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Sample records for polar stratospheric clouds

  1. Physical processes in polar stratospheric ice clouds

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Turco, Richard; Jordan, Joseph

    1988-01-01

    A one dimensional model of cloud microphysics was used to simulate the formation and evolution of polar stratospheric ice clouds. Some of the processes which are included in the model are outlined. It is found that the clouds must undergo preferential nucleation upon the existing aerosols just as do tropospheric cirrus clouds. Therefore, there is an energy barrier between stratospheric nitric acid particles and ice particles implying that nitric acid does not form a continuous set of solutions between the trihydrate and ice. The Kelvin barrier is not significant in controlling the rate of formation of ice particles. It was found that the cloud properties are sensitive to the rate at which the air parcels cool. In wave clouds, with cooling rates of hundreds of degrees per day, most of the existing aerosols nucleate and become ice particles. Such clouds have particles with sizes on the order of a few microns, optical depths on order of unity and are probably not efficient at removing materials from the stratosphere. In clouds which form with cooling rates of a few degrees per day or less, only a small fraction of the aerosols become cloud particles. In such clouds the particle radius is larger than 10 microns, the optical depths are low and water vapor is efficiently removed. Seasonal simulations show that the lowest water vapor mixing ratio is determined by the lowest temperature reached, and that the time when clouds disappear is controlled by the time when temperatures begin to rise above the minimum values.

  2. Polar stratospheric clouds inferred from satellite data

    NASA Technical Reports Server (NTRS)

    Austin, J.; Jones, R. L.; Remsberg, E. E.; Tuck, A. F.

    1986-01-01

    Anomalously high radiances from the ozone channel of the Limb Infrared Monitor of the Stratosphere (LIMS) sounding instrument have been observed in the Northern Hemisphere winter lower stratosphere. Such events, thought to be due to polar stratospheric clouds (PSCs), are examined further by computing relative humidities using Stratospheric Sounding Unit temperatures and water vapor measurements from the LIMS Map Archive Tape analyses. Regions identified as PSCs are found to correspond closely to regions of high humidity. While instances of saturation were found, the average humidity at the centers of 39 PSCs was calculated to be 58 percent. Possible reasons for this apparent discrepancy are discussed. Applying a similar approach to the Southern Hemisphere, in 1979, virtually no PSCs are found in the vortex after September 10 at 20 km. This result has important implications for a number of proposed explanations for the Antarctic ozone hole.

  3. Sulfate aerosols and polar stratospheric cloud formation

    SciTech Connect

    Tolbert, M.A. )

    1994-04-22

    Before the discovery of the Antarctic ozone hole, it was generally assumed that gas-phase chemical reactions controlled the abundance of stratospheric ozone. However, the massive springtime ozone losses over Antarctica first reported by Farman et al in 1985 could not be explained on the basis of gas-phase chemistry alone. In 1986, Solomon et al suggested that chemical reactions occurring on the surfaces of polar stratospheric clouds (PSCs) could be important for the observed ozone losses. Since that time, an explosion of laboratory, field, and theoretical research in heterogeneous atmospheric chemistry has occurred. Recent work has indicated that the most important heterogeneous reaction on PSCs is ClONO[sub 2] + HCl [yields] Cl[sub 2] + HNO[sub 3]. This reaction converts inert chlorine into photochemically active Cl[sub 2]. Photolysis of Cl[sub 2] then leads to chlorine radicals capable of destroying ozone through very efficient catalytic chain reactions. New observations during the second Airborne Arctic Stratospheric Expedition found stoichiometric loss of ClONO[sub 2] and HCl in air processed by PSCs in accordance with reaction 1. Attention is turning toward understanding what kinds of aerosols form in the stratospheric, their formation mechanism, surface area, and specific chemical reactivity. Some of the latest findings, which underline the importance of aerosols, were presented at a recent National Aeronautics and Space Administration workshop in Boulder, Colorado.

  4. The ozone hole - The role of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Turco, R. P.

    1988-01-01

    The role of polar stratospheric clouds in the formation of the Antarctic ozone hole is considered. Several researchers have suggested that the decrease in ozone over Antarctica is related to the polar stratospheric clouds (PSCs) which had been observed in the antarctic winter stratosphere. Some of the pertinent characteristics of polar stratospheric clouds are discussed, and it is shown how these clouds may participate in the ozone destruction process. The satellite data for PSCs is analyzed, and statistical information regarding the number and maximum extinctions of these clouds is presented. Evidence that the polar stratospheric clouds are composed of frozen nitric acid is considered. It is suggested that the evaporation of the clouds, in late August and September, will release HOCl and HNO3 to the environment. This could be followed by the photodissociation of HOCl to OH and Cl, which would very effectively destroy ozone. However, the ozone destruction mechanism could be halted when enough of the evaporated nitric acid is photolized.

  5. Polar stratospheric clouds and ozone depletion

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Turco, Richard P.

    1991-01-01

    A review is presented of investigations into the correlation between the depletion of ozone and the formation of polar stratospheric clouds (PSCs). Satellite measurements from Nimbus 7 showed that over the years the depletion from austral spring to austral spring has generally worsened. Approximately 70 percent of the ozone above Antarctica, which equals about 3 percent of the earth's ozone, is lost during September and October. Various hypotheses for ozone depletion are discussed including the theory suggesting that chlorine compounds might be responsible for the ozone hole, whereby chlorine enters the atmosphere as a component of chlorofluorocarbons produced by humans. The three types of PSCs, nitric acid trihydrate, slowly cooling water-ice, and rapidly cooling water-ice clouds act as important components of the Antarctic ozone depletion. It is indicated that destruction of the ozone will be more severe each year for the next few decades, leading to a doubling in area of the Antarctic ozone hole.

  6. CALIOP Polar Stratospheric Cloud Data Product

    NASA Astrophysics Data System (ADS)

    Pitts, M. C.; Poole, L. R.; Baskin, W. E.; Lucker, P. L.

    2012-12-01

    Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying polar stratospheric cloud (PSC) characteristics. We have developed an approach for both detection and composition classification of PSCs based on CALIOP backscatter and depolarization measurements. The algorithm includes both the CALIOP 532-nm scattering ratio and perpendicular backscatter coefficient for cloud detection, which significantly improves the detection of tenuous PSC mixtures with Nitric Acid Trihydrate (NAT) particles in low number density, and incorporates an innovative successive horizontal averaging scheme to enable the detection of strongly backscattering PSCs at fine horizontal resolution (5-km) and more tenuous clouds at increasingly coarser averaging scales. The algorithm also includes a scheme for classifying PSCs by composition based on the CALIOP aerosol depolarization and inverse scattering ratio. To date, only a research version of this PSC data product has been available on request. An autonomous production version is currently under development with the beta version scheduled to be released by the end of 2012. The PSC product will be archived and distributed by the Atmospheric Science Data Center (http://eosweb.larc.nasa.gov/). This poster presents an overview of the PSC detection and composition algorithms, describes the output parameters of the new PSC production version, and show examples to illustrate the utility of the data product. The poster also describes ancillary data chosen to better facilitate the use of the PSC data product for science applications.

  7. How do Polar Stratospheric Clouds Form?

    NASA Technical Reports Server (NTRS)

    Drdla, Katja; Gandrud, Bruce; Baumgardner, Darrel; Herman, Robert; Gore, Warren J. (Technical Monitor)

    2000-01-01

    SOLVE measurements have been compared with results from a microphysical model to understand the composition and formation of the polar stratospheric clouds (PSCs) observed during SOLVE. Evidence that the majority of the particles remain liquid throughout the winter will be presented. However, a small fraction of the particles do freeze, and the presence of these frozen particles can not be explained by current theories, in which the only freezing mechanism is homogeneous freezing to ice below the ice frost point. Alternative formation mechanisms, in particular homogeneous freezing above the ice frost point and heterogeneous freezing, have been explored using the microphysical model. Both nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) have been considered as possible compositions for the solid-phase nitric acid aerosols. Comparisons between the model results and the SOLVE measurements will be used to constrain the possible formation mechanisms. Other effects of these frozen particles will also be discussed, in particular denitrification.

  8. Polar stratospheric clouds and ozone depletion

    SciTech Connect

    Toon, O.B. ); Turco, R.P. )

    1991-06-01

    During the Antarctic winter, strange and often invisible clouds form in the stratosphere over the pole. These clouds of ice and frozen nitric acid play a crucial role in the chemical cycle responsible for the recent appearance of the annual ozone hole. Their chemistry removes compounds that would normally trap ozone-destroying free chlorine produced by the breakdown of CFCs. The paper describes these clouds, their formation, and the mechanisms by which these clouds help chlorine destroy ozone.

  9. Chemistry and microphysics of polar stratospheric clouds and cirrus clouds.

    PubMed

    Zondlo, M A; Hudson, P K; Prenni, A J; Tolbert, M A

    2000-01-01

    Ice particles found within polar stratospheric clouds (PSCs) and upper tropospheric cirrus clouds can dramatically impact the chemistry and climate of the Earth's atmosphere. The formation of PSCs and the subsequent chemical reactions that occur on their surfaces are key components of the massive ozone hole observed each spring over Antarctica. Cirrus clouds also provide surfaces for heterogeneous reactions and significantly modify the Earth's climate by changing the visible and infrared radiation fluxes. Although the role of ice particles in climate and chemistry is well recognized, the exact mechanisms of cloud formation are still unknown, and thus it is difficult to predict how anthropogenic activities will change cloud abundances in the future. This article focuses on the nucleation, chemistry, and microphysical properties of ice particles composing PSCs and cirrus clouds. A general overview of the current state of research is presented along with some unresolved issues facing scientists in the future. PMID:11031290

  10. Composition of Polar Stratospheric Clouds from Infrared Spectroscopy

    NASA Technical Reports Server (NTRS)

    Tolbert, M. A.; Anthony, S. E.; Disselkamp, R.; Toon, O. B.; Condon, Estelle P. (Technical Monitor)

    1995-01-01

    Heterogeneous reactions on polar stratospheric clouds (PSCs) have recently been implicated in Arctic and Antarctic ozone destruction. Although the chemistry is well documented, the composition of the clouds remains uncertain. The most common PSCs (type I) are thought to be composed of HNO3/H2O mixtures. Although the exact process is not clear, type I PSCs are believed to nucleate on preexisting stratospheric sulfate aerosols (SSAs) composed of sulfuric acid and water. We are using infrared spectroscopy to study the composition and formation mechanism of type I PSCs. In the laboratory, we have used FTIR spectroscopy to probe the composition and phase of H2SO4/HNO3/H2O aerosols under winter polar stratospheric conditions. We have also used recently measured infrared optical constants for HNO3/H2O mixtures to analyze solar infrared extinction measurements of type I PSCs obtained in September 1987 over Antarctica. The results of these studies will be discussed in the context of current theories for polar stratospheric clouds formation.

  11. Composition of polar stratospheric clouds from infrared spectroscopy

    SciTech Connect

    Tolbert, M.A.; Anthony, S.E.; Disselkamp, R.; Toon, O.B.

    1995-12-31

    Heterogeneous reactions on polar stratospheric clouds (PSCs) have recently been implicated in Arctic and Antarctic ozone destruction. Although the chemistry is well documented, the composition of the clouds remains uncertain. The most common PSCs (type I) are thought to be composed of HNO{sub 3}/H{sub 2}O mixtures. Although the exact process is not clear, type I PSCs are believed to nucleate on preexisting stratospheric sulfate aerosols (SSAs) composed of sulfuric acid and water. We are using infrared spectroscopy to study the composition and formation mechanism of type I PSCs. In the laboratory, we have used FTIR spectroscopy to probe the composition and phase of H{sub 2}SO{sub 4}/HNO{sub 3}/H{sub 2}O aerosols under winter polar stratospheric conditions. We have also used recently measured infrared optical constants for HNO{sub 3}/H{sub 2}O mixtures to analyze solar infrared extinction measurements of type I PSCs obtained in September, 1987 over Antarctica. The results of these studies will be discussed in the context of current theories for polar stratospheric cloud formation.

  12. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    SciTech Connect

    Massie, S.T.; Bailey, P.L.; Gille, J.C.; Lee, E.C.; Mergenthaler, J.L.; Roche, A.E.; Kumer, J.B.; Fishbein, E.F.; Waters, J.W.; Lahoz, W.A.

    1994-10-15

    Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605 cm{sup {minus}1} (10.8, 8.0, and 6.2 {mu}m) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheroidal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculation and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles. 47 refs., 22 figs., 3 tabs.

  13. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    NASA Technical Reports Server (NTRS)

    Massie, S. T.; Bailey, P. L.; Gille, J. C.; Lee, E. C.; Mergenthaler, J. L.; Roche, A. E.; Kumer, J. B.; Fishbein, E. F.; Waters, J. W.; Lahoz, W. A.

    1994-01-01

    Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite (UARS) are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605/cm (10.8, 8.0, and 6.2 micrometers) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheriodal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.

  14. The polar stratospheric cloud event of January 24. II - Photochemistry

    NASA Technical Reports Server (NTRS)

    Jones, R. L.; Mckenna, D. S.; Solomon, S.; Poole, L. R.; Brune, W. H.

    1990-01-01

    During the 1988/89 Airborne Arctic Stratospheric Expedition (AASE), observations of the chemical composition, aerosol characteristics and atmospheric state were obtained from two aircraft, a NASA ER-2 and a DC-8. This paper presents a diagnosis of observations obtained using the ER-2 on January 24, 1989, using a Lagrangian coupled microphysical-photochemical model. The high chlorine monoxide mixing ratios observed from the ER-2 on the afternoon of January 24, 1989 are interpreted as a result of in situ heterogeneous release of reactive chlorine from the reservoirs HCl and CIONO2 on type-1 polar stratospheric cloud particles observed to be present at that time. This essential element in theories of polar ozone depletion has never before been observed directly in the stratosphere.

  15. Observation of Polar Stratospheric Clouds down to the Mediterranean coast

    NASA Astrophysics Data System (ADS)

    Keckhut, P.; David, Ch.; Marchand, M.; Bekki, S.; Jumelet, J.; Hauchecorne, A.

    2007-05-01

    A Polar Stratospheric Cloud (PSC) was detected for the first time in January 2006 over Southern Europe after 25 years of systematic lidar observations. This cloud was observed while the polar vortex was highly distorted during the initial phase of a major stratospheric warming. Very cold stratospheric temperatures (<190 K) centred over the Northern-Western Europe were reported, extending down to the South of France where lidar observations were performed. CTM (Chemical Transport Model) investigations show that this event led to a significant direct ozone destruction (35 ppb/day), within and outside the vortex as chlorine activated air masses were moved to sunlight regions allowing ozone destruction. If such exceptional events of mid-latitudes PSCs were to become frequent in the future, they should not compromise the ozone recovery because their effect appears to be limited temporally and spatially. More importantly, these events might tend to be associated with the initial phase of a stratospheric warming that results into a weakening and warming of the polar vortex and hence into a reduced probability occurrence of PSC temperatures during the rest of the winter.

  16. Observation of Polar Stratospheric Clouds down to the Mediterranean coast

    NASA Astrophysics Data System (ADS)

    Keckhut, P.; David, Ch.; Marchand, M.; Bekki, S.; Jumelet, J.; Hauchecorne, A.; Höpfner, M.

    2007-10-01

    A Polar Stratospheric Cloud (PSC) was detected for the first time in January 2006 over Southern Europe after 25 years of systematic lidar observations. This cloud was observed while the polar vortex was highly distorted during the initial phase of a major stratospheric warming. Very cold stratospheric temperatures (<190 K) centred over the Northern-Western Europe were reported, extending down to the South of France where lidar observations were performed. CTM (Chemical Transport Model) investigations show that this event led to a significant direct ozone destruction (35 ppb/day), within and outside the vortex as chlorine activated air masses were moved to sunlight regions allowing ozone destruction. If such exceptional events of mid-latitudes PSCs were to become frequent in the future, they should not compromise the ozone recovery because their effect appears to be limited temporally and spatially. More importantly, these events might tend to be associated with the initial phase of a stratospheric warming that results into a weakening and warming of the polar vortex and hence into a reduced probability occurrence of PSC temperatures during the rest of the winter.

  17. Monstrous Ice Cloud System in Titan's Present South Polar Stratosphere

    NASA Astrophysics Data System (ADS)

    Anderson, Carrie; Samuelson, Robert; McLain, Jason; Achterberg, Richard; Flasar, F. Michael; Milam, Stefanie

    2015-11-01

    During southern autumn when sunlight was still available, Cassini's Imaging Science Subsystem discovered a cloud around 300 km near Titan's south pole (West, R. A. et al., AAS/DPS Abstracts, 45, #305.03, 2013); the cloud was later determined by Cassini's Visible and InfraRed Mapping Spectrometer to contain HCN ice (de Kok et al., Nature, 514, pp 65-67, 2014). This cloud has proven to be only the tip of an extensive ice cloud system contained in Titan's south polar stratosphere, as seen through the night-vision goggles of Cassini's Composite InfraRed Spectrometer (CIRS). As the sun sets and the gloom of southern winter approaches, evidence is beginning to accumulate from CIRS far-IR spectra that a massive system of nitrile ice clouds is developing in Titan's south polar stratosphere. Even during the depths of northern winter, nothing like the strength of this southern system was evident in corresponding north polar regions.From the long slant paths that are available from limb-viewing CIRS far-IR spectra, we have the first definitive detection of the ν6 band of cyanoacetylene (HC3N) ice in Titan’s south polar stratosphere. In addition, we also see a strong blend of nitrile ice lattice vibration features around 160 cm-1. From these data we are able to derive ice abundances. The most prominent (and still chemically unidentified) ice emission feature, the Haystack, (at 220 cm-1) is also observed. We establish the vertical distributions of the ice cloud systems associated with both the 160 cm-1 feature and the Haystack. The ultimate aim is to refine the physical and possibly the chemical relationships between the two. Transmittance thin film spectra of nitrile ice mixtures obtained in our Spectroscopy for Planetary ICes Environments (SPICE) laboratory are used to support these analyses.

  18. Cirrus and Polar Stratospheric Cloud Studies using CLAES Data

    NASA Technical Reports Server (NTRS)

    Mergenthaler, John L.; Douglass, A. (Technical Monitor)

    2001-01-01

    We've concluded a 3 year (Period of Performance- January 21, 1998 to February 28, 2001) study of cirrus and polar stratospheric clouds using CLAES (Cryogenic Limb Array Etalon Spectrometer) data. We have described the progress of this study in monthly reports, UARS (Upper Atmosphere Research Satellite) science team meetings, American Geophysical Society Meetings, refereed publications and collaborative publications. Work undertaken includes the establishment of CLAES cloud detection criteria, the refinement of CLAES temperature retrieval techniques, compare the findings of CLAES with those of other instruments, and present findings to the larger community. This report describes the progress made in these areas.

  19. Formation of Polar Stratospheric Clouds in the Atmosphere

    NASA Astrophysics Data System (ADS)

    Aloyan, Artash; Yermakov, Alex; Arutyunyan, Vardan; Larin, Igor

    2014-05-01

    A new mathematical model of the global transport of gaseous species and aerosols in the atmosphere and the formation of polar stratospheric clouds (PSCs) in both hemispheres was constructed. PSCs play a significant role in ozone chemistry since heterogeneous reactions proceed on their particle surfaces and in the bulk, affecting the gas composition of the atmosphere, specifically, the content of chlorine and nitrogen compounds, which are actively involved in the destruction of ozone. Stratospheric clouds are generated by co-condensation of water vapor and nitric acid on sulfate particles and in some cases during the freezing of supercooled water as well as when nitric acid vapors are dissolved in sulfate aerosol particles [1]. These clouds differ in their chemical composition and microphysics [2]. In this study, we propose new kinetic equations describing the variability of species in the gas and condensed phases to simulate the formation of PSCs. Most models for the formation of PSCs use constant background values of sulfate aerosols in the lower stratosphere. This approach is too simplistic since sulfate aerosols in the stratosphere are characterized by considerably nonuniform spatial and temporal variations. Two PSC types are considered: Type 1 refers to the formation of nitric acid trihydrate (NAT) and Type 2 refers to the formation of particles composed of different proportions of H2SO4/HNO3/H2O. Their formation is coupled with the spatial problem of sulfate aerosol generation in the upper troposphere and lower stratosphere incorporating the chemical and kinetic transformation processes (photochemistry, nucleation, condensation/evaporation, and coagulation) and using a non-equilibrium particle-size distribution [3]. In this formulation, the system of equations is closed and allows an adequate description of the PSC dynamics in the stratosphere. Using the model developed, numerical experiments were performed to reproduce the spatial and temporal variability of

  20. Proceedings of a Workshop on Polar Stratospheric Clouds: Their Role in Atmospheric Processes

    NASA Technical Reports Server (NTRS)

    Hamill, P. (Editor); Mcmaster, L. R. (Editor)

    1984-01-01

    The potential role of polar stratospheric clouds in atmospheric processes was assessed. The observations of polar stratospheric clouds with the Nimbus 7 SAM II satellite experiment were reviewed and a preliminary analysis of their formation, impact on other remote sensing experiments, and potential impact on climate were presented. The potential effect of polar stratospheric clouds on climate, radiation balance, atmospheric dynamics, stratospheric chemistry and water vapor budget, and cloud microphysics was assessed. Conclusions and recommendations, a synopsis of materials and complementary material to support those conclusions and recommendations are presented.

  1. Homogenous Surface Nucleation of Solid Polar Stratospheric Cloud Particles

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Hamill, P.; Salcedo, D.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    A general surface nucleation rate theory is presented for the homogeneous freezing of crystalline germs on the surfaces of aqueous particles. While nucleation rates in a standard classical homogeneous freezing rate theory scale with volume, the rates in a surface-based theory scale with surface area. The theory is used to convert volume-based information on laboratory freezing rates (in units of cu cm, seconds) of nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) aerosols into surface-based values (in units of sq cm, seconds). We show that a surface-based model is capable of reproducing measured nucleation rates of NAT and NAD aerosols from concentrated aqueous HNO3 solutions in the temperature range of 165 to 205 K. Laboratory measured nucleation rates are used to derive free energies for NAT and NAD germ formation in the stratosphere. NAD germ free energies range from about 23 to 26 kcal mole, allowing for fast and efficient homogeneous NAD particle production in the stratosphere. However, NAT germ formation energies are large (greater than 26 kcal mole) enough to prevent efficient NAT particle production in the stratosphere. We show that the atmospheric NAD particle production rates based on the surface rate theory are roughly 2 orders of magnitude larger than those obtained from a standard volume-based rate theory. Atmospheric volume and surface production of NAD particles will nearly cease in the stratosphere when denitrification in the air exceeds 40 and 78%, respectively. We show that a surface-based (volume-based) homogeneous freezing rate theory gives particle production rates, which are (not) consistent with both laboratory and atmospheric data on the nucleation of solid polar stratospheric cloud particles.

  2. Measurements in polar stratospheric clouds over Antarctica in September 1989

    NASA Technical Reports Server (NTRS)

    Deshler, Terry

    1991-01-01

    The results of six balloon flights at McMurdo Station, Antarctica, under varying temperature conditions, are used in a study of polar stratospheric clouds during Sept. 1989. A particle counter, with size resolution in the 0.5 micron radius region, indicates that cloud size distributions are always bimodal. Mode radii ranging from 0.05 to 0.10 microns were observed for the small particle mode, representing the sulfate layer or condensational growth enhancements of it. The data are not inconsistent with the expected increase in size with decreasing temperature of the small particle mode in the sulfate layer owing to deliquescence although this phenomenon is often masked by nitric acid trihydrate (NAT) condensation when temperatures are sufficiently low. Mode radii generally ranged from 1.5 to 3.5 micron for the large particle mode at concentrations 3 to 4 orders of magnitude lower than the small particle mode. The large particle mode, which normally comprises most of the mass, is presumably caused by NAT condensation on larger particles of the sulfate layer and indicates HNO3 mixing ratios of 1 to 5 ppbv for most of the cloud layers observed, suggesting substantial denitrification. On several occasions, distributions were observed with mode radii as high as 7 microns, and correspondingly large inferred mass, indicating water ice clouds in the 12 to 15 km region. On other occasions, absence of such clouds at very low temperatures indicated water vapor mixing ratios of less than 3 ppmv suggesting dehydration. Generally, the inferred HNO3 mixing ratios were higher in the lower stratosphere, suggesting redistribution through particle sedimentation.

  3. Polar stratospheric clouds as deduced from MLS and CLAES measurements

    SciTech Connect

    Ricaud, P.D.; Carr, E.S.; Harwood, R.S.; Lahoz, W.A.

    1995-08-01

    From 30 August 1992 to 3 September 1992 a supersaturated area at 465 K potential temperature ({approximately}50 hPa) is deduced from MLS water vapour measurements over western Antarctica, where high extinction coefficients measured by CLAES indicate Polar Stratospheric Clouds (PSCs). These PSCs are attributed partly to the effect of an anticyclone located over South America and partly to localized orographic waves, which raise the isentropes and generate rapid adiabatic cooling. A local minimum in column O{sub 3} ({<=}200DU) is observed in this area, which is believed to be a consequence of the dynamics. Enhanced ClO abundances downstream of the region indicate PSC processing and chlorine activation. 18 refs., 2 figs.

  4. Nitric acid in polar stratospheric clouds - Similar temperature of nitric acid condensation and cloud formation

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F.; Snetsinger, Kenneth G.; Hamill, Patrick; Goodman, Jindra K.; Mccormick, M. Patrick

    1990-01-01

    As shown independently by two different techniques, nitric acid aerosols and polar stratospheric clouds (PSCs) both form below similar threshold temperatures. This supports the idea that the PSC particles involved in chlorine activation and ozone depletion in the winter polar stratosphere are composed of nitric acid. One technique used to show this is the inertial impaction of nitric acid aerosols using an Er-2 aircraft; the other method is remote sensing of PSCs by the Stratospheric Aerosol Measurement (SAM II) satellite borne optical sensor. Both procedures were in operation during the Arctic Airborne Stratospheric Expedition in 1989, and the Airborne Antarctic Ozone Experiment in 1987. Analysis of Arctic particles gathered in situ indicates the presence of nitric acid below a 'first appearance' temperature Tfa = 202 K. This is the same highest temperature at which PSCs are seen by the SAM II satellite. In comparison, a 'first appearance' temperature Tfa = 198 K as found for the Antarctic samples.

  5. Spectroscopic Evidence Against Nitric Acid Trihydrate in Polar Stratospheric Clouds

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Tolbert, Margaret A.

    1995-01-01

    Heterogeneous reactions on polar stratospheric clouds (PSC's) play a key role in the photochemical mechanism thought to be responsible for ozone depletion in the Antarctic and Arctic. Reactions of PSC particles activate chlorine to forms that are capable of photochemical ozone destruction, and sequester nitrogen oxides (NOx) that would otherwise deactivate the chlorine. Although the heterogeneous chemistry is now well established, the composition of the clouds themselves is uncertain. It is commonly thought that they are composed of nitric acid trihydrate, although observations have left this question unresolved. Here we reanalyse infrared spectra of type 1 PSCs obtained in Antarctica in September 1987, using recently measured optical constants of the various compounds that might be present in PSCs. We find these PSCs were not composed of nitric acid trihydrate but instead had a more complex compositon, perhaps that of a ternary solution. Because cloud formation is sensitive to their composition, this finding will alter our understanding of the locations and conditions in which PSCs form. In addition, the extent of ozone loss depends on the ability of the PSCs to remove NOx permanently through sedimentation, The sedimentation rates depend on PSC particle size which in turn is controlled by the composition and formation mechanism.

  6. CALIPSO Polar Stratospheric Cloud Observations from 2006-2015

    NASA Technical Reports Server (NTRS)

    Pitts, Michael C.; Poole, Lamont R.

    2015-01-01

    Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than nine-year data

  7. CALIPSO Polar Stratospheric Cloud Observations from 2006-2015

    NASA Astrophysics Data System (ADS)

    Pitts, Michael; Poole, Lamont

    2015-04-01

    Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55 and 82 degrees in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than nine

  8. On the theories of type 1 polar stratospheric cloud formation

    NASA Astrophysics Data System (ADS)

    MacKenzie, A. Robert; Kulmala, Markku; Laaksonen, Ari; Vesala, Timo

    1995-06-01

    Several mechanisms for the production of polar stratospheric cloud (PSC) particles are investigated using the classical theories of nucleation and freezing and the multicomponent condensation theory. These mechanisms invoke particle compositions ranging from binary (H2SO4/H2O) solution, solid sulfuric acid tetrahydrate (SAT) and ternary (HNO3/H2O/H2SO4) solution to binary (HNO3/H2O) solution and solid nitric acid trihydrate (NAT). Empirical relations, derived from classical nucleation studies, are used to calculate the surface energies required in calculations of nucleation and freezing. Using these data, we calculate that the nucleation of nitric acid solutions or solid phases onto SAT particles is not efficient. Homogeneous freezing of SAT or NAT from ternary solutions does not occur under stratospheric conditions. Homogeneous freezing of water ice can occur at temperatures near the frost point of pure water. Heterogeneous freezing is a strong function of the contact parameter between the emergent crystal and the initiating seed particle. Heterogeneous freezing of the stratospheric aerosol to SAT and NAT at temperatures above the frost point is not ruled out by our calculations. If formed, NAT can deplete the gas phase nitric acid concentration, by condensational growth, more efficiently than ternary droplets. We conclude that the most likely route to type 1 PSC particles is via condensational growth of ternary solution droplets followed by rapid freezing to NAT, SAT, and water ice at temperatures near the ice frost point. The particles formed are then stable and can reduce nitric acid vapor pressures to the saturation vapor pressure over NAT at all temperatures below the NAT point. Such a mechanism is consistent with observations.

  9. Mixed-phased particles in polar stratospheric ice clouds

    NASA Astrophysics Data System (ADS)

    Bogdan, Anatoli; Molina, Mario J.; Loerting, Thomas

    2010-05-01

    Keywords: polar stratospheric clouds (PSCs), ozone depletion, differential scanning calorimeter. The rate of chlorine activation reactions, which lead to ozone depletion in the winter/spring polar stratosphere (Molina, 1994), depends on the phase state of the surface of polar stratospheric cloud (PSC) ice crystals (McNeil et al., 2006). PSCs are thought to consist of solid ice and NAT (nitric acid trihydrate, HNO3× 3H2O) particles and supercooled HNO3/H2SO4/H2O droplets. The corresponding PSCs are called Type II, Ia, and Ib PSCs, respectively (Zondlo et al., 1998). Type II PSCs are formed in the Antarctic region below the ice frost point of 189 K by homogeneous freezing of HNO3/H2SO4/H2O droplets (Chang et al., 1999) with the excess of HNO3. The PSC ice crystals are thought to be solid. However, the fate of H+, NO3-, SO42- ions during freezing was not investigated. Our differential scanning calorimetry (DSC) studies of freezing emulsified HNO3/H2SO4/H2O droplets of sizes and compositions representative of the polar stratosphere demonstrate that during the freezing of the droplets, H+, NO3-, SO42- are expelled from the ice lattice. The expelled ions form a residual solution around the formed ice crystals. The residual solution does not freeze but transforms to glassy state at ~150 K (Bogdan et al., 2010). By contrast to glass-formation in these nitric-acid rich ternary mixtures the residual solution freezes in the case of sulphuric-acid rich ternary mixtures (Bogdan and Molina, 2009). For example, we can consider the phase separation into ice and a residual solution during the freezing of 23/3 wt% HNO3/H2SO4/H2O droplets. On cooling, ice is formed at ~189 K. This is inferred from the fact that the corresponding melting peak at ~248 K exactly matches the melting point of ice in the phase diagram of HNO3/H2SO4/H2O containing 3 wt % H2SO4. After the ice has formed, the glass transition occurs at Tg ≈ 150 K. The appearance of the glass transition indicates that the

  10. Nitric acid in polar stratospheric clouds: Similar temperature of nitric acid condensation and cloud formation

    SciTech Connect

    Pueschel, R.F.; Snetsinger, K.G. ); Hamill, P.; Goodman, J.K. ); McCormick, M.P. )

    1990-03-01

    As shown independently by two different techniques, nitric acid aerosols and polar stratospheric clouds both form below similar threshold temperatures. This supports the idea that the polar stratospheric cloud (PSC) particles involved in chlorine activation and ozone depletion in the winter polar stratosphere are composed of nitric acid. One technique used to show this is inertial impaction of nitric acid aerosols using an ER-2 aircraft; the other method is remote sensing of PSCs by the Stratospheric Aerosol Measurement (SAM II) satellite borne optical sensor. Both procedures were in operation during the Arctic Airborne Stratospheric Expedition in 1989, and the Airborne Antarctic Ozone Experiment in 1987. Analysis of Arctic particles gathered in situ indicates the presence of nitric acid below a first appearance temperature T{sub fa} = 202 K. This is the same highest temperature at which PSCs are seen by the SAM II satellite. In comparison, a first appearance temperature T{sub fa} = 198 K was found for the Antarctic samples.

  11. More rapid polar ozone depletion through the reaction of HOCl with HCl on polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Prather, Michael J.

    1992-01-01

    The direct reaction of HOCl with HCl is shown here to play a critical part in polar ozone loss. Observations of high levels of OClO and ClO in the springtime Antarctic stratosphere confirm that most of the available chlorine is in the form of ClO(x). But current photochemical models have difficulty converting HCl to ClO(x) rapidly enough in early spring to account fully for the observations. Here, a chemical model is used to show that the direct reaction of HOCl with HCl provides the missing mechanism. As alternative sources of nitrogen-containing oxidants have been converted in the late autumn to inactive HNO3 by known reactions on the sulfate layer aerosols, the reaction of HOCl with HCl on polar stratospheric clouds becomes the most important pathway for releasing that stratospheric chlorine which goes into polar night as HCl.

  12. Spectroscopic studies of model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Koehler, Birgit G.; Middlebrook, Ann M.

    1993-01-01

    Fourier transform infrared (FTIR) spectroscopy has been used to study nitric-acid/ice films representative of type I polar stratospheric clouds (PSCs). These studies reveal that in addition to amorphous nitric acid/ice mixtures, there are three stable stoichiometric hydrates of nitric acid: nitric-acid monohydrate (NAM), dihydrate (NAD), and trihydrate (NAT). We also observe two distinct crystalline forms of the trihydrate, which we denote alpha- and beta-NAT. These two forms appear to differ in their concentration of crystalline defects, but not in their chemical composition. In addition to probing the composition of type I PSCs, we have also used FTIR spectroscopy to study the interaction of HCl with model PSC films. In this work we find that for HCl pressures in the range 10 exp -5 to 10 exp -7 Torr, HCl is taken up by ice at 155 K to form a thin layer of HCl.6H2O. At 193 K, the uptake of HCl by ice was consistent with less than or equal to monolayer coverage. Uptake of HCl by alpha and beta-NAT at 175 K was also consistent with less than or equal to monolayer coverage.

  13. Nonorographic generation of Arctic polar stratospheric clouds during December 1999

    NASA Astrophysics Data System (ADS)

    Hitchman, Matthew H.; Buker, Marcus L.; Tripoli, Gregory J.; Browell, Edward V.; Grant, William B.; McGee, Thomas J.; Burris, John F.

    2003-03-01

    During December 1999, polar stratospheric clouds (PSCs) were observed in the absence of conditions conducive to generation by topographic gravity waves. The possibility is explored that PSCs can be generated by inertia gravity waves (IGW) radiating from breaking synoptic-scale Rossby waves on the polar front jet. The aerosol features on 7 and 12 December are selected for comparison with theory and with simulations using the University of Wisconsin Nonhydrostatic Modeling System (UWNMS). Consistent with Rossby adjustment theory, a common feature in the UWNMS simulations is radiation of IGW from the tropopause polar front jet, especially from sectors which are evolving rapidly in the Rossby wave breaking process. Packets of gravity wave energy radiate upward and poleward into the cold pool, while individual wave crests propagate poleward and downward, causing mesoscale variations in vertical motion and temperature. On 12 December the eastbound DC-8 lidar observations exhibited a fairly uniform field of six waves in aerosol enhancement in the 14-20 km layer, consistent with vertical displacement by a field of IGW propagating antiparallel to the flow, with characteristic horizontal and vertical wavelengths of ˜300 and ˜10 km. UWNMS simulations show emanation of a field of IGW upward and southwestward from a northward incursion of the polar front jet. The orientation and evolution of the aerosol features on 7 December are consistent with a single PSC induced by an IGW packet propagating from a breaking Rossby wave over western Russia toward the northeast into the coldest part of the base of the polar vortex, with characteristic period ˜9 hours, vertical wavelength ˜12 km, and horizontal wavelength ˜1000 km. Linear theory shows that for both of these cases, IGW energy propagates upward at ˜1 km/hour and horizontally at ˜100 km/hour, with characteristic trace speed ˜30 m/s. The spatial orientation of the PSC along IGW phase lines is contrasted with the nearly

  14. Simultaneous Observations fo Polar Stratospheric Clouds and HNO3 over Scandinavia in January, 1992

    NASA Technical Reports Server (NTRS)

    Massie, S. T.; Santee, M. L.; Read, W. G.; Grainger, R. G.; Lambert, A.; Mergenthaler, J. L.; Dye, J. E.; Baumbardner, D.; Randel, W. J.; Tabazadeh, A.; Tie, X.; Pan, L.; Figarol, F.; Wu, F.; Brasseur, G. P.

    1996-01-01

    Simultaneous observations of Polar Stratospheric Cloud aerosol extinction and HNO3 mixing ratios over Scandinavia are examined for January 9-10, 1992. Data measured by the Microwave Limb Sounder (MLS), Cryogenic Limb Array Etalon, Spectrometer (CLAES), and Improved Stratospheric and Mesospheric Sounder (ISAMA) experiments on the Upper Atmosphere Research Satellite (UARS) are examined at locations adjacent to parcel trajectory positions.

  15. Status of Numerical Modelling of Polar Stratospheric Clouds and Their Effect on Stratospheric Chemistry

    NASA Astrophysics Data System (ADS)

    Wang, X.; Michelangeli, D. V.; Kletskin, I.

    2003-04-01

    A multi-dimensional stratospheric model for aerosols including detailed Polar Stratospheric Cloud (PSC) microphysical processes, heterogeneous chemistry and comprehensive gas phase chemistry is being developed to study the formation and evolution of PSCs and the effect of heterogeneous reactions occurring on the surface of PSCs on polar stratospheric ozone. The model can be used in parcel mode or one, two, three dimensions. Background sulfate aerosols, frozen sulfate aerosols (sulfuric acid tetrahydrate, SAT) , Type 1a PSCs (nitric acid trihydrate, NAT ), Type 1b PSCs (supercooled ternary solution, STS ), and Type 2 PSCs (water ice crystals) are all treated as interactive elements in the model. The possible microphysical processes included in the model are: uptake of HNO_3 and H_2O on background sulphate droplets to form Type 1b and evaporation of HNO_3 and H_2O from Type 1b to return background sulphate droplets; homogenous freezing of Type 1b to form Type 2 PSCs; heterogeneous nucleation of SAT to form NAT particles, and NAT to form Type 2 PSC ice; deliquescence of SAT to form Type 1b STS and melting of SAT to form background sulphate droplets. In addition, the model involves the growth of ice and NAT by H_2O and HNO_3 deposition, evaporation, coagulation, sedimentation and transport processes. Heterogeneous reactions of nitrogen, chlorine, and bromine compounds in and on sulphate droplets, ternary, and ice particles are considered in the model. In this paper, preliminary simulation results of sensitivity tests are presented to display the basic features of PSCs and their effects on polar ozone. Comparisons with satellite measurements will be discussed.

  16. Heterogeneous reactions on nitric acid trihydrate. [on surfaces of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Moore, S. B.; Keyser, L. F.; Leu, M.-T.; Smith, R. H.; Turco, R. P.

    1990-01-01

    The first direct measurements are reported of the reaction probabilities at stratospheric temperatures for two important heterogeneous reactions on nitric acid trihydrate (NAT), the compound which makes up the predominant, type I form of polar stratospheric cloud (PSC). Sticking coefficients and solubilities of HCl and NAT, which are important in modeling physicochemical processes in the stratosphere, are also reported. The results show that the conversion of the chlorine reservoir species in the stratosphere to photochemically active forms can occur within a few days of the first appearance of type I PSCs during the polar winter.

  17. Dual-polarization airborne lidar observations of polar stratospheric cloud evolution

    NASA Technical Reports Server (NTRS)

    Poole, L. R.; Mccormick, M. P.; Kent, G. S.; Hunt, W. H.; Osborn, M. T.

    1990-01-01

    Dual-polarization 0.532 micron lidar data show systematic polar stratospheric cloud (PSC) evolution along a portion of the Airborne Arctic Stratospheric Expedition DC-8 flight of January 31, 1989. This flight leg was roughly aligned with air parcel motion on isentropic surfaces from 400-500 K, where the local adiabatic cooling rate was about 20 K/day. Type 1 PSCs show low depolarization ratios and scattering ratios which approach intermediate limiting values as ambient temperature decreases. These data suggest that Type 1 particles formed by rapid cooling may be nearly spherical and are restricted in size by partitioning of a limited HNO3 vapor supply among many competing growth sites. Type 2 PSCs appear at temperatures below estimated local frost points with increases in depolarization and scattering typical of larger ice crystals.

  18. Radiative effects of polar stratospheric clouds during the Airborne Antarctic Ozone Experiment and the Airborne Arctic Stratospheric Expedition

    NASA Technical Reports Server (NTRS)

    Rosenfield, Joan E.

    1992-01-01

    Results are presented of a study of the radiative effects of polar stratospheric clouds during the Airborne Antarctic Ozone Experiment (AAOE) and the Airborne Arctic Stratospheric Expedition (AASE) in which daily 3D Type I nitric acid trihydrate (NAT) and Type II water ice polar stratospheric clouds (PSCs) were generated in the polar regions during AAOE and the AASE aircraft missions. Mission data on particular composition and size, together with NMC-analyzed temperatures, are used. For AAOE, both Type I and Type II clouds were formed for the time period August 23 to September 17, after which only Type I clouds formed. During AASE, while Type I clouds were formed for each day between January 3 and February 10, Type II clouds formed on only two days, January 24 and 31. Mie theory and a radiative transfer model are used to compute the radiative heating rates during the mission periods, for clear and cloudy lower sky cases. Only the Type II water ice clouds have a significant radiative effect, with the Type I NATO PSCs generating a net heating or cooling of 0.1 K/d or less.

  19. Arctic polar stratospheric cloud measurements by means of a four wavelength depolarization lidar

    NASA Technical Reports Server (NTRS)

    Stefanutti, L.; Castagnoli, F.; Delguasta, M.; Flesia, C.; Godin, S.; Kolenda, J.; Kneipp, H.; Kyro, Esko; Matthey, R.; Morandi, M.

    1994-01-01

    A four wavelength depolarization backscattering lidar has been operated during the European Arctic Stratospheric Ozone Experiment (EASOE) in Sodankyl, in the Finnish Arctic. The lidar performed measurements during the months of December 1991, January, February and March 1992. The Finnish Meteorological Institute during the same period launched regularly three Radiosondes per day, and three Ozone sondes per week. Both Mt. Pinatubo aerosols and Polar Stratospheric Clouds were measured. The use of four wavelengths, respectively at 355 nm, 532 nm , 750 nm, and 850 nm permits an inversion of the lidar data to determine aerosol particle size. The depolarization technique permits the identification of Polar Stratospheric Clouds. Frequent correlation between Ozone minima and peaks in the Mt. Pinatubo aerosol maxima were detected. Measurements were carried out both within and outside the Polar Vortex.

  20. Correlating Polar Stratospheric Cloud Occurrence at the South Pole with Transport and Polar Geopotential Height Anomalies

    NASA Astrophysics Data System (ADS)

    Campbell, J. R.; Sassen, K.

    2007-12-01

    In a recent paper, we describe the macrophysical and thermodynamic properties of polar stratospheric clouds (PSC) at the South Pole based on continuous eye-safe lidar measurements made over five seasons (2000, 2003-2006). In this paper, we describe the relationship between PSC occurrence and the propensity for transport within the austral polar vortex. The southern lower-stratospheric polar airmass may be approximated as a closed system from May to September. Saturation vapor pressures for background concentrations of sulfuric and nitric acid and water vapor are reached either through radiational cooling or isentropic lift. Once nucleated, PSC acquire fall-velocities that remove these compounds from these heights. Satellite measurements (e.g., MLS) depict the widening proximity of the depleted airmass through the polar night. Yet, our measurements show that PSC occurrence can occur up to 20 km late in the season, which suggests replenishment of these species in air originating near the edges of the vortex. We examine 120-h back-trajectories during July and August and temperature histories to identify conditions and circumstances favorable to this occurring. Furthermore, we describe geopotential height anomalies averaged along 60° - 90° S, and compared to a twenty-year mean, as a proxy for the dynamic character of the polar vortex. Negative/positive anomalies indicate a strong/weak and deep/shallow vortex where its circulation inhibits/promotes meridional transport, replenishment and the likelihood of PSC at South Pole. We test this hypothesis using our dataset and reach conclusions on the influence of the polar vortex on total PSC observed each season, which, in turn, may influence the severity of annual ozone losses.

  1. Case Studies of The Dynamical Development of Polar Stratospheric Clouds Using Multistatic Imaging

    NASA Astrophysics Data System (ADS)

    Enell, C.-F.; Stebel, K.; Gustavsson, B.; Kirkwood, S.; Brändström, U.; Steen, Å.

    The important role of polar stratospheric clouds (PSCs) in stratospheric chemistry is firmly established. The formation of PSCs is closely related to temperature, which is affected by wave activity on different scales. PSC occurrence thus reflects radiative and/or dynamical stratospheric temperature changes. The most obvious indication of PSC presence is the visual observation of mother-of- pearl clouds. We present case studies of the development of visual PSCs undertaken by means of ground-based cameras. Our observations show that the presence of mother- of-pearl clouds varies on a scale smaller than that of typical mesoscale models. The images are studied further in the context of the meteorological, dynamical situa- tion, and visibility conditions (solar elevation and tropospheric cloudiness).

  2. Polar stratospheric clouds observed by lidar at McMurdo Station during the 1993 winter

    SciTech Connect

    Adriani, A.; Gobbi, G.P.; Donfrancesco, G.D.

    1994-12-31

    Since 1990, a lidar system has been operating at McMurdo Station (78{degrees}S 167{degrees}E) during the local spring. In 1993, it performed measurements between 1 March and 10 October. The lidar can monitor the presence of clouds by measuring the light backscattered from the atmosphere. After system calibration, the received signal is compared with the one expected from an atmosphere not containing particles. On such a basis, a parameter called backscattering ratio, R, is calculated. When particles are not present R is 1. Any value larger than 1 is related to the presence of particles. Lidar can be used to monitor clouds in the lower stratosphere (polar stratospheric clouds - PSCs- or volcanic clouds). PSCs have an important role in the heterogeneous chemistry of the polar stratosphere, and their presence is strictly linked with the `ozone hole`. During the 1993 winter and spring, the antarctic stratosphere still presented a measurable amount of volcanic aerosol from the Mount Pinatubo eruption. The volcanic aerosols facilitated the formation of PSCs observed during the 1993 winter because they need condensation nuclei to form. 3 refs., 2 figs.

  3. Vapor pressures of solid hydrates of nitric Acid: implications for polar stratospheric clouds.

    PubMed

    Worsnop, D R; Zahniser, M S; Fox, L E; Wofsy, S C

    1993-01-01

    Thermodynamic data are presented for hydrates of nitric acid: HNO(3).H(2)O, HNO(3).2H(2)O, HNO(3).3H(2)O, and a higher hydrate. Laboratory data indicate that nucleation and persistence of metastable HNO(3).2H(2)O may be favored in polar stratospheric clouds over the slightly more stable HNO(3).3H(2)O. Atmospheric observations indicate that some polar stratospheric clouds may be composed of HNO(3).2H(2)O and HNO(3).3H(2)O. Vapor transfer from HNO(3).2H(2)O to HNO(3).3H(2)O could be a key step in the sedimentation of HNO(3), which plays an important role in the depletion of polar ozone. PMID:17757475

  4. Vapor pressures of solid hydrates of nitric acid - Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Worsnop, Douglas R.; Fox, Lewis E.; Zahniser, Mark S.; Wofsy, Steven C.

    1993-01-01

    Thermodynamic data are presented for hydrates of nitric acid: HNO3.H2O, HNO3.2H2O, HNO3.3H2O, and a higher hydrate. Laboratory data indicate that nucleation and persistence of metastable HNO3.2H2O may be favored in polar stratospheric clouds over the slightly more stable HNO3.3H2O. Atmospheric observations indicate that some polar stratospheric clouds may be composed of HNO3.2H2O and HNO3.3H2O. Vapor transfer from HNO3.2H2O to HNO3.3H2O could be a key step in the sedimentation of HNO3, which plays an important role in the depletion of polar ozone.

  5. Chemical analysis of refractory stratospheric aerosol particles collected within the arctic vortex and inside polar stratospheric clouds

    NASA Astrophysics Data System (ADS)

    Ebert, Martin; Weigel, Ralf; Kandler, Konrad; Günther, Gebhard; Molleker, Sergej; Grooß, Jens-Uwe; Vogel, Bärbel; Weinbruch, Stephan; Borrmann, Stephan

    2016-07-01

    Stratospheric aerosol particles with diameters larger than about 10 nm were collected within the arctic vortex during two polar flight campaigns: RECONCILE in winter 2010 and ESSenCe in winter 2011. Impactors were installed on board the aircraft M-55 Geophysica, which was operated from Kiruna, Sweden. Flights were performed at a height of up to 21 km and some of the particle samples were taken within distinct polar stratospheric clouds (PSCs). The chemical composition, size and morphology of refractory particles were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis. During ESSenCe no refractory particles with diameters above 500 nm were sampled. In total 116 small silicate, Fe-rich, Pb-rich and aluminum oxide spheres were found. In contrast to ESSenCe in early winter, during the late-winter RECONCILE mission the air masses were subsiding inside the Arctic winter vortex from the upper stratosphere and mesosphere, thus initializing a transport of refractory aerosol particles into the lower stratosphere. During RECONCILE, 759 refractory particles with diameters above 500 nm were found consisting of silicates, silicate / carbon mixtures, Fe-rich particles, Ca-rich particles and complex metal mixtures. In the size range below 500 nm the presence of soot was also proven. While the data base is still sparse, the general tendency of a lower abundance of refractory particles during PSC events compared to non-PSC situations was observed. The detection of large refractory particles in the stratosphere, as well as the experimental finding that these particles were not observed in the particle samples (upper size limit ˜ 5 µm) taken during PSC events, strengthens the hypothesis that such particles are present in the lower polar stratosphere in late winter and have provided a surface for heterogeneous nucleation during PSC formation.

  6. Observations of Antarctic Polar Stratospheric Clouds by Geoscience Laser Altimeter System (GLAS)

    NASA Technical Reports Server (NTRS)

    Palm, Stephen P.; Fromm, Michael; Spinhirne, James

    2005-01-01

    Polar Stratospheric Clouds (PSCs) frequently occur in the polar regions during winter and are important because they play a role in the destruction of stratospheric ozone. During late September and early October 2003, GLAS frequently observed PSCs over western Antarctica. At the peak of this activity on September 29 and 30 we investigate the vertical structure and extent, horizontal coverage and backscatter characteristics of the PSCs using the GLAS data. The PSCs were found to cover an area approximately 10 to 15 % of the size of Antarctica in a region where enhanced PSC frequency has been noted by previous PSC climatology studies. The area of PSC formation was found to coincide with the coldest temperatures in the lower stratosphere. In addition, extensive cloudiness was seen within the troposphere below the PSCs indicating that tropospheric disturbances might have played a role in their formation.

  7. Influence of polar stratospheric clouds on the depletion of Antarctic ozone

    NASA Technical Reports Server (NTRS)

    Salawitch, Ross J.; Wofsy, Steven C.; Mcelroy, Michael B.

    1988-01-01

    Precipitation of nitrate in polar stratospheric clouds (PSCs) can provide a significant sink for Antarctic stratospheric odd nitrogen. It is argued that the depth of the Ozone Hole is sensitive to the occurrence of temperatures below about 196 K. An increase in the prevalence of temperatures below 196 K would enhance ozone loss by increasing the spatial extent and persistence of PSCs, and by decreasing the level of HNO3 that remains following PSC evaporation. Concentrations of halogen gases in the 1960s and earlier were insufficient to support major ozone loss, even if thermal conditions were favorable.

  8. Characteristics of polar stratospheric clouds as observed by SAM II, SAGE, and lidar

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Hamill, P.; Farrukh, U. O.

    1985-01-01

    Satellite and lidar data sets developed over several years of observations are analyzed to detail the macroscopic and microphysical characteristics of polar stratospheric clouds (PSCs). Mappings were made of the sizes, locations, probabilities of occurrence and temperature dependence of the PSCs, and indicated that PSCs are correlated with an extended stratospheric cloud bank in the cold polar vortex region. The bank is bounded by a 188 K isotherm, and the probability of occurrence drops to 50 percent at the 193 K isotherm. Values of 6.3 particles/cu cm and radii averaging 0.0725 micron/particle are calculated, along with an estimated downward velocity of 0.01 m/sec.

  9. Case study of the development of polar stratospheric clouds using bistatic imaging

    NASA Astrophysics Data System (ADS)

    Enell, C.-F.; Brändström, U.; Gustavsson, B.; Kirkwood, S.; Stebel, K.; Steen, A.

    2003-08-01

    The formation of polar stratospheric clouds (PSCs) is closely related to wave activity on different scales since waves propagating into the stratosphere perturb the temperature profile. We present here a case study of the development of visible PSCs (mother-of-pearl clouds), appearing at the polar vortex edge on 9 January 1997, under-taken by means of ground-based cameras. It is shown that the presence of stratospheric clouds may be detected semi-automatically and that short-term dynamics such as altitude variations can be tracked in three dimensions. The PSC field showed distinct features separated by approximately 20 km, which implies wave-induced temperature variations on that scale. The wave-induced characteristics were further emphasised by the fact that the PSCs moved within a sloping spatial surface. The appearance of visible mother-of-pearl clouds seems to be related to leewave-induced cooling of air masses, where the synoptic temperature has been close to (but not necessarily below) the threshold temperatures for PSC condensation.

  10. Particle size distributions in Arctic polar stratospheric clouds, growth and freezing of sulfuric acid droplets, and implications for cloud formation

    NASA Technical Reports Server (NTRS)

    Dye, James E.; Baumgardner, D.; Gandrud, B. W.; Kawa, S. R.; Kelly, K. K.; Loewenstein, M.; Ferry, G. V.; Chan, K. R.; Gary, B. L.

    1992-01-01

    The paper uses particle size and volume measurements obtained with the forward scattering spectrometer probe model 300 during January and February 1989 in the Airborne Arctic Stratospheric Experiment to investigate processes important in the formation and growth of polar stratospheric cloud (PSC) particles. It is suggested on the basis of comparisons of the observations with expected sulfuric acid droplet deliquescence that in the Arctic a major fraction of the sulfuric acid droplets remain liquid until temperatures at least as low as 193 K. It is proposed that homogeneous freezing of the sulfuric acid droplets might occur near 190 K and might play a role in the formation of PSCs.

  11. Effects of a polar stratospheric cloud parameterization on ozone depletion due to stratospheric aircraft in a two-dimensional model

    SciTech Connect

    Considine, D.B.; Douglass, A.R.; Jackman, C.H.

    1994-09-20

    A parameterization of Type 1 and 2 polar stratospheric cloud (PSC) formation is presented which is appropriate for use in two-dimensional (2-D) photochemical models of the stratosphere. The calculation of PSC frequency of occurrence and surface area density uses climatological temperature probability distributions obtained from National Meteorological Center data to avoid using zonal mean temperatures, which are not good predictors of PSC behavior. The parameterization does not attempt to model the microphysics of PSCs. The parameterization predicts changes in PSC formation and heterogeneous processing due to perturbations of stratospheric trace constituents. It is therefore useful in assessing the potential effects of a fleet of stratospheric aircraft (high speed civil transports, or HSCTs) on stratospheric composition. The model calculated frequency of PSC occurrence agrees well with a climatology based on stratospheric aerosol measurement (SAM) II observations. PSCs are predicted to occur in the tropics. Their vertical range is narrow, however, and their impact on model O{sub 3} fields is small. When PSC and sulfate aerosol heterogeneous processes are included in the model calculations, the O{sub 3} change for 1980-1990 is in substantially better agreement with the total ozone mapping spectrometer (TOMS) - derived O{sub 3} trend than otherwise. However, significant discrepancies in the northern midlatitudes remain. The overall changes in model O{sub 3} response to standard HSCT perturbation scenarios produced by the parameterization are small and tend to decrease the model sensitivity to the HSCT perturbation. However, in the southern hemisphere spring a significant increase in O{sub 3} sensitivity to HSCT perturbations is found. At this location and time, increased PSC formation leads to increased levels of active chlorine, which produce the O{sub 3} decrease. 38 refs., 13 figs., 3 tabs.

  12. Effects of a polar stratosphere cloud parameterization on ozone depletion due to stratospheric aircraft in a two-dimensional model

    NASA Technical Reports Server (NTRS)

    Considine, David B.; Douglass, Anne R.; Jackman, Charles H.

    1994-01-01

    A parameterization of Type 1 and 2 polar stratospheric cloud (PSC) formation is presented which is appropriate for use in two-dimensional (2-D) photochemical models of the stratosphere. The calculations of PSC frequency of occurrence and surface area density uses climatological temperature probability distributions obtained from National Meteorological Center data to avoid using zonal mean temperatures, which are not good predictors of PSC behavior. The parameterization does not attempt to model the microphysics of PSCs. The parameterization predicts changes in PSC formation and heterogeneous processing due to perturbations of stratospheric trace constituents. It is therefore useful in assessing the potential effects of a fleet of stratospheric aircraft (high speed civil transports, or HSCTs) on stratospheric composition. the model calculated frequency of PSC occurrence agrees well with a climatology based on stratospheric aerosol measurement (SAM) 2 observations. PSCs are predicted to occur in the tropics. Their vertical range is narrow, however, and their impact on model O3 fields is small. When PSC and sulfate aerosol heterogeneous processes are included in the model calculations, the O3 change for 1980 - 1990 is in substantially better agreement with the total ozone mapping spectrometer (TOMS)-derived O3 trend than otherwise. The overall changes in model O3 response to standard HSCT perturbation scenarios produced by the parameterization are small and tend to decrease the model sensitivity to the HSCT perturbation. However, in the southern hemisphere spring a significant increase in O3 sensitivity to HSCT perturbations is found. At this location and time, increased PSC formation leads to increased levels of active chlorine, which produce the O3 decreases.

  13. Laboratory measurements of polar stratospheric cloud rate parameters

    NASA Technical Reports Server (NTRS)

    Kenner, Rex D.; Plumb, Ian C.; Ryan, Keith R.

    1994-01-01

    It is now clear that heterogeneous reactions play an important role in controlling the concentration of ozone in the stratosphere. In this work, the loss of N2O5 on ice substrates has been studied in a flow reactor in an attempt to gain a more fundamental understanding of these reactions. The apparent reaction probability in this system was found to decrease as the substrate was exposed to N2O5. A model which corrected for the loss of surface sites was developed and although it appears to fit the data for a given experiment quite well, it is concluded that the loss of reactive sites is not the full explanation. In addition, the results of an experimental and modeling study suggest that reaction on the internal surface of the ice substrates is not a major loss mechanism for N2O5 in the current work.

  14. Extreme stratospheric springs and their consequences for the onset of polar mesospheric clouds

    NASA Astrophysics Data System (ADS)

    Siskind, David E.; Allen, Douglas R.; Randall, Cora E.; Harvey, V. Lynn; Hervig, Mark E.; Lumpe, Jerry; Thurairajah, Brentha; Bailey, Scott M.; Russell, James M.

    2015-09-01

    We use data from the Aeronomy of Ice in the Mesosphere (AIM) explorer and from the NASA Modern Era Retrospective Analysis for Research and Applications (MERRA) stratospheric analysis to explore the variability in the onset of the Northern Hemisphere (NH) Polar Mesospheric Cloud (PMC) season. Consistent with recently published results, we show that the early onset of the NH PMC season in 2013 was accompanied by a warm springtime stratosphere; conversely, we show that the late onset in 2008 coincides with a very cold springtime stratosphere. Similar stratospheric temperature anomalies for 1997 and 2011 also are connected either directly, through observed temperatures, or indirectly, through an early PMC onset, to conditions near the mesopause. These 4 years, 2008, 1997, 2011, and 2013 represent the extremes of stratospheric springtime temperatures seen in the MERRA analysis and correspond to analogous extrema in planetary wave activity. The three years with enhanced planetary wave activity (1997, 2011 and 2013) are shown to coincide with the recently identified stratospheric Frozen In Anticyclone (FrIAC) phenomenon. FrIACs in 1997 and 2013 are associated with early PMC onsets; however, the dramatic FrIAC of 2011 is not. This may be because the 2011 FrIAC occurred too early in the spring. The link between NH PMC onset and stratospheric FrIAC occurrences represents a new mode of coupling between the stratosphere and mesosphere. Since FrIACs appear to be more frequent in recent years, we speculate that as a result, PMCs may occur earlier as well. Finally we compare the zonal mean zonal winds and observed gravity wave activity for the FrIACs of 2011 and 2013. We find no evidence that gravity wave activity was favored in 2013 relative to 2011, thus suggesting that direct forcing by planetary waves was the key mechanism in accelerating the cooling and moistening of the NH mesopause region in May of 2013.

  15. A Laboratory Study on the Phase Transition for Polar Stratospheric Cloud Particles

    NASA Technical Reports Server (NTRS)

    Teets, Edward H., Jr.

    1997-01-01

    The nucleation and growth of different phases of simulated polar stratospheric cloud (PSC) particles were investigated in the laboratory. Solutions and mixtures of solutions at concentrations 1 to 5 m (molality) of ammonium sulfate, ammonium bisulfate, sodium chloride, sulfuric acid, and nitric acid were supercooled to prescribed temperatures below their equilibrium melting point. These solutions were contained in small diameter glass tubing of volumes ranging from 2.6 to 0.04 ml. Samples were nucleated by insertion of an ice crystal, or in some cases by a liquid nitrogen cooled wire. Crystallization velocities were determined by timing the crystal growth front passages along the glass tubing. Solution mixtures containing aircraft exhaust (soot) were also examined. Crystallization rates increased as deltaT2, where deltaT is the supercooling for weak solutions (2 m or less). The higher concentrated solutions (greater than 3 m) showed rates significantly less than deltaT2. This reduced rate suggested an onset of a glass phase. Results were applied to the nucleation of highly concentrated solutions at various stages of polar stratospheric cloud development within the polar stratosphere.

  16. Continuous Lidar Monitoring of Polar Stratospheric Clouds at the South Pole

    NASA Technical Reports Server (NTRS)

    Campbell, James R.; Welton, Ellsworth J.; Spinhirne, James D

    2009-01-01

    Polar stratospheric clouds (PSC) play a primary role in the formation of annual ozone holes over Antarctica during the austral sunrise. Meridional temperature gradients in the lower stratosphere and upper troposphere, caused by strong radiative cooling, induce a broad dynamic vortex centered near the South Pole that decouples and insulates the winter polar airmass. PSC nucleate and grow as vortex temperatures gradually fall below equilibrium saturation and frost points for ambient sulfate, nitrate, and water vapor concentrations (generally below 197 K). Cloud surfaces promote heterogeneous reactions that convert stable chlorine and bromine-based molecules into photochemically active ones. As spring nears, and the sun reappears and rises, photolysis decomposes these partitioned compounds into individual halogen atoms that react with and catalytically destroy thousands of ozone molecules before they are stochastically neutralized. Despite a generic understanding of the ozone hole paradigm, many key components of the system, such as cloud occurrence, phase, and composition; particle growth mechanisms; and denitrification of the lower stratosphere have yet to be fully resolved. Satellite-based observations have dramatically improved the ability to detect PSC and quantify seasonal polar chemical partitioning. However, coverage directly over the Antarctic plateau is limited by polar-orbiting tracks that rarely exceed 80 degrees S. In December 1999, a NASA Micropulse Lidar Network instrument (MPLNET) was first deployed to the NOAA Earth Systems Research Laboratory (ESRL) Atmospheric Research Observatory at the Amundsen-Scott South Pole Station for continuous cloud and aerosol profiling. MPLNET instruments are eye-safe, capable of full-time autonomous operation, and suitably rugged and compact to withstand long-term remote deployment. With only brief interruptions during the winters of 2001 and 2002, a nearly continuous data archive exists to the present.

  17. Heterogeneous Formation of Polar Stratospheric Clouds- Part 1: Nucleation of Nitric Acid Trihydrate (NAT)

    NASA Technical Reports Server (NTRS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooss, J.-U.; Peter, T.

    2013-01-01

    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.

  18. Heterogeneous formation of polar stratospheric clouds - Part 1: Nucleation of nitric acid trihydrate (NAT)

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooß, J.-U.; Peter, T.

    2013-09-01

    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.

  19. On the size and composition of particles in polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Kinne, Stefan; Toon, Owen B.; Toon, Goeff C.; Farmer, Crofton B.; Browell, Edward V.

    1988-01-01

    Attenuation measurements of the solar radiation between 1.5 and 15 micron wavelengths were performed with the airborne (DC-8) JPL MARK 4 interferometer during the 1987 Antarctic Expedition. The opacities not only provide information about the abundance of stratospheric gases but also about the optical depths of polar stratospheric clouds (PSCs) at wavelengths of negligible gas absorption (windows). The optical depth of PSCs can be determined for each window once the background attenuation, due to air-molecules and aerosol has been filtered out with a simple extinction law. The ratio of optical thicknesses at different wavelengths reveals information about particle size and particle composition. Among the almost 700 measured spectra only a few PSC cases exist. PSC events are identified by sudden reductions in the spectrally integrated intensity value and are also verified with backscattering data from an upward directed lidar instrument, that was mounted on the DC-8. For the selected case on September 21st at 14.40 GMT, lidar data indicate an optically thin cloud at 18k and later an additional optically thick cloud at 15 km altitude. All results still suffer from: (1) often arbitrary definitions of a clear case, that often already may have contained PSC particles and (2) noise problems that restrict the calculations of optical depths to values larger than 0.001. Once these problems are handled, this instrument may become a valuable tool towards a better understanding of the role PSCs play in the Antarctic stratosphere.

  20. Balloon borne Antarctic frost point measurements and their impact on polar stratospheric cloud theories

    NASA Technical Reports Server (NTRS)

    Rosen, James M.; Hofmann, D. J.; Carpenter, J. R.; Harder, J. W.; Oltmans, S. J.

    1988-01-01

    The first balloon-borne frost point measurements over Antarctica were made during September and October, 1987 as part of the NOZE 2 effort at McMurdo. The results indicate water vapor mixing ratios on the order of 2 ppmv in the 15 to 20 km region which is somewhat smaller than the typical values currently being used significantly smaller than the typical values currently being used in polar stratospheric cloud (PSC) theories. The observed water vapor mixing ratio would correspond to saturated conditions for what is thought to be the lowest stratospheric temperatures encountered over the Antarctic. Through the use of available lidar observations there appears to be significant evidence that some PSCs form at temperatures higher than the local frost point (with respect to water) in the 10 to 20 km region thus supporting the nitric acid theory of PSC composition. Clouds near 15 km and below appear to form in regions saturated with respect to water and thus are probably mostly ice water clouds although they could contain relatively small amounts of other constituents. Photographic evidence suggests that the clouds forming above the frost point probably have an appearance quite different from the lower altitude iridescent, colored nacreous clouds.

  1. Autonomous full-time lidar measurements of polar stratospheric clouds at the South Pole

    NASA Astrophysics Data System (ADS)

    Campbell, James R.

    Polar stratospheric clouds (PSC) are an artifact of extremely low temperatures in the lower-stratosphere caused by a lack of sunlight during winter. Their presence induces increased concentrations of chlorine and bromine radicals that drive catalytic ozone destruction upon the return of sunlight in spring. An eye-safe micropulse lidar (MPL; 0.23 mum) was installed at the Scott-Amundsen South Pole Station, Antarctica in December 1999 to collect continuous long-term measurements of polar clouds. A four-year data subset for analyzing PSC is derived from measurements for austral winters 2000 and 2003--2005. A statistical algorithm based on MPL signal uncertainties is designed to retrieve PSC boundary heights, attenuated scattering ratios and demonstrate instrument performance for low signal-to-noise measurements. The MPL measurements consist mostly of Type II PSC (i.e., ice). The likelihood for Type I measurements are described for specific conditions. Seasonal PSC macrophysical properties are examined relative to thermodynamic and chemical characteristics. The potential for dehumidification and denitrification of the lower Antarctic stratosphere is examined by comparing PSC observations to theoretical predictions for cloud based on common scenarios for water vapor and nitric acid concentrations. Conceptual models for seasonal PSC occurrence, denitrification and dehumidification and ozone loss are described. A linear relationship is established between total integrated PSC scattering and ozone loss, with high correlation. Polar vortex dynamics are investigated in relation to PSC occurrence, including synoptic-scale geopotential height anomalies, isentropic airmass trajectories and local-scale gravity waves. Moisture overrunning, from quasi-adiabatic cooling and transport along isentropic boundaries, is considered a primary mechanism for PSC occurrence. Middle and late-season PSC are found to be the result of mixing of moist air from the outer edges of the vortex that

  2. SAGE II observations of polar stratospheric clouds near 50 deg N January 31 - February 2, 1989

    NASA Technical Reports Server (NTRS)

    Pitts, M. C.; Poole, L. R.; Mccormick, M. P.

    1990-01-01

    Polar stratospheric clouds (PSCs) form at very cold temperatures which typically occur only at high latitudes during local winter. However, meteorological circumstances in the Arctic during late January 1989 led to PSC formation unusually far to the south, at latitudes (near 50 deg N) being sampled during the period by the orbiting SAGE II instrument. These unusual PSC sightings and the evolution of meteorological conditions which produced the episode are described. Profiles of SAGE II extinction measurements at 0.525 and 1.02 microns show clear signatures of PSCs and indicate that the cloud particles were considerably larger than the background aerosol. It is most important to note that the clouds were sighted at a latitude where there was extensive sunlight, thus increasing the likelihood of ozone loss both locally and downstream due to enhancements in reactive chlorine expected from heterogeneous chemical processing within the PSCs.

  3. Measurements of size and composition of particles in polar stratospheric clouds from infrared solar absorption spectra

    NASA Technical Reports Server (NTRS)

    Kinne, S.; Toon, O. B.; Toon, G. C.; Farmer, C. B.; Browell, E. V.; Mccormick, M. P.

    1989-01-01

    Results are presented on polar stratospheric cloud (PSC) observations, based on IR measurements of solar extinction, made by the airborne JPL Mark IV interferometer during the Airborne Antarctic Ozone Expedition in 1987, together with the instrumentation and the theoretical aspects of data analysis. Thirty-three PSC cases were analyzed and categorized into two types, I and II, which were found to occur at different altitudes during September. Type I clouds, seen at altitudes above 15 km, contained particles with radii of about 0.5 micarons and nitric acid concentrations greater than 40 percent, while type II clouds, found usually below 15 km, contained particles with radii of 6 microns and larger, composed of water ice. In addition, particles of larger than the 15-micron-size detection limit were encounterd.

  4. Sensitivity of polar stratospheric cloud formation to changes in water vapour and temperature

    NASA Astrophysics Data System (ADS)

    Khosrawi, F.; Urban, J.; Lossow, S.; Stiller, G.; Weigel, K.; Braesicke, P.; Pitts, M. C.; Rozanov, A.; Burrows, J. P.; Murtagh, D.

    2016-01-01

    More than a decade ago it was suggested that a cooling of stratospheric temperatures by 1 K or an increase of 1 ppmv of stratospheric water vapour could promote denitrification, the permanent removal of nitrogen species from the stratosphere by solid polar stratospheric cloud (PSC) particles. In fact, during the two Arctic winters 2009/10 and 2010/11 the strongest denitrification in the recent decade was observed. Sensitivity studies along air parcel trajectories are performed to test how a future stratospheric water vapour (H2O) increase of 1 ppmv or a temperature decrease of 1 K would affect PSC formation. We perform our study based on measurements made during the Arctic winter 2010/11. Air parcel trajectories were calculated 6 days backward in time based on PSCs detected by CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder satellite observations). The sensitivity study was performed on single trajectories as well as on a trajectory ensemble. The sensitivity study shows a clear prolongation of the potential for PSC formation and PSC existence when the temperature in the stratosphere is decreased by 1 K and water vapour is increased by 1 ppmv. Based on 15 years of satellite measurements (2000-2014) from UARS/HALOE, Envisat/MIPAS, Odin/SMR, Aura/MLS, Envisat/SCIAMACHY and SCISAT/ACE-FTS it is further investigated if there is a decrease in temperature and/or increase of water vapour (H2O) observed in the polar regions similar to that observed at midlatitudes and in the tropics. Performing linear regression analyses we derive from the Envisat/MIPAS (2002-2012) and Aura/MLS (2004-2014) observations predominantly positive changes in the potential temperature range 350 to 1000 K. The linear changes in water vapour derived from Envisat/MIPAS observations are largely insignificant, while those from Aura/MLS are mostly significant. For the temperature neither of the two instruments indicate any significant changes. Given the strong inter-annual variation observed in

  5. Denitrification of the polar winter stratosphere - Implications of SAM II cloud formation temperatures

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Toon, O. B.

    1990-01-01

    The SAM II extinction profiles and the associated temperature profiles are used to determine the amount of denitrification of the winter polar stratospheres. Clear evidence of the denitrification process in the Antarctic data is seen. There are indications in the Arctic data that denitrification mechanisms may be at work there also. At the latitudes observed by the SAM II satellite system, denitrification begins before the formation of extensive ice clouds and may be due to sedimentation of nitric acid particles. However, the possibility of dinitrification by type II PSCs at latitudes not observed by SAM II cannot be excluded.

  6. A case of type I polar stratospheric cloud formation by heterogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Ferry, G. V.; Snetsinger, K. G.; Goodman, J.; Dye, J. E.; Baumgardner, D.; Gandrud, B. W.

    1992-01-01

    The NASA ER-2 aircraft flew on January 24, 1989, from Stavanger to Spitsbergen, Norway, at the 430-440 K potential temperature surface (19.2-19.8 km pressure altitude). Aerosols were sampled continuously by an optical particle counter (PMS-FSSP300) for concentration and size analyses, and during five 10-min intervals by four wire and one replicator impactor for concentration, size, composition, and phase analysis. During sampling, the air saturation of H2O with respect to ice changed from 20 to 100 percent, and of HNO3 with respect to nitric acid trihydrate (NAT) from subsaturation to supersaturation. Data from both instruments indicate a condensation of hydrochloric acid and, later, nitric acid on the background aerosol particles as the ambient temperature decreases along the flight track. This heterogeneous nucleation mechanism generates type I polar stratospheric cloud particles of 10-fold enhanced optical depth, which could play a role in stratospheric ozone depletion.

  7. Application of physical adsorption thermodynamics to heterogeneous chemistry on polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Elliott, Scott; Turco, Richard P.; Toon, Owen B.; Hamill, Patrick

    1991-01-01

    Laboratory isotherms for the binding of several nonheterogeneously active atmospheric gases and for HCl to water ice are translated into adsorptive equilibrium constants and surface enthalpies. Extrapolation to polar conditions through the Clausius Clapeyron relation yields coverage estimates below the percent level for N2, Ar, CO2, and CO, suggesting that the crystal faces of type II stratospheric cloud particles may be regarded as clean with respect to these species. For HCl, and perhaps HF and HNO3, estimates rise to several percent, and the adsorbed layer may offer acid or proton sources alternate to the bulk solid for heterogeneous reactions with stratospheric nitrates. Measurements are lacking for many key atmospheric molecules on water ice, and almost entirely for nitric acid trihydrate as substrate. Adsorptive equilibria enter into gas to particle mass flux descriptions, and the binding energy determines rates for desorption of, and encounter between, potential surface reactants.

  8. Lidar observations of polar stratospheric clouds at McMurdo, Antarctica, during NOZE-2

    NASA Technical Reports Server (NTRS)

    Morley, Bruce M.

    1988-01-01

    SRI International operated a dual wavelength (1.064 micrometer and .532 micrometer) aerosol lidar at McMurdo Station, Antarctica, as part of the National Ozone Expedition-2 (NOZE-2). The objective of the project was to map the vertical distributions of polar stratospheric clouds (PSCs), which are believed to play an important role in the destruction of ozone in the Antarctic spring. Altitude, thickness, homogeneity, and duration of PSC events as well as information on particle shape, size or number density will be very useful in determining the exact role of PSCs in ozone destructions, and when combined with measurements of other investigators, additional properties of PSCs can be estimated. The results are currently being analyzed in terms of PSC properties which are useful for modeling the stratospheric ozone depletion mechanism.

  9. Investigating Type I Polar Stratospheric Cloud Formation Mechanisms with POAM Satellite Observations

    NASA Technical Reports Server (NTRS)

    Strawa, Anthony W.; Drdla, K.; Fromm, M.; Hoppel, K.; Browell, E.; Hamill, P.; Dempsey, D.; Gore, Warren J. (Technical Monitor)

    2001-01-01

    Type Ia PSCs are believed to be composed of nitric acid hydrate particles. Recent results from the SOLVE/THESEO 2000 campaign showed evidence that this type of PSC was composed of a small number of very large particles capable of sedimentary denitrification of regions of the stratosphere. It is unknown whether homogeneous or heterogeneous nucleation is responsible for the formation of these PSCs. Arctic winters are tending to be colder in response to global tropospheric warming. The degree to which this influences ozone depletion will depend on the freezing mechanism of nitric acid hydrate particles. If nucleation is homogeneous it implies that the freezing process is an inherent property of the particle, while heterogeneous freezing means that the extent of PSCs will depend in part on the number of nuclei available. The Polar Ozone and Aerosol Measurement (POAM)II and III satellites have been making observations of stratospheric aerosols and Polar Stratospheric Clouds (PSCs) since 1994. Recently, we have developed a technique that can discriminate between Type Ia and Ib PSCs using these observations. A statistical approach is employed to demonstrate the robustness of this approach and results are compared with lidar measurements. The technique is used to analyze observations from POAM II and II during Northern Hemisphere winters where significant PSC formation occurred with the objective of exploring Type I PSC formation mechanisms. The different PSCs identified using this method exhibit different growth curve as expressed as extinction versus temperature.

  10. Condensed Acids In Antartic Stratospheric Clouds

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Snetsinger, K. G.; Toon, O. B.; Ferry, G. V.; Starr, W. L.; Oberbeck, V. R.; Chan, K. R.; Goodman, J. K.; Livingston, J. M.; Verma, S.; Fong, W.

    1992-01-01

    Report dicusses nitrate, sulfate, and chloride contents of stratospheric aerosols during 1987 Airborne Antarctic Ozone Experiment. Emphasizes growth of HNO3*3H2O particles in polar stratospheric clouds. Important in testing theories concerning Antarctic "ozone hole".

  11. An experimental study of growth and phase change of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hallett, John; Teets, Edward

    1992-01-01

    This report describes the progress made on understanding phase changes related to solutions which may comprise Polar Stratospheric Clouds. In particular, it is concerned with techniques for investigating specific classes of metastability and phase change which may be important not only in Polar Stratospheric Clouds but in all atmospheric aerosols in general. While the lower level atmospheric aerosol consists of mixtures of (NH4)(SO4)2, NH4HSO4, NaCl among others, there is evidence that aerosol at PSC levels is composed of acid aerosol, either injected from volcanic events (such as Pinatubo) or having diffused upward from the lower atmosphere. In particular, sulfuric acid and nitric acid are known to occur at PSC levels, and are suspected of catalyzing ozone destruction reactions by adsorption on surfaces of crystallized particles. The present study has centered on two approaches: (1) the extent of supercooling (with respect to ice) and supersaturation (with respect to hydrate) and the nature of crystal growth in acid solutions of specific molality; and (2) the nature of growth from the vapor of HNO3 - H2O crystals both on a substrate and on a pre-existing aerosol.

  12. Subsidence-induced methane clouds in Titan's winter polar stratosphere and upper troposphere

    NASA Astrophysics Data System (ADS)

    Anderson, C. M.; Samuelson, R. E.; Achterberg, R. K.; Barnes, J. W.; Flasar, F. M.

    2014-11-01

    Titan's atmospheric methane most likely originates from lakes at the surface and subsurface reservoirs. Accordingly, it has been commonly assumed that Titan's tropopause region, where the vertical temperature profile is a minimum, acts as a cold trap for convecting methane, leading to the expectation that the formation of methane clouds in Titan's stratosphere would be rare. The additional assumption that Titan's tropopause temperatures are independent of latitude is also required. However, Cassini Composite InfraRed Spectrometer (CIRS) and Radio Science Subsystem (RSS) data sets reveal colder temperatures in Titan's tropopause region near the winter pole than those at low latitudes and in the summer hemisphere. This, combined with the presence of a cross-equatorial meridional circulation with winter polar subsidence, as suggested by current general circulation models, implies the inevitable formation of Subsidence-Induced Methane Clouds (SIMCs) over Titan's winter pole. We verified this by retrieving the stratospheric methane mole fraction at 70°N from the strength of the far infrared methane pure rotation lines observed by CIRS and by assuming the RSS-derived thermal profile at 74.1°N. Our retrieved methane mole fraction of 1.50 ± 0.15% allows for methane to condense and form SIMCs at altitudes between ∼48 and ∼20 km. Radiative transfer analyses of a color composite image obtained by the Cassini Visible and Infrared Mapping Spectrometer (VIMS) during northern winter appear to corroborate the existence of these clouds.

  13. A Climatology of Polar Stratospheric Cloud Types by MIPAS-Envisat

    NASA Astrophysics Data System (ADS)

    Spang, Reinhold; Hoffmann, Lars; Griessbach, Sabine; Orr, Andrew; Höpfner, Michael; Müller, Rolf

    2015-04-01

    For Chemistry Climate Models (CCM) it is still a challenging task to properly represent the evolution of the polar vortices over the entire winter season. The models usually do not include comprehensive microphysical modules to evolve the formation of different types of polar stratospheric clouds (PSC) over the winter. Consequently, predictions on the development and recovery of the future ozone hole have relatively large uncertainties. A climatological record of hemispheric measurement of PSC types could help to better validate and improve the PSC schemes in CCMs. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument onboard the ESA Envisat satellite operated from July 2002 to April 2012. The infra-red limb emission measurements compile a unique dataset of day and night measurements of polar stratospheric clouds up to the poles. From the spectral measurements in the 4.15-14.6 microns range it is possible to select a number of atmospheric window regions and spectral signatures to classify PSC cloud types like nitric acid hydrates, sulfuric ternary solution droplets, and ice particles. The cloud detection sensitivity is similar to space borne lidars, but MIPAS adds complementary information due to its different measurement technique (limb instead of nadir) and wavelength region. Here we will describe a new classification method for PSCs based on the combination of multiple brightness temperature differences (BTD) and colour ratios. Probability density functions (PDF) of the MIPAS measurements in conjunction with a database of radiative transfer model calculations of realistic PSC particle size distributions enable the definition of regions attributed to specific or mixed types clouds. Applying a naive bias classifier for independent criteria to all defined classes in four 2D PDF distributions, it is possible to assign the most likely PSC type to any measured cloud spectrum. Statistical Monte Carlo test have been applied to quantify

  14. Microphysical Simulation of Polar Stratospheric Clouds Within the Community Earth System Model

    NASA Astrophysics Data System (ADS)

    Zhu, Yunqian

    Polar stratospheric clouds (PSCs) are critical elements for polar ozone depletion. A new PSC model coupling stratospheric chemistry, microphysics and climate is constructed and the formation of STS (Super-cooled Ternary Solution) and NAT (Nitric-Acid Trihydrate) PSCs are explored. STS particle properties are dominated by thermodynamics. Simulations of particle volumes and size distributions are generally within the observational error bars. STS particles are not in equilibrium with their environment when the particle surface area is smaller than 4 mum2/cm 3. A new nucleation rate equation for NAT is derived based on observed denitrification in the 2010-2011 Arctic winter. The homogeneous nucleation scheme leads to supermicron NAT particles as observed. The simulated the lidar backscatter, and denitrification are generally within observational error bars. However, the simulations are very sensitive to temperature. Using the same STS and NAT schemes, as well as a prognostic treatment for ice PSC formation and dehydration, the PSCs are simulated during the Antarctic winter of 2010. The current model correctly simulates large NAT particles and denitrification, but cannot produce NAT with high backscattering ratio/number density sometimes observed by CALIPSO. However, our simulated ice has similar backscatter and depolarization which is often attributed to NAT by CALIPSO. Possibly the CALIPSO algorithm misclassifies ice as NAT when the stratosphere is denitrified or dehydrated. STS and NAT form near the pole in May and June, but form a ring outside 80?S later in the winter when polar HNO3 is depleted. Ice always forms in the coldest area, but becomes less abundant later in the winter. The model is missing some processes forming NAT such as gravity waves or evaporating ice. These processes should be added to the model in the future.

  15. Characterization of Polar Stratospheric Clouds With Spaceborne Lidar: CALIPSO and the 2006 Antarctic Season

    NASA Technical Reports Server (NTRS)

    Pitts, Michael C.; Thomason, L. W.; Poole, Lamont R.; Winker, David M.

    2007-01-01

    The role of polar stratospheric clouds in polar ozone loss has been well documented. The CALIPSO satellite mission offers a new opportunity to characterize PSCs on spatial and temporal scales previously unavailable. A PSC detection algorithm based on a single wavelength threshold approach has been developed for CALIPSO. The method appears to accurately detect PSCs of all opacities, including tenuous clouds, with a very low rate of false positives and few missed clouds. We applied the algorithm to CALIPSO data acquired during the 2006 Antarctic winter season from 13 June through 31 October. The spatial and temporal distribution of CALIPSO PSC observations is illustrated with weekly maps of PSC occurrence. The evolution of the 2006 PSC season is depicted by time series of daily PSC frequency as a function of altitude. Comparisons with virtual solar occultation data indicate that CALIPSO provides a different view of the PSC season than attained with previous solar occultation satellites. Measurement-based time series of PSC areal coverage and vertically-integrated PSC volume are computed from the CALIPSO data. The observed area covered with PSCs is significantly smaller than would be inferred from a temperature-based proxy such as TNAT but is similar in magnitude to that inferred from TSTS. The potential of CALIPSO measurements for investigating PSC microphysics is illustrated using combinations of lidar backscatter coefficient and volume depolarization to infer composition for two CALIPSO PSC scenes.

  16. Detection of Ice Polar Stratospheric Clouds from Assimilation of Atmospheric Infrared Sounder Data

    NASA Technical Reports Server (NTRS)

    Stajner, Ivanka; Benson, Craig; Liu, Hui-Chun; Pawson, Steven; Chang, Ping; Riishojgaard, Lars Peter

    2006-01-01

    A novel technique is presented for detection of ice polar stratospheric clouds (PSCs) that form at extremely low temperatures in the lower polar stratosphere during winter. Temperature is a major factor in determining abundance of PSCs, which in turn provide surfaces for heterogeneous chemical reactions leading to ozone loss and radiative cooling. The technique infers the presence of ice PSCs using radiances from the Atmospheric Infrared Sounder (AIRS) in the Goddard Earth Observing System version 5 (GEOS-5) data assimilation system. Brightness temperatures are computed from short-term GEOS-5 forecasts for several hundred AIRS channels, using a radiation transfer module. The differences between collocated AIRS observations and these computed values are the observed-minus-forecast (O-F) residuals in the assimilation system. Because the radiation model assumes clear-sky conditions, we hypothesize that these O-F residuals contain quantitative information about PSCs. This is confirmed using sparse data from the Polar Ozone and Aerosol Measurement (POAM) III occultation instrument. The analysis focuses on 0-F residuals for the 6.79pm AIRS moisture channel. At coincident locations, when POAM III detects ice clouds, the AIRS O-F residuals for this channel are lower than -2K. When no ice PSCs are evident in POAM III data, the AIRS 0-F residuals are larger. Given this relationship, the high spatial density of AIRS data is used to construct maps of regions where 0-F residuals are lower than -2K, as a proxy for ice PSCs. The spatial scales and spatio-temporal variations of these PSCs in the Antarctic and Arctic are discussed on the basis of these maps.

  17. Fourier transform infrared studies of the interaction of HCl with model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

    Koehler, Birgit G.; Mcneill, Laurie S.; Middlebrook, Ann M.; Tolbert, Margaret A.

    1993-01-01

    Heterogeneous reactions involving hydrochloric acid adsorbed on the surfaces of polar stratospheric clouds (PSCs) are postulated to contribute to polar ozone loss. Using FTIR spectroscopy to probe the condensed phase, we have examined the interaction of HCl with ice and nitric acid trihydrate (NAT) films representative of types II and I PSCs, respectively. For HCl pressures in the range of 10 exp -7 to 10 exp -5 Torr, our FTIR studies show that a small amount of crystalline HCl-6H2O formed on or in ice at 155 K. However, for higher HCl pressures, we observed that the entire film of ice rapidly converted into an amorphous 4:1 H2O:HCl mixture. From HCl-uptake experiments with P(HCl) = 8 x 10 exp -7 Torr, we estimate roughly that the diffusion coefficient of HCl in ice is around 2 x 10 exp -12 sq cm/s at 158 K. For higher temperatures more closely approximating those found in the stratosphere, we were unable to detect bulk HCl uptake by ice. Indirect evidence suggests that HCl adsorption onto the surface of model PSC films inhibited the evaporation of both ice and NAT by 3-5 K.

  18. Stratospheric Ozone Changes and Polar Mesospheric Cloud (PMC) Trends Observed in SBUV Data

    NASA Astrophysics Data System (ADS)

    DeLand, M. T.; Thomas, G. E.; Shettle, E. P.; Olivero, J. J.

    2013-12-01

    Polar mesospheric clouds (PMCs) are observed at 80-85 km altitude and high latitudes (typically > 50°) only during summer months. It has been suggested that long-term variations of PMC occurrence frequency and brightness are indicators of global climate change as represented through changes in mesospheric temperature and water vapor. The Solar Backscatter Ultraviolet (SBUV) series of satellite instruments, although designed to measure stratospheric profile and total column ozone, have made global observations of bright PMCs since November 1978. Previous analysis of SBUV data found that long-term variations in PMC brightness and occurrence frequency were anti-correlated with solar activity, and that a positive secular trend was present at most latitudes. The limited database of mesospheric temperature and water vapor data has precluded further determination of the source of this trend. Motivated by recent studies with the LIMA general circulation model [Berger and Lübken 2011], which relate mesospheric temperature trends to changes in stratospheric ozone, we have investigated the use of stratospheric ozone changes as a proxy for changes in mesospheric heating and temperature. The decrease in ozone from 1979 to the mid-1990s leads to a cooler mesosphere, and is thus consistent with the rise in PMC ice water content observed in the SBUV record during this period. Similarly, stratospheric ozone changes are smaller from the mid-1990s to the present, and PMC ice water content trends are also reduced in recent years. We will discuss these results and their implications for both previous (before 1979) and future PMC behavior.

  19. Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter

    NASA Technical Reports Server (NTRS)

    Webster, C. R.; May, R. D.; Toohey, D. W.; Avallone, L. M.; Anderson, J. G.; Newman, P.; Lait, L.; Schoeberl, M. R.; Elkins, J. W.; Chan, K. R.

    1993-01-01

    Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses of up to 1 ppbv, which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less than 196 -/+ 4 kelvin. High ClO was always accompanied by loss of HCl mixing ratios equal to 1/2(ClO+ 2Cl2O2). These data indicate that the heterogeneous reaction HCl + ClONO2 - Cl2 + HNO3 on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO2, not HCl.

  20. Diffusion and location of hydorchloric acid in ice: Implications for polar stratosphere clouds and ozone depletion

    SciTech Connect

    Wolff, E.W.; Mulvaney, R. ); Oates, K. )

    1989-06-01

    The authors have carried out experiments to study the incorporation and movement of HCl within the structure of ice. These involved freezing HCl solutions, and observing them in a scanning electron microscope fitted with an X-ray microanalysis system. The authors are able to show that HCl is not easily incorporated into ice crystals, but is strongly partitioned towards the grain boundaries. Furthermore, the diffusion of HCl through ice crystals is slow. These results contradict the interpretation of earlier experiments. They mean that if HCl is to be available for reaction on polar stratospheric cloud particles, as required by current theories of Antarctic ozone depletion, then it must be present in some form other than a solid solution.

  1. Polar Stratospheric Cloud evolution and chlorine activation measured by CALIPSO and MLS, and modelled by ATLAS

    NASA Astrophysics Data System (ADS)

    Nakajima, H.; Wohltmann, I.; Wegner, T.; Takeda, M.; Pitts, M. C.; Poole, L. R.; Lehmann, R.; Santee, M. L.; Rex, M.

    2015-08-01

    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.

  2. Polar stratospheric cloud evolution and chlorine activation measured by CALIPSO and MLS, and modeled by ATLAS

    NASA Astrophysics Data System (ADS)

    Nakajima, Hideaki; Wohltmann, Ingo; Wegner, Tobias; Takeda, Masanori; Pitts, Michael C.; Poole, Lamont R.; Lehmann, Ralph; Santee, Michelle L.; Rex, Markus

    2016-03-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Spang, Reinhold; Hoffmann, Lars; Höpfner, Michael; Griessbach, Sabine; Müller, Rolf; Pitts, Michael C.; Orr, Andrew M. W.; Riese, Martin

    2016-08-01

    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 MIPAS 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

  4. Microphysical Modelling of Polar Stratospheric Clouds During the 1999-2000 Winter

    NASA Technical Reports Server (NTRS)

    Drdla, Katja; Schoeberl, Mark; Rosenfield, Joan; Gore, Warren J. (Technical Monitor)

    2000-01-01

    The evolution of the 1999-2000 Arctic winter has been examined using a microphysical/photochemical model run along diabatic trajectories. A large number of trajectories have been generated, filling the vortex throughout the region of polar stratospheric cloud (PSC) formation, and extending from November until the vortex breakup, in order to provide representative sampling of the evolution of PSCs and their effect on stratospheric chemistry. The 1999-2000 winter was particularly cold, allowing extensive PSC formation. Many trajectories have ten-day periods continuously below the Type I PSC threshold; significant periods of Type II PSCs are also indicated. The model has been used to test the extent and severity of denitrification and dehydration predicted using a range of different microphysical schemes. Scenarios in which freezing only occurs below the ice frost point (causing explicit coupling of denitrification and dehydration) have been tested, as well as scenarios with partial freezing at warmer temperatures (in which denitrification can occur independently of dehydration). The sensitivity to parameters such as aerosol freezing rates and heterogeneous freezing have been explored. Several scenarios cause sufficient denitrification to affect chlorine partitioning, and in turn, model-predicted ozone depletion, demonstrating that an improved understanding of the microphysics responsible for denitrification is necessary for understanding ozone loss rates.

  5. Modeling the formation of polar stratospheric clouds with allowance for kinetic and heterogeneous processes

    NASA Astrophysics Data System (ADS)

    Aloyan, A. E.; Yermakov, A. N.; Arutyunyan, V. O.

    2015-05-01

    A new mathematical model of global transport of multicomponent gaseous admixtures and aerosols in the atmosphere and the formation of polar stratospheric clouds (PSC) in both hemispheres has been constructed. Two types of PSCs are considered: type Ia, nitric acid trihydrate (NAT), and type Ib, supercooled ternary solutions of H2SO4/HNO3/H2O (STS). New equations are used to describe the variation in gas- and condensed-phase components on the basis of their thermodynamic properties. The formation of PSCs is coupled with sulfate aerosols generated in the upper troposphere and lower stratosphere, and with chemical and kinetic transformation processes (photochemistry, nucleation, condensation/evaporation, and coagulation). Using this coupled model, numerical experiments were performed to reproduce the spatial and temporal variability of PSCs in winter in both hemispheres. First, the formation of primary sulfate aerosols in the atmosphere is considered and then these aerosols are incorporated to the PSC model. The results of the numerical experiments are analyzed.

  6. Experimental Insights into the Sulfuric Acid/Water Phase Diagram: Implications for Polar Stratospheric Clouds

    NASA Astrophysics Data System (ADS)

    Beyer, K. D.; Hansen, A. R.

    2002-05-01

    We have investigated the H2SO4/H2O binary liquid/solid phase diagram using a highly sensitive differential scanning calorimeter (DSC) and infrared spectroscopy of thin films. In particular we have sought to investigate the region from pure ice to sulfuric acid hemihexahydrate (SAH, H2SO4ú6.5H2O), including a detailed look at the sulfuric acid octahydrate (SAO). Our studies have found that there is a unique, repeatable IR spectra for SAO, which is not merely a combination of spectra of ice and sulfuric acid tetrahydrate (SAT), as has been previously suggested could be the case. From our DSC studies, we have identified the melting, or solid/solid phase transition of the octahydrate. We have also determined from our studies using the energy of fusion for SAO that SAO is a major component of H2SO4 solutions in the range 20 - 40 wt.% when they freeze. Our results indicate that SAO could be a significant portion of solid or partially frozen polar stratospheric cloud particles. As such, key stratospheric reactions should be studied on SAO surfaces.

  7. Simulations of Polar Stratospheric Clouds and Denitrification Using Laboratory Freezing Rates

    NASA Technical Reports Server (NTRS)

    Drdla, Katja; Tabazadeh, Azadeh; Gore, Warren J. (Technical Monitor)

    2001-01-01

    During the 1999-2000 Arctic winter, the SAGE (Stratospheric Aerosol and Gas Experiment) III Ozone Loss and Validation Experiment (SOLVE) provided evidence of widespread solid-phase polar stratospheric clouds (PSCs) accompanied by severe nitrification. Previous simulations have shown that a freezing process occurring at temperatures above the ice frost point is necessary to explain these observations. In this work, the nitric acid freezing rates measured by Salcedo et al. and discussed by Tabazadeh et al. have been examined. These freezing rates have been tested in winter-long microphysical simulations of the 1999-2000 Arctic vortex evolution in order to determine whether they can explain the observations. A range of cases have been explored, including whether the PSC particles are composed of nitric acid dihydrate or trihydrate, whether the freezing process is a bulk process or occurs only on the particle surfaces, and uncertainties in the derived freezing rates. Finally, the possibility that meteoritic debris enhances the freezing rate has also been examined. The results of these simulations have been compared with key PSC and denitrification measurements made by the SOLVE campaign. The cases that best reproduce the measurements will he highlighted, with a discussion of the implications for our understanding of PSCs.

  8. Analysis of the physical state of one Arctic polar stratospheric cloud based on observations

    NASA Technical Reports Server (NTRS)

    Drdla, K.; Tabazadeh, A.; Turco, R. P.; Jacobson, M. Z.; Dye, J. E.; Twohy, C.; Baumgardner, D.

    1994-01-01

    During the Arctic Airborne Stratospheric Expedition (AASE) simultaneous measurements of aerosol size distribution and NO(y)(HN03 + NO + NO2 + 2(N205)) were made along ER-2 flight paths. The flow characteristics of the NO(y) instrument allow us to derive the condensed NO(y) amount (assumed to be HN03) present during polar stratospheric cloud (PSC) events. Analysis of the January 24th flight indicates that this condensed HN03 amount does not agree well with the aerosol volume if the observed PSCs are composed of solid nitric acid trihydrate (NAT), as is generally assumed. However, the composition agrees well with that predicted for liquid H2S04/HN03/H20 solution droplets using a new Aerosol Physical Chemistry Model (APCM). The agreement corresponds in detail to variations in temperature and humidity. The weight percentages of H2SO4, HN03, and H2O derived from the measurements all correspond to those predicted for ternary, liquid solutions.

  9. The interannual variability of polar stratospheric clouds and related parameters in Antarctica during September and October

    SciTech Connect

    Poole, L.R.; McCormick, M.P. ); Solomon, S. ); Pitts, M.C. )

    1989-10-01

    Antarctic polar stratospheric cloud (PSC) sightings by the orbiting SAM II sensor during September and October show a pronounced Quasi-Biennial Oscillation (QBO) signal, and October sightings have increased markedly over the past 10 years in years of westerly QBO phase. The QBO in PSC frequency is likely to affect the rate of Antarctic heterogeneous chemical processes and, hence, ozone depletion. Studies of the observed long-term temperature trend suggest that the decadal PSC trend probably results from the ozone decline through its effect on stratospheric heating rates. A more detailed analysis of data from 1986 and 1987 shows that there were more PSCs in 1987 and that they persisted much later into the spring season as compared to 1986. Qualitatively similar behavior was found for the OClO column abundances and 18-km ozone depletion observed at McMurdo Station during these 2 years. These observations suggest that both the intensity and duration of heterogeneous chemical processes are likely greater during colder, QBO-westerly phase years.

  10. Retrieval of Polar Stratospheric Cloud Microphysical Properties from Lidar Measurements: Dependence on Particle Shape Assumptions

    NASA Technical Reports Server (NTRS)

    Reichardt, J.; Reichardt, S.; Yang, P.; McGee, T. J.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    A retrieval algorithm has been developed for the microphysical analysis of polar stratospheric cloud (PSC) optical data obtained using lidar instrumentation. The parameterization scheme of the PSC microphysical properties allows for coexistence of up to three different particle types with size-dependent shapes. The finite difference time domain (FDTD) method has been used to calculate optical properties of particles with maximum dimensions equal to or less than 2 mu m and with shapes that can be considered more representative of PSCs on the scale of individual crystals than the commonly assumed spheroids. Specifically. these are irregular and hexagonal crystals. Selection of the optical parameters that are input to the inversion algorithm is based on a potential data set such as that gathered by two of the lidars on board the NASA DC-8 during the Stratospheric Aerosol and Gas Experiment 0 p (SAGE) Ozone Loss Validation experiment (SOLVE) campaign in winter 1999/2000: the Airborne Raman Ozone and Temperature Lidar (AROTEL) and the NASA Langley Differential Absorption Lidar (DIAL). The 0 microphysical retrieval algorithm has been applied to study how particle shape assumptions affect the inversion of lidar data measured in leewave PSCs. The model simulations show that under the assumption of spheroidal particle shapes, PSC surface and volume density are systematically smaller than the FDTD-based values by, respectively, approximately 10-30% and approximately 5-23%.

  11. Simultaneous ozone and polar stratospheric cloud observations at South Pole Station during winter and spring 1991

    SciTech Connect

    Rosen, J.M.; Kjome, N.T.; Oltmans, S.J.

    1993-07-20

    Simultaneous polar stratospheric cloud (PSC) and ozone measurements were made over South Pole Station using a two-wavelength backscattersonde. This instrument produces aerosol profiles similar to those obtained with a ground-based lidar system but with higher vertical resolution. In one sounding, depolarization of the PSCs was also measured. The backscattersondes were supplemented with occasional frost point soundings. The measurements made before the appearance of PSCs do not show clear evidence of particle deliquescence, suggesting that the background sulfate particles may be frozen solids rather than liquids. PSCs began appearing at {approximately}20 km when the temperature at that altitude dropped to {minus}80{degrees}C (193 K). Initially, there was apparent evidence of supersaturation (with respect to nitric acid trihydrate) associated with some type I PSCs, while other examples indicated that the condensation of nitric acid was in quantitative agreement with that expected from the saturation vapor pressure and available nitric acid vapor. The apparent supersaturated layers (which occurred within the first 2 weeks of the onset of PSCs) can alternatively be interpreted as denitrified regions. In the polarization sensitive sounding, two varieties of type I PSCs were observed, one of which exhibited significant depolarization and another which produced very little depolarization. This observation would be consistent with the classification of types Ia and Ib, respectively. At the precise time that sunlight was returning to the stratosphere near South Pole Station, a strong inverse correlation in the structure of PSCs and ozone mixing ratio was observed. Using trajectory analysis, it is argued that the effect is probably the result of chemical depletion rather than transport processes. This chance observation is consistent with enhanced ozone depletion occurring in association with sunlit PSCs during the early spring. 36 refs., 13 figs., 2 tabs.

  12. Heterogeneous formation of polar stratospheric clouds - Part 1: Nucleation of nitric acid trihydrate (NAT)

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooß, J.-U.; Peter, T.

    2013-03-01

    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.

  13. Effects of polar stratospheric clouds in the Nimbus 7 LIMS Version 6 data set

    NASA Astrophysics Data System (ADS)

    Remsberg, Ellis; Harvey, V. Lynn

    2016-07-01

    The historic Limb Infrared Monitor of the Stratosphere (LIMS) measurements of 1978-1979 from the Nimbus 7 satellite were re-processed with Version 6 (V6) algorithms and archived in 2002. The V6 data set employs updated radiance registration methods, improved spectroscopic line parameters, and a common vertical resolution for all retrieved parameters. Retrieved profiles are spaced about every 1.6° of latitude along orbits and include the additional parameter of geopotential height. Profiles of O3 are sensitive to perturbations from emissions of polar stratospheric clouds (PSCs). This work presents results of implementing a first-order screening for effects of PSCs using simple algorithms based on vertical gradients of the O3 mixing ratio. Their occurrences are compared with the co-located, retrieved temperatures and related to the temperature thresholds needed for saturation of H2O and/or HNO3 vapor onto PSC particles. Observed daily locations where the major PSC screening criteria are satisfied are validated against PSCs observed with the Stratospheric Aerosol Monitor (SAM) II experiment also on Nimbus 7. Remnants of emissions from PSCs are characterized for O3 and HNO3 following the screening. PSCs may also impart a warm bias in the co-located LIMS temperatures, but by no more than 1-2 K at the altitudes of where effects of PSCs are a maximum in the ozone; thus, no PSC screening was applied to the V6 temperatures. Minimum temperatures vary between 187 and 194 K and often occur 1 to 2 km above where PSC effects are first identified in the ozone (most often between about 21 and 28 hPa). Those temperature-pressure values are consistent with conditions for the existence of nitric acid trihydrate (NAT) mixtures and to a lesser extent of super-cooled ternary solution (STS) droplets. A local, temporary uptake of HNO3 vapor of order 1-3 ppbv is indicated during mid-January for the 550 K surface. Seven-month time series of the distributions of LIMS O3 and HNO3 are shown

  14. Using back-propagation neural networks to analyze hyperspatial and hypertemporal data to detect polar stratospheric clouds over antarctica

    SciTech Connect

    Foschi, P.G.; Pagan, K.L.; Garcia, O.

    1996-11-01

    A study to support ozone depletion and climatic change research is briefly summarized. The goal of the study to to develop back-propagation neural network techniques for detection of optically thin polar stratospheric clouds in Advanced Very High Resolution Radiometer thermal infrared imagery. The neural networks are being used to analyze hyperspatial and hypertemporal data; these data sets are defined in the paper. Assessments of the neural network are very briefly described; these include verification, accuracy, and robustness over time.

  15. Polar stratospheric clouds over Finland in the 2012/2013 Arctic winter measured by two Raman lidars

    NASA Astrophysics Data System (ADS)

    Hoffmann, Anne; Giannakaki, Eleni; Kivi, Rigel; Schrems, Otto; Immler, Franz; Komppula, Mika

    2013-04-01

    Already in December 2012, the Arctic stratospheric vortex reached temperatures sufficiently low for polar stratospheric cloud (PSC) formation over wide areas of Northern Europe and whole Finland. Within Finland, stratospheric aerosol lidar measurements have been and are performed with two Raman lidar systems, the PollyXT, owned by the Finnish Meteorological Institute (FMI) and situated well below the Arctic circle close to Kuopio (63 N, 27 E) and the MARL lidar owned by the Alfred-Wegener-Institute for Polar and Marine Research (AWI), and situated at the FMI Arctic Research Centre in Sodankylä (67 N, 26 E). The PollyXT has been designed as an autonomous tropospheric lidar system, but it has proven to be able to detect aerosol backscatter and depolarization at least as high up as 25 km. Measurements are ongoing as far as low clouds allow for stratospheric analysis with both lidars until the end of PSC season in February. For the winter 2012/2013, PSC occurrence frequency, types and characteristics will be determined. Comparative analysis with Calipso lidar profiles covering Finland will be performed. Preliminary results from December 17-24 show PSCs detected in Kuopio during seven days with the PollyXT lidar. The altitude of the clouds varied in the range of 17-25 km. In Sodankylä the measurements were running on one day during the period and PSCs were observed between altitudes 17-25 km. For the same time period (December 17-24, 2012) CALIPSO has observed stratospheric layers at all overpasses over Finland (9 tracks on five days). The clouds were observed between 18.5 and 26 km, with varying geometric and optical thickness.

  16. Retrieval of Polar Stratospheric Cloud Microphysical Properties From Lidar Measurements: Dependence on Particle Shape Assumptions

    NASA Technical Reports Server (NTRS)

    Reichardt, Susanne; Reichardt, Jens; Yang, Ping; McGee, Thomas J.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Knowledge of particle sizes and number densities of polar stratospheric clouds (PSCs) is highly important, because they are critical parameters for the modeling of the ozone chemistry of the stratosphere. In situ measurements of PSC particles are rare. the main instrument for the accumulation of PSC data are lidar systems. Therefore the derivation of some microphysical properties of PSCS from the optical parameters measured by lidars would be highly beneficial for ozone research. Inversion of lidar data obtained in the presence of PSCs formed from crystalline particles type 11 and the various nitric acid tri Ydrrate (NAT) types cannot be easily accomplished, because a suitable scattering theory for small faceted crystals has not been readily available tip to now. As a consequence, the T-matrix method is commonly used for the interpretation of these PSC lidar data. Here the assumption is made that the optical properties of an ensemble of spheroids resemble those of crystalline PSCs, and microphysical properties of the PSC are inferred from the optical signatures of the PSC at two or more wavelengths. The problem with the T-matrix approach is that the assumption of spheroidal instead of faceted particles can lead to dramatically wrong results: Usually cloud particle properties are deduced from analysis of lidar profiles of backscatter ratio and depolarization ratio. The particle contribution to the backscatter ratio is given by the product of the particle number density and the backscattering cross section. The latter is proportional to the value of the particle's scattering phase function at 180 degrees scattering angle. At 180 degrees however, the phase functions of rough, faceted crystals and of spheroids with same maximum dimension differ by a factor of 6. From this it follows that for a PSC consisting of faceted crystals, the particle number density is underestimated by roughly the same factor if spheroidal particles are unrealistically assumed. We are currently

  17. On the influence of polar stratospheric cloud formation on chemical composition during the 1988/89 Arctic winter

    SciTech Connect

    Jones, R.L.; McKenna, D.S. ); Poole, L.R. ); Solomon, S. )

    1990-03-01

    The northern winter polar vortex is more disturbed dynamically and warmer than the Antarctic equivalent, and correspondingly fewer polar stratospheric clouds (PSCs) are observed to form. However, the rapid flow of stratospheric air through slow moving synoptically forced PSC regions can result in exposure of both vortical and extra vortical air to PSCs intermittently throughout the winter months. This periodic exposure to PSCs may be sufficient to perturb the chemical composition of large volumes of northern hemisphere air. The synoptic forcing also leads to marked meridional flow which has a profound effect on chemical composition, having major impacts on both short term ozone depletion and the longer term recovery to lower ClOx abundances. Accurate simulation of the air flow is thus essential for the reliable calculation of ozone loss in polar regions.

  18. Effects of the El Chichon volcanic cloud in the stratosphere on the polarization of light from the sky.

    PubMed

    Coulson, K L

    1983-04-01

    A dense volcanic cloud from the El Chichon volcanic eruption has been observed in the stratosphere over Hawaii since it was first discovered at the Mauna Loa Observatory 9 Apr. 1982. Lidar observations have shown the cloud to have been dense and highly layered in its early stages, but as the cloud matured it became more homogeneous and the top portion underwent considerable enhancement. Measurements of the degree of polarization of skylight at the zenith and across the sky in the sun's vertical show that the polarization field is strongly modified by the effects of the cloud and that the modifications are of a different nature from those produced by high turbidity in the lower layers of the atmosphere. The degree of polarization at the zenith during twilight shows a secondary maximum at a solar depression D = 4.8-5 degrees, a secondary minimum at D = 4 degrees, a primary maximum at D = 1-2 degrees, and a rapid decrease to values generally <10% in the immediate sunrise period. The positions of the neutral points are strongly affected by the cloud, the Arago point being shifted from its normal position by as much as 15-20 degrees and the Babinet point being shifted even farther. Multiple Babinet points were observed on some occasions. The measurements indicate the polarization field to be modified more by the El Chichon cloud than it was by the clouds from previous eruptions which have occurred during this century. PMID:18195919

  19. Properties of Northern Hemisphere polar stratospheric clouds and volcanic aerosol in 1991/92 from UARS/ISAMS satellite measurements

    SciTech Connect

    Taylor, F.W.; Lambert, A.; Grainger, R.G.; Rodgers, C.D.; Remedios, J.J.

    1994-10-15

    Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from volcanic aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92 northern winter, one of which took place in sunlight. The latter correlates well with UARS/Microwave Limb Sounder observations of enhanced chlorine monoxide, but substantial amounts of chlorine monoxide were also reported at times and places with at most very minor PSC activity. 17 refs., 7 figs.

  20. SAGE II (Stratospheric Aerosol and Gas Experiment) observations of polar stratospheric clouds near 50 degree N January 31-February 2, 1989

    SciTech Connect

    Pitts, M.C. ); Poole, L.R.; McCormick, M.P. )

    1990-03-01

    Polar stratospheric clouds (PSCs) form at very cold temperatures which typically occur only at high latitudes during local winter. However, meteorological circumstances in the Arctic during late January 1989 led to PSC formation unusually far to the south, at latitudes (near 50{degree}N) being sampled during the period (January 31-February 2) by the orbiting SAGE II instrument. These unusual PSC sightings and the evolution of meteorological conditions which produced the episode are described. Profiles of SAGE II extinction measurements at 0.525 and 1.02 {mu}m show clear signatures of PSCs and indicate that the cloud particles were considerably larger than the background aerosol. It is most important to note that the clouds were sighted at a latitude where there was extensive sunlight, thus increasing the likelihood of ozone loss both locally and downstream due to enhancements in reactive chlorine expected from heterogeneous chemical processing within the PSCs.

  1. Physical Chemistry of the H2SO4/HNO3/H2O System: Implications for Polar Stratospheric Clouds.

    PubMed

    Molina, M J; Zhang, R; Wooldridge, P J; McMahon, J R; Kim, J E; Chang, H Y; Beyer, K D

    1993-09-10

    Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO(3) hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H(2)SO(4)/H(2)O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO(3) vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO(3) and H(2)O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H(2)SO(4) solutions and on solid H(2)SO(4) hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles. PMID:17745351

  2. Physical chemistry of the H2SO4/HNO3/H2O system - Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Molina, M. J.; Zhang, R.; Wooldridge, P. J.; Mcmahon, J. R.; Kim, J. E.; Chang, H. Y.; Beyer, K. D.

    1993-01-01

    Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO3 hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H2SO4/H2O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO3 vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO3 and H2O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H2SO4 solutions and on solid H2SO4 hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles.

  3. A Unified Satellite-Observation Polar Stratospheric Cloud (PSC) Database for Long-Term Climate-Change Studies

    NASA Technical Reports Server (NTRS)

    Fromm, Michael; Pitts, Michael; Alfred, Jerome

    2000-01-01

    This report summarizes the project team's activity and accomplishments during the period 12 February, 1999 - 12 February, 2000. The primary objective of this project was to create and test a generic algorithm for detecting polar stratospheric clouds (PSC), an algorithm that would permit creation of a unified, long term PSC database from a variety of solar occultation instruments that measure aerosol extinction near 1000 nm The second objective was to make a database of PSC observations and certain relevant related datasets. In this report we describe the algorithm, the data we are making available, and user access options. The remainder of this document provides the details of the algorithm and the database offering.

  4. 21st Century Trends in Antarctic Temperature and Polar Stratospheric Cloud (PSC) Area in the GEOS Chemistry-Climate Model

    NASA Technical Reports Server (NTRS)

    Hurwitz, M. M.; Newman, P. A.

    2010-01-01

    This study examines trends in Antarctic temperature and APSC, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO2-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1.3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in APSC, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, APSC trends have the same sign as the prescribed halogen trends. That is, there are negative APSC trends in "grealistic future" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO2 continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version.

  5. The Sensitivity of Arctic Ozone Loss to Polar Stratospheric Cloud Volume and Chlorine and Bromine Loading in a Chemistry and Transport Model

    NASA Technical Reports Server (NTRS)

    Douglass, A. R.; Stolarski, R. S.; Strahan, S. E.; Polansky, B. C.

    2006-01-01

    The sensitivity of Arctic ozone loss to polar stratospheric cloud volume (V(sub PSC)) and chlorine and bromine loading is explored using chemistry and transport models (CTMs). A simulation using multi-decadal output from a general circulation model (GCM) in the Goddard Space Flight Center (GSFC) CTM complements one recycling a single year s GCM output in the Global Modeling Initiative (GMI) CTM. Winter polar ozone loss in the GSFC CTM depends on equivalent effective stratospheric chlorine (EESC) and polar vortex characteristics (temperatures, descent, isolation, polar stratospheric cloud amount). Polar ozone loss in the GMI CTM depends only on changes in EESC as the dynamics repeat annually. The GSFC CTM simulation reproduces a linear relationship between ozone loss and Vpsc derived from observations for 1992 - 2003 which holds for EESC within approx.85% of its maximum (approx.1990 - 2020). The GMI simulation shows that ozone loss varies linearly with EESC for constant, high V(sub PSC).

  6. Investigation of Polar Stratospheric Cloud Solid Particle Formation Mechanisms Using ILAS and AVHRR Observations in the Arctic

    NASA Technical Reports Server (NTRS)

    Irie, H.; Pagan, K. L.; Tabazadeh, A.; Legg, M. J.; Sugita, T.

    2004-01-01

    Satellite observations of denitrification and ice clouds in the Arctic lower stratosphere in February 1997 are used with Lagrangian microphysical box model calculations to evaluate nucleation mechanisms of solid polar stratospheric cloud (PSC) particles. The occurrences of ice clouds are not correlated in time and space with the locations of back trajectories of denitrified air masses, indicating that ice particle surfaces are not always a prerequisite for the formation of solid PSCs that lead to denitrification. In contrast, the model calculations incorporating a pseudoheterogeneous freezing process occurring at the vapor-liquid interface can quantitatively explain most of the observed denitrification when the nucleation activation free energy for nitric acid dihydrate formation is raised by only approx.10% relative to the current published values. Once nucleated, the conversion of nitric acid dihydrate to the stable trihydrate phase brings the computed levels of denitrification closer to the measurements. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and SblctureC: loud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere-composition and chemistry

  7. Aerosol measurements in the winter/spring Antarctic stratosphere. I - Correlative measurements with ozone. II - Impact on polar stratospheric cloud theories

    NASA Technical Reports Server (NTRS)

    Hofmann, D. J.; Rosen, J. M.; Harder, J. W.

    1988-01-01

    Aerosol measurements collected from August 25-November 3, 1986 at McMurdo Station using balloon-borne optical particle counters are examined in order to study the relationship between aerosol and ozone distribution and the formation of polar stratospheric clouds (PSCs). Ozone, aerosol, and condensation nuclei profiles, and pressure, temperature, and humidity measurements are analyzed. It is observed that the height of the stratospheric sulfate layer decreases over the period of measurement suggesting that upwelling in the votex is not important in the zone depletion process. Three theories on PSC formation are described, and the effects of the aerosol measurements on the theories are considered. The three theories are: (1) the original theory of water vapor pressure over a solution of H2SO4 of Steele et al. (1983) and Hamill and Mc Master (1984); (2) the nitric acid theory of PSCs of Toon et al. (1986) and Hamill et al. (1986); and (3) the quasi-cirrus cloud theory of Heymsfield (1986).

  8. Unprecedented Evidence for Large Scale Heterogeneous Nucleation of Polar Stratospheric Clouds, Likely by Nanometer-Sized Meteoritic Particles

    NASA Astrophysics Data System (ADS)

    Engel, I.; Pitts, M. C.; Luo, B.; Hoyle, C. R.; Zobrist, B.; Jacot, L.; Poole, L. R.; Grooss, J.; Weigel, R.; Borrmann, S.; Ebert, M.; Duprat, J.; Peter, T.

    2012-12-01

    Recent observations cast serious doubts on our understanding of the processes responsible for polar stratospheric cloud (PSC) formation. PSCs play crucial roles in polar ozone chemistry by hosting heterogeneous reactions and by removal of reactive nitrogen through sedimenting nitric acid trihydrate (NAT) particles. An extensive field campaign took place in the Arctic during the winter 2009/2010 within the European Union project RECONCILE, complemented by measurements from the spaceborne CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) instrument. Through trajectory and microphysical box model calculations, we analyzed CALIOP data from the RECONCILE winter to investigate the nucleation of PSC particles in detail. One significant finding was that liquid/NAT mixture PSCs were prevalent in late December 2009, a period during which no ice PSCs were observed, and temperatures were higher by 6 K than required for homogeneous ice freezing at the onset of PSC formation. These NAT particles must have formed through some non-ice nucleation mechanism, which runs counter to the widely held view that the only efficient NAT nuclei were ice crystals formed by homogeneous freezing of STS droplets. Furthermore, in mid-January 2010, a large region of the Arctic vortex cooled below the frost point, leading to widespread synoptic-scale ice PSCs, unusual for the Arctic. Our modeling studies indicate that a match with the CALIOP data calls for new heterogeneous nucleation mechanisms for both NAT and ice particles, namely freezing on nanometer-sized, solid nuclei immersed in the liquid stratospheric aerosols. Number concentrations of non-volatile particles were measured in situ during RECONCILE by means of the heated channel of the condensation nuclei (CN) counter COPAS on board of the high-flying aircraft Geophysica. 60-80 % of all CN survived heating to 250 °C. Offline Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis of RECONCILE impactor samples

  9. Cloud formation, convection, and stratospheric dehydration

    NASA Astrophysics Data System (ADS)

    Schoeberl, Mark R.; Dessler, Andrew E.; Wang, Tao; Avery, Melody A.; Jensen, Eric J.

    2014-12-01

    Using the Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis winds, temperatures, and anvil cloud ice, we use our domain-filling, forward trajectory model combined with a new cloud module to show that convective transport of saturated air and ice to altitudes below the tropopause has a significant impact on stratospheric water vapor and upper tropospheric clouds. We find that including cloud microphysical processes (rather than assuming that parcel water vapor never exceeds saturation) increases the lower stratospheric average H2O by 10-20%. Our model-computed cloud fraction shows reasonably good agreement with tropical upper troposphere (TUT) cloud frequency observed by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument in boreal winter with poorer agreement in summer. Our results suggest that over 40% of TUT cirrus is due to convection, and it is the saturated air from convection rather than injected cloud ice that primarily contributes to this increase. Convection can add up to 13% more water to the stratosphere. With just convective hydration (convection adds vapor up to saturation), the global lower stratospheric modeled water vapor is close to Microwave Limb Sounder observations. Adding convectively injected ice increases the modeled water vapor to ~8% over observations. Improving the representation of MERRA tropopause temperatures fields reduces stratospheric water vapor by ~4%.

  10. Fourier transform infrared studies of model polar stratospheric cloud surfaces - Growth and evaporation of ice and nitric acid/ice

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Middlebrook, Ann M.

    1990-01-01

    Fourier-transform infrared surface studies are used to probe the microphysical properties of nitric acid trihydrate (NAT) and ice films representative of type I and II polar stratospheric clouds (PSC). Experiments indicate that, on initial exposure to 1.8 microtorr of HNO3, a layer of ice is quantitatively converted to NAT. However, conversion of ice to NAT does not proceed indefinitely, but rather the system reaches saturation. For longer exposures or higher HNO3 pressures, NAM becomes the dominant nitric acid containing species on the surface. Evaporation studies were performed to test the feasibility of a recent denitrification mechanism. The results indicate that ice coated with 0.20 micron of NAT evaporates at a temperature of about 4 C higher than uncoated ice.

  11. Melting of H_2SO_4\\cdot4H_2O Particles upon Cooling: Implications for Polar Stratospheric Clouds

    NASA Astrophysics Data System (ADS)

    Koop, Thomas; Carslaw, Kenneth S.

    1996-06-01

    Polar stratospheric clouds (PSCs) are important for the chemical activation of chlorine compounds and subsequent ozone depletion. Solid PSCs can form on sulfuric acid tetrahydrate (SAT) (H_2SO_4\\cdot4H_2O) nuclei, but recent laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. A PSC formation mechanism is proposed in which SAT particles melt upon cooling in the presence of HNO_3 to form liquid HNO_3-H_2SO_4\\cdotH_2O droplets 2 to 3 kelvin above the ice frost point. This mechanism offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.

  12. Lidar observations of Arctic polar stratospheric clouds, 1988 - Signature of small, solid particles above the frost point

    NASA Technical Reports Server (NTRS)

    Poole, L. R.; Osborn, M. T.; Hunt, W. H.

    1988-01-01

    The paper presents recent (January 1988) Arctic airborne lidar data which suggest that Type I polar stratospheric clouds (PSCs) are composed of small solid particles with radii on the order of 0.5 micron. PSCs were observed remotely in the 21-24 km altitude range north of Greenland during a round-trip flight from Andenes, Norway on January 29, 1988, aboard the NASA Wallops Flight Facility P-3 Orion aircraft. Synoptic analyses at the 30-mb level show local temperatures of 191-193 K, which are well above the estimated frost point temperature of 185 K; this suggests that the PSCs were probably of the binary HNO3-H2O (Type I) class.

  13. Laboratory studies of the formation of polar stratospheric clouds: Nitric acid condensation on thin sulfuric acid films

    NASA Astrophysics Data System (ADS)

    Iraci, Laura T.; Middlebrook, Ann M.; Tolbert, Margaret A.

    1995-10-01

    Thin sulfuric acid films were exposed to 5 × 10-8 - 8 × 10-7 torr HNO3 and 2 - 3 × 10-4 torr H2O and cooled to temperatures near the ice frost point. Fourier transform infrared (FTIR) spectroscopy was used to probe the condensed-phase species during isothermal experiments, and gas pressures were monitored with mass spectrometry. Supercooled liquid sulfuric acid films exposed to HNO3 (6 ≤ SNAT ≤ 114) showed indications of HNO3 uptake to form ternary solutions of approximately 4 wt % HNO3, 38 wt % H2SO4, and 59 wt % H2O, followed by crystallization of nitric acid trihydrate (NAT). NAT crystallization did not initiate significant crystallization of the supercooled H2SO4, but the H2SO4 often crystallized to sulfuric acid tetrahydrate (SAT) upon warming. In contrast, when crystalline SAT films were exposed to HNO3 and water, NAT did not condense within several hours, even at HNO3 saturation ratios of 30 or higher. Calculations of the contact parameter from experimental data indicate that m <0.76 for NAT on SAT. Our film studies suggest that crystalline polar stratospheric cloud (PSC) growth is most easily accomplished when stratospheric sulfate aerosols (SSAs) remain liquid, absorb HNO3, and produce crystalline nitric acid trihydrate via heterogeneous nucleation. If SSAs crystallize to SAT at some point during the winter, nitric acid condensation is hindered, and PSC formation could become more difficult.

  14. Role of lee waves in the formation of solid polar stratospheric clouds: Case studies from February 1997

    NASA Astrophysics Data System (ADS)

    Rivière, E. D.; Huret, N.; Taupin, F. G.-; Renard, J.-B.; Pirre, M.; Eckermann, S. D.; Larsen, N.; Deshler, T.; Lefèvre, F.; Payan, S.; Camy-Peyret, C.

    2000-03-01

    Recent theories of solid polar stratospheric clouds (PSCs) formation have shown that particles could remain liquid down to 3 K or 4 K below the ice frost point. Such temperatures are rarely reached in the Arctic stratosphere at synoptic scale, but nevertheless, solid PSCs are frequently observed. Mesoscale processes such as mountain-induced gravity waves could be responsible for their formation. In this paper, a microphysical-chemical Lagrangian model (MiPLaSMO) and a mountain wave model (NRL/MWFM) are used to interpret balloon-borne measurements made by an optical particle counter (OPC) and by the Absorption par Minoritaires Ozone et NOx (AMON) instrument above Kiruna on February 25 and 26, 1997, respectively. The model results show good agreement with the particle size distributions obtained by the OPC in a layer of large particles, and allow us to interpret this layer as an evaporating mesoscale type Ia PSC (nitric acid trihydrate) mixed with liquid particles. The detection of a layer of solid particles by AMON is also qualitatively reproduced by the model and is interpreted to be frozen sulfate acid aerosols (SAT). In this situation, the impact of mountain waves on chlorine activation is studied. It appears that mesoscale perturbations amplify significantly the amount of computed ClO, as compared to synoptic runs. Moreover, MiPLaSMO chemical results concerning HNO3 and HCl agree with measurements made by the Limb Profile Monitor of the Atmosphere (LPMA) instrument on February 26 at a very close location to AMON, and explain part of the differences between LPMA measurement and Reactive Processes Ruling the Ozone Budget in the Stratosphere (REPROBUS) model outputs.

  15. What role do type I polar stratospheric cloud and aerosol parameterizations play in modelled lower stratospheric chlorine activation and ozone loss?

    NASA Astrophysics Data System (ADS)

    Sessler, J.; Good, P.; MacKenzie, A. R.; Pyle, J. A.

    1996-12-01

    The chlorine activation and subsequent ozone loss of the northern winter lower stratosphere have been modelled using different schemes for type I polar stratospheric clouds (PSCs) and sulphate aerosols. Type I PSCs were assumed to consist of either nitric acid trihydrate (NAT) at equilibrium, supercooled ternary solutions (STS) at equilibrium, or to follow a hysteresis cycle between frozen and liquid particles depending on the temperature history. The sulphate aerosol was assumed to be present as either liquid binary H2SO4/H2O aerosol (LBA) or as solid sulphuric acid tetrahydrate (SAT). Our box model integrations show that NAT and STS, representing the upper and lower limits of lower stratospheric chlorine activation, respectively, appear to destroy ozone equally efficiently after a cold PSC event (Tmin ≤ 190K at 50 mbar). For higher minimum temperatures, up to the equilibrium NAT point, there is significantly more ozone loss in the NAT scheme than in the STS scheme. On NAT, chlorine is activated directly by ClONO2 + HCl → 2Cl + HNO3, whereas on STS, indirect activation by ClONO2 + H2O → HOCl + HNO3 followed by HOCl + HCl → 2Cl + H2O, dominates. During the processing period, the indirect activation on STS will produce a temporary peak in HOCl. Box model integrations also show that direct chlorine activation is faster on SAT than on LBA, yielding significantly more ozone loss in air parcels which remain below the SAT melting point (215-220 K). Our single-layer chemical transport model simulations (θ = 465K) of the lower stratospheric chlorine activation during Arctic winter 1994/1995 show that chlorine is activated more quickly on NAT than on STS. However, in mid December 1994, when temperatures are low enough for substantial STS particle growth, maximum active chlorine becomes similar in both schemes and remains similar until the end of January 1995. A model integration which includes SAT produces up to 200 parts per trillion by volume more ClOx, inside

  16. Assessing lidar-based classification schemes for polar stratospheric clouds based on 16 years of measurements at Esrange, Sweden

    NASA Astrophysics Data System (ADS)

    Achtert, P.; Tesche, M.

    2014-02-01

    Lidar measurements of polar stratospheric clouds (PSCs) are commonly analyzed in classification schemes that apply the backscatter ratio and the particle depolarization ratio. This similarity of input data suggests comparable results of different classification schemes—despite measurements being performed with a variety of mostly custom-made instruments. Based on a time series of 16 years of lidar measurements at Esrange (68°N, 21°E), Sweden, we show that PSC classification differs substantially depending on the applied scheme. The discrepancies result from varying threshold values of lidar-derived parameters used to define certain PSC types. The resulting inconsistencies could impact the understanding of long-term PSC observations documented in the literature. We identify two out of seven considered classification schemes that are most likely to give reliable results and should be used in future lidar-based studies. Using polarized backscatter ratios gives the advantage of increased contrast for observations of weakly backscattering and weakly depolarizing particles. Improved confidence in PSC classification can be achieved by a more comprehensive consideration of the effect of measurement uncertainties. The particle depolarization ratio is the key to a reliable identification of different PSC types. Hence, detailed information on the calibration of the polarization-sensitive measurement channels should be provided to assess the findings of a study. Presently, most PSC measurements with lidar are performed at 532 nm only. The information from additional polarization-sensitive measurements in the near infrared could lead to an improved PSC classification. Coincident lidar-based temperature measurements at PSC level might provide useful information for an assessment of PSC classification.

  17. Polar stratospheric clouds observed at Eureka (80°N, 86°W) in the Canadian Arctic during the 1994/1995 winter

    NASA Astrophysics Data System (ADS)

    Nagai, T.; Uchino, O.; Itabe, T.; Shibata, T.; Mizutani, K.; Fujimoto, T.

    1997-09-01

    A lidar system was installed at Eureka (80°N, 86°W) in January 1993 to monitor stratospheric aerosols and polar stratospheric clouds (PSCs). In the winter of 1994/1995, PSCs were found at altitudes of around 20km in the middle of December. In early January 1995, PSCs were observed at altitudes from 14.3 km to 16 km, where the temperature ranged from 199K to 202K. Since this range is higher than the frost point of nitric acid trihydrate (NAT), the particles in these PSCs may have consisted of sulfuric acid tetrahydrate (SAT).

  18. In-situ measurements of total reactive nitrogen, total water vapor, and aerosols in polar stratospheric clouds in the Antarctic stratosphere

    NASA Technical Reports Server (NTRS)

    Fahey, D. W.; Kelly, K. K.; Ferry, G. V.; Poole, L. R.; Wilson, J. C.; Murphy, D. M.; Chan, K. Roland

    1988-01-01

    Measurements of total reactive nitrogen, NOy, total water vapor, and aerosols were made as part of the Airborne Antarctic Ozone Experiment. The measurements were made using instruments located onboard the NASA ER-2 aircrafts which conducted twelve flights over the Antarctic continent reaching altitudes of 18 km at 72 S latitude. Each instrument utilized an ambient air sample and provided a measurement up to 1 Hz or every 200 m of flight path. The data presented focus on the flights of Aug. 17th and 18th during which Polar Stratospheric Clouds (PSCs) were encountered containing concentrations of 0.5 to 1.0 micron diameter aerosols greater than 1 cm/cu. The temperature pressure during these events ranged as low as 184 K near 75 mb pressure, with water values near 3.5 ppm by volume (ppmv). With the exception of two short periods, the PSC activity was observed at temperatures above the frost point of water over ice. The data gathered during these flights are analyzed and presented.

  19. The potential for ozone depletion in the Arctic polar stratosphere

    SciTech Connect

    Brune, W.H. ); Anderson, J.G.; Toohey, D.W. ); Fahey, D.W.; Kawa, S.R. ); Jones, R.L. ); McKenna, D.S. ); Poole, L.R. )

    1991-05-31

    The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. most of the available chlorine (HCl and ClONO{sub 2}) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl{sub 2}O{sub 2} throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO{sub 3}, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15% at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8% losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50% over the next two decades, ozone losses recognizable as an ozone hole may well appear.

  20. The potential for ozone depletion in the Arctic polar stratosphere

    NASA Technical Reports Server (NTRS)

    Brune, W. H.; Anderson, J. G.; Toohey, D. W.; Fahey, D. W.; Kawa, S. R.; Poole, L. R.

    1991-01-01

    The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. Most of the available chlorine (CHl and ClONO2) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl2O2 thoroughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO3, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15 percent at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8 percent losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50 percent over the next two decades, ozone losses recognizable as an ozone hole may well appear.

  1. Large-scale variations in ozone and polar stratospheric clouds measured with airborne lidar during formation of the 1987 ozone hole over Antarctica

    NASA Technical Reports Server (NTRS)

    Browell, Edward V.; Poole, Lamont R.; Mccormick, M. Patrick; Ismail, Syed; Butler, Carolyn F.; Kooi, Susan A.; Szedlmayer, Margaret M.; Jones, Rod; Krueger, Arlin J.; Tuck, Adrian

    1988-01-01

    A joint field experiment between NASA and NOAA was conducted during August to September 1987 to obtain in situ and remote measurements of key gases and aerosols from aircraft platforms during the formation of the ozone (O3) hole over Antarctica. The ER-2 (advanced U-2) and DC-8 aircraft from the NASA Ames Research Center were used in this field experiment. The NASA Langley Research Center's airborne differential absorption lidar (DIAL) system was operated from the DC-8 to obtain profiles of O3 and polar stratospheric clouds in the lower stratosphere during long-range flights over Antarctica from August 28 to September 29, 1987. The airborne DIAL system was configured to transmit simultaneously four laser wavelengths (301, 311, 622, and 1064 nm) above the DC-8 for DIAL measurements of O3 profiles between 11 to 20 km ASL (geometric altitude above sea level) and multiple wavelength aerosol backscatter measurements between 11 to 24 km ASL. A total of 13 DC-8 flights were made over Antarctica with 2 flights reaching the South Pole. Polar stratospheric clouds (PSC's) were detected in multiple thin layers in the 11 to 21 km ASL altitude range with each layer having a typical thickness of less than 1 km. Two types of PSC's were found based on aerosol backscattering ratios: predominantly water ice clouds (type 2) and clouds with scattering characteristics consistent with binary solid nitric acid/water clouds (type 1). Large-scale cross sections of O3 distributions were obtained. The data provides additional information about a potentially important transport mechanism that may influence the O3 budget inside the vortex. There is also some evidence that strong low pressure systems in the troposphere are associated with regions of lower stratospheric O3. This paper discusses the spatial and temporal variations of O3 inside and outside the polar vortex region during the development of the O3 hole and relates these data to other measurements obtained during this field experiment.

  2. Facet shapes and thermo-stabilities of H₂SO₄•HNO₃ hydrates involved in polar stratospheric clouds.

    PubMed

    Verdes, Marian; Paniagua, Miguel

    2015-09-01

    The nucleation, ice crystal shapes and thermodynamic stability of polar stratospheric clouds particles are interesting concerns owing to their implication in the ozone layer destruction. Some of these particles are formed by conformers of H2O, HNO3, and H2SO4. We carried out calculations using density functional theory (DFT) to obtain optimized structures. Several stable trimers are achieved -divided in two groups, one with HNO3 moiety, second with H2SO4 moiety- after pre-optimization at B3LYP/6-31G and subsequently optimization at B3LYP/aug-cc-pVTZ level of theory. For both most stable conformers five H2O molecules are added to their optimized trimers to calculate hydrated geometries. The OH stretching harmonic frequencies are provided for all aggregates. The zero-point energy correction (ZEPC), relative electronic energies (∆E), relative reaction Gibbs free energies ∆(∆G)k-relative, and cooling constant (K cooling ) are reported at three temperatures: 188 K, 195 K, and 210 K. Shapes given in our calculations are compared with various experimental shapes as well as comparisons with their thermo-stabilities. PMID:26287119

  3. Changes in the character of Polar stratospheric clouds over Antarctica in 1992 due to the Pinatubo volcanic aerosol

    SciTech Connect

    Deshler, T.; Johnson, B.J.; Rozier, W.R. )

    1994-02-15

    Vertical profiles of aerosol concentration were measured on 8 occasions from McMurdo Station, Antarctica (78[degrees]S), between late August and early October 1992. Polar stratospheric clouds (PSCs) were observed on 6 of these soundings. The characteristics of PSCs, and ozone, were quite different above and below about 16 km. Above 16 km PSCs were variable in time, with particles > 1.0 [mu]m radius contributing significantly to the surface area, generally < 8 [mu]m[sup 2] cm[sup [minus]3]. Below 16 km PSCs were much more stable and were dominated by high concentrations of smaller particles, < 1.0 [mu]m, with surface areas of 20-30 [mu]m[sup 2] cm[sup [minus]3]. This lower layer coincided with the altitude of the primary Pinatubo volcanic aerosol as measured in mid September and October, and with the 4 km region of the atmosphere where ozone was virtually completed destroyed over Antarctica in 1992. 12 refs., 4 figs.

  4. The vapor pressures of supercooled NHO3/H2O solutions. [in polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Hanson, David R.

    1990-01-01

    A procedure utilizing the Gibbs-Duhem relation is used to extrapolate vapor pressures of supercooled HNO3 mixtures to 190 K. Values of A and B from the equation logP = A - B/T are presented for solutions between 0.20 and 0.25 mole fraction HNO3. In the stratosphere, if sufficient HNO3 vapor is present because it has not come into equilibrium with the nitric acid trihydrate, supercooled nitric acid solutions could condense at temperatures up to 1.5 + or - 0.8 K above the ice point.

  5. Balloon borne Antarctic frost point measurements and their impact on polar stratospheric cloud theories

    NASA Technical Reports Server (NTRS)

    Rosen, James M.; Hofmann, D. J.; Carpenter, J. R.; Harder, J. W.; Oltsmans, S. J.

    1988-01-01

    Balloon-borne frost point measurements were performed over Antarctica during September-October 1987 as part of the NOZE II effort at McMurdo. The results show water mixing ratios on the order of 2 ppmv in the 20 km region, suggesting that models of the springtime Antarctic stratosphere should be based on approximately 2 ppmv water vapor. Evidence indicating that some PSCs form at temperatures higher than the frost point in the 15 to 20 km region is discussed. This supports the binary HNO3-H2O theory of PSC composition.

  6. A comparison of the longitudinal distributions of polar stratospheric clouds and temperatures for the 1987 Antarctic spring

    SciTech Connect

    Watterson, I.G. ); Tuck, A.F. )

    1989-11-30

    The Stratospheric Aerosol Measurement (SAM) II stratospheric extinction coefficients have been analyzed to provide information on the geographical distribution of Antarctic stratospheric clouds in 1987. The peak extinction above 15 km was determined for each of the approximately 14 vertical profiles each day. A longitude by time graph of this extinction is presented, extending from early June to late October. Similar graphs for extinction at 17 km and for temperature at 17 km and 70 mbar geopotential height from the National Meteorological Center at the measurement locations are also shown. It is assumed that extinction is a measure of cloud density. Statistics of the fractional incidence of cloud and of temperature and pressure for five time periods and 24 longitudinal sectors are presented. Cloud incidences for latitudes which either cross or pass to the south of the Antarctic Peninsula are shown. In order to remove the effect of the latitudinal drift of the measurements the statistics are also shown for data binned by 70-mbar geopotential height relative to the minimum within the vortex. In general, there is a good correlation between enhanced extinctions and cold temperatures. Both exhibit a planetary wave structure which tends to move eastward. However, the distribution of dense clouds is highly zonally asymmetric and unlike that of temperature. These clouds are very rare over East Antarctica even when temperatures are low there. After July, clouds are also rare close to the center of the vortex, as determined by the 70-mbar geopotential height of the measurement locations. It is concluded that both cold temperature and the availability of condensable material are important in determining the location of cloud.

  7. SAGE II observations of a previously unreported stratospheric volcanic aerosol cloud in the northern polar summer of 1990

    NASA Technical Reports Server (NTRS)

    Yue, Glenn K.; Veiga, Robert E.; Wang, Pi-Huan

    1994-01-01

    Analysis of aerosol extinction profiles obtained by the spaceborne SAGE II sensor reveals that there was an anomalous increase of aerosol extinction below 18.5 km at latitudes poleward of 50 deg N from July 28 to September 9, 1990. This widespread increase of aerosol extinction in the lower stratosphere was apparently due to a remote high-latitude volcanic eruption that has not been reported to date. The increase in stratospheric optical depth in the northern polar region was about 50% in August and had diminished by October 1990. This eruption caused an increase in stratospheric aerosol mass of about 0.33 x 10(exp 5) tons, assuming the aerosol was composed of sulfuric acid and water.

  8. Real refractive indices of infrared-characterized nitric-acid/ice films: Implications for optical measurements of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Middlebrook, Ann M.; Berland, Brian S.; George, Steven M.; Tolbert, Margaret A.; Toon, Owen B.

    1994-01-01

    The infrared spectra of nitric-acid/ice films representative of polar stratospheric clouds (PSCs) were collected with simultaneous optical interference measurements to determine the real refractive indices at lambda = 632 nm. Ice and amphorous nitric-acid/ice films were prepared by condensation of water and nitric acid vapors onto a wedged Al2O3 substrate. The real refractive indices of these films were determined from the optical interference of a reflected helium-neon laser during film growth. The indices of the amphorous films varied smoothly from n = 1.30 for ice to n = 1.49 for nitric acid, similar to observations in previous work. We were unable to obtain the refractive index of crystlline films during adsorption because of optical scattering caused by surface roughness. Therefore crystlline nitric acid hydrate films were prepared by annealing amphorous nitric-acid/ice films. Further heating caused desorption of the crystalline hydrate films. During desorption, the refractive indices for ice, NAM (nitric acid monohydrate), alpha- and beta-NAT (nitric acid trihydrate) films were measured using the optical interference technique. In agreement with earlier data, the real refractive indices for ice and NAM determined in desorption were n = 1.30 +/- 0.01 and n = 1.53 +/- 0.03, respectively. The real refractive indices for alpha- and beta-NAT were found to be n = 1.51 +/- 0.01 and n greater than or equal to 1.46, respectively. Our measurements also suggest that the shape of crystalline nitric acid particles may depend on whether they nucleate from the liquid or by vapor deposition. If confirmed by future studies, this observation may provide a means of distinguishing the nucleation mechanism of crystalline PSCs.

  9. Polar stratospheric clouds in the 1998-2003 Antarctic vortex: Microphysical modeling and Polar Ozone and Aerosol Measurement (POAM) III observations

    NASA Astrophysics Data System (ADS)

    Benson, C. M.; Drdla, K.; Nedoluha, G. E.; Shettle, E. P.; Alfred, J.; Hoppel, K. W.

    2006-09-01

    The Integrated Microphysics and Aerosol Chemistry on Trajectories (IMPACT) model is used to study polar stratospheric cloud (PSC) formation and evolution in the Antarctic vortex. The model is applied to individual air parcel trajectories driven by UK Met Office (UKMO) wind and temperature fields. The IMPACT model calculates the parcel microphysics, including the formation and sedimentation of ice, nitric acid trihydrate (NAT), sulfuric acid tetrahydrate (SAT), and supercooled ternary solution (STS) aerosols. Model results are validated by comparison with data obtained by the Polar Ozone and Aerosol Measurement (POAM) III solar occultation instrument and are examined for 6 years of POAM data (1998-2003). Comparisons of POAM water vapor and aerosol extinction measurements to the model results help to constrain three microphysical parameters influencing the formation and growth of both type I and type II PSCs. Principally, measurements of aerosol extinction prove to be valuable in differentiating model runs; the relationship of aerosol extinction to temperature is determined by the various particle types as they form and grow. Comparison of IMPACT calculations of this relationship to POAM measurements suggests that the initial fraction of nuclei available for heterogeneous NAT freezing is approximately 0.02% of all aerosols. Constraints are also placed on the accommodation coefficient of ice and the NAT-ice lattice compatibility. However, these two parameters have similar effects on the extinction-temperature relationship, and thus a range of values are permissible for each.

  10. Nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions

    NASA Technical Reports Server (NTRS)

    Hallett, John; Queen, Brian; Teets, Edward; Fahey, James

    1995-01-01

    Laboratory studies examine phase changes of hygroscopic substances which occur as aerosol in stratosphere and troposphere (sodium chloride, ammonium sulfate, ammonium bisulfate, nitric acid, sulfuric acid), under controlled conditions, in samples volume 1 to 10(exp -4) ml. Crystallization of salts from supersaturated solutions is examined by slowly evaporating a solution drop on a substrate, under controlled relative humidity, until self nucleation occurs; controlled nucleation of ice in a mm capillary U-tube gives a measured ice crystallization velocity at known supercooling. Two states of crystallization occur for regions where hydrates exist. It is inferred that all of the materials readily exist as supersaturated/supercooled solutions; the degree of metastability appears to be slightly enhanced by inclusion of aircraft produced soot. The crystallization velocity is taken as a measure of viscosity. Results suggest an approach to a glass transition at high molality, supersaturation and/or supercooling within the range of atmospheric interest. It is hypothesized that surface reactions occur more readily on solidified particles - either crystalline or glass, whereas volume reactions are more important on droplets with sufficiently low viscosity and volume diffusivity. Implications are examined for optical properties of such particles in the atmosphere. In a separate experiment, crystal growth was examined in a modified thermal vapor diffusion chamber over the range of cirrus temperature (-30 to -70 C) and under controlled supersaturation and air pressure. The crystals grew at a velocity of 1-2 microns/s, thickness 60-70 micron, in the form of thin column crystals. Design criteria are given for a system to investigate particle growth down to -100 C, (PSC temperatures) where nitric acid particles can be grown under similar control and in the form of hydrate crystals.

  11. Characteristics of cirrus clouds in the tropical lower stratosphere

    NASA Astrophysics Data System (ADS)

    Iwasaki, Suginori; Luo, Zhengzhao Johnny; Kubota, Hisayuki; Shibata, Takashi; Okamoto, Hajime; Ishimoto, Hiroshi

    2015-10-01

    A unique type of cloud in the tropical lower stratosphere, which we call "stratospheric cirrus", is described in this study. Stratospheric cirrus clouds are generally detached from overshooting deep convection and are much smaller than subvisual cirrus often observed near the tropical tropopause. We analyzed two cases of stratospheric cirrus in the tropical and subtropical lower stratosphere captured by the space-borne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Both cases occurred 2-3 hours after the most active phase of the nearby convective cloud clusters. Case 1 has a double-layer structure above the cold point height (CPH); the CPH and two cloud top heights are, respectively, 17.8, 18.9, and 19.9 km. Case 2 has a single cloud layer where CPH and the cloud top height are, respectively, 16.5 and 18.7 km. The mode radius and ice water content of the stratospheric cirrus clouds are estimated to be 4-10 μm and 0.2-0.8 mg/m3 based on the radar-lidar method and consideration of the cloud particle terminal velocity. Comparisons with previous numerical model simulation studies suggest that the double-layer stratospheric cirrus clouds are likely from an overshooting plume, pushed up into the stratosphere in an overshoot when warm stratospheric air is inhomogeneously mixed with cold overshooting air. The single-layer stratospheric cirrus cloud is associated with some non-negligible wind shear, so it could be a jumping cirrus cloud, although we cannot rule out the possibility that it came from an overshooting plume because of the similarity in cloud characteristics and morphology between the two cases. Guided by the case studies, an automatic algorithm was developed to select stratospheric cirrus clouds for global survey and statistical analysis. A total of four years of CALIPSO and space-borne cloud radar (CloudSat) data were analyzed. Statistical analysis suggests that stratospheric cirrus clouds occur on the order of 3.0 × 103 times a year

  12. The January 30, 1989 Arctic polar stratospheric clouds (PSC) event - Evidence for a mechanism of dehydration

    NASA Technical Reports Server (NTRS)

    Gandrud, B. W.; Dye, J. E.; Baumgardner, D.; Ferry, G. V.; Loewenstein, M.; Chan, K. R.; Sanford, L.; Gary, B.

    1990-01-01

    In-situ particle measurements made aboard the NASA ER-2 in the Arctic on 890130 (YYMMDD) show Type 1 PSC particles over much of the flight, with instances of embedded Type 2 PSCs. The Type 2 particles were observed at temperatures warmer than the local frost-point temperature of water; extended up to the upper size cutoff of the instrument (about 24-micron diameter); and are shown to contain too large a volume to be primarily NAT. Based on measured vertical temperature profiles, it is concluded that the Type 2 particles observed on this day were formed above the aircraft in a region where saturation with respect to ice was achieved and were sufficiently large to have fallen into the path of the ER-2. Although the amount of material in the particles, expressed as water, is small by comparison to the total (vapor + aerosol) water concentration, the flux of water from the falling particles is of sufficient magnitude, if sustained, to lead to dehydration of the source region. These observations verify the mechanism for dehydration of polar vortex air masses by precipitation of ice particles.

  13. Heterogeneous reactions of chlorine nitrate and hydrogen chloride on type I polar stratospheric clouds

    SciTech Connect

    Mingtaun Leu; Moore, S.B.; Keyser, L.F. )

    1991-10-03

    The heterogeneous reactions ClONO{sub 2} + NCl {yields} Cl{sub 2} + NHO{sub 3} (1) and ClONO{sub 2} + H{sub 2}O {yields} HOCl + HNO{sub 3} (2) on vapor-deposited NHO{sub 3}-H{sub 2}O ice substrates have been investigated at 196 K by using a fast-flow reactor coupled with a quadrupole mass spectrometer. The reaction probability for (1) is 0.10 {plus minus} 0.02 and independent of both the HNO{sub 3} and HCl concentrations in the substrate compositions studied. For (2), the reaction probability is approximately 1 {times} 10{sup {minus}5} near 53.8 wt% HNO{sub 3}, the composition of pure nitric acid trihydrate (NAT), and is about 1 {times} 10{sup {minus}3} at 46 wt% HNO{sub 3}. The sticking coefficient of HCl on these substrates was also found to be a strong function of the substrate composition, ranging from about 2 {times} 10{sup {minus}5} at NAT composition to 6 {times} 10{sup {minus}3} at 45 wt% HNO{sub 3}. The HNO{sub 3}-H{sub 2}O ice substrates were found to have large internal surface areas, and corrections for gas-phase diffusion within the porous ices were applied to observed loss rates. The large decrease in the HCl sticking coefficient and the reaction probability for (2) as the composition of pure NAT is approached from the water-enriched side can be semiquantatively explained in terms of a simple two-solid-phase model. Finally, the relation of these results to the depletion of polar ozone is discussed.

  14. Heterogeneous physicochemistry of the winter polar stratosphere

    NASA Technical Reports Server (NTRS)

    Turco, R. P.; Toon, O. B.

    1988-01-01

    Present chemical theories of the Antarctic ozone hole assume that heterogeneous reactions involving polar stratospheric clouds (PSCs) are the precursor of springtime ozone depletions. However, none of the theories quantify the rates of proposed heterogeneous processed, and none utilize the extensive data base on PSC's. Thus, all of the theories must be considered incomplete until the heterogeneous mechanisms are properly defined. A unified treatment developed of the cloud related processes, both physical and chemical, and the importance of these processes using observation data is calibrated. The rates are compared competitive heterogeneous processes to place reasonable limits on critical mechanisms such as the denitrification and dechlorination of the polar winter stratosphere. Among the subjects addressed here are the physical/chemical properties of PSC's including their relevant microphysical, optical and compositional characteristics, mass transfer rates of gaseous constituents to cloud particles, adsorption, accommodation and sticking coefficients on cloud particles, time constants for condensation, absorption and other microphysical processes, effects of solubility and vapor pressure on cloud composition, the statistics of cloud processing of chemically active condensible species, rate limiting steps in heterogeneous chemical reactions, and the nonlinear dependence of ozone loss on physical and chemical parameters.

  15. STRAPOLETE : Studying summer polar stratosphere

    NASA Astrophysics Data System (ADS)

    Payan, Sebastien

    2010-05-01

    The polar stratosphere in the summertime remains largely unexplored. Dynamical conditions are characterized by large scale transport and mixing between air masses of higher and lower latitude origins. Understanding these exchanges is crucial since they have a large impact on the distribution of trace gases and aerosols at polar latitudes, and thus on the stratospheric ozone budget. Ozone change affects the radiative balance, the coupling between troposphere and stratosphere, and therefore the climate. In the framework of the International Polar Year, the STRAPOLETE project starts on January 2009. It is associated with a successful balloon borne campaign which took place close to Kiruna (Sweeden) from 2 August 2009 to 12 September 2009 with eight balloon flights. During this campaign the main characteristics of the summertime arctic stratosphere have been captured. The data set obtained using UV-visible and infrared instruments, remote and in situ sensing embarked spectrometers provided detailed information on vertical distributions of more than fifteen chemical tracers and reactive species from the upper troposphere to the middle stratosphere. A number of in situ optical aerosol counters, a UV-visible remote spectrometer for the aerosol extinction and a photopolarimeter provided information on the nature and size distribution of the stratospheric aerosols. These balloon measurements with high precision and high vertical resolution are relevant to qualify the dynamical processes occurring in this region during summertime, the aerosols variability, the bromine abundance and establish a reference state of the polar summer stratosphere. The data set is completed by satellite data offering large spatial coverage of the region of interest. Data analysis is made using relevant dynamical (trajectory calculations, contour advection model) and chemistry-transport models (CTM) to highlight major mechanisms that control the distribution of tracers, aerosols and bromine. An

  16. A new parameterization of polar stratospheric clouds based on the effective growth of NAT particles in the chemistry-climate-model EMAC

    NASA Astrophysics Data System (ADS)

    Kirner, Ole; Ruhnke, Roland; Hoepfner, Michael

    2013-04-01

    Polar stratospheric clouds (PSCs), consisting of STS, NAT and ice particles, play a major role in polar ozone depletion. On the one hand there is the activation of chlorine reservoirs at the surface of the PSCs, on the other hand PSCs lead to the stratospheric denitrification with the effect of a delay in the deactivation of active chlorine in polar spring. Due to the relevance of a good representation of these PSCs in global chemistry-climate-models (CCMs) a new algorithm based on efficient growth of NAT particles, developed by van den Broek et al. [2004], has been implemented into the submodel PSC of the CCM ECHAM5/MESSy for Atmospheric Chemistry (EMAC). We present results of an EMAC simulation from 2000 to 2012, performed with the new NAT parameterization. The simulated results are analyzed regarding the composition of PSCs and their distribution in the polar regions as well as their influence to the ozone related chemistry. The new results are compared with an EMAC simulation with the old standard thermodynamical NAT parameterization. A comparison with PSC measurements retrieved by the satellite instrument MIPAS on ENVISAT [Höpfner et al., 2006] show the quality of the new PSC scheme in EMAC. With the help of an additional sensitivity simulation it can be shown that the significance of heterogeneous reactions on ice particles, in comparison to liquid particles, is subordinate regarding chlorine activation and ozone depletion in Antarctic winter and spring as noted in Drdla and Mueller [2012].

  17. Observational Evidence Against Mountain-Wave Generation of Ice Nuclei as a Prerequisite for the Formation of Three Solid Nitric Acid Polar Stratospheric Clouds Observed in the Arctic in Early December 1999

    NASA Technical Reports Server (NTRS)

    Pagan, Kathy L.; Tabazadeh, Azadeh; Drdla, Katja; Hervig, Mark E.; Eckermann, Stephen D.; Browell, Edward V.; Legg, Marion J.; Foschi, Patricia G.

    2004-01-01

    A number of recently published papers suggest that mountain-wave activity in the stratosphere, producing ice particles when temperatures drop below the ice frost point, may be the primary source of large NAT particles. In this paper we use measurements from the Advanced Very High Resolution Radiometer (AVHRR) instruments on board the National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites to map out regions of ice clouds produced by stratospheric mountain-wave activity inside the Arctic vortex. Lidar observations from three DC-8 flights in early December 1999 show the presence of solid nitric acid (Type Ia or NAT) polar stratospheric clouds (PSCs). By using back trajectories and superimposing the position maps on the AVHRR cloud imagery products, we show that these observed NAT clouds could not have originated at locations of high-amplitude mountain-wave activity. We also show that mountain-wave PSC climatology data and Mountain Wave Forecast Model 2.0 (MWFM-2) raw hemispheric ray and grid box averaged hemispheric wave temperature amplitude hindcast data from the same time period are in agreement with the AVHRR data. Our results show that ice cloud formation in mountain waves cannot explain how at least three large scale NAT clouds were formed in the stratosphere in early December 1999.

  18. Microphysical properties of synoptic-scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3-containing particles in the Arctic vortex

    NASA Astrophysics Data System (ADS)

    Molleker, S.; Borrmann, S.; Schlager, H.; Luo, B.; Frey, W.; Klingebiel, M.; Weigel, R.; Ebert, M.; Mitev, V.; Matthey, R.; Woiwode, W.; Oelhaf, H.; Dörnbrack, A.; Stratmann, G.; Grooß, J.-U.; Günther, G.; Vogel, B.; Müller, R.; Krämer, M.; Meyer, J.; Cairo, F.

    2014-10-01

    In January 2010 and December 2011, synoptic-scale polar stratospheric cloud (PSC) fields were probed during seven flights of the high-altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 and 40μm were recorded by four different optical in situ instruments. Three of these particle instruments are based on the detection of forward-scattered light by single particles. The fourth instrument is a grayscale optical array imaging probe. Optical particle diameters of up to 35μm were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas-phase and particle-bound NOy was measured, as well as water vapor concentrations. The optical characteristics of the clouds were measured by the remote sensing lidar MAL (Miniature Aerosol Lidar) and by the in situ backscatter sonde MAS (Multiwavelength Aerosol Scatterometer), showing the synoptic scale of the encountered PSCs. The particle mode below 2μm in size diameter has been identified as supercooled ternary solution (STS) droplets. The PSC particles in the size range above 2μm in diameter are considered to consist of nitric acid hydrates, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. Therefore the measurement uncertainties concerning probable overestimations of measured particle sizes and volumes are discussed in detail. We hypothesize that either a strong asphericity or an alternate particle composition (e.g., water ice coated with NAT) could explain our observations. In particular

  19. The impact of polar stratospheric ozone loss on Southern Hemisphere stratospheric circulation and climate

    NASA Astrophysics Data System (ADS)

    Keeble, J.; Braesicke, P.; Abraham, N. L.; Roscoe, H. K.; Pyle, J. A.

    2014-12-01

    The impact of polar stratospheric ozone loss resulting from chlorine activation on polar stratospheric clouds is examined using a pair of model integrations run with the fully coupled chemistry climate model UM-UKCA. Suppressing chlorine activation through heterogeneous reactions is found to produce modelled ozone differences consistent with observed ozone differences between the present and pre-ozone hole period. Statistically significant high-latitude Southern Hemisphere (SH) ozone loss begins in August and peaks in October-November, with > 75% of ozone destroyed at 50 hPa. Associated with this ozone destruction is a > 12 K decrease of the lower polar stratospheric temperatures and an increase of > 6 K in the upper stratosphere. The heating components of this temperature change are diagnosed and it is found that the temperature dipole is the result of decreased short-wave heating in the lower stratosphere and increased dynamical heating in the upper stratosphere. The cooling of the polar lower stratosphere leads, through thermal wind balance, to an acceleration of the polar vortex and delays its breakdown by ~ 2 weeks. A link between lower stratospheric zonal wind speed, the vertical component of the Eliassen-Palm (EP) flux, Fz and the residual mean vertical circulation, w*, is identified. In November and December, increased westerly winds and a delay in the breakup of the polar vortex lead to increases in Fz, indicating increased wave activity entering the stratosphere and propagating to higher altitudes. The resulting increase in wave breaking, diagnosed by decreases to the EP flux divergence, drives enhanced downwelling over the polar cap. Many of the stratospheric signals modelled in this study propagate down to the troposphere, and lead to significant surface changes in December.

  20. Combined system for observations of tropospheric and stratospheric thin clouds

    SciTech Connect

    Adriani, A.; Gobbi, G.P.; Viterbini, M.; Ugazio, S. CNR, Ist. di Fisica dello Spazio Interplanetario, Frascati )

    1993-02-01

    A balloon-borne sonde and a polarization lidar have been developed to make combined observations of thin tropospheric and stratospheric clouds. Their first application was a campaign organized to study Antarctic polar stratospheric clouds, which are involved in the process of ozone depletion. The sonde collects cloud particles larger than 4 microns in diameter on a transparent impactor and observes them by means of a CCD camera microscope. Images are transmitted in real time to the ground station for recording and analysis. Shape, dimension, and size distribution of the particles are obtained from these frames. The lidar provides complementary information about the cloud optical depth, backscattering, depolarization, vertical distribution, and temporal evolution. Characteristics of both instruments are described. The experiments performed during the 1990 spring campaign at McMurdo Station, Antarctica, are discussed, and some results are reported to show the capabilities of the combined system. 14 refs.

  1. Polar stratospheric clouds climatology over Dumont d'Urville between 1989 and 1993 and the influence of volcanic aerosols on their formation

    NASA Astrophysics Data System (ADS)

    David, C.; Bekki, S.; Godin, S.; MéGie, G.; Chipperfield, M. P.

    1998-09-01

    The first polar stratospheric clouds (PSCs) climatology ever established from lidar data and relative to a specific site is presented here. It is based on lidar backscatter and depolarization measurements of PSCs carried out between 1989 and 1993 at Dumont d'Urville (66°S, 140°E), which is a primary station of the Network for Detection of Stratospheric Changes (NDSC). The climatology was subdivided based on the stratospheric sulphuric acid aerosol content (background aerosols in 1989-1991 and volcanic aerosols in 1992-1993 following the Mount Pinatubo eruption). PSCs were mainly observed in July and August. Very few water ice clouds (type II) were detected. Most of the PSCs tended to form around the peak in sulphuric acid aerosol, between 17 and 23 km in 1989-1991 and between 11 and 20 km in 1992-1993. This tendency suggests that sulphuric acid aerosols are very likely to act as condensation nuclei for PSCs. As shown by previous lidar studies [Browell et al, 1990], two type I subclasses were identified: depolarizing (nonspherical) particles (type Ia) and nondepolarizing (spherical) particles (type Ib). No type Ia PSCs were detected above the nitric acid trihydrate (NAT) saturation temperature, TNAT, lending support to the theory that NAT is the main component of type Ia PSCs. There was also no evidence of the existence of sulphuric acid tetrahydrate (SAT) in the data. Some type Ib PSCs were observed close to the frost point, showing that supersaturation with respect to NAT is a necessary, but not sufficient, condition for the existence of solid PSCs. No type Ib PSCs were clearly detected above TNAT in 1989-1991 whereas 18% of the PSCs seem to be found at temperatures above TNAT in 1992-1993. This difference might be linked to the HNO3 uptake by volcanic sulphuric acid particles starting at higher temperatures. The fraction of type Ia out of the total PSCs observations was lower in 1992-1993 than in 1989-1991. This difference was not found to be highly

  2. The impact of polar stratospheric ozone loss on Southern Hemisphere stratospheric circulation and climate

    NASA Astrophysics Data System (ADS)

    Keeble, J.; Braesicke, P.; Abraham, N. L.; Roscoe, H. K.; Pyle, J. A.

    2014-07-01

    The impact of polar stratospheric ozone loss resulting from chlorine activation on polar stratospheric clouds is examined using a pair of model integrations run with the fully coupled chemistry climate model UM-UKCA. Suppressing chlorine activation through heterogeneous reactions is found to produce modelled ozone differences consistent with observed ozone differences between the present and pre-ozone hole period. Statistically significant high latitude Southern Hemisphere (SH) ozone loss begins in August and peaks in October-November, with >75% of ozone destroyed at 50 hPa. Associated with this ozone destruction is a >12 K decrease of the lower polar stratospheric temperatures and an increase of >6 K in the upper stratosphere. The heating components of this temperature change are diagnosed and it is found that the temperature dipole is the result of decreased shortwave heating in the lower stratosphere and increased dynamical heating in the upper stratosphere. The cooling of the polar lower stratosphere leads, through thermal wind balance, to an acceleration of the polar vortex and delays its breakdown by ~2 weeks. A link between lower stratospheric zonal wind speed, the vertical component of the EP flux, Fz, and the residual mean vertical circulation, w*, is identified. In December and January, increased westerly winds lead to increases in Fz, associated with an increase in tropopause height. The resulting increase in wavebreaking leads to enhanced downwelling/reduced upwelling over the polar cap. Many of the stratospheric signals modelled in this study propagate down to the troposphere, and lead to significant surface changes in December.

  3. Monitoring of the Polar Stratospheric Clouds formation and evolution in Antarctica in August 2007 during IPY with the MATCH method applied to lidar data

    NASA Astrophysics Data System (ADS)

    Montoux, Nadege; David, Christine; Klekociuk, Andrew; Pitts, Michael; di Liberto, Luca; Snels, Marcel; Jumelet, Julien; Bekki, Slimane; Larsen, Niels

    2010-05-01

    The project ORACLE-O3 ("Ozone layer and UV RAdiation in a changing CLimate Evaluated during IPY") is one of the coordinated international proposals selected for the International Polar Year (IPY). As part of this global project, LOLITA-PSC ("Lagrangian Observations with Lidar Investigations and Trajectories in Antarctica and Arctic, of PSC") is devoted to Polar Stratospheric Clouds (PSC) studies. Indeed, understanding the formation and evolution of PSC is an important issue to quantify the impact of climate changes on their frequency of formation and, further, on chlorine activation and subsequent ozone depletion. In this framework, three lidar stations performed PSC observations in Antarctica during the 2006, 2007, and 2008 winters: Davis (68.58°S, 77.97°E), McMurdo (77.86°S, 166.48°E) and Dumont D'Urville (66.67°S, 140.01°E). The data are completed with the lidar data from CALIOP ("Cloud-Aerosol Lidar with Orthogonal Polarization") onboard the CALIPSO ("Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation") satellite. Lagrangian trajectory calculations are used to identify air masses with PSCs sounded by several ground-based lidar stations with the same method, called MATCH, applied for the first time in Arctic to study the ozone depletion with radiosoundings. The evolution of the optical properties of the PSCs and thus the type of PSCs formed (supercooled ternary solution, nitric acid trihydrate particles or ice particles) could thus be linked to the thermodynamical evolution of the air mass deduced from the trajectories. A modeling with the microphysical model of the Danish Meteorological Institute allows assessing our ability to predict PSCs for various environmental conditions. Indeed, from pressure and temperature evolution, the model allows retrieving the types of particles formed as well as their mean radii, their concentrations and could also simulate the lidar signals. In a first step, a case in August 2007 around 17-18 km, involving

  4. Phase equilibria of H2SO4, HNO3, and HCl hydrates and the composition of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  5. Phase Equilibria of H2SO4, HNO3, and HCl Hydrates and the Composition of Polar Stratospheric Clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  6. Development of a Polar Stratospheric Cloud Model within the Community Earth System Model using constraints on Type I PSCs from the 2010-2011 Arctic winter

    NASA Astrophysics Data System (ADS)

    Zhu, Yunqian; Toon, Owen B.; Lambert, Alyn; Kinnison, Douglas E.; Brakebusch, Matthias; Bardeen, Charles G.; Mills, Michael J.; English, Jason M.

    2015-06-01

    Polar stratospheric clouds (PSCs) are critical elements of Arctic and Antarctic ozone depletion. We establish a PSC microphysics model using coupled chemistry, climate, and microphysics models driven by specific dynamics. We explore the microphysical formation and evolution of STS (Supercooled Ternary Solution) and NAT (Nitric Acid Trihydrate). Characteristics of STS particles dominated by thermodynamics compare well with observations. For example, the mass of STS is close to the thermodynamic equilibrium assumption when the particle surface area is >4 µm2/cm3. We derive a new nucleation rate equation for NAT based on observed denitrification in the 2010-2011 Arctic winter. The homogeneous nucleation scheme leads to supermicron NAT particles as observed. We also find that as the number density of NAT particles increases, the denitrification also increases. Simulations of the PSC lidar backscatter, denitrification, and gas phase species are generally within error bars of the observations. However, the simulations are very sensitive to temperature, which limits our ability to fully constrain some parameters (e.g., denitrification, ozone amount) based on observations.

  7. Polarization of clouds

    NASA Astrophysics Data System (ADS)

    Goloub, Philippe; Herman, Maurice; Parol, Frederic

    1995-12-01

    This paper reports the main results concerning polarization by clouds derived from POLDER (polarization and directionality of earth's reflectances) airborne version. These results tend to confirm the high information content in the polarization (phase, altimetry). The preliminary results of EUCREX'94 (European Cloud Radiation Experiment) evidenced the drastically different polarized signatures for ice crystals and water droplets. Here we report systematic and statistically significative observations over the whole EUCREX data set. The results show that the cirrus exhibit their own signature. Preliminary observations performed during CLEOPATRA'91 (Cloud Experiment Ober Pfaffenhofen And Transport) and EUCREX'94 campaigns have shown the feasibility of cloud altimetry using spectral information (443 nm and 865 nm) of the polarized light over liquid water droplets clouds. Altimetry technique has been generalized on ASTEX-SOFIA'92 and EUCREX'94 data sets. All these results are presented and discussed in this paper.

  8. On the Influence of the Tibetan High on the Distribution of Column Ozone and Polar Stratospheric Clouds in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Hitchman, M. H.; Rogal, M. J.; Harvey, V. L.

    2003-12-01

    We describe a new hypothesis regarding a teleconnection between the boreal summer and austral winter: the distribution of ozone in the southern hemisphere is controlled primarily by outflow from the top of the northern Asian monsoon (Tibetan High). The anthropogenic ozone hole which appears each September and October over Antarctica is surrounded by a croissant-shaped ozone maximum in the 40-60S latitude band, characterized by a broad maximum of larger column ozone amounts centered south of Australia (in the Australian High) and lower amounts over the South Atlantic. The shape of the ozone croissant relates directly to the longitudinal distribution of polar stratospheric clouds (PSCs) at high latitudes. The existence of this structure and its particular longitudinal distribution is hitherto unexplained. Observational analyses and numerical simulations will be shown which illuminate the process by which the ozone croissant is established. Solar occultation data from HALOE, SAGE, and POAM are used to characterize the distribution of ozone and PSCs. A major current of air flows out of the Tibetan High across the Indian Ocean, where it runs into the southern hemisphere winter westerly flow. Outflow surges occur in pulses lasting several days, with southward flow generating an anticyclone over the Indian Ocean - Australia sector. The pulsed flow excites a train of Rossby waves which propagate eastward. Descent of ozone-rich air occurs preferentially just to the east of the synoptic anticyclones. Extensive mixing occurs within the train of breaking Rossby waves. The coincident climatological ozone maximum and Australian High are viewed as a 3D mixing lens of higher ozone from above and higher potential vorticity from the tropics. This mechanism brings chemicals from the upper troposphere over Asia into juxtaposition with stratospheric air in the southern middle latitudes and is thus important for a variety of global climate change problems. It contributes to our

  9. Studies on the Effect of Cloud Coverage and Galactic Cosmic Ray on Stratospheric Moistening

    NASA Astrophysics Data System (ADS)

    Maitra, Animesh; Saha, Upal; Das, Saurabh

    2012-07-01

    Increased stratospheric water vapor is one of the significant causes of global warming as increased stratospheric water vapor acts to cool the stratosphere but it warms the underlying troposphere. The sun can influence the clouds by mediating through Galactic cosmic rays (GCR) which controls the nucleation of water droplets in the atmosphere. The role of primary GCR in generating low-level cloud condensation nuclei reflects solar energy back into space affecting the temperature on earth. In the present study, variations of different types of cloud coverage (low, mid and high) are correlated with the intensity of GCR flux and their effects on the stratospheric moistening in the equatorial, mid- latitude and polar region have been investigated for the years 2004 and 2005 using the Aura's Microwave Limb Sounder (MLS) water vapor data, ISCCP cloud data and GCR from neutron monitor observations at Calgary (51.080 N, 245.870 E). The relation between GCR and stratospheric moistening is also investigated in this paper. Additionally, the latitudinal variation of different types of cloud coverage is also studied for the same period. The southern mid-latitudinal region has the highest coverage of low-level cloud, followed by the equatorial region. Both the Polar Regions are highly covered with mid-level cloud. The mid-latitudinal region shows highest coverage of high-cloud, followed by the equatorial region. Lower level clouds exert a large net cooling effect on the climate indicating an inter-relationship between cosmic ray and cloud coverage. However, the mid and high cloud coverage have no significant correlation with GCR flux. The stratospheric moistening is controlled by transport of water vapour from troposphere to stratosphere through the tropopause region and the oxidation of methane within the stratosphere. Water vapour plays a major role in the chemistry and radiative budget of the stratosphere. One possible water vapor source in the stratosphere is the advection of

  10. Condensation of HNO3 and HCl in the winter polar stratospheres

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Pinto, Joseph; Hamill, Patrick; Turco, Richard P.

    1986-01-01

    Nitric acid and hydrochloric acid vapors may condense in the winter polar stratospheres. Nitric acid clouds, unlike water ice clouds, would form at the temperatures at which polar stratospheric clouds (PSCs) are observed and would have optical depths of the magnitude observed suggesting that HNO3 is a dominant component of PSCs. ClO, N2O5 and ClNO3 may react on cloud particle surfaces yielding additional HNO3, HCl, and HOCL. In the vicinity of PSCs these reactions could deplete the stratosphere of photochemically active NO(x) species. The sedimentation of PSCs may remove these materials from the stratosphere. The loss of vapor phase NO(x) might allow halogen-based chemistry to create the ozone hole.

  11. Solubility and equilibrium vapor pressures of HC1 dissolved in polar stratospheric cloud materials - Ice and the trihydrate of nitric acid

    NASA Technical Reports Server (NTRS)

    Hanson, David; Mauersberger, Konrad

    1988-01-01

    Measurements of the pressure-solubility behavior of HC1 in water ice and in the nitric acid trihydrate (NAT) crystal at 200 K are reported. It was found that HC1 is about 20 times more soluble in NAT than in ice for stratospheric conditions. A relation between HC1 pressure and substrate composition based on the Gibbs-Duhem equation is developed. This relation, along with other thermodynamic data, can be used to obtain the HC1 pressure-solubility behavior at different temperatures. Implications of these results for the south polar ozone hole are discussed.

  12. Arctic stratospheric sulphur injections: radiative forcings and cloud responses

    NASA Astrophysics Data System (ADS)

    Lohmann, U.; Gasparini, B.; Miriam, K.; Kravitz, B.; Rasch, P. J.

    2014-12-01

    Observations and climate projections show a high sensitivity of the Arctic climate to the increase in greenhouse gas emissions, known as the polar amplification. This study evaluates the options of counteracting the rising polar temperatures by stratospheric sulphur injections in the Northern Hemisphere high latitudes.10 Mt of sulphur dioxide are emitted in a point emission source setup centred at the 100 hPa pressure level over Svalbard island (80°N,15°E). We perform simulations with the general circulation models ECHAM5, ECHAM6, and GISS ModelE. We study pulsed emission simulations that differ among themselves by the injection starting date (March-September), injection length (1, 30, or 90 day emission period), and the vertical resolution of the model (for ECHAM6). We find injections in April to be the most efficient in terms of the shortwave radiative forcing at the top-of-the atmosphere over the Arctic region. The distribution of sulphate aerosol spreads out beyond the injection region, with a significant share reaching the Southern Hemisphere. Results from ModelE show high latitude injections could counteract the spring and summer temperature increase due to higher atmospheric CO2 concentrations. Preliminary results with a more realistic description of clouds in ECHAM-HAM reveal a complex pattern of responses, most notably: a decrease in Northern Hemisphere cirrus clouds strengthening the effect of stratospheric aerosols in ECHAM5 a decrease in low-level clouds over the Arctic increasing the incoming solar radiation and causing a net positive radiative balance cirrus clouds are resilient to stratospheric sulphur injections in the absence of sulphate warming

  13. Cloud Condensation in Titan's Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Romani, Paul N.; Anderson, Carrie M.

    2011-01-01

    A 1-D condensation model is developed for the purpose of reproducing ice clouds in Titan's lower stratosphere observed by the Composite Infrared Spectrometer (CIRS) onboard Cassini. Hydrogen cyanide (HCN), cyanoacetylene (HC3N), and ethane (C2H6) vapors are treated as chemically inert gas species that flow from an upper boundary at 500 km to a condensation sink near Titan's tropopause (-45 km). Gas vertical profiles are determined from eddy mixing and a downward flux at the upper boundary. The condensation sink is based upon diffusive growth of the cloud particles and is proportional to the degree of supersaturation in the cloud formation regIOn. Observations of the vapor phase abundances above the condensation levels and the locations and properties of the ice clouds provide constraints on the free parameters in the model. Vapor phase abundances are determined from CIRS mid-IR observations, whereas cloud particle sizes, altitudes, and latitudinal distributions are derived from analyses of CIRS far-IR observations of Titan. Specific cloud constraints include: I) mean particle radii of2-3 J.lm inferred from the V6 506 cm- band of HC3N, 2) latitudinal abundance distributions of condensed nitriles, inferred from a composite emission feature that peaks at 160/cm , and 3) a possible hydrocarbon cloud layer at high latitudes, located near an altitude of 60 km, which peaks between 60 and 80 cm l . Nitrile abundances appear to diminish substantially at high northern latitudes over the time period 2005 to 2010 (northern mid winter to early spring). Use of multiple gas species provides a consistency check on the eddy mixing coefficient profile. The flux at the upper boundary is the net column chemical production from the upper atmosphere and provides a constraint on chemical pathways leading to the production of these compounds. Comparison of the differing lifetimes, vapor phase transport, vapor phase loss rate, and particle sedimentation, sheds light on temporal stability

  14. Polar Stratospheric Clouds and heterogeneous chemistry: Comparison between a 3D-CTM with detailed online PSC microphysics and CALIPSO observations

    NASA Astrophysics Data System (ADS)

    Viscardy, Sébastien; Errera, Quentin; Pitts, Michael C.; Poole, Lamont R.; Chabrillat, Simon; Daerden, Frank

    2013-04-01

    A 3-D Chemical Transport Model (CTM), with full stratospheric chemistry and driven by the ECMWF temperature and wind fields, has been coupled to a detailed PSC microphysical model to simulate polar winters. The formation and evolution of four types of PSC particles (STS, SAT, NAT, and ice) are described through relevant microphysical processes which alter interactively the nitric acid and water vapor concentrations of the atmosphere. Each particle type is described by a binned size distribution for the number density and chemical composition. This set-up allows for detailed calculation of optical properties and surface area densities used to compute the heterogeneous reaction rates. After comparing the evolution of the stratospheric chemical structure to satellite observations, we will investigate how the model reproduces the PSC coverage detected by CALIPSO. A comparison between the model and CALIPSO optical properties will be used to discuss the PSC composition. Finally, we aim at estimating the contribution of each PSC particle type to the chlorine activation.

  15. Influence of wave activity on the composition of the polar stratosphere

    NASA Astrophysics Data System (ADS)

    Smyshlyaev, S. P.; Pogoreltsev, A. I.; Galin, V. Ya.; Drobashevskaya, E. A.

    2016-01-01

    The planetary wave impact on the polar vortex stability, polar stratosphere temperature, and content of ozone and other gases was simulated with the global chemical-climatic model of the lower and middle atmosphere. It was found that the planetary waves propagating from the troposphere into the stratosphere differently affect the gas content of the Arctic and Antarctic stratosphere. In the Arctic region, the degree of wave activity critically affects the polar vortex formation, the appearance of polar stratospheric clouds, the halogen activation on their surface, and ozone anomaly formation. Ozone anomalies in the Arctic region as a rule are not formed at high wave activity and can be registered at low activity. In the Antarctic Regions, wave activity affects the stability of polar vortex and the depth of ozone holes, which are formed at almost any wave activity, and the minimal ozone values depend on the strong or weak wave activity that is registered in specific years.

  16. Theoretical Studies of Stratospheric and Tropospheric Clouds and Aerosols in Support of SOLVE

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    2002-01-01

    We proposed a number of theoretical efforts to support NASA's SOLVE Mission which took place in Kiruna, Sweden in the winter of 1999-2000. We proposed to serve as one of the DC-8 project scientists, to work with various instrument teams to better understand the composition of polar stratospheric clouds, and their properties, and to help understand the physical conditions which lead to cloud formation in the polar winter.

  17. The dynamics of the stratospheric polar vortex and its relation to springtime ozone depletions

    NASA Technical Reports Server (NTRS)

    Schoeberl, Mark R.; Hartmann, Dennis L.

    1991-01-01

    Recent aircraft observations have determined the structure of polar vortices during winter and their relationship to polar ozone depletions, based on high dynamical isolation and the extremely low temperatures required for stratospheric cloud formation. The aircraft data reveal large gradients of potential vorticity and concentrations of conservative trace species at the transition from high-latitude to polar air, implying that the inward mixing of heat and constituents is strongly inhibited, and that the perturbed polar stratospheric chemistry associated with the ozone hole is isolated from the rest of the stratosphere until the vortex breaks up in late spring. It is therefore the overall polar vortex which limits the annual polar ozone depletions' maximum area-coverage.

  18. Stratospheric Polar Freezing Belt Causes Denitrification

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Jensen, E. J.; Toon, O. B.; Drdla, K.; Schoeberl, M. R.; Gore, Warren J. (Technical Monitor)

    2001-01-01

    Trajectory cloud model calculations are presented to show that homogeneous freezing of nitric acid hydrates can produce a polar freezing belt in both hemispheres that can cause denitrification. While hydrate cloud microphysical properties are similar over both poles, the shorter persistence of clouds in the Arctic prevents the depth of the denitrified layers from growing beyond a few kilometers. The 1999-2000 Arctic winter is unique in showing a distinct denitrification profile with a depth of approx. 4.5 km that is nearly half as deep as that computed for a typical Antarctic winter.

  19. Persistence of the Lower Stratospheric Polar Vortices

    NASA Technical Reports Server (NTRS)

    Waugh, Darryn W.; Randel, William J.; Pawson, Steven; Newman, Paul A.; Nash, Eric R.

    1999-01-01

    The persistence of the Arctic and Antarctic lower stratospheric vortices is examined over the period 1958 to 1998. Three different vortex-following diagnostics (two using potential vorticity and one based solely on the zonal winds) are compared, and shown to give very similar results for the break up date. The variability in the timing of the breakup of each vortex is qualitatively the same: there are large interannual variations together with smaller decadal-scale variations and there is a significant increase in the persistence since the mid-1980s (all variations are larger for the Arctic vortex). Also, in both hemispheres there is a high correlation between the persistence and the strength and coldness of the spring vortex, with all quantities having the same interannual and decadal variability. However, there is no such correlation between the persistence and the characteristics of the mid-winter vortex. In the northern hemisphere there is also a high correlation between the vortex persistence and the upper tropospheric/lower stratospheric eddy heat flux averaged over the two months prior to the breakup. This indicates that the variability in the wave activity entering the stratosphere over late-winter to early-spring plays a key role in the variability of the vortex persistence (and spring polar temperatures) on both interannual and decadal time scales. However, the decadal variation in the Arctic vortex coldness and persistence for the 1990's falls outside the range of natural variability, while this is not the case for the eddy heat flux. This suggests that the recent increase in vortex persistence is not due solely to changes in the wave activity entering the stratosphere.

  20. Can we modify stratospheric water vapor by deliberate cloud seeding?

    NASA Astrophysics Data System (ADS)

    Chen, Baojun; Yin, Yan

    2014-02-01

    Stratospheric water vapor has an important effect on Earth's climate. Considering the significance of overshooting deep convection in modulating the water vapor content (WVC) of the lower stratosphere (LS), we use a three-dimensional convective cloud model to simulate the effects of various silver iodide (AgI) seeding scenarios on tropical overshooting deep convection that occurred on 30 November 2005 in Darwin, Australia. The primary motivation for this study is to investigate whether the WVC in the LS can be artificially modified by deliberate cloud seeding. It is found that AgI seeding done at the early stages of clouds produces significant effects on cloud microphysical and dynamical properties, and that further affects the WVC in the LS, while seeding at the mature stages of clouds has only a slight impact. The response of stratospheric water vapor to changes in the amount of seeding agent is nonlinear. The seeding with a small (large) amount of AgI increases (decreases) the WVC in the LS, due to enhanced (reduced) production and vertical transport of cloud ice from the troposphere and subsequent sublimation in the stratosphere. The results show that stratospheric water vapor can be artificially altered by deliberate cloud seeding with proper amount of seeding agent. This study also shows an important role of graupel in regulating cloud microphysics and dynamics and in modifying the WVC in the LS.

  1. Diabatic Descent In The Stratospheric Polar Vortex

    NASA Astrophysics Data System (ADS)

    Rosenfield, J.; Schoeberl, M.

    Polar regions experience diabatic cooling during the fall and winter months, resulting in a downward mass flux. An accurate measure of this fall and winter diabatic descent, as well as an understanding of the transport of air into and out of the winter polar vor- tices, is required for estimates of polar ozone depletion. We have calculated diabatic cooling rates using a radiative transfer code and U.K. Met Office (UKMO) tempera- tures for the years 1992-2000. These cooling rates, together with UKMO horizontal winds, have been used to compute three-dimensional forward and backward diabatic trajectories for the seven month fall to spring period in both the NH and the SH. The forward calculations estimate the maximum amount of descent that can occur. How- ever, they are not necessarily a good indicator of the origin of the springtime vortex air because more equatorward air from lower altitudes can be entrained within the vortex during its formation. The back trajectories, starting in the springtime lower middle stratosphere, show a complex final distribution of parcels. One population originates in the fall in the upper stratosphere and mesosphere and experiences considerable de- scent, while the remaining parcels originate at lower altitudes in the midlatitudes and are mixed into the polar regions during vortex formation. The amount of descent ex- perienced by the first population shows little variability from year to year, while the computed descent and mixing of the remaining parcels show considerable interannual variability due to the varying polar meteorology. Because of this complex parcel dis- tribution it is not meaningful to speak of a net amount of descent experienced over the entire winter period. We have also compared diabatic trajectories with kinematic tra- jectories, in which the vertical motion is given by the UKMO analysed omega fields. These show that the kinematic trajectory descent is much less than the diabatic tra- jectory descent and exhibits

  2. Volcanoes, Polar Clouds and Arctic Ozone

    NASA Technical Reports Server (NTRS)

    Tabazadeh, Azadeh; Gore, Warren J. (Technical Monitor)

    2001-01-01

    Satellite observations and model calculations show 5 to 10% local column ozone loss in some tropical and mid latitude locations, following El Chichon and Mount Pinatubo eruptions. The rapid deepening of the Antarctic ozone hole in the early 1980s has also been partially attributed to chemistry on volcanic aerosols from a number of large eruptions. Here the effects of volcanoes on Arctic polar processes are explored. Large polar stratospheric cloud particles that cause denitrification cannot form in a volcanically perturbed environment. Denitrification can increase Arctic ozone loss by up to 30% in a future colder climate. However, we show that enhanced chemical processing on volcanic aerosols can increase Arctic ozone loss in a cold year by about 60% independent of denitrification. A coupled chemistry-microphysics model is used to show that widespread distribution of volcanic aerosols in 2000 could have caused severe springtime ozone depletion in the Arctic stratosphere. While, volcanic aerosols can strongly affect the current Arctic column ozone abundance in a cold year, denitrification effects on ozone can only become important in a much colder lower stratosphere.

  3. Tropical Tropopause Layer Cloud Formation, Convection and Stratospheric Dehydration

    NASA Astrophysics Data System (ADS)

    Schoeberl, M. R.; Dessler, A. E.; Wang, T.; Avery, M. A.; Jensen, E. J.

    2014-12-01

    Using MERRA reanalysis winds, temperatures and anvil cloud ice, we use our domain-filling, forward trajectory model to study the impact that more realistic cloud formation and convective water injection has on stratospheric water vapor. Our model computed cloud fraction shows reasonable agreement with cloud frequency observed by HIRDLS and CALIOP in the tropical troposphere layer (TTL). Our results suggest that ~64% of the cirrus formed in the TTL are due convection. Overall we find that inclusion of cloud microphysical processes increases stratospheric water vapor by 0.5 ppmv. Adding anvil ice increases stratospheric water vapor by an additional 0.5-0.6 ppmv but has a bigger impact on cloud formation with an increase of ~20-30% in TTL cloud fraction. With convection and cloud dehydration global 18-30 km average water vapor is ~5-7% higher than MLS water vapor observations. Adding waves to the MERRA temperature fields reduces stratospheric water vapor bringing our estimates to within 3% of MLS.

  4. Clouds in the Tropical Lowermost Stratosphere Observed by ACE

    NASA Astrophysics Data System (ADS)

    Sloan, J. J.; Galkina, I.; Sioris, C. E.; Nowlan, C. R.; McElroy, T.; Zou, J.; Hu, J.; Drummond, J. R.; McLinden, C. A.

    2008-12-01

    Evidence for the occurrence of cloud particles in the tropical lowermost stratosphere in the 2004-2007 period is presented. This study is based on measurements by the three Atmospheric Chemistry Experiment (ACE) instruments onboard SCI-SAT. The Vis & NIR Imagers are used to determine the presence of clouds and their top height. The Fourier Transform Spectrometer (FTS) observations are used to determine the size distribution and composition of the aerosols. The FTS has a 4 km field-of-view. Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) provide more precise altitude determination of the thermal tropopause and the cloud tops by virtue of its smaller FOV (~1 km). Clouds in the tropical lower stratosphere are a rare occurrence but April 2005 produced a few such cases, consistent with previous observations by OSIRIS. We discuss several individual case studies that demonstrate the presence of large particles (mode radius of ~8 microns) clearly above the tropopause.

  5. Analysis of cloud polarization measurements

    NASA Technical Reports Server (NTRS)

    Hansen, J. E.; Coffeen, D. L.

    1975-01-01

    The polarization of sunlight reflected by various cloud types was measured in the near-infrared with a polarimeter flown aboard the NASA Convair 990. The data reduction has been completed and detailed comparisons have been made between the observations and theoretical computations. The analysis presented shows that the polarization in the near-infrared can be used on a routine basis to reliably yield the cloud particle phase (water or ice) and the average particle size in the top part of water clouds (usually within + or - 25%). In some cases the polarization also yields the cloud optical thickness (or a lower limit) and a measure of the width of the particle size distribution in the top of the water clouds.

  6. Evaluation of Antarctic polar stratospheric clouds data obtained by ground based lidars (at Dome C, McMurdo and Dumont D'Urville) and the satellite based CALIOP lidar system versus a subset of CCMVAL-2 chemistry-climate models.

    NASA Astrophysics Data System (ADS)

    Snels, Marcel; Fierli, Federico; de Muro, Mauro; Cagnazzo, Chiara; Cairo, Francesco; Di Liberto, Luca

    2016-04-01

    Polar stratospheric clouds play an important role in the ozone depletion process in polar regions and are thus strongly linked to climate changes. Long term observations are needed to monitor the presence of PSCs and to compare to climate models. The last decades PSCs in Antarctica have been observed by using the CALIOP lidar system on the CALIPSO satellite and by ground based lidars at Dumont D'Urville, McMurdo, Casey, and since 2014 at Dome C. We evaluate the Antarctic PSC observational databases of CALIPSO and the ground-based lidars of NDACC (Network for Detection of Atmospheric Composition Changes) located in McMurdo and Dumont D'Urville and Dome C stations and provide a process-oriented evaluation of PSC in a subset of CCMVAL-2 chemistry-climate models. Lidar observatories have a decadal coverage, albeit with discontinuities, spanning from 1992 to today hence offering a unique database. A clear issue is the representativeness of ground-based long-term data series of the Antarctic stratosphere conditions that may limit their value in climatological studies and model evaluation. The comparison with the CALIPSO observations with a global coverage is, hence, a key issue. In turn, models can have a biased representation of the stratospheric conditions and of the PSC microphysics leading to large discrepancies in PSC occurrence and composition. Point-to-point comparison is difficult due to sparseness of the database and to intrinsic differences in spatial distribution between models and observations. However, a statistical analysis of PSC observations shows a satisfactory agreement between ground-based and satellite borne-lidar. The differences may be attributed to averaging processes for data with a bad signal to noise ratio, which tends to smear out the values of the optical parameters. Data from some Chemistry Climate models (CCMs) having provided PSC surface areas on daily basis have been evaluated using the same diagnostic type that may be derived CALIPSO (i

  7. Post-equinox evolution of Titan's south-polar stratosphere

    NASA Astrophysics Data System (ADS)

    Teanby, Nicholas A.; Vinatier, Sandrine; de Kok, Remco; Nixon, Conor A.; Irwin, Patrick GJ

    2015-11-01

    Since northern spring equinox in mid-2009, Titan's atmosphere has demonstrated dramatic changes in temperature (Achterberg et al 2014), composition (Teanby et al 2012, Vinatier et al 2015, Coustenis et al 2015), and aerosol/ice distribution (de Kok et al 2014, Jennings et al 2015, West et al 2015). Changes have been greatest at the southern winter pole, which continues to enter deeper into Titan's shadow following the 2009 equinox. Observational highlights include development of a south polar hot-spot, nitrile ice clouds, dense condensate clouds, and extreme trace gas concentrations.Here we use recent infrared spectral limb observations by Cassini/CIRS to determine the evolution of temperature and composition of the south polar region since equinox. Our observations show that the south polar hot-spot initially observed following equinox has now disappeared and been replaced by extremely low temperatures throughout the stratosphere, suspected to be due to enhanced radiative cooling. There also appears to be an unusual distribution of nitrile species, which suggests trace gases are now escaping the newly formed winter vortex. Thus providing clues to the underlying circulation. The new observations will be presented and implications for Titan's polar atmospheric dynamics discussed.Achterberg et al (2014), DPS46, 102.07, Tucson.Coustenis et al (2015), Icarus (in press).de Kok et al (2014), Nature, 514, 65-67.Jennings et al (2015), ApJL, 804, L34.Teanby et al (2012), Nature, 491, 732-735.Vinatier et al (2015), Icarus, 250, 95-115.West et al (2015), Icarus (in press).

  8. Temperature thresholds for chlorine activation and ozone loss in the polar stratosphere

    NASA Astrophysics Data System (ADS)

    Drdla, K.; Müller, R.

    2012-07-01

    Low stratospheric temperatures are known to be responsible for heterogeneous chlorine activation that leads to polar ozone depletion. Here, we discuss the temperature threshold below which substantial chlorine activation occurs. We suggest that the onset of chlorine activation is dominated by reactions on cold binary aerosol particles, without the formation of polar stratospheric clouds (PSCs), i.e. without any significant uptake of HNO3 from the gas phase. Using reaction rates on cold binary aerosol in a model of stratospheric chemistry, a chlorine activation threshold temperature, TACL, is derived. At typical stratospheric conditions, TACL is similar in value to TNAT (within 1-2 K), the highest temperature at which nitric acid trihydrate (NAT) can exist. TNAT is still in use to parameterise the threshold temperature for the onset of chlorine activation. However, perturbations can cause TACL to differ from TNAT: TACL is dependent upon H2O and potential temperature, but unlike TNAT is not dependent upon HNO3. Furthermore, in contrast to TNAT, TACL is dependent upon the stratospheric sulfate aerosol loading and thus provides a means to estimate the impact on polar ozone of strong volcanic eruptions and some geo-engineering options, which are discussed. A parameterisation of TACL is provided here, allowing it to be calculated for low solar elevation (or high solar zenith angle) over a comprehensive range of stratospheric conditions. Considering TACL as a proxy for chlorine activation cannot replace a detailed model calculation, and polar ozone loss is influenced by other factors apart from the initial chlorine activation. However, TACL provides a more accurate description of the temperature conditions necessary for chlorine activation and ozone loss in the polar stratosphere than TNAT.

  9. Microphysical properties of synoptic scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3 containing particles in the Arctic vortex

    NASA Astrophysics Data System (ADS)

    Molleker, S.; Borrmann, S.; Schlager, H.; Luo, B.; Frey, W.; Klingebiel, M.; Weigel, R.; Ebert, M.; Mitev, V.; Matthey, R.; Woiwode, W.; Oelhaf, H.; Dörnbrack, A.; Stratmann, G.; Grooß, J.-U.; Günther, G.; Vogel, B.; Müller, R.; Krämer, M.; Meyer, J.; Cairo, F.

    2014-05-01

    In January 2010 and December 2011 synoptic scale PSC fields were probed during seven flights of the high altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction.) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 μm and 40 μm were recorded simultaneously by up to four different optical in situ instruments. Three of these particle instruments are based on the detection of forward scattered light by single particles. The fourth instrument is a grey scale optical array imaging probe. Optical particle diameters of up to 35 μm were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas phase and particle bound NOy were measured, as well as water vapor concentrations, and other variables. Two remote sensing particle instruments, the Miniature Aerosol Lidar (MAL) and the backscatter sonde (MAS, Multiwavelenght Aerosol Scatterometer) showed the synoptic scale of the encountered PSCs. The particle mode below 2 μm in size diameter has been identified as supercooled ternary solution droplets (STS). The PSC particles in the size range above 2 μm in diameter are considered to consist of nitric acid hydrates or ice, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. In particular, with respect to the denitrification by sedimentation of large HNO3-contaning particles, generally considered as NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Measurement uncertainties are discussed concerning probable overestimations of measured particle sizes

  10. Denitrification mechanisms in the polar stratospheres

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Turco, R. P.; Hamill, P.

    1990-01-01

    Microphysical simulations suggest that the time required for nitric acid particles to sediment from the stratosphere is comparable to the time required for falling ice particles to incorporate nitric acid vapor from the vapor phase. Since nitric acid particles form earlier in the winter than ice particles, these simulations favor denitrification being a separate process from dehydration, with denitrification being due to nitric acid particles and dehydration due to ice particles. In the simulations, the column abundance of nitric acid is only depleted if temperatures low enough for nitric acid particles to exist extend to the altitude above which the column is measured. Such low temperatures are infrequent in the Arctic lower stratosphere, which may be the main reason that the Arctic stratospheric column shows little loss of nitric acid during winter, while the colder Antarctic stratospheric column shows a substantial loss of nitric acid.

  11. Cloud-to-stratosphere lightning discharges - A radio emission model

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Desch, M. D.

    1992-01-01

    Recent observations of rare cloud-to-stratospheric lightning discharges suggest the events are inherently 'slow-rising', with the emitted energy reaching peak values in about 10 milliseconds. Applying a dipole radiation model, it is demonstrated that the emitted radio wave energy from such slow-rising events is strongest below about 50 Hz, and possesses a significant rolloff at higher frequencies. In the analysis, various current distributions are considered in order to determine the effect on the radio spectrum. Near 10 kHz, the emission from cloud-to-stratospheric lightning is significantly reduced as compared to the typical cloud-to-ground return stroke, with amplitudes as much as 50 dB lower. This result may explain the lack of detection of VLF signals from recently observed long-lasting discharge events.

  12. Simultaneous balloonborne measurements of stratospheric water vapor and ozone in the polar regions

    SciTech Connect

    Hofmann, D.J.; Oltmans, S.J. ); Deshler, T. )

    1991-06-01

    Vertical profiles of stratospheric water vapor and ozone were measured together at McMurdo and South Pole Stations in Antarctica, and at Kiruna, Sweden, on several occasions during the austral spring of 1990 and the boreal winter of 1991. The Antarctic data indicated that major dehydration had occurred on a continental scale over the winter stratospheric cloud formation period leaving only 2 to 3 ppmv water vapor between 11 and 19 km. Measurements before and after movement of the boundary of the polar vortex across McMurdo detected increases in both water vapor and ozone in the 17 to 20 km region. This injected layer was still observed at South Pole Station a month later suggesting continental proportions. In early November, with the vortex still intact, South Pole measurements indicated a substantial degree of inhomogeneity in both water vapor and ozone in the lower stratosphere. In comparison, stratospheric water vapor measurements in the Arctic gave values of 4 to 5 ppmv indicating the absence of the gross stratospheric dehydration effects obvious in the Antarctic, and they did not reveal significant structure except on one occasion with very cold temperatures ({minus}90C) at 25 km and nacreous cloud displays.

  13. Researchers Focus on Fire Clouds That Reach to the Stratosphere

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2010-08-01

    Volcanic eruptions are not the only violent events that can inject smoke-colored and cauliflower-textured clouds into the stratosphere. Pyrocumulonimbus (pyroCB) storms can, too. These recently discovered phenomena are storms caused or aided by fire; they have many characteristics similar to thunderstorms, including lightning, hail, and extreme vertical height through the troposphere and into the lower stratosphere. Common wisdom had held that “the only event that can explosively pollute the stratosphere is a volcanic eruption,” Michael Fromm, a meteorologist with the Naval Research Laboratory in Washington, D. C., said at a 9 August press briefing at the 2010 Meeting of the Americas in Foz do Iguaçu, Brazil. “Now we know that pyroCBs can do a version of this, thanks to the heat from fire.”

  14. Stratospheric cooling and polar ozone loss due to H2 emissions of a global hydrogen economy

    NASA Astrophysics Data System (ADS)

    Feck, T.; Grooß, J.-U.; Riese, M.; Vogel, B.

    2009-04-01

    "Green" hydrogen is seen as a major element of the future energy supply to reduce greenhouse gas emissions substantially. However, due to the possible interactions of hydrogen (H2) with other atmospheric constituents there is a need to analyse the implications of additional atmospheric H2 that could result from hydrogen leakage of a global hydrogen infrastructure. Emissions of molecular H2 can occur along the whole hydrogen process chain which increase the tropospheric H2 burden. Across the tropical tropopause H2 reaches the stratosphere where it is oxidised and forms water vapour (H2O). This causes increased IR-emissions into space and hence a cooling of the stratosphere. Both effects, the increase of stratospheric H2O and the cooling, enhances the potential of chlorine activation on liquid sulfate aerosol and polar stratospheric clouds (PSCs), which increase polar ozone destruction. Hence a global hydrogen economy could provoke polar ozone loss and could lead to a substantial delay of the current projected recovery of the stratospheric ozone layer. Our investigations show that even if 90% of the current global fossil primary energy input could be replaced by hydrogen and approximately 9.5% of the product gas would leak to the atmosphere, the ozone loss would be increased between 15 to 26 Dobson Units (DU) if the stratospheric CFC loading would retain unchanged. A consistency check of the used approximation methods with the Chemical Lagrangian Model of the Stratosphere (CLaMS) shows that this additional ozone loss can probably be treated as an upper limit. Towards more realistic future H2 leakage rate assumptions (< 3%) the additional ozone loss would be rather small (? 10 DU). However, in all cases the full damage would only occur if stratospheric CFC-levels would retain unchanged. Due to the CFC-prohibition as a result of the Montreal Protocol the forecasts suggest a decline of the stratospheric CFC loading about 50% until 2050. In this case our calculations

  15. On the motion of air through the stratospheric polar vortex

    NASA Technical Reports Server (NTRS)

    Manney, G. L.; Zurek, R. W.; O'Neill, A.; Swinbank, R.

    1994-01-01

    Trajectory calculations using horizontal winds from the U.K. Meteorological Office data assimilation system and vertical velocities from a radiation calculation are used to simulate the three-dimensional motion of air through the stratospheric polar vortex for Northern Hemisphere (NH) and Southern Hemisphere (SH) winters since the launch of the Upper Atmosphere Research Satellite (UARS). Throughout the winter, air from the upper stratosphere moves poleward and descends into the middle stratosphere. In the SH lower to middle stratosphere, strongest descent occurs near the edge of the polar vortex, with that edge defined by mixing characteristics. The NH shows a similar pattern in late winter, but in early winter strongest descent is near the center of the vortex, except when wave activity is particularly strong. Strong barriers to latitudinal mixing exist above about 420 K throughout the winter. Below this, the polar night jet is weak in early winter, so air descending below that level mixes between polar and middle latitudes. In late winter, parcels descend less and the polar night jet moves downward, so there is less latitudinal mixing. The degree of mixing in the lower stratosphere thus depends strongly on the position and evolution of the polar night jet and on the amount of descent experienced by the air parcels; these characteristics show considerable interannual variability in both hemispheres. The computed trajectories provide a three-dimensional picture of air motion during the final warming. Large tongues of air are drawn off the vortex and stretched into increasingly long and narrow tongues extending into low latitudes. This vortex erosion process proceeds more rapidly in the NH than in he SH. In the lower stratosphere, the majority of air parcels remain confined within a lingering region of strong potential vorticity gradients into December in the SH and April in the NH, well after the vortex breaks up in the midstratosphere.

  16. Wintertime Polar Ozone Evolution during Stratospheric Vortex Break-Down

    NASA Astrophysics Data System (ADS)

    Tweedy, O.; Limpasuvan, V.; Smith, A. K.; Richter, J. H.; Orsolini, Y.; Stordal, F.; Kvissel, O.

    2011-12-01

    Stratospheric Sudden Warming (SSW) is characterized by the rapid warming of the winter polar stratosphere and the weakening of the circumpolar flow. During the onset of a major SSW (when the circumpolar flow reverses direction), the warm stratopause layer (SL) descends from its climatological position to the mid-stratosphere level. As the vortex recovers from SSW, a "new" SL forms in the mid-mesosphere region before returning to its typical level. This SL discontinuity appears in conjunction with enhanced downward intrusion of chemical species from the lower thermosphere/upper mesosphere to the stratosphere. The descended species can potentially impact polar ozone. In this study, the NCAR's Whole Atmosphere Community Climate Model (WACCM) is used to investigate the behavior of polar ozone related to major SSWs. Specifically, dynamical evolution and chemistry of NOx, CO, and O3 are examined during three realistic major SSWs and compared with a non-SSW winter season. The simulated (zonal-mean) polar ozone distribution exhibits a "primary" maximum near 40 km, a "secondary" maximum between 90-105 km, and a "tertiary" maximum near 70 km. The concentration of the secondary maximum reduces by ~1.5 parts per million by volume (ppmv) as the vortex recovers and the upper mesospheric polar easterlies return. Enhanced downwelling above the newly formed SL extends up to just above this secondary maximum (~110 km). With an averaged concentration of 2 ppmv, the tertiary ozone maximum layer displaces upward with enhanced upwelling during SSW in conjunction with the lower mesospheric cooling. The downward propagation of the stratospheric wind reversal is accompanied by CO intrusion toward the lowermost stratosphere and anomalous behavior in the primary ozone maximum. Overall, the major SSW, SL, and polar ozone evolution mimic recently reported satellite observations.

  17. SAM 2 measurements of the polar stratospheric aerosol. Volume 9: October 1982 - April 1983

    NASA Technical Reports Server (NTRS)

    Mcmaster, L. R.; Powell, K. A.

    1991-01-01

    The Stratospheric Aerosol Measurement (SAM) II sensor aboard Nimbus 7 is providing 1.0 micron extinction measurements of Antarctic and Arctic stratospheric aerosols with a vertical resolution of 1 km. Representative examples and weekly averages including corresponding temperature profiles provided by NOAA for the time and place of each SAM II measurement are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted, and aerosol optical depths are calculated for each week. Typical values of aerosol extinction and stratospheric optical depth in the Arctic are unusually large due to the presence of material from the El Chichon volcano eruption in the Spring of 1982. For example, the optical depth peaked at 0.068, more than 50 times background values. Typical values of aerosol extinction and stratospheric optical depth in the Antarctic varied considerably during this period due to the transport and arrival of the material from the El Chichon eruption. For example, the stratospheric optical depth varied from 0.002 in October 1982, to 0.021 in January 1983. Polar stratospheric clouds were observed during the Arctic winter, as expected. A representative sample is provided of the ninth 6-month period of data to be used in atmospheric and climatic studies.

  18. SAM 2 Measurements of the Polar Stratospheric Aerosol, volume 2. April 1979 to October 1979

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Steele, H. M.; Hamill, P.

    1982-01-01

    The Stratospheric Aerosol Measurement (SAM) II sensor is abroad the Earth orbiting Nimbus 7 spacecraft proving extinction measurements of the Antarctic and Arctic stratospheric aerosol with a vertical resolution of 1 km. Representative examples and weekly averages of aerosol data and corresponding temperature profiles for the time and place of each SAM II measurement (April 29, 1979, to October 27, 1979) is presented. Contours of aerosol extinction as a function of altitude and longitude or time were plotted and weekly aerosol optical depths were calculated. Seasonal variations and variations in space (altitude and longitude) for both polar regions are easily seen. Typical values of aerosol extinction at the SAM II wavelength of 1.0 micron for the time priod were 1 to 3 x 10 to the -4th power km -1 in the main stratospheric aerosol layer. Optical depths for the stratosphere were about 0.002. Polar stratospheric clouds at altitudes between the tropopause and 20 km were observed during the Antarctic winter at various times and locations. A ready-to-use format containing a representative sample of the second 6 months of data to be used in atmospheric and climatic studies is presented.

  19. Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

    1995-01-01

    Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  20. Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

    SciTech Connect

    Santee, M.L.; Read, W.G.; Waters, J.W.; Froidevaux, L.; Manney, G.L.; Flower, D.A.; Jarnot, R.F.; Harwood, R.S.; Peckham, G.E.

    1995-02-01

    Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone `hole` is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  1. Interhemispheric Differences in Polar Stratospheric HNO3, H2O, CIO, and O3.

    PubMed

    Santee, M L; Read, W G; Waters, J W; Froidevaux, L; Manney, G L; Flower, D A; Jarnot, R F; Harwood, R S; Peckham, G E

    1995-02-10

    Simultaneous global measurements of nitric acid (HNO(3)), water (H(2)O), chlorine monoxide (CIO), and ozone (O(3)) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO(3) was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H(2)O after mid-July. By mid-August, near the time of peak CIO, abundances of gas-phase HNO(3) and H(2)O were extremely low. The concentrations of HNO(3) and H(2)O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO(3) or H(2)O were observed in the 1992-1993 Arctic winter vortex. Although CIO was enhanced over the Arctic as it was over the Antarctic, Arctic O(3) depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone "hole" is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone. PMID:17813911

  2. Semi-Empirical Models of Polar Stratospheric Ozone Depletion and Their Applications

    NASA Astrophysics Data System (ADS)

    Huck, P. E.; Bodeker, G. E.; Shepherd, T. G.; Struthers, H.; Santee, M. L.; McDonald, A. J.

    2007-12-01

    Inter- and intra-annual variability in polar stratospheric ozone depletion is controlled by the interaction of gas- phase chemistry, heterogeneous chemistry, and transport. Two semi-empirical models were developed to relate the conversion of total polar stratospheric chlorine (Cly) to activated chlorine (ClOx), and to then relate the rate of ozone destruction to ClOx. The first semi-empirical model was used to calculate the daily total mass of ClOx through a given season when provided with stratospheric temperature fields and a definition of the vortex edge. The equation is a first order differential equation relating the time rate of change of ClOx to unactivated stratospheric chlorine (Cly - ClOx) multiplied by the fraction of the vortex area containing polar stratospheric clouds and the fraction of the vortex area exposed to sunlight, and to a decay term to account for conversion back to reservoir species. The second semi-empirical model relates the time rate of change of ozone mass deficit (OMD) to the mass of activated chlorine as derived from the first equation, in-situ production of ozone and a term for dynamical entrainment of ozone rich air from lower latitudes into the polar vortex. The coefficients of both equations have been derived by optimally fitting the equations to observations and/or to output from chemistry-climate models (CCMs). The coefficients from these equations capture key sensitivities in the atmosphere that determine the interaction between climate change and polar ozone depletion. Potential applications of these coefficients include intra- seasonal projection of the severity of polar ozone depletion, evaluation of pre-1980 ozone depletion and process oriented validation of CCMs.

  3. Pattern recognition analysis of polar clouds during summer and winter

    NASA Technical Reports Server (NTRS)

    Ebert, Elizabeth E.

    1992-01-01

    A pattern recognition algorithm is demonstrated which classifies eighteen surface and cloud types in high-latitude AVHRR imagery based on several spectral and textural features, then estimates the cloud properties (fractional coverage, albedo, and brightness temperature) using a hybrid histogram and spatial coherence technique. The summertime version of the algorithm uses both visible and infrared data (AVHRR channels 1-4), while the wintertime version uses only infrared data (AVHRR channels 3-5). Three days of low-resolution AVHRR imagery from the Arctic and Antarctic during January and July 1984 were analyzed for cloud type and fractional coverage. The analysis showed significant amounts of high cloudiness in the Arctic during one day in winter. The Antarctic summer scene was characterized by heavy cloud cover in the southern ocean and relatively clear conditions in the continental interior. A large region of extremely low brightness temperatures in East Antarctica during winter suggests the presence of polar stratospheric cloud.

  4. Chemistry Climate Model Simulations of Polar Stratospheric Ozone

    NASA Astrophysics Data System (ADS)

    Brakebusch, Matthias

    Stratospheric ozone (O3) plays a crucial role in protecting organisms on Earth from lethal shortwave solar radiation. Because it is radiatively active, O3 also determines the temperature structure of the stratosphere, so its distribution affects the circulation. For these reasons, understanding polar stratospheric O3 has been a high priority of the scientific community for decades. Of primary interest in recent years is explaining and predicting variations in O3 in a changing climate. Stratospheric O3 distributions are affected by both chemistry and transport, which in turn are controlled by temperature, circulation, and dynamics. Hence, investigations of polar stratospheric O3 require the separation of these intertwined processes, and an understanding of the relevant feedbacks. Investigations of these processes require global observations as well as coupled chemistry climate model simulations. This thesis focuses on chemical O 3 loss due to halogen and odd nitrogen (NOX) catalytic cycles, and utilizes satellite measurements from several instruments and the Specified Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). The science questions are: (1) Is SD-WACCM a tool sophisticated enough for quantitative O3 evolution investigations? (2) How much O 3 loss can be accurately attributed to the stratospheric O3 loss processes induced by halogens, energetic particle precipitation, and NOX individually? (3) Why is the observed O 3 in the Arctic 2010/2011 winter exceptionally low, despite high dynamical variability, which is usually associated with less O3 loss? The questions are addressed by: (1) iteratively evaluating and improving SD-WACCM simulations of the Arctic 2004/2005 winter through comparisons with satellite observations; (2) comparing multiple experimental SD-WACCM simulations of the Antarctic 2005 winter omitting individual O3 loss processes to a reference simulation; (3) testing a hypothesis by means of a comprehensive model simulation of the Arctic

  5. Stratospheric cloud observations during formation of the Antarctic ozone hole in 1989

    SciTech Connect

    Hofmann, D.J.; Deshler, T. )

    1991-02-20

    The results of six balloon flights at McMurdo Station, Antarctica, under varying temperature conditions, are used in a study of polar stratospheric clouds during September 1989. A new particle counter, with size resolution in the 0.5 {mu}m radius region, indicated that size distributions observed in the clouds were bimodal. Mode radii ranging from 0.05 to 0.10 {mu}m were observed for the small particle mode, representing the sulfate layer or condensational growth enhancements of it. Mode radii generally ranged from 1.5 to 3.5 {mu}m for the large particle mode at concentrations 3 to 4 orders of magnitude lower than the small particle mode. The large particle mode, when observed at temperatures above the water ice point, is believed to be the result of nitric acid trihydrate (NAT) condensation on larger particles of the sulfate layer. In this case the HNO{sub 3} condensed mass mixing ratios were 1 to 5 ppbv for most of the cloud layers. Generally, the large particle NAT concentrations were higher in the lower stratosphere, indicating the redistribution of HNO{sub 3} through particle sedimentation. On several occasions, distributions were observed with mode radii as high as 7 {mu}m, and correspondingly large inferred mass, indicating water ice clouds in the 12 to 15 km region. On other occasions, absence of such clouds at very low temperatures inferred water vapor mixing ratios of less than 3 ppmv.

  6. HCl dissolved in solid mixtures of nitric acid and ice - Implications for the polar stratosphere

    NASA Technical Reports Server (NTRS)

    Marti, James; Mauersberger, Konrad; Hanson, David

    1991-01-01

    The solubility of HCl in polar stratospheric cloud (PSC) particles plays an important role in the heterogeneous chemistry of the lower polar stratosphere. New laboratory studies are reported showing a strong dependence of the HCl solubility on the HNO3 content in ice particles. At 200 K and a partial HCl pressure of 10 exp -6 torr, the HCl content in NAT is 0.35 mol pct, decreasing about a factor of 3 for every ten-fold decrease in the substrate's HNO3 content. At an HCl pressure of 10 exp -7 torr, the content is about 40 percent of that at 10 exp -6 torr. HCL dissolved in pure water ice at these partial pressures is less than 0.002 mol pct. The surface coverage of HCl on small ice samples was estimated to be about 0.1 monolayer at 10 exp -6 torr exposure.

  7. Clouds, hazes, and the stratospheric methane abundance in Neptune.

    PubMed

    Baines, K H; Hammel, H B

    1994-05-01

    Analysis of high-spatial-resolution (approximately 0.8 arcsec) methane band and continuum imagery of Neptune's relatively homogeneous Equatorial Region yields significant constraints on (1) the stratospheric gaseous methane mixing ratio (fCH4,s), (2) the column abundances and optical properties of stratospheric and tropospheric hydrocarbon hazes, and (3) the wavelength-dependent single-scattering albedo of the 3-bar opaque cloud. From the center-to-limb behavior of the 7270-angstroms and 8900-angstrom sCH4 bands, the stratospheric methane mixing ratio is limited to fCH4,s < 1.7 x 10(-3), with a nominal value of fCH4,s = 3.5 x 10(-4), one to two orders of magnitude less than pre-Voyager estimates, but in agreement with a number of recent ultraviolet and thermal infrared measurements, and largely in agreement with the tropopause mixing ratio implied by Voyager temperature measurements. Upper limits to the stratospheric haze mass column abundance and 6190-angstroms and 8900-angstroms haze opacities are 0.61 microgram cm-2 and 0.075 and 0.042, respectively, with nominal values of 0.20 microgram cm-2 and 0.025 and 0.014 for the 0.2-micrometer radius particles preferred by the recent Voyager PPS analysis of Pryor et al. (1992, Icarus 99, 302-316). The tropospheric CH4 haze opacities are comparable to that found in the stratosphere, upper limits of 0.104 and 0.065 at 6190 angstroms and 8900 angstroms, respectively, with nominal values of 0.085 and 0.058. This indicates a column abundance less than 11.0 micrograms cm-2, corresponding to the methane gas content within a well-mixed 3% methane tropospheric layer only 0.1 cm thick near the 1.5-bar CH4 condensation level. Constraints on the single-scattering albedos of these hazes include (1) for the stratospheric component, 6190-angstroms and 8900-angstroms imaginary indices of refraction less than 0.047 and 0.099, respectively, with 0.000 (conservative scattering) being the nominal value at both wavelengths, and (2) CH4 haze

  8. Antarctic polar stratospheric aerosols: The roles of nitrates, chlorides and sulfates

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Snetsinger, K. G.; Goodman, J. K.; Ferry, G. V.; Oberbeck, V. R.; Verma, S.; Fong, W.

    1988-01-01

    Nitric and hydrochloric acids have been postulated to condense in the winter polar stratosphere to become an important component of polar stratospheric clouds. One implication is that the removal of NO(y) from the gas phase by this mechanism allows high Cl(x) concentrations to react with O3, because the formation of ClNO3 is inhibited. Contributions of NO3 and Cl to the stratospheric aerosol were determined during the 1987 Airborne Antarctic Ozone Experiment by testing for the presence of nitrates and chlorides in the condensed phase. Aerosol particles were collected on four 500 micron diameter gold wires, each pretreated differently to give results that were specific to certain physical and chemical aerosol properties. One wire was carbon-coated for concentration and size analyses by scanning electron microscopy; X-ray energy dispersive analyses permitted the detection of S and Cl in individual particles. Three more wires were coated with Nitron, barium chloride and silver nitrate, respectively, to detect nitrate, sulfate and chloride in aerosol particles. All three ions, viz., sulfates, nitrates and chlorides were detected in the Antarctic stratospheric aerosol. In terms of number concentrations, the aerosol was dominated by sulfates, followed by chlorides and nitrates. An inverse linear regression can be established between nitrate concentrations and ozone mixing ratio, and between temperature and nitrates.

  9. Theoretical Investigations of Clouds and Aerosols in the Stratosphere and Upper Troposphere

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    2005-01-01

    support of the Atmospheric Chemistry Modeling and Data Analysis Program. We investigated a wide variety of issues involving ambient stratospheric aerosols, polar stratospheric clouds or heterogeneous chemistry, analysis of laboratory data, and particles in the upper troposphere. The papers resulting from these studies are listed below. In addition, I participated in the 1999-2000 SOLVE mission as one of the project scientists and in the 2002 CRYSTAL field mission as one of the project scientists. Several CU graduate students and research associates also participated in these mission, under support from the ACMAP program, and worked to interpret data. During the past few years my group has completed a number of projects under the

  10. Effects of stratospheric sulfate aerosol geo-engineering on cirrus clouds

    NASA Astrophysics Data System (ADS)

    Kuebbeler, Miriam; Lohmann, Ulrike; Feichter, Johann

    2012-12-01

    Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced stratospheric aerosol loadings as proposed by several GE approaches will likely lead to a reduced ice crystal nucleation rate and thus optically thinner cirrus clouds. These optically thinner cirrus clouds exert a strong negative cloud forcing in the long-wave which contributes by 60% to the overall net GE forcing. This shows that indirect effects of stratospheric aerosols on cirrus clouds may be important and need to be considered in order to estimate the maximum cooling derived from stratospheric GE.

  11. Clouds, hazes, and the stratospheric methane abundance in Neptune

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Hammel, Heidi B.

    1994-01-01

    Analysis of high-spatial-resolution (approximately 0.8 arcsec) methane band and continuum imagery of Neptune's relatively homogeneous Equatorial Region yields significant constraints on (1) the stratospheric gaseous methane mixing ratio (f(sub CH4, S)), (2) the column abundances and optical properties of stratospheric and tropospheric hydrocarbon hazes, and (3) the wavelength-dependent single-scattering albedo of the 3-bar opaque cloud. From the center-to-limb behavior of the 7270-A and 8900-A CH4 bands, the stratospheric methane mixing ratios is limited to f(sub CH4, S) less than 1.7 x 10(exp -3), with a nominal value of f(sub CH4, S) = 3.5 x 10(exp -4), one to two orders of magnitude less than pre-Voyager estimates, but in agreement with a number of recent ultraviolet and thermal infrared measurements, and largely in agreement with the tropopause mixing ratio implied by Voyager temperature measurements. Upper limits to the stratospheric haze mass column abundance and 6190-A and 8900-A haze opacities are 0.61 micrograms/sq cm and 0.075 and 0.042, respectively, with nominal values of 0.20 micrograms/sq cm and 0.025 and 0.014 for the 0.2 micrometers radius particles preferred by the recent Voyager PPS analysis of Pryor et al. (1992). The tropospheric CH4 haze opacities are comparable to that found in the stratosphere, i.e., upper limits of 0.104 and 0.065 at 6190 A and 8900 A, respectively, with nominal values of 0.085 and 0.058. This indicates a column abundance less than 11.0 micrograms/sq cm, corresponding to the methane gas content within a well-mixed 3% methane tropospheric layer only 0.1 cm thick near the 1.5-bar CH4 condensation level. Conservative scattering is ruled out for the opaque cloud near 3 bars marking the bottom of the visible atmosphere. Specifically, we find cloud single-scattering albedos of 0.915 +/- 0.006 at 6340 A, 0.775 +/- 0.012 at 7490 A, and 0.803 +/- 0.010 at 8260 A. Global models utilizing a complete global spectrum confirm the red

  12. Interannual Variability of the North Polar Vortex in the Lower Stratosphere During the UARS Mission

    NASA Technical Reports Server (NTRS)

    Zurek, R. W.; Manney, G. L.; Miller, A. J.; Gelman, M. E.; Nagatani, R. M.

    1996-01-01

    Northern winters since the 1991 launch of UARS are compared to earlier years (1978 -1991) with respect to the potential for formation of Polar Stratospheric Clouds and for isolation of the north polar vortex. Daily NMC temperature minima at 465 K late in the winter of 1993-94 and again in December 1994 were the lowest values experienced during these times of the year (since 1978). Northern PV gradients were unusually strong in 1991-92 prior to late January and throughout the winter in both 1992-93 and 1994-95. Of all northern winters since 1978, 1994-95 with its early extended cold spell and persistently strong PV gradients most resembled the Antarctic winter lower stratosphere. Even so, temperatures was never as low, nor was the polar vortex as large, as during a typical southern winter. Judged by daily temperature minima and PV gradients at 465 K, meteorological conditions in the Arctic winter lower stratosphere during the UARS period were more conducive to vortex ozone loss by heterogeneous chemistry than in most previous winters since 1978-79.

  13. Solid-state photochemistry as a formation mechanism for Titan's stratospheric C4N2 ice clouds

    NASA Astrophysics Data System (ADS)

    Anderson, C. M.; Samuelson, R. E.; Yung, Y. L.; McLain, J. L.

    2016-04-01

    We propose that C4N2 ice clouds observed in Titan's springtime polar stratosphere arise due to solid-state photochemistry occurring within extant ice cloud particles of HCN-HC3N mixtures. This formation process resembles the halogen-induced ice particle surface chemistry that leads to condensed nitric acid trihydrate (NAT) particles and ozone depletion in Earth's polar stratosphere. As our analysis of the Cassini Composite Infrared Spectrometer 478 cm-1 ice emission feature demonstrates, this solid-state photochemistry mechanism eliminates the need for the relatively high C4N2 saturation vapor pressures required (even though they are not observed) when the ice is produced through the usual procedure of direct condensation from the vapor.

  14. SAM II measurements of the polar stratospheric aerosol. Volume 6: April to October 1981

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Brandl, D.

    1985-01-01

    The Stratospheric Aerosol Measurement (SAM) II sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric aerosols with a vertical resolution of 1 km. Representative examples and weekly averages of these aerosol data and corresponding temperature profiles (Apr. 1981 to Oct. 1981) are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are calculated. Stratospheric optical depths are 0.002 to 0.003 for the Antarctic region and 0.006 to 0.007 at the beginning to 0.003 to 0.004 at the end of the time period for the Arctic region. Polar stratospheric clouds at altitudes between the tropopause and 20 km were observed during the Antarctic winter. A ready-to-use format containing a representative sample of the sixth 6 months of data to be used in atmospheric and climatic studies is reported.

  15. Origin of Condensation Nuclei in the Springtime Polar Stratosphere

    NASA Technical Reports Server (NTRS)

    Zhao, Jingxia; Toon, Owen B.; Turco, Richard P.

    1995-01-01

    An enhanced sulfate aerosol layer has been observed near 25 km accompanying springtime ozone depletion in the Antarctic stratosphere. We use a one-dimensional aerosol model that includes photochemistry, particle nucleation, condensational growth, coagulation, and sedimentation to study the origin of the layer. Annual cycles of sunlight, temperature, and ozone are incorporated into the model. Our results indicate that binary homogeneous nucleation leads to the formation of very small droplets of sulfuric acid and water under conditions of low temperature and production of H2SO4 following polar sunrise. Photodissociation of carbonyl sulfide (OCS) alone, however, cannot provide sufficient SO2 to create the observed condensation nuclei (CN) layer. When subsidence of SO2 from very high altitudes in the polar night vortex is incorporated into the model, the CN layer is reasonably reproduced. The model predictions, based on the subsidence in polar vortex, agree with in situ measurements of particle concentration, vertical distribution, and persistence during polar spring.

  16. Origin of condensation nuclei in the springtime polar stratosphere

    NASA Technical Reports Server (NTRS)

    Zhao, Jingxia; Toon, Owen B.; Turco, Richard P.

    1995-01-01

    An enhanced sulfate aerosol layer has been observed near 25 km accompanying springtime ozone depletion in the Antarctic stratosphere. We use a one-dimensional aerosol model that includes photochemistry, particle nucleation, condensational growth, coagulation, and sedimentation to study the origin of the layer. Annual cycles of sunlight, temperature, and ozone are incorporated into the model. Our results indicate that binary homogeneous nucleation leads to the formation of very small droplets of sulfuric acid and water under conditions of low temperature and production of H2SO4 following polar sunrise. Photodissociation of carbonyl sulfide (OCS) alone, however, cannot provide sufficient SO2 to create the observed condensation nuclei (CN) layer. When subsidence of SO2 from very high altitudes in the polar night vortex is incorporated into the model, the CN layer is reasonably reproduced. The model predictions, based on the subsidence in polar vortex, agree with in situ measurements of particle concentration, vertical distribution, and persistence during polar spring.

  17. NAT nucleation and denitrification in the polar stratosphere

    NASA Astrophysics Data System (ADS)

    Grooß, Jens-Uwe; Engel, Ines; Hoyle, Christopher R.; Luo, Beiping; Peter, Thomas; Frey, Wiebke; Molleker, Sergej; Borrmann, Stephan; Schlager, Hans; Vömel, Holger; Kivi, Rigel; Walker, Kaley A.; Santee, Michelle L.; Stiller, Gabriele; Pitts, Michael; Müller, Rolf

    2013-04-01

    Nitric acid trihydrate (NAT) particles in the polar stratosphere are known to influence the chemistry of ozone depletion. NAT particles, along with other liquid and crystalline particles, provide heterogeneous surfaces for chlorine activation. More importantly, they can take up significant amounts of HNO3 from the gas phase and transport HNO3 downward by sedimentation. This can lead to denitrification, in the Arctic typically at altitudes above about 20 km, and a re-nitrification below, at the level where the NAT particles evaporate. The nucleation rate of NAT particles is a critical parameter for the simulation of this process. Very low NAT nucleation rates around 2?10-9cm-3s-1 have been deduced for low NAT supersaturations from observations. In previous studies, vertical HNO3 transport has been successfully simulated by Lagrangian 3-D simulations using a constant NAT nucleation rate of around 2?10-9cm-3s-1, for the Arctic winters in the years 2003 and 2005. However, for winter 2009/2010, this approach does not generate satisfying results. Here, saturation dependent NAT nucleation rates were derived from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), observations under the assumption that NAT nucleates heterogeneously on dust particles that are characterized by active sites with a certain occurrence probability distribution depending on the contact angle. Simulations with the Zurich Optical and Microphysical box Model (ZOMM) along back-trajectories starting from points where PSCs were observed by CALIPSO allow the parametrisation of heterogeneous nucleation rates for NAT and ice on dust, and the reproduction of the different PSC classes observed. We present simulations by the Chemical Lagrangian Model of the Stratosphere (CLaMS) of the winter 2009/2010 applying this new parametrisation of heterogeneous NAT nucleation rates. The CLaMS simulation is initialized using a combination of MLS, MIPAS-ENVISAT and ACE-FTS data. The simulation

  18. Technical Note: SWIFT - a fast semi-empirical model for polar stratospheric ozone loss

    NASA Astrophysics Data System (ADS)

    Rex, M.; Kremser, S.; Huck, P.; Bodeker, G.; Wohltmann, I.; Santee, M. L.; Bernath, P.

    2014-07-01

    An extremely fast model to estimate the degree of stratospheric ozone depletion during polar winters is described. It is based on a set of coupled differential equations that simulate the seasonal evolution of vortex-averaged hydrogen chloride (HCl), nitric acid (HNO3), chlorine nitrate (ClONO2), active forms of chlorine (ClOx = Cl + ClO + 2 ClOOCl) and ozone (O3) on isentropic levels within the polar vortices. Terms in these equations account for the chemical and physical processes driving the time rate of change of these species. Eight empirical fit coefficients associated with these terms are derived by iteratively fitting the equations to vortex-averaged satellite-based measurements of HCl, HNO3 and ClONO2 and observationally derived ozone loss rates. The system of differential equations is not stiff and can be solved with a time step of one day, allowing many years to be processed per second on a standard PC. The inputs required are the daily fractions of the vortex area covered by polar stratospheric clouds and the fractions of the vortex area exposed to sunlight. The resultant model, SWIFT (Semi-empirical Weighted Iterative Fit Technique), provides a fast yet accurate method to simulate ozone loss rates in polar regions. SWIFT's capabilities are demonstrated by comparing measured and modeled total ozone loss outside of the training period.

  19. Technical Note: SWIFT - a fast semi-empirical model for polar stratospheric ozone loss

    NASA Astrophysics Data System (ADS)

    Rex, M.; Kremser, S.; Huck, P.; Bodeker, G.; Wohltmann, I.; Santee, M. L.; Bernath, P.

    2013-12-01

    An extremely fast model to estimate the degree of stratospheric ozone depletion during polar winters is described. It is based on a set of coupled differential equations that simulate the seasonal evolution of vortex-averaged hydrogen chloride (HCl), nitric acid (HNO3), chlorine nitrate (ClONO2), active forms of chlorine (ClOx = Cl + ClO + 2 ClOOCl) and ozone (O3) on isentropic levels within the polar vortices. Terms in these equations account for the chemical and physical processes driving the time rate of change of these species. Eight empirical fit coefficients associated with these terms are derived by iteratively fitting the equations to vortex-averaged satellite-based measurements of HCl, HNO3 and ClONO2 and observationally derived ozone loss rates. The system of differential equations is not stiff and can be solved with a time step of one day, allowing many years to be processed per second on a standard PC. The inputs required are the daily fractions of the vortex area covered by polar stratospheric clouds and the fractions of the vortex area exposed to sunlight. The resultant model, SWIFT (Semi-empirical Weighted Iterative Fit Technique), provides a fast yet accurate method to simulate ozone loss rates in polar regions. SWIFT's capabilities are demonstrated by comparing measured and modeled total ozone loss outside of the training period.

  20. First results of tropospheric and stratospheric aerosols measurements during the Iceland Polar Vortex 2016 (IPV2016) campaign

    NASA Astrophysics Data System (ADS)

    Ólafsson, Haraldur; Renard, Jean-Baptiste; Berthet, Gwenaël; Duverger, Vincent; Vignelles, Damien

    2016-04-01

    The Iceland Polar Vortex 2016 (IPV2016) campaign was carried out during the passage of the stratospheric polar vortex over Iceland in early January 2016. During the period 9-13 January, a total of four meteorological balloon sondes were sent into the stratosphere, carrying the Light Optical Aerosol Counter (LOAC) up to altitude of 26 km. LOAC provides concentrations, size distribution and typology of the aerosols in the 0.2 - 100 micrometer size range. The measurements show background liquid and solid aerosol concentrations greater than conventional values in the mid-latitude stratosphere. LOAC has detected layers of cirrus around the tropopause and has provided their size distribution in the 5 - 40 micrometre range. Liquid polar stratospheric cloud particles, greater than a few micrometre, were detected in the 12 - 24 km altitude range. Finally, abornmal high concentrations of submicronic carbonaceus particles were observed from the middle tropopshere to the middle stratosphere. The origin of all these particles will be tentatively interpreted using modelling calculation and backward trajectories

  1. Aerosol chamber study of optical constants and N2O5 uptake on supercooled H2SO4/H2O/HNO3 solution droplets at polar stratospheric cloud temperatures.

    PubMed

    Wagner, Robert; Naumann, Karl-Heinz; Mangold, Alexander; Möhler, Ottmar; Saathoff, Harald; Schurath, Ulrich

    2005-09-15

    The mechanism of the formation of supercooled ternary H(2)SO(4)/H(2)O/HNO(3) solution (STS) droplets in the polar winter stratosphere, i.e., the uptake of nitric acid and water onto background sulfate aerosols at T < 195 K, was successfully mimicked during a simulation experiment at the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. Supercooled sulfuric acid droplets, acting as background aerosol, were added to the cooled AIDA vessel at T = 193.6 K, followed by the addition of ozone and nitrogen dioxide. N(2)O(5), the product of the gas phase reaction between O(3) and NO(2), was then hydrolyzed in the liquid phase with an uptake coefficient gamma(N(2)O(5)). From this experiment, a series of FTIR extinction spectra of STS droplets was obtained, covering a broad range of different STS compositions. This infrared spectra sequence was used for a quantitative test of the accuracy of published infrared optical constants for STS aerosols, needed, for example, as input in remote sensing applications. The present findings indicate that the implementation of a mixing rule approach, i.e., calculating the refractive indices of ternary H(2)SO(4)/H(2)O/HNO(3) solution droplets based on accurate reference data sets for the two binary H(2)SO(4)/H(2)O and HNO(3)/H(2)O systems, is justified. Additional model calculations revealed that the uptake coefficient gamma(N(2)O(5)) on STS aerosols strongly decreases with increasing nitrate concentration in the particles, demonstrating that this so-called nitrate effect, already well-established from uptake experiments conducted at room temperature, is also dominant at stratospheric temperatures. PMID:16834200

  2. Martian north polar water ice clouds

    NASA Technical Reports Server (NTRS)

    Tamppari, L. K.; Bass, D.

    2000-01-01

    The Viking Orbiter determined that the surface of Mars' northern residual cap consists of water ice. An examination of north polar water-ice clouds could lend insight into the fate of the water vapor during this time period.

  3. Comment on the polarity of magnetic clouds

    NASA Technical Reports Server (NTRS)

    Gonzalez, W. D.; Lee, L.-C.; Tsurutani, B. T.

    1990-01-01

    The initial description of magnetic clouds by Klein and Burlaga (1982) and the models that have been developed for their representation (e.g., by Goldstein, 1983) are examined. The results show that a definition of the cloud's polarity only in terms of the Bz component of the IMF is not always correct. It is suggested that, for the description polarities of quasi-transverse and quasi-parallel clouds, a combination of directions in the Bz and By components of the IMF should be used.

  4. Ozone laminae near the edge of the stratospheric polar vortex

    NASA Technical Reports Server (NTRS)

    Reid, S. J.; Vaughan, Geraint

    1994-01-01

    Analysis of ozonesonde data collected at high northern latitudes in winter and spring shows that laminae of enhanced and depleted ozone are associated with the polar vortex. In January and February, they are most common at all latitudes in the potential temperature range 370-430 K, but are abundant up to 500 K between 60 and 70 deg N. In March and April they occur most frequently northward of 75 deg N, and are abundant up to 520 K, whereas they are largely confined to the range 320-440 K at lower latitudes. Analysis of ozone lidar data obtained during AASE-1 depicts clearly the extrusion of laminae of enhanced ozone concentration from the polar regions in the altitude range 13-15 km. These extrusions form a class of laminae which transport ozone equatorward in the lowest levels of the stratosphere.

  5. Circular polarization of sunlight reflected by clouds.

    NASA Technical Reports Server (NTRS)

    Hansen, J. E.

    1971-01-01

    Measurements of circular polarization of visible light from planets have recently been reported. It is pointed out that the values measured for the circular polarization for Jupiter and Venus are of the magnitude expected for sunlight reflected by a cloudy planetary atmosphere. The variations of the sense of the polarization with phase angle and with location on the planetary disk are also consistent with expectations for reflection by clouds.

  6. Analysis of a jet stream induced gravity wave associated with an observed stratospheric ice cloud over Greenland

    NASA Astrophysics Data System (ADS)

    Buss, S.; Hertzog, A.; Hostettler, C.; Bui, T. B.; Lüthi, D.; Wernli, H.

    2004-08-01

    A polar stratospheric ice cloud (PSC type II) was observed by airborne lidar above Greenland on 14 January 2000. It was the unique observation of an ice cloud over Greenland during the SOLVE/THESEO 2000 campaign. Mesoscale simulations with the hydrostatic HRM model are presented which, in contrast to global analyses, are capable to produce a vertically propagating gravity wave that induces the low temperatures at the level of the PSC afforded for the ice formation. The simulated minimum temperature is ~8 K below the driving analyses and ~4.5 K below the frost point, exactly coinciding with the location of the observed ice cloud. Despite the high elevations of the Greenland orography the simulated gravity wave is not a mountain wave. Analyses of the horizontal wind divergence, of the background wind profiles, of backward gravity wave ray-tracing trajectories, of HRM experiments with reduced Greenland topography and of several diagnostics near the tropopause level provide evidence that the wave is emitted from an intense, rapidly evolving, anticyclonically curved jet stream. The precise physical process responsible for the wave emission could not be identified definitely, but geostrophic adjustment and shear instability are likely candidates.

    In order to evaluate the potential frequency of such non-orographic polar stratospheric cloud events, the non-linear balance equation diagnostic is performed for the winter 1999/2000. It indicates that ice-PSCs are only occasionally generated by gravity waves emanating from spontaneous adjustment.

  7. Measurements of condensation nuclei in the Airborne Arctic Stratospheric Expedition - Observations of particle production in the polar vortex

    NASA Technical Reports Server (NTRS)

    Wilson, J. C.; Stolzenburg, M. R.; Clark, W. E.; Loewenstein, M.; Ferry, G. V.; Chan, K. R.

    1990-01-01

    The ER-2 Condensation Nucleus Counter (ER-2 CNC) was operated in the Airborne Arctic Stratospheric Expedition (AASE) in January and February 1989. The ER-2 CNC measures the mixing ratio of particles, CN, with diameters from approximately 0.02 to approximately 1 micron. The spatial distribution of CN in the Arctic polar vortex was found to resemble that measured in the Antarctic in the Spring of 1987. The vertical profile of CN in the vortex was lowered by subsidence. At altitudes above the minimum in the CN mixing ratio profile, CN mixing ratios correlated negatively with that of N2O, demonstrating new particle production. CN serve as nuclei in the formation of Polar Stratospheric Clouds (PSCs) and the concentration of CN can affect PSC properties.

  8. Measurements of condensation nuclei in the Airborne Arctic Stratospheric Expedition: Observations of particle production in the polar vortex

    SciTech Connect

    Wilson, J.C.; Stolzenburg, M.R. ); Clark, W.E. ); Loewenstein, M.; Ferry, G.V.; Chan, K.R. )

    1990-03-01

    The ER-2 Condensation Nucleus Counter (ER-2 CNC) was operated in the Airborne Arctic Stratospheric Expedition (AASE) in January and February 1989. The ER-2 CNC measures the mixing ratio of particles, CN, with diameters from approximately 0.02 {mu}m to approximately 1 {mu}m. The spatial distribution of CN in the Arctic polar vortex was found to resemble that measured in the Antarctic in the Spring of 1987. The vertical profile of CN in the vortex was lowered by subsidence. At altitudes above the minimum in the CN mixing ratio profile, CN mixing ratios correlated negatively with that of N{sub 2}O, demonstrating new particle production. CN serve as nuclei in the formation of Polar Stratospheric Clouds (PSC's) and the concentration of CN can affect PSC properties.

  9. Visualization of stratospheric ozone depletion and the polar vortex

    NASA Technical Reports Server (NTRS)

    Treinish, Lloyd A.

    1995-01-01

    Direct analysis of spacecraft observations of stratospheric ozone yields information about the morphology of annual austral depletion. Visual correlation of ozone with other atmospheric data illustrates the diurnal dynamics of the polar vortex and contributions from the upper troposphere, including the formation and breakup of the depletion region each spring. These data require care in their presentation to minimize the introduction of visualization artifacts that are erroneously interpreted as data features. Non geographically registered data of differing mesh structures can be visually correlated via cartographic warping of base geometries without interpolation. Because this approach is independent of the realization technique, it provides a framework for experimenting with many visualization strategies. This methodology preserves the fidelity of the original data sets in a coordinate system suitable for three-dimensional, dynamic examination of atmospheric phenomena.

  10. North Polar Water-ice Clouds

    NASA Astrophysics Data System (ADS)

    Tamppari, L. K.; Smith, M. D.; Bass, DS

    2002-09-01

    Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) limb sounding and nadir pointed data in the north polar region of Mars have been analyzed during northern spring and summer to find water-ice clouds. There has been uncertainty about the amount of water cycling in and out of the polar region, as evidenced by visible brightness changes in the residual polar cap from year to year which were originally though to be interannual variations (James and Martin, 1995; Kieffer, 1990). Bass et al. (2000) re-examined Viking data and found that 14-35 pr microns of water -ice appeared to be deposited on the cap later in the summer season. This deposition could be due to adsorption directly onto the cap surface or due to snowfall. In addition, Viking IRTM albedo and MAWD water vapor data were examined throughout this season (Bass and Paige, 2000), and water vapor was observed to increase in the cap area as the residual cap brightened. The possibility that some of the water is seasonally sequestered in water-ice clouds and may allow later precipitation had not been previously considered. Water-ice clouds, in the north polar region, have previously been tentatively identified in the Viking data (Tamppari and Bass, 2000), and some water-ice cloud identifications have been made in the north polar region during the MGS era (M. Smith, pers. comm., 2001). The detection of water-ice clouds over a cold surface is difficult (Tamppari et al., 2000) and during northern spring, the CO2 cap is retreating. Therefore, it is advantageous to examine TES limb-pointed observations over the seasonal polar cap regions and to combine those data with nadir-pointed data over the non-frost covered areas. We are examining these two data sets together to identify and track water-ice clouds and current results will be presented.

  11. Analysis of Satellite-Based Polar Mesospheric Cloud Observations

    NASA Astrophysics Data System (ADS)

    Benze, Susanne

    Polar Mesospheric Clouds (PMCs) are thin water-ice clouds that form in the summer polar mesopause region. Since PMCs are sensitive to changes in the upper atmospheric temperature and water vapor abundance, they can be used to understand the dynamics of the upper mesosphere. It has also been suggested that they are important indicators of mesospheric climate change. PMCs have been successfully observed from the ground and with remote sensing instruments, for example the Cloud Imaging and Particle Size (CIPS) experiment on the Aeronomy of Ice in the Mesosphere (AIM) satellite, and the Solar Backscatter UltraViolet (SBUV) instruments. This thesis presents validation of CIPS observations by showing a comparison of PMC occurrence frequency, cloud and background albedo as observed by CIPS and SBUV. It is found that frequency and cloud albedo are in excellent agreement, with a small (10%) low bias in the CIPS v3.20 operational frequencies at more equatorward PMC latitudes on the descending node. The background albedo, however, shows a still unresolved bias that depends on hemisphere. Overall, the results show that CIPS PMC data are valid for scientific analysis. Furthermore, this thesis investigates and quantifies the relative importance of several coupling mechanisms that contribute to variability in the PMC season onset, such as the solar cycle and intra-hemispheric and inter-hemispheric coupling. It is found that the Southern Hemisphere (SH) PMC season onset is controlled primarily by the timing of the SH stratospheric wind reversal from its winter to summer state, with a smaller but still important contribution from the solar cycle. Inter-hemispheric coupling triggered by winter stratospheric wind variations plays a significant role in controlling the Northern Hemisphere (NH) PMC season onset dates, again with additional control by the solar cycle. These couplings explain most of the observed variability in the PMC onset dates as observed by SBUV over the past three

  12. Tropical Stratospheric Cloud climatology from the PATMOS-x dataset - an assessment of convective contributions to stratospheric water

    NASA Astrophysics Data System (ADS)

    Nielsen, J. K.; Heidinger, A. K.; Foster, M. J.

    2012-04-01

    The PATMOS-x level 2b climatology, generated using three decades of AVHRR measurements, contains valuable information about the past global cloud record. We extract climatologies of tropical deep convective clouds from the PATMOS-x data set, based on the 10.30-11.30 micro meter brightness temperature. A comparison of the cross ropopause convective cloud frequency between ISCCP and PATMOS-x shows that PATMOS-x has a greater frequency of occurrence than does the ISCCP, and this enhanced frequency is attributed to greater horizontal resolution (2 km) in the PATMOS-x data. The high resolution makes this dataset suitable for a search for cross tropopause convection, which happens on length scales down to 1 km. We find there have been several changes in deep convective activity over land during the period 1982 to 2009. We explore specifically the epoch of the HALOE satellite, and find a correlation between land deep convective activity and anomalies in the HALOE stratospheric water retrievals. A simple model is able to predict stratospheric water vapor concentrations highly correlated to that observed using only frequency of deep convection. From this we conclude that deep convection over land contributes to moistening of the lowest tropical stratosphere on seasonal, annual and decadal timescales[1]. [1] GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L18801, 5 PP., 2011 doi:10.1029/2011GL049429

  13. Tropical Stratospheric Cloud climatology from the PATMOS-x dataset - an assessment of convective contributions to stratospheric water

    NASA Astrophysics Data System (ADS)

    Nielsen, J. K.; Foster, M. J.; Heidinger, A. K.

    2011-12-01

    The PATMOS-x level 2b climatology, generated using three decades of AVHRR measurements, contains valuable information about the past global cloud record. We extract climatologies of tropical deep convective clouds from the PATMOS-x data set, based on the 10.30-11.30 micro meter brightness temperature. A comparison of the cross ropopause convective cloud frequency between ISCCP and PATMOS-x shows that PATMOS-x has a greater frequency of occurrence than does the ISCCP, and this enhanced frequency is attributed to greater horizontal resolution (1 km) in the PATMOS-x data. The high resolution makes this dataset suitable for a search for cross tropopause convection, which happens on length scales down to 1 km. We find there have been several changes in deep convective activity over land during the period 1982 to 2009. We explore specifically the epoch of the HALOE satellite, and find a correlation between land deep convective activity and anomalies in the HALOE stratospheric water retrievals. A simple model is able to predict stratospheric water vapor concentrations highly correlated to that observed using only frequency of deep convection. From this we conclude that deep convection over land contributes to moistening of the lowest tropical stratosphere on seasonal, annual and decadal timescales.

  14. Tropical stratospheric cloud climatology from the PATMOS-x dataset: An assessment of convective contributions to stratospheric water

    NASA Astrophysics Data System (ADS)

    Nielsen, J. K.; Foster, M.; Heidinger, A.

    2011-09-01

    The PATMOS-x level 2b climatology, generated using three decades of AVHRR measurements, contains valuable information about the past global cloud record. We extract climatologies of tropical deep convective clouds from the PATMOS-x data set, based on the 10.30-11.30 μm brightness temperature. A comparison of the cross tropopause convective cloud frequency between ISCCP and PATMOS-x shows that PATMOS-x has a greater frequency of occurrence than does the ISCCP, and this enhanced frequency is attributed to greater horizontal resolution (2 km) in the PATMOS-x data. The high resolution makes this dataset suitable for a search for cross tropopause convection, which happens on length scales down to 1 km. We find there have been several changes in deep convective activity over land during the period 1982 to 2009. We explore specifically the epoch of the HALOE satellite, and find a correlation between land deep convective activity and anomalies in the HALOE stratospheric water retrievals. A simple model is able to predict stratospheric water vapor concentrations highly correlated to that observed using only frequency of deep convection. From this we conclude that deep convection over land contributes to moistening of the lowest tropical stratosphere on seasonal, annual and decadal timescales.

  15. Measurements of Chlorine Partitioning in the Winter Arctic Stratosphere

    NASA Technical Reports Server (NTRS)

    Stachnik, R.; Salawitch, R.; Engel, A.; Schmidt, U.

    1999-01-01

    Under the extremely cold conditions in the polar winter stratosphere, heterogeneous reactions involving HCl and CIONO(sub 2) on the surfaces of polar stratospheric cloud particles can release large amounts of reactive chlorine from these reservoirs leading to rapid chemical loss of ozone in the Arctic lower stratosphere during late winter and early spring.

  16. Stratospheric ion and aerosol chemistry and possible links with cirrus cloud microphysics - A critical assessment

    NASA Technical Reports Server (NTRS)

    Mohnen, Volker A.

    1990-01-01

    Aspects of stratospheric ion chemistry and physics are assessed as they relate to aerosol formation and the transport of aerosols to upper tropospheric regions to create conditions favorable for cirrus cloud formation. It is found that ion-induced nucleation and other known phase transitions involving ions and sulfuric acid vapor are probably not efficient processes for stratospheric aerosol formation, and cannot compete with condensation of sulfuric acid on preexisting particles of volcanic or meteoritic origin which are larger than about 0.15 micron in radius. Thus, galactic cosmic rays cannot have a significant impact on stratospheric aerosol population. Changes in the stratospheric aerosol burden due to volcanos are up to two orders of magnitude larger than changes in ion densities. Thus, volcanic activity may modulate the radiative properties of cirrus clouds.

  17. A microphysical connection among biomass burning, cumulus clouds, and stratospheric moisture.

    PubMed

    Sherwood, Steven

    2002-02-15

    A likely causal chain is established here that connects humidity in the stratosphere, relative humidity near the tropical tropopause, ice crystal size in towering cumulus clouds, and aerosols associated with tropical biomass burning. The connections are revealed in satellite-observed fluctuations of each quantity on monthly to yearly time scales. More aerosols lead to smaller ice crystals and more water vapor entering the stratosphere. The connections are consistent with physical reasoning, probably hold on longer time scales, and may help to explain why stratospheric water vapor appears to have been increasing for the past five decades. PMID:11847336

  18. The Polar Stratosphere in a Changing Climate (POLSTRACC)

    NASA Astrophysics Data System (ADS)

    Oelhaf, Hermann; Sinnhuber, Björn-Martin; Woiwode, Wolfgang; Rapp, Markus; Dörnbrack, Andreas; Engel, Andreas; Boenisch, Harald

    2015-04-01

    The POLSTRACC mission aims at providing new scientific knowledge on the Arctic lowermost stratosphere (LMS) and upper troposphere under the present load of halogens and state of climate variables. POLSTRACC is the only HALO (High Altitude and LOng Range Research Aircraft, German Research Community) mission dedicated to study the UTLS at high latitudes several years after the last intensive Arctic campaigns. The scientific scope of POLSTRACC will be broadened by its combination with the SALSA (Seasonality of Air mass transport and origin in the Lowermost Stratosphere using the HALO Aircraft) and GW-LCYCLE (Gravity Wave Life Cycle Experiment, a BMBF/ROMIC project) missions, which address complementary scientific goals sharing the same HALO payload. POLSTRACC, SALSA and GW-LCYCLE will offer the unique opportunity to study the bottom of the polar vortex and the high-latitude UTLS along with their impact on lower latitudes throughout an entire winter/spring cycle. The POLSTRACC consortium includes national (KIT, Forschungszentrum Jülich, DLR, Max Planck Institute for Chemistry, Universities of Frankfurt, Heidelberg, Mainz and Wuppertal) and international partners (e.g. NASA). The payload for the combined POLSTRACC, SALSA and GW-LCYCLE campaigns comprises an innovative combination of remote sensing techniques providing 2- and 3-D distributions of temperature and a large number of substances, and precise in-situ instruments measuring T, O3, H2O, tracers of different lifetimes and chemically active species at the aircraft level with high time-resolution. Drop sondes will add information about temperature, humidity and wind in the atmosphere underneath the aircraft. The field campaign will be divided into three phases for addressing (i) the early polar vortex and its wide-scale vicinity in December 2015 (from Oberpfaffenhofen, Germany), (ii) the mid-winter vortex from January to March 2016 (from Kiruna, Sweden), and (iii) the late dissipating vortex and its wide

  19. Strong modification of stratospheric ozone forcing by cloud and sea-ice adjustments

    NASA Astrophysics Data System (ADS)

    Xia, Yan; Hu, Yongyun; Huang, Yi

    2016-06-01

    We investigate the climatic impact of stratospheric ozone recovery (SOR), with a focus on the surface temperature change in atmosphere-slab ocean coupled climate simulations. We find that although SOR would cause significant surface warming (global mean: 0.2 K) in a climate free of clouds and sea ice, it causes surface cooling (-0.06 K) in the real climate. The results here are especially interesting in that the stratosphere-adjusted radiative forcing is positive in both cases. Radiation diagnosis shows that the surface cooling is mainly due to a strong radiative effect resulting from significant reduction of global high clouds and, to a lesser extent, from an increase in high-latitude sea ice. Our simulation experiments suggest that clouds and sea ice are sensitive to stratospheric ozone perturbation, which constitutes a significant radiative adjustment that influences the sign and magnitude of the global surface temperature change.

  20. Generation of waves by jet-stream instabilities in winter polar stratosphere/mesosphere

    NASA Astrophysics Data System (ADS)

    Shpynev, B. G.; Churilov, S. M.; Chernigovskaya, M. A.

    2015-12-01

    In the paper we investigate the manifestation of large-scale and middle-scale atmospheric irregularities observed on stratosphere/mesosphere heights. We consider typical patterns of circulation in stratosphere and lower mesosphere which are formed due to a difference of air potential energy between equatorial and polar latitudes, especially in polar night conditions. On the base of ECMWF Era Interim reanalysis data we consider the dynamics of midlatitude winter jet-streams which transfer heat from low latitudes to polar region and which develop due to equator/pole baroclinic instabilities. We consider typical patterns of general circulation in stratosphere/lower mesosphere and reasons for creation of flaky structure of polar stratosphere. Also we analyze conditions that are favorable for splitting of winter circumpolar vortex during sudden stratosphere warming events and role of phase difference tides in this process. The analysis of vertical structure of the stratosphere wind shows the presence of regions with significant shear of horizontal velocity which favors for inducing of shear-layer instability that appears as gravity wave on boundary surface. During powerful sudden stratosphere warming events the main jet-stream can amplify these gravity waves to very high amplitudes that causes wave overturning and releasing of wave energy into the heat due to the cascade breakdown and turbulence. For the dynamics observed in reanalysis data we consider physical mechanisms responsible for observed phenomena.

  1. Chlorine Deactivation in the Lower Stratospheric Polar Regions during late Winter: Results from UARS

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Froidevaux, L.; Manney, G. L.; Read, W. G.; Waters, J. W.; Chipperfield, M. P.; Roche, A. E.; Kumer, J. B.; Mergenthaler, J. L.; Russell, J. M., III

    1996-01-01

    Recovery from enhanced chlorine conditions in the lower stratospheric polar regions of both hemispheres is investigated using data from the Upper Atmosphere Research Satellite (UARS). Microwave Limb Sounder (MLS) measurements of ClO within the polar vortices are used to infer ClO(sub x) (ClO + 2Cl202) abundances that are then correlated with simultaneous Cryogenic Limb Array Etalon Spectrometer (CLAES) measurements of ClON02 and Halogen Occultation Experiment (HALOE) measurements of HCl obtained starting within 5 days of the end of the MLS and CLAES high-latitude observing periods in each hemisphere. Time series of vortex-averaged mixing ratios are calculated on two potential temperature surfaces (585 K and 465 K) in the lower stratosphere for approximately month-long intervals during late winter: August 17 - September 17, 1992, in the southern hemisphere and February 12 - March 16, 1993, in the northern hemisphere. The observed mixing ratios are adjusted for the effects of vertical transport using diabatic vertical velocities estimated from CLAES tracer data. In the northern hemisphere, the decrease in ClO, is balanced on both surfaces by an increase in ClON02- In the southern hemisphere, continuing polar stratospheric cloud activity prevents ClO from undergoing sustained decline until about September 3. In contrast to the northern hemisphere, there is no significant chemical change in vortex-averaged ClON02 at 465 K, and there is an apparent decrease in ClON02 at 585 K, even after the enhanced ClO abundances have started to recede. Results from the SLIMCAT chemical transport model initialized with UARS data and run with OH + ClO yields HCl + 02 as an 8% channel suggest that the primary recovery product in the south during this time period is not ClON02, but HCl. HALOE HCl mixing ratios are extrapolated back to the time of the MLS and CLAES data. At 585 K, the chlorine budget can be made to balance by extrapolating HCl back to a value of 0.6 parts per billion by

  2. Polarized View of Supercooled Liquid Water Clouds

    NASA Technical Reports Server (NTRS)

    Alexandrov, Mikhail D.; Cairns, Brian; Van Diedenhoven, Bastiaan; Ackerman, Andrew S.; Wasilewski, Andrzej P.; McGill, Matthew J.; Yorks, John E.; Hlavka, Dennis L.; Platnick, Steven E.; Arnold, G. Thomas

    2016-01-01

    Supercooled liquid water (SLW) clouds, where liquid droplets exist at temperatures below 0 C present a well known aviation hazard through aircraft icing, in which SLW accretes on the airframe. SLW clouds are common over the Southern Ocean, and climate-induced changes in their occurrence is thought to constitute a strong cloud feedback on global climate. The two recent NASA field campaigns POlarimeter Definition EXperiment (PODEX, based in Palmdale, California, January-February 2013) and Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS, based in Houston, Texas in August- September 2013) provided a unique opportunity to observe SLW clouds from the high-altitude airborne platform of NASA's ER-2 aircraft. We present an analysis of measurements made by the Research Scanning Polarimeter (RSP) during these experiments accompanied by correlative retrievals from other sensors. The RSP measures both polarized and total reflectance in 9 spectral channels with wavelengths ranging from 410 to 2250 nm. It is a scanning sensor taking samples at 0.8deg intervals within 60deg from nadir in both forward and backward directions. This unique angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135deg and 165deg. Simple parametric fitting algorithms applied to the polarized reflectance provide retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT),which allows retrieval of the droplet size distribution without assuming a size distribution shape. We present an overview of the RSP campaign datasets available from the NASA GISS website, as well as two detailed examples of the retrievals. In these case studies we focus on cloud fields with spatial features

  3. The relationship between the polar vortex and ozone in the boreal stratosphere from ERA-40 reanalysis

    NASA Astrophysics Data System (ADS)

    González-Merino, Beatriz; Serrano, Encarna

    2010-05-01

    The relation between the ozone and the polar vortex in the stratosphere has an outstanding role in climate studios, and also a large repercussion in the improvement of the climate models. This importance is due to the combination of two reasons: the key role of the stratospheric ozone in the Earth climate due to its radiative properties, and that the most important dynamic activity in the high-latitude stratosphere is associated with the polar vortex (present during the whole winter and part of the spring). This work focuses on the spring months, a transitional period in the stratospheric circulation between the winter westerlies (the stratospheric polar vortex, SPV, is completely developed) and summer easterlies (SPV has already disappeared). This breakdown of the SPV is known as the Stratospheric Final Warming, SFW. Using ERA-40 data, currently the longest-period reanalysis (1979-2002) with a sufficiently realistic representation of the stratosphere circulation, we analyze different aspects about the relation between the ozone concentration and the intensity of polar vortex in the boreal stratosphere during the springtime. Among other results, we see that the 24-yr mean evolution of the stratospheric ozone, averaged over the polar region (60°N-80°N), exhibits a slow increase along March followed by a progressive decrease during April and May. The interannual variability of the monthly mean of zonal wind and ozone mixing ratio at 50 hPa in the analyzed polar region decreases gradually along the season as well. When analyzing the springtime stratospheric preconditioning, we found that almost all the warm Februaries are not associated with low ozone content and strong SPV at the beginning of March; and that none cold February was followed by a weak SPV in the first third of March. Also, the stratospheric conditions around the SFW occurrence have been studied. It is seen that the 50-hPa ozone over the polar region is nearly constant prior to the SFW, while it gets

  4. The 1980 eruptions of Mount St. Helens - Physical and chemical processes in the stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Turco, R. P.; Toon, O. B.; Whitten, R. C.; Hamill, P.; Keesee, R. G.

    1983-01-01

    The large and diverse set of observational data collected in the high-altitude plumes of the May 18, May 25, and June 13, 1980 eruptions is organized and analyzed with a view to discerning the processes at work. The data serve to guide and constrain detailed model simulations of the volcanic clouds. For this purpose, use is made of a comprehensive one-dimensional model of stratospheric sulfate aerosols, sulfur precursor gases, and volcanic ash and dust. The model takes into account gas-phase and condensed-phase (heterogeneous) chemistry in the clouds, aerosol nucleation and growth, and cloud expansion. Computational results are presented for the time histories of the gaseous species concentrations, aerosol size distributions, and ash burdens of the eruption clouds. Also investigated are the long-term buildup of stratospheric aerosols in the Northern Hemisphere and the persistent effects of injected chlorine and water vapor on stratospheric ozone. It is concluded that SO2, water vapor, and ash were probably the most important substances injected into the stratosphere by the Mount St. Helens volcano, both with respect to their widespread effects on composition and their effect on climate.

  5. Study of cloud properties and processes in the polar regions by combining satellite and ground-based remote sensing measurements

    NASA Astrophysics Data System (ADS)

    Adhikari, Loknath

    Clouds in the polar regions play an important roles in the hydrologic cycle, the local radiative balance, and polar sea ice. However, harsh climatic conditions and perennial snow and ice cover limits the collection of cloud data from the surface as well as the effectiveness of cloud detection with satellite passive sensors. Therefore, there is a lack of reliable data on polar clouds and their properties. This study combines active and passive measurements from the NASA A-Train satellites to overcome these shortcomings and to provide a novel approach to study on polar clouds. Multi-year CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are used to investigate the characteristics of tropospheric clouds and precipitation systems, and their effect on the occurrence and microphysical properties of polar stratospheric clouds in the Antarctic region, south of 60 °S. The lidar and radar data are collocated to derive a combined cloud mask to improve detection of cloud vertical structure. Polar stratospheric clouds were detected using CALIPSO attenuated lidar scattering ratios (ALSR) at a horizontal resolution of 20 km to achieve good signal-to-noise ratios to allow the detection of tenuous PSCs. Clouds in the Antarctic region exhibit distinct land-sea and seasonal variabilities. The mean annual cloud occurrence is ~ 50 % over the continent and ~ 85 % over the ocean. Over the ocean the mean occurrence is higher in summer (90 %) than in winter (70 %). Low-level clouds contribute to more than 60 % of the total clouds. However, due to the extensive snow cover and cold surfaces in winter these low-level cloud occurrences are smaller in winter (50 %) than in summer (65 %). For ice clouds, both the effective radius and ice water content are larger in summer than in winter. High-level and deep tropospheric clouds strongly affect polar stratospheric cloud (PSC) occurrence and their microphysical properties by providing additional cooling

  6. Titan's Tropopause Temperatures from CIRS: Implications for Stratospheric Methane Cloud Formation

    NASA Technical Reports Server (NTRS)

    Anderson, C. M.; Samuelson, R. E.; Achterberg, R. K.; Barnes, J. W.; Flasar, F. M.

    2012-01-01

    Analysis of Cassini Composite Infrared Spectrometer (CIRS) far-IR spectra enable the construction of Titan's temperature profile in the altitude region containing the tropopause. Whereas the methane V4 band at 1306/cm (7.7 microns) is the primary opacity source for deducing thermal structure between 100 km and 500 km, N2-N2 collision-induced absorption between 70 and 140/cm (143 microns and 71 microns) is utilized to determine temperatures at Titan's tropopause. Additional opacity due to aerosol and nitrile ices must also be taken into account in this part of the far-IR spectral region. The spectral characteristics of these particulate opacities have been deduced from CIRS limb data at 58degS, 15degS, 15degN, and 85degN. Empirically, the spectral shapes of these opacities appear to be independent of both latitude and altitude below 300 km (Anderson and Samuelson, 2011, Icarus 212, 762-778), justifying the extension of these spectral properties to all latitudes. We find that Titan's tropopause temperature is cooler than the HAS! value of 70.5K by approx. 6K. This leads to the possibility that subsidence at high northern latitudes can cause methane condensation in the winter polar stratosphere. A search for methane clouds in this region is in progress.

  7. Stratospheric temperature and composition of Jupiter's polar aurora from IRTF-TEXES

    NASA Astrophysics Data System (ADS)

    Sinclair, J.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Irwin, P. G. J.

    2015-10-01

    We perform an analysis of TEXES (Texas Echelon Cross Echelle Spectrograph, 5- to 25- μm,[1]) spectra of Jupiter's high latitudes observed in December 2014 in order to study the jovian polar aurora. The high resolving power (R˜85000) of TEXES allows a large altitude range (10 mbar to 0.01 mbar) in Jupiter's stratosphere to be sounded. Retrievals of temperature and stratospheric composition of these measurements therefore: 1) allow the vertical deposition of auroral energy to be determined and 2) quantify how the auro-ral processes modify the thermal structure and composition of the jovian stratosphere.

  8. Lidar Observations of Stratospheric Clouds After Volcanic Eruption of Pinatubo

    NASA Technical Reports Server (NTRS)

    Sun, Jinhui; Qiu, Jinhuan; Xia, Qilin; Zhang, Jinding

    1992-01-01

    A very large increase of backscattered light from the stratospheric aerosol layer was observed by using a ruby laser in Beijing (39 degrees 54 minutes N, 116 degrees 27 minutes E) from the end of July 1991 to March 1992. It was concluded that this increase was almost certainly due to the volcanic eruption of Mt. Pinatubo in the Philippines in June 1991. The measuring instruments used are described. Information is given in graphical form for vertical profiles, fluctuation of the maximum backscattering ratio above 20 km during the nine month period, and the time variation of the integrated backscattering coefficient at a height of 15 to 30 km.

  9. Radiatively driven stratosphere-troposphere interactions near the tops of tropical cloud clusters

    NASA Technical Reports Server (NTRS)

    Churchill, Dean D.; Houze, Robert A., Jr.

    1990-01-01

    Results are presented of two numerical simulations of the mechanism involved in the dehydration of air, using the model of Churchill (1988) and Churchill and Houze (1990) which combines the water and ice physics parameterizations and IR and solar-radiation parameterization with a convective adjustment scheme in a kinematic nondynamic framework. One simulation, a cirrus cloud simulation, was to test the Danielsen (1982) hypothesis of a dehydration mechanism for the stratosphere; the other was to simulate the mesoscale updraft in order to test an alternative mechanism for 'freeze-drying' the air. The results show that the physical processes simulated in the mesoscale updraft differ from those in the thin-cirrus simulation. While in the thin-cirrus case, eddy fluxes occur in response to IR radiative destabilization, and, hence, no net transfer occurs between troposphere and stratosphere, the mesosphere updraft case has net upward mass transport into the lower stratosphere.

  10. Airborne brightness temperature measurements of the polar winter troposphere as part of the Airborne Arctic Stratosphere Experiment 2 and the effect of brightness temperature variations on the diabatic heating in the lower stratosphere

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.; Platnick, Steven; Kinne, Stefan; Pilewskie, Peter; Bucholtz, Anthony

    1993-01-01

    In this paper we report radiometric measurements of tropospheric brightness temperatures obtained during the AASE 2 experiment. These measurements represent the first attempt to characterize effective radiative temperatures as seen from above the troposphere during the Arctic winter. The reported measurements include brightness temperatures at 6.7 and 10.5 microns as seen from the NASA DC-8 aircraft flying at about 11 km altitude. We also present radiative transfer calculations to estimate the effect of tropospheric brightness temperature on the lower stratospheric heating rates. Because of the recent massive eruption of the Pinatubo volcano, we also discuss the effects of a volcanic aerosol layer. It is concluded that small particles like the volcanic aerosol or polar stratospheric clouds (PSCs) type 1 do not affect stratospheric heating rates by much; on the other hand, larger particles, PSCs types 2 and 3, may have significant effects on heating rates and consequently on dynamics of the lower stratosphere. The dynamical effects of local stratospheric temperature variations are briefly discussed.

  11. Dynamics of the 4-day wave in the Southern Hemisphere polar stratosphere

    SciTech Connect

    Randel, W.J. ); Lait, L.R. )

    1991-12-01

    Dynamics of the 4-day wave in the Southern Hemisphere polar stratosphere is investigated using horizontal wind and temperature data. These were derived from synoptic maps of satellite-measured brightness temperatures, which were generated using the fast Fourier synoptic mapping technique of Salby. Circulation statistics from these data are compared to those from the National Meteorological Center (NMC) operational stratospheric analyses, demonstrating improvements afforded by detailed treatment of asynoptic sampling effects. The 4-day wave is isolated using temporally filtered data. Several events of wave growth and decay are observed in the upper stratosphere during August 1980. Derived zonal-mean and eddy statistics suggest that the 4-day wave results from an instability of the zonal-mean flow near 55[degrees]-60[degrees]S, at and above 1 mb. Inspection of climatological data suggests the source of the instability to be the [open quotes]double-jet[close quotes] structure in the upper stratosphere and mesosphere (the subtropical mesospheric jet near 30[degrees]S and the high-latitude extension of the polar night jet near 70[degrees]S). Contribution of the 4-day wave to the general circulation of the stratosphere is discussed: one feature attributable to the 4-day wave is a region of positive EP flux divergence in the upper stratosphere near 50[degrees]-60[degrees]S. 22 refs., 12 figs.

  12. Catastrophic loss of stratospheric ozone in dense volcanic clouds

    NASA Technical Reports Server (NTRS)

    Prather, Michael

    1992-01-01

    Rapid, localized loss of ozone is predicted to occur in the midlatitude and tropical stratosphere in the presence of very large concentrations of sulfate aerosols. Volcanic eruptions can increase the effective surface area of sulfuric acid so that heterogeneous reactions involving ClONO2, and secondarily N2O5, are able to suppress NO(x) abundances by more than a factor of 10 relative to gas phase chemistry. When NO(x) levels fall below a threshold, e.g., 0.6 ppb at 24 km in mid-latitudes, the chlorine-catalyzed loss of O3 proceeds at rates comparable to those during the formation of the Antarctic ozone hole, more than 50 ppb per day. If such losses occurred following the eruption of Mount Pinatubo in the most volcanically perturbed regions over the tropics and mid-latitudes, this model predicts that they are driven primarily by the suppression of NO(x) below these critical levels. The increase in stratospheric chlorine since El Chichon has made Mount Pinatubo more than twice as effective in causing rapid O3 loss.

  13. QBO Influence on Polar Stratospheric Variability in the GEOS Chemistry-Climate Model

    NASA Technical Reports Server (NTRS)

    Hurwitz, M. M.; Oman, L. D.; Li, F.; Slong, I.-S.; Newman, P. A.; Nielsen, J. E.

    2010-01-01

    The quasi-biennial oscillation modulates the strength of both the Arctic and Antarctic stratospheric vortices. Model and observational studies have found that the phase and characteristics of the quasi-biennial oscillation (QBO) contribute to the high degree of variability in the Arctic stratosphere in winter. While the Antarctic stratosphere is less variable, recent work has shown that Southern Hemisphere planetary wave driving increases in response to "warm pool" El Nino events that are coincident with the easterly phase of the QBO. These events hasten the breakup of the Antarctic polar vortex. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is now capable of generating a realistic QBO, due a new parameterization of gravity wave drag. In this presentation, we will use this new model capability to assess the influence of the QBO on polar stratospheric variability. Using simulations of the recent past, we will compare the modeled relationship between QBO phase and mid-winter vortex strength with the observed Holton-Tan relation, in both hemispheres. We will use simulations of the 21 St century to estimate future trends in the relationship between QBO phase and vortex strength. In addition, we will evaluate the combined influence of the QBO and El Nino/Southern Oscillation (ENSO) on the timing of the breakup of the polar stratospheric vortices in the GEOS CCM. We will compare the influence of these two natural phenomena with trends in the vortex breakup associated with ozone recovery and increasing greenhouse gas concentrations.

  14. Lidar Observations of the Pinatubo Stratospheric Aerosol Cloud over Frascati, Italy

    NASA Technical Reports Server (NTRS)

    Congeduti, Fernando; Adriani, Alberto; Gobbi, Gian Paolo; Centurioni, Sante

    1992-01-01

    The Pinatubo eruption of June 1991 introduced large plumes into the local stratosphere. On several occasions, volcanic gases and particles reached altitudes of about 30 km, and spread towards the west. A lidar system has been operating to monitor the evolution of the stratospheric aerosol cloud. The backscattering ratio profiles of eight different measurements were chosen to summarize the most significant occurrences of the event. Since the beginning of the winter planetary wave activity, the Pinatubo cloud integrated backscatter exceeded El Chichon's. In this context, the perturbation generated by El Chichon can only be assumed as a lower limit of the one which will follow the Pinatubo eruption. Observations of the event are still in progress.

  15. A possible water ice cloud in Jupiter's stratosphere

    NASA Astrophysics Data System (ADS)

    López-Puertas, M.; Montañés-Rodríguez, M. P.; González-Merino, B.; Pallé, E.; García-Melendo, E.; Höpfner, M.; García-Comas, M.; Funke, B.

    2015-10-01

    Jupiter's atmosphere has been sounded in transmission from UV to IR, as if it were a transiting exoplanet by observing one of its satellites, Ganymede, while passing through Jupiter's shadow during a solar eclipse from Ganymede. The spectra show strong extinction due to the presence of aerosols and haze in the atmosphere and strong absorption features from CH4.In addition, the spectra show two broad features near 1.5 and 2.0μm that we tentatively attribute to a layer of H2O ice in Jupiter's stratosphere. While the spectral signatures seem to be unequivocally attributed to crystalline water ice, to explain the strong absorption features requires a large amount of water ice.

  16. Measurements of cloud condensation nuclei in the stratosphere around the plume of Mount St. Helens

    SciTech Connect

    Rogers, C.F.; Hudson, J.G.; Kocmond, W.C.

    1981-01-01

    Measurements of cloud condensation nuclei were made from small samples of stratospheric air taken from a U-2 aircraft at altitudes ranging from 13 to 19 kilometers. The measured concentrations of nuclei both in and outside the plume from the May and June 1980 eruptions of Mount St. Helens were higher than expected, ranging from about 100 to about 1000 per cubic centimeter active at 1 percent supersaturation.

  17. Toward a Better Quantitative Understanding of Polar Stratospheric Ozone Loss

    NASA Technical Reports Server (NTRS)

    Frieler, K.; Rex, M.; Salawitch, R. J.; Canty, T.; Streibel, M.; Stimpfle, R. M.; Pfeilsticker, K.; Dorf, M.; Weisenstein, D. K.; Godin-Beekmann, S.

    2006-01-01

    Previous studies have shown that observed large O3 loss rates in cold Arctic Januaries cannot be explained with current understanding of the loss processes, recommended reaction kinetics, and standard assumptions about total stratospheric chlorine and bromine. Studies based on data collected during recent field campaigns suggest faster rates of photolysis and thermal decomposition of ClOOCl and higher stratospheric bromine concentrations than previously assumed. We show that a model accounting for these kinetic changes and higher levels of BrO can largely resolve the January Arctic O3 loss problem and closely reproduces observed Arctic O3 loss while being consistent with observed levels of ClO and ClOOCl. The model also suggests that bromine catalyzed O3 loss is more important relative to chlorine catalyzed loss than previously thought.

  18. Rocket- and aircraft-borne trace gas measurements in the winter polar stratosphere

    NASA Technical Reports Server (NTRS)

    Arnold, F.; Moehler, O.; Pfeilsticker, K.; Ziereis, H.

    1988-01-01

    In January and February 1987 stratospheric rocket- and aircraft-borne trace gas measurements were done in the North Polar region using ACIMS (Active Chemical Ionization Mass Spectrometry) and PACIMS (PAssive Chemical Ionization Mass Spectrometry) instruments. The rocket was launched at ESRANGE (European Sounding Rocket Launching Range) (68 N, 21 E, Northern Sweden) and the twin-jet research aircraft operated by the DFVLR (Deutsche Forschungs- und Versuchs-anstalt fuer Luft- und Raumfahrt), and equipped with a mass spectrometer laboratory was stationed at Kiruna airport. Various stratospheric trace gases were measured including nitric acid, sulfuric acid, non-methane hydrocarbons (acetone, hydrogen cyanide, acetonitrile, methanol etc.), and ambient cluster ions. The experimental data is presented and possible implications for polar stratospheric ozone discussed.

  19. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Key, J. R.; Maslanik, J. A.

    1988-01-01

    The principal objectives of this project are: (1) to develop suitable validation data sets to evaluate the effectiveness of the International Satellite Cloud Climatology Project (ISCCP) operational algorithm for cloud retrieval in polar regions and to validate model simulations of polar cloud cover; (2) to identify limitations of current procedures for varying atmospheric surface conditions, and to explore potential means to remedy them using textural classifiers; and (3) to compare synoptic cloud data from a control run experiment of the GISS climate model II with typical observed synoptic cloud patterns.

  20. Precursors of weak stratospheric polar vortex events: intra-seasonal variability

    NASA Astrophysics Data System (ADS)

    Díaz-Durán, Adelaida; Ayarzagüena, Blanca; Serrano, Encarna; Ábalos, Marta; de la Camara, Álvaro

    2016-04-01

    It is known that changes in the strength of stratospheric polar vortex are related to forcings that can affect the tropospheric upward wave propagation. In particular, an anomalous weak polar vortex (WPV) is preceded by a strong wave activity from the troposphere into the stratosphere causing a warming over the polar region and a consequent weakening of the polar cyclonic circulation. El Niño-Southern Oscillation (ENSO), Quasi-Biennial Oscillation (QBO) or certain tropospheric anomalous circulation structure, among others, have been identified in many studies as potential precursors of WPV events. However, although the timing of the most effective impact of those precursors on the stratospheric polar vortex is already known, the generation of WPV events at any given time of winter is still unknown in detail. The aim of this work is to explore the WPV occurred in different boreal winter sub-seasons and their possible precursors. Namely, we consider early winter (from October to December), mid-winter (January and February) and late winter (March and April) separately. For this purpose, we use daily-mean data from ERA-Interim for the period 1979-2011. Preliminary results by the authors give evidence of intra-winter variability in the state of the polar stratosphere prior to WPV events, in the characteristics of the anomalous wave activity triggering them and in the tropospheric circulation structures related to this enhancement of wave activity. In this work we show that mid- and late winter WPV events are preceded by an anomalously strong vortex and a peak of high wave activity with relevant contribution of wavenumber-1 and wavenumber-2 components. In contrast, a preconditioning in the stratosphere is observed for early winter WPVs, which are preceded by a weak enhancement of wavenumber-1 wave activity. The contribution of precursors of WVP events, such as QBO, Arctic sea ice anomalies or ENSO, presents differences among the three winter sub-seasons.

  1. Dehydration of the Upper Troposphere and Lower Stratosphere by Subvisible Cirrus Clouds Near the Tropical Tropopause

    NASA Technical Reports Server (NTRS)

    Jensen, Eric J.; Toon, Owen B.; Pfister, Leonhard; Selkirk, Henry B.

    1996-01-01

    The extreme dryness of the lower stratosphere is believed to be caused by freeze-drying of air as it enters the stratosphere through the cold tropical tropopause. Previous investigations have been focused on dehydration occurring at the tops of deep convective cloud systems, However, recent observations of a ubiquitous stratiform cirrus cloud layer near the tropical tropopause suggest the possibility of dehydration as air is slowly lifted by large-scale motions, In this study, we have evaluated this possibility using a detailed ice cloud model. Simulations of ice cloud formation in the temperature minima of gravity waves (wave periods of 1 - 2 hours) indicate that large numbers of ice crystals will likely form due to the low temperatures and rapid cooling. As a result, the crystals do not grow larger than about 10 microns, fallspeeds are no greater than a few cm/s, and little or no precipitation or dehydration occurs. However, ice cloud's formed by large-scale vertical motions (with lifetimes of a day or more) should have,fever crystals and more time for crystal sedimentation to occur, resulting in water vapor depletions as large as 1 ppmv near the tropopause. We suggest that gradual lifting near the tropical tropopause, accompanied by formation of thin cirrus, may account for the dehydration.

  2. Astronomical polarization studies at radio and infrared wavelengths. Part 2: Far infrared polarization of dust clouds

    NASA Technical Reports Server (NTRS)

    Dennison, B. K.

    1976-01-01

    Far infrared polarization of dust clouds is examined. The recently observed 10 micron polarization of the Orion Nebula and the Galactic Center suggests that far infrared polarization may be found in these objects. Estimates are made of the degree of far infrared polarization that may exist in the Orion Nebula. An attempt to observe far infrared polarization from the Orion Nebula was carried out.

  3. Weakening of the Stratospheric Polar Vortex by Arctic Sea-Ice Loss

    SciTech Connect

    Kim, Baek-Min; Son, Seok-Woo; Min, Seung-Ki; Jeong, Jee-Hoon; Kim, Seong-Joong; Zhang, Xiangdong; Shim, Taehyoun; Yoon, Jin-Ho

    2014-09-02

    Successive cold winters of severely low temperatures in recent years have had critical social and economic impacts on the mid-latitude continents in the Northern Hemisphere. Although these cold winters are thought to be partly driven by dramatic losses of Arctic sea ice, the mechanism that links sea ice loss to cold winters remains a subject of debate. Here, by conducting observational analyses and model experiments, we show how Arctic sea ice loss and cold winters in extra-polar regions are dynamically connected through the polar stratosphere. We find that decreased sea ice cover during early winter months (November-December), especially over the Barents-Kara seas, enhance the upward propagation of planetary-scale waves with wavenumbers of 1 and 2, subsequently weakening the stratospheric polar vortex in mid-winter (January- February). The weakened polar vortex preferentially induces a negative phase of Arctic Oscillation at the surface, resulting in low temperatures in mid-latitudes.

  4. Stratospheric and solar cycle effects on long-term variability of mesospheric ice clouds

    NASA Astrophysics Data System (ADS)

    Lübken, F.-J.; Berger, U.; Baumgarten, G.

    2009-01-01

    Model results of mesospheric ice layers and background conditions at 69°N from 1961 to 2008 are analyzed. The model nudges to European Centre for Medium-Range Weather Forecasts data below ˜45 km. Greenhouse gas concentrations in the mesosphere are kept constant. At polar mesospheric cloud (PMC) altitudes (83 km) temperatures decrease until the mid 1990s by -0.08 K/yr resulting in trends of PMC brightness, occurrence rates, and, to a lesser extent, in PMC altitudes (-0.0166 km/yr). Ice layer trends are consistent with observations by ground-based and satellite instruments. Water vapor increases at PMC heights and decreases above due to increased freeze-drying caused by the temperature trend. Temperature trends in the mesosphere mainly come from shrinking of the stratosphere and from dynamical effects. A solar cycle modulation of H2O is observed in the model consistent with satellite observations. The effect on ice layers is reduced because of redistribution of H2O by freeze-drying. The accidental coincidence of low temperatures and solar cycle minimum in the mid 1990s leads to an overestimation of solar effects on ice layers. A strong correlation between temperatures and PMC altitudes is observed. Applied to historical measurements this gives negligible temperature trends at PMC altitudes (˜0.01-0.02 K/yr). Strong correlations between PMC parameters and background conditions deduced from the model confirm the standard scenario of PMC formation. The PMC sensitivity on temperatures, water vapor, and Ly-α is investigated. PMC heights show little variation with background parameters whereas brightness and occurrence rates show large variations. None of the background parameters can be ignored regarding its influence on ice layers.

  5. Stratospheric and solar cycle effects on long-term variability of mesospheric ice clouds

    NASA Astrophysics Data System (ADS)

    Lübken, F.-J.; Berger, U.; Baumgarten, G.

    2009-11-01

    Model results of mesospheric ice layers and background conditions at 69°N from 1961 to 2008 are analyzed. The model nudges to European Centre for Medium-Range Weather Forecasts data below ˜45 km. Greenhouse gas concentrations in the mesosphere are kept constant. At polar mesospheric cloud (PMC) altitudes (83 km) temperatures decrease until the mid 1990s by -0.08 K/yr resulting in trends of PMC brightness, occurrence rates, and, to a lesser extent, in PMC altitudes (-0.0166 km/yr). Ice layer trends are consistent with observations by ground-based and satellite instruments. Water vapor increases at PMC heights and decreases above due to increased freeze-drying caused by the temperature trend. Temperature trends in the mesosphere mainly come from shrinking of the stratosphere and from dynamical effects. A solar cycle modulation of H2O is observed in the model consistent with satellite observations. The effect on ice layers is reduced because of redistribution of H2O by freeze-drying. The accidental coincidence of low temperatures and solar cycle minimum in the mid 1990s leads to an overestimation of solar effects on ice layers. A strong correlation between temperatures and PMC altitudes is observed. Applied to historical measurements this gives negligible temperature trends at PMC altitudes (˜0.01-0.02 K/yr). Strong correlations between PMC parameters and background conditions deduced from the model confirm the standard scenario of PMC formation. The PMC sensitivity on temperatures, water vapor, and Ly-α is investigated. PMC heights show little variation with background parameters whereas brightness and occurrence rates show large variations. None of the background parameters can be ignored regarding its influence on ice layers.

  6. Condensation of HNO3 on falling ice particles - Mechanism for denitrification of the polar stratosphere

    NASA Technical Reports Server (NTRS)

    Wofsy, S. C.; Salawitch, R. J.; Yatteau, J. H.; Mcelroy, M. B.; Gandrud, B. W.

    1990-01-01

    Ice particles created in polar stratospheric cooling events are predicted to descend into Type I PSCs and accrete a coating of nitric acid trihydrate (NAT) that inhibits evaporation. Coated particles efficiently strip HNO3 from the atmosphere, providing a mechanism for denitrification without significant dehydration. Coatings that disintegrate may release large particles of NAT that influence subsequent particle growth.

  7. What Controls the Arctic Lower Stratosphere Temperature?

    NASA Technical Reports Server (NTRS)

    Newman, Paul A.; Nash, Eric R.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    The temperature of the Arctic lower stratosphere is critical for understanding polar ozone levels. As temperatures drop below about 195 K, polar stratospheric clouds form, which then convert HCl and ClONO2 into reactive forms that are catalysts for ozone loss reactions. Hence, the lower stratospheric temperature during the March period is a key parameter for understanding polar ozone losses. The temperature is basically understood to be a result of planetary waves which drive the polar temperature away from a cold "radiative equilibrium" state. This is demonstrated using NCEP/NCAR reanalysis calculations of the heat flux and the mean polar temperature. The temperature during the March period is fundamentally driven by the integrated impact of large scale waves moving from the troposphere to the stratosphere during the January through February period. We will further show that the recent cold years in the northern polar vortex are a result of this weakened wave driving of the stratosphere.

  8. Microphysical and radiative changes in cirrus clouds by geoengineering the stratosphere

    NASA Astrophysics Data System (ADS)

    Cirisan, A.; Spichtinger, P.; Luo, B. P.; Weisenstein, D. K.; Wernli, H.; Lohmann, U.; Peter, T.

    2013-05-01

    In the absence of tangible progress in reducing greenhouse gas emissions, the implementation of solar radiation management has been suggested as measure to stop global warming. Here we investigate the impacts on northern midlatitude cirrus from continuous SO2emissions of 2-10 Mt/a in the tropical stratosphere. Transport of geoengineering aerosols into the troposphere was calculated along trajectories based on ERA Interim reanalyses using ozone concentrations to quantify the degree of mixing of stratospheric and tropospheric air termed "troposphericity". Modeled size distributions of the geoengineered H2SO4-H2O droplets have been fed into a cirrus box model with spectral microphysics. The geoengineering is predicted to cause changes in ice number density by up to 50%, depending on troposphericity and cooling rate. We estimate the resulting cloud radiative effects from a radiation transfer model. Complex interplay between the few large stratospheric and many small tropospheric H2SO4-H2O droplets gives rise to partly counteracting radiative effects: local increases in cloud radiative forcing up to +2 W/m2for low troposphericities and slow cooling rates, and decreases up to -7.5 W/m2for high troposphericities and fast cooling rates. The resulting mean impact on the northern midlatitudes by changes in cirrus is predicted to be low, namely <1% of the intended radiative forcing by the stratospheric aerosols. This suggests that stratospheric sulphate geoengineering is unlikely to have large microphysical effects on the mean cirrus radiative forcing. However, this study disregards feedbacks, such as temperature and humidity changes in the upper troposphere, which must be examined separately.

  9. Observations of denitrification and dehydration in the winter polar stratospheres

    NASA Technical Reports Server (NTRS)

    Fahey, D. W.; Kelly, K. K.; Kawa, S. R.; Tuck, A. F.; Loewenstein, M.

    1990-01-01

    It is argued that denitrification of the Arctic stratosphere can be explained by the selective growth and sedimentation of aerosol particles rich in nitric acid. Because reactive nitrogen species moderate the destruction of ozone by chlorine-catalyzed reactions by sequestering chlorine in reservoir species such as ClONO2, the possibility of the removal of reactive nitrogen without dehydration should be allowed for in attempts to model ozone depletion in the Arctic. Indeed, denitrification along with elevated concentrations of reactive chlorine observed in 1989 indicate that the Arctic was chemically primed for ozone destruction without an extended period of temperatures below the frost point, as is characteristic of the Antarctic.

  10. Using FTIR measurements of stratospheric composition to identify midlatitude polar vortex intrusions over Toronto

    NASA Astrophysics Data System (ADS)

    Whaley, C.; Strong, K.; Adams, C.; Bourassa, A. E.; Daffer, W. H.; Degenstein, D. A.; Fast, H.; Fogal, P. F.; Manney, G. L.; Mittermeier, R. L.; Pavlovic, B.; Wiacek, A.

    2013-11-01

    Using 11 years of trace gas measurements made at the University of Toronto Atmospheric Observatory (43.66°N, 79.40°W) and Environment Canada's Centre for Atmospheric Research Experiments (44.23°N, 79.78°W), along with derived meteorological products, we identify a number of polar intrusion events, which are excursions of the polar vortex or filaments from the polar vortex extending down to midlatitudes. These events are characterized by enhanced stratospheric columns (12-50 km) of hydrogen fluoride (HF), by diminished stratospheric columns of nitrous oxide (N2O), and by a scaled potential vorticity above 1.2 × 10-4s-1. The events comprise 16%of winter/spring (November to April inclusive) Fourier transform infrared (FTIR) spectroscopic measurements from January 2002 to March 2013, and we find at least two events per year. The events are corroborated by Modèle Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection, Modern-Era Retrospective Analysis for Research and Applications potential vorticity maps, and Global Modeling Initiative N2O maps. During polar intrusion events, the stratospheric ozone (O3) columns over Toronto are usually greater than when there is no event. Our O3 measurements agree with the Optical Spectrograph and Infrared Imaging System satellite instrument and are further verified with the Earth Probe Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument satellite observations. We find six cases out of 53 for which chemical O3depletion within the polar vortex led to a reduction in stratospheric O3 columns over Toronto. We have thus identified a dynamical cause for most of the winter/spring variability of stratospheric trace gas columns observed at our midlatitude site. While there have been a number of prior polar intrusion studies, this is the first study to report in the context of 11 years of ground-based FTIR column measurements, providing insight into the frequency of midlatitude polar vortex intrusions