.

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