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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.; Ferry, G.; Turco, R. P.; Jordan, J.; Goodman, J.

    1989-01-01

    The formulation and evolution of polar stratospheric ice clouds are simulated using a one-dimensional model of cloud microphysics. It is found that the optical thickness and particle size of ice clouds depend on the cooling rate of the air in which the cloud formed. It is necessary that there be an energy barrier to ice nucleation upon the preexisting aerosols in order to account for the cooling rate dependence of the cloud properties.

  2. Optical studies of polar stratospheric clouds

    NASA Astrophysics Data System (ADS)

    Enell, Carl-Fredrik; Gustavsson, Bjorn; Steen, Ake; Brandstrom, Urban; Rydesater, Peter; Johansson, P.; Wagner, T.; Friess, U.; Pfeilsticker, K.; Platt, Ulrich

    1999-12-01

    Polar Stratospheric Clouds (PSC) appear in the polar zones of the Earth in the winter. These clouds are known to cause enhanced chemical ozone destruction. Methods for optical remote-sensing of PSC in use or under development at the Swedish Institute of Space Physics are discussed with respect to their advantages and limitations. Especially multistatic imaging may become a valuable additional tool for PSC studies.

  3. 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.

  4. Polar stratospheric clouds inferred from satellite data

    NASA Astrophysics Data System (ADS)

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

    1986-11-01

    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.

  5. 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.

  6. Polar stratospheric clouds inferred from satellite data

    NASA Astrophysics Data System (ADS)

    1986-11-01

    Anomalously high radiances from the ozone channel of the Limb Infra-red Monitor of the Statosphere (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 (SSU) temperatures and water vapor measurements from the LIMS Map Archive Tape (MAT) 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%. 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 10 September at 20 km. This result has important implications for a number of proposed explanations for the Antarctic ozone hole.

  7. Formation of model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Fourier transform infrared spectroscopy was used to examine the competitive growth of films representative of polar stratospheric clouds. These experiments show that either crystalline nitric acid trihydrate (beta-NAT) or amorphous films with H2O:HNO3 ratios close to 3:1 formed at temperatures 3-7 K warmer than the ice frost point under stratospheric pressure conditions. In addition, with higher HNO3 pressure, we observed nitric acid dihydrate (NAD) formation at temperatures warmer than ice formation. However, our experiments also show that NAD surfaces converted to beta-NAT upon exposure to stratospheric water pressures. Finally, we determined that the net uptake coefficient for HNO3 on beta-NAT is close to unity, whereas the net uptake coefficient for H2O is much less.

  8. 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.

  9. 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.

  10. 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.

  11. Persistence of Antarctic polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Mccormick, M. Patrick; Trepte, C. R.

    1988-01-01

    The persistence of Polar Stratospheric Clouds (PSCs) observed by the Stratospheric Aerosol Measurement (SAM) 2 satellite sensor over a 9-year period is compared and contrasted. Histograms of the SAM 2 1.0 micron extinction ratio data (aerosol extinction normalized by the molecular extinction) at an altitude of 18 km in the Antarctic have been generated for three 10-day periods in the month of September. Statistics for eight different years (1979 to 1982 and 1984 to 1987) are shown in separate panels for each figure. Since the SAM 2 system is a solar occultation experiment, observations are limited to the edge of the polar night and no measurements are made deep within the vortex where temperatures could be colder. For this reason, use is made of the NMC global gridded fields and the known temperature-extinction relationship to infer additional information on the occurrence and areal coverage of PSCs. Calculations of the daily areal coverage of the 195 K isotherm will be presented for this same period of data. This contour level lies in the range of the predicted temperature for onset of the Type 1 particle enhancement mode at 50 mb (Poole and McCormick, 1988b) and should indicate approximately when formation of the binary HNO3-H2O particles begins.

  12. 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.

  13. 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.

  14. 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.

  15. Optical backscatter characteristics of Arctic polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Kent, G. S.; Schaffner, S. K.; Poole, L. R.; Mccormick, M. P.; Hunt, W. H.

    1990-01-01

    Airborne lidar measurements have been made of polar stratospheric clouds (PSCs) during the Airborne Arctic Stratospheric Expedition in January-February 1989. These show the existence of a systematic relationship between the backscatter depolarization ratio and the (aerosol + molecular)/molecular backscatter ratio. The data are consistent with a two population PSC particle model.

  16. Persistence of polar stratospheric clouds in the southern polar region

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.; Pitts, M. C.

    1989-01-01

    Observations of Antarctic polar stratospheric clouds (PSCs) were examined using the 1-micron aerosol extinction ratio data from the SAM II satellite experiment for the years 1979-1982 and 1984-1987. PSCs were sighted between 10 and 25 km and were usually first observed by mid-June. Clouds disappeared earlier at higher altitudes (late August near 24 km, in most cases) and later at lower altitudes (late September or October near 16 km). It was found that PSCs persisted longer in 1985 and 1987 at 18 km and were more frequently observed in September and October 1987 than the other years. Inference of likely PSC formation regions from National Meteorological Center temperature data indicated that clouds would begin forming in late May and usually disappear in September. This analysis confirmed the persistence of colder conditions during the spring of 1987.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Airborne lidar observations of Arctic polar stratospheric clouds

    NASA Astrophysics Data System (ADS)

    Poole, L. R.; Kent, G. S.

    1986-08-01

    Polar stratospheric clouds (PSC's) have been detected repeatedly during Arctic and Antarctic winters since 1978/1979 by the SAM II (Stratospheric Aerosol Measurement II) instrument aboard the NIMBUS-7 satellite. PSC's are believed to form when supercooled sulfuric acid droplets freeze, and subsequently grow by deposition of ambient water vapor as the local stratospheric temperature falls below the frost point. In order to study the characteristics of PSC's at higher spatial and temporal resolution than that possible from the satellite observations, aircraft missions were conducted within the Arctic polar night vortex in Jan. 1984 and Jan. 1986 using the NASA Langley Research Center airborne dual polarization ruby lidar system. A synopsis of the 1984 and 1986 PSC observations is presented illustrating short range spatial changes in cloud structure, the variation of backscatter ratio with temperature, and the depolarization characterics of cloud layers. Implications are noted with regard to PSC particle characteristics and the physical process by which the clouds are thougth to form.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Polar stratospheric cloud sightings by SAM II. [Stratospheric Aerosol Measurement onboard Nimbus 7

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Chu, W. P.; Steele, H. M.; Hamill, P.; Swissler, T. J.

    1982-01-01

    The functions and data gained regarding stratospheric cloud sightings by the stratospheric aerosol measurement (SAM) II experiment on board the Numbus 7 spacecraft are reported. SAM II comprises a single channel sun photometer centered at 1.0 micron wavelength for measuring the solar intensity when the sun descends below an apparent 300 km altitude until the sun is occulted by clouds or the horizon. Readings are also made during sunrise in an opposite fashion. Transmission profiles are developed from the data and used to construct profiles of aerosol extinction with a 1 km resolution. Polar stratospheric clouds have been observed in more than 90% of the cases when the minimum temperature is 185 K or less, and 45% of the time when the temperature is 193 K or less. The clouds were more prevalent in the Antarctic winter than during the Arctic winter, and cloud height was lower than indicated by previous data.

  7. The Discovery of Polar Stratospheric Clouds by SAM II

    NASA Astrophysics Data System (ADS)

    Poole, L. R.; McCormick, M. P.

    2005-12-01

    Until the advent of spaceborne observations, clouds were thought to occur very rarely in the extremely dry stratosphere. This view changed dramatically following the launch of the Stratospheric Aerosol Measurement (SAM) II instrument on the Nimbus 7 spacecraft in October 1978. SAM II was a single channel solar photometer designed to measure stratospheric aerosol extinction profiles at a wavelength of 1.0 micron at latitudes from 64-80 degrees in both hemispheres. An analysis of SAM II data from the Arctic for January 1979 revealed a number of profiles in which the extinction was 1-2 orders of magnitude larger than expected. Careful study showed that these large extinction values were not artifacts, but were indeed due to dramatic reductions in the amount of solar radiance reaching the instrument. Further analyses showed that these so-called polar stratospheric clouds (PSCs) were observed only when the local stratospheric temperature was very low (185-200 K). The interest in PSCs was primarily academic until the discovery of the Antarctic ozone hole in 1985, which was quickly followed by studies associating this ozone depletion with the release of active chlorine through heterogeneous chemical reactions catalyzed by PSC particles. A large body of research over the ensuing two decades has firmly established this link. In this paper, we will recount the serendipitous discovery of PSCs in SAM II data more than 25 years ago and highlight other advances in our understanding of PSCs that have stemmed from spaceborne observations.

  8. 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.

  9. Radiative feedback of polar stratospheric clouds on Antarctic temperatures

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Joan E.

    1993-01-01

    A one-dimensional time marching radiative transfer model has been used to investigate the potential effects of polar stratospheric clouds (PSCs) on winter and spring temperatures in the Antarctic lower stratosphere. High, middle, and low PSC amounts were specified from lidar backscatter profiles and were chosen to represent the likely range of PSC amounts present in the Antarctic region. The computed effects of the PSCs on temperatures depend strongly on the surface temperature and on the extent of tropospheric cloudiness, and range from a maximum increase of 6 K for a high amount of PSCs over a warm surface and clear troposphere to a maximum decrease of 2 K for a high amount of PSCs over a cold surface and a troposphere with high clouds. The average effect is unlikely to be more than a 1 or 2 K temperature change.

  10. The formation of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Steele, H. M.; Hamill, P.; Swissler, T. J.; Mccormick, M. P.

    1983-01-01

    Measurements of the stratospheric aerosol by SAM II during the northern and southern winters of 1979 showed a pronounced increase in extinction on occasions when the temperature fell to a low value (below 200 K). The correlation between extinction and temperature is evaluated on the basis of thermodynamic considerations. As the temperature falls, the hygroscopic aerosols absorb water vapor from the atmosphere, growing as they do so. The effect of the temperature on the size distribution and composition of the aerosol is determined, and the optical extinction at 1 micron wavelength is calculated using Mie scattering theory. The theoretical predictions of the change in extinction with temperature and humidity are compared with the SAM II results at 100 mb, and the water vapor mixing ratio and aerosol number density are inferred from these results. A best fit of the theoretical curves to the SAM II data gives a water vapor content of 5-6 ppmv, and a total particle number density of 6-7 particles/cu cm.

  11. Seasonal and Interannual Variability of Polar Stratospheric Cloud Optical Depth

    NASA Astrophysics Data System (ADS)

    Pitts, M. C.; Poole, L. R.; Thomason, L. W.; Damadeo, R. P.

    2013-12-01

    In addition to their important role in ozone depletion, polar stratospheric clouds (PSCs) may also impact stratospheric radiation and dynamics. Earlier studies indicated that PSCs could significantly affect radiative heating rates, but the magnitude and even the sign of the effect varied greatly from study to study, depending on many factors, e.g. PSC optical depth and underlying tropospheric cloud cover. A more recent study, which assumed nominal PSC conditions of 100% cloud fraction and visible optical depth of 0.01 for non-ice PSCs and 0.04 for ice PSCs, suggested that PSCs could produce significant perturbations to the radiative heating rates in the Antarctic stratosphere. A comprehensive evaluation of the radiative effects of PSCs requires more accurate knowledge of PSC characteristics over the entire polar region and throughout complete seasons. With the advent of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission in 2006, a more complete picture of PSC composition and occurrence is now emerging. The polarization-sensitive CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) lidar system onboard the CALIPSO spacecraft is acquiring, on average, over 300,000 backscatter profiles per day at latitudes poleward of 55° (including the polar night region up to 82°), providing a unique opportunity to examine the distribution of PSC optical depth on vortex-wide scales and over entire PSC seasons. In this paper, we describe an approach to calculate PSC optical depth from the CALIOP 532-nm attenuated backscatter measurements. We retrieve the PSC extinction profile downward from cloud top using a composition-dependent extinction-to-backscatter ratio and then integrate the extinction profile to derive PSC optical depth. We then examine this multi-year PSC optical depth record to determine the spatial and seasonal variability for the Arctic and Antarctic, respectively. Multi-year composites provide insight to the interannual

  12. Factors That Influence Polar Stratospheric Cloud Formation Over Antarctica

    NASA Astrophysics Data System (ADS)

    Steele, H.; Lumpe, J.; Bevilacqua, R.; Hoppel, K.; Turco, R.

    2001-05-01

    Polar stratospheric clouds (PSCs), the precursors of springtime ozone loss in the polar stratosphere, are formed under the conditions of extreme cold found in the winter polar stratosphere. Analysis of the first satellite observations of these clouds concluded that unrealistically high concentrations of water vapor would be required to account for their formation by dissolution of sulfate aerosols alone, and that freezing to ice, which would require a lower water vapor mixing ratio, was therefore more likely. Freezing to water ice is now thought to be only one of the plausible mechanisms for cloud formation, and the resultant clouds have been labelled type II PSCs. More recent observations of PSCs by in-situ and satellite instruments have revealed their nature to be more heterogeneous. Lidar measurements have recorded a wide range of depolarisations which suggest the presence of both liquid and frozen particles. It is now thought that possible compositions include nitric acid trihydrate (NAT) (type Ia PSCs), nitric acid dihydrate (NAD) and supercooled ternary solutions (STS) of sulfuric acid, nitric acid and water (type Ib clouds). Although there are plausible and well-accepted mechanisms for cloud formation, there remain many unanswered questions, and modellers have been unable to explain all the observations within the scope of a single theory. Many observations are best be explained by a model in which PSCs are ternary solution droplets, but with a small fraction forming NAT primarily in conjunction with water ice after exposure to temperatures below the ice frost point. It has therefore been suggested that perhaps temperature history, as well as ambient temperature, plays a role in determining which clouds form. It is also thought that rapid cooling caused by orographically induced lee-waves might trigger the crystallisation of NAT from STS droplets. Some investigators have hypothesized that exposure time to temperatures below the NAT frost point are a

  13. 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

  14. Evolution of polar stratospheric clouds during the Antarctic winter

    NASA Technical Reports Server (NTRS)

    Ramaswamy, V.

    1988-01-01

    The occurrence of Polar Stratospheric Clouds (PSCs), initially inferred from satellite measurements of solar extinction, have now also been noted by the recent scientific expeditions in the Antarctic. The presence of such clouds in the Antarctic has been postulated to play a significant role in the depletion of ozone during the transition from winter to spring. The mechanisms suggested involve both dynamical and chemical processes which, explicity or implicitly, are associated with the ice particles constituting the PSCs. It is, thus, both timely and necessary to investigate the evolution of these clouds and ascertain the nature and magnitude of their influences on the state of the Antarctic stratosphere. To achieve these objectives, a detailed microphysical model of the processes governing the growth and sublimation of ice particles in the polar stratosphere was developed, based on the investigations of Ramaswamy and Detwiler. The present studies focus on the physical processes that occur at temperatures below those required for the onset of ice deposition from the vapor phase. Once these low temperatures are attained, the deposition of water vapor onto nucleation particles becomes extremely significant. First, the factors governing the magnitude of growth and the growth rate of ice particles at various altitudes are examined. Second, the ice phase mechanisms are examined in the context of a column model with altitudes ranging from 100 to 5 mb pressure levels. The column microphysical model was used to perform simulations of the cloud evolution, using the observed daily temperatures. The effect due to the growth of the particles on the radiation fields are also investigated using a one dimensional radiative transfer model. Specifically, the perturbations in the longwave cooling and that in the shortwave heating for the late winter/early spring time period are analyzed.

  15. On the temperature dependence of polar stratospheric clouds

    SciTech Connect

    Fiocco, G.; Cacciani, M.; Di Girolamo, P. ); Fua, D. CNR De Luisi, J. )

    1991-03-01

    Polar stratospheric clouds were frequently observed by lidar at the Amundsen-Scott South Pole Station during May-October 1988. The dependence of the backscattering cross section on the temperature can be referred to transitions of the HNO{sub 3}/H{sub 2}O system: it appears possible to distinguish the pure trihydrate from the mixed ice-trihydrate phase in the composition of the aerosol and, in some cases, to bracket the HNO{sub 3} and H{sub 2}O content of the ambient gas, and to provide indications on the size of the particles.

  16. Arctic polar stratospheric cloud observations by airborne lidar

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Lidar observations obtained from January 24 to February 2, 1989, during the Airborne Arctic Stratospheric expedition (AASE) mission further support the existence of two distinct classes (Types 1 and 2) of polar stratospheric clouds (PSCs). Most of the Type 1 PSCs observed were formed by rapid adiabatic cooling and exhibited very low depolarization ratios and low-to-intermediate scattering ratios. Type 2 PSCs were observed in regions of lowest temperature and showed much larger depolarization and scattering ratios, as would be expected from larger ice crystals. PSCs with low scattering ratios but moderate depolarization ratios were observed near the center of the vortex on one flight. These may have been either sparse Type 2 PSCs or Type 1 PSCs formed by less rapid cooling.

  17. 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.

  18. Airborne lidar observations in the wintertime Arctic stratosphere - Polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Browell, E. V.; Ismail, S.; Carter, A. F.; Higdon, N. S.; Butler, C. F.; Robinette, P. A.; Toon, O. B.; Schoeberl, M. R.

    1990-01-01

    Polar stratospheric cloud (PSC) distributions in the wintertime Arctic stratosphere and their optical characteristics were measured with a multiwavelength airborne lidar system as part of the 1989 Airborne Arctic Stratospheric Expedition. PSCs were observed on 10 flights between January 6 and February 2, 1989, into the polar vortex. The PSCs were found in the 14-27 km altitude range in regions where the temperatures were less than 195 K. Two types of aerosols with different optical characteristics (Types 1a and 1b) were observed in PSCs thought to be composed of nitric acid trihydrate. Water ice PSCs (Type 2) were observed to have high scattering ratios (greater than 10) and high aerosol depolarizations (greater than 10 percent) at temperatures less than 190 K.

  19. 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.

  20. 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.

  1. Reactions on sulphuric acid aerosol and on polar stratospheric clouds in the Antarctic stratosphere

    SciTech Connect

    Wolff, E.W.; Mulvaney, R.

    1991-06-01

    Heterogeneous chemistry producing active chlorine has been identified as crucial to Antarctic ozone depletion. Most attention has focused on reactions on solid polar stratospheric cloud (PSC) particles, although there is still no satisfactory understanding of the microchemical incorporation of HCl in PSCs. The alternative mechanism involving sulphuric acid aerosol as the reaction surface has been considered at lower latitudes, but its role in the special conditions of the polar stratosphere has been largely ignored. Recent data from the Antarctic stratosphere have suggested the HCl is present in sulphuric acid aerosol that remains liquid even at the lowest stratospheric temperatures. The available laboratory data show that cold, relatively dilute, sulphuric acid is particularly able to take up HCl that is available for reaction provided the aerosol remains liquid. Fast heterogeneous reaction rates compared to those at mid-latitudes will produce active chlorine rapidly. Since the aerosol is present with significant surface area throughout the lower stratosphere, it should be very effective for heterogeneous reaction once temperatures drop. These surfaces, rather than PSCs, could host the initial conversion of Cl to its active form over the Antarctic.

  2. 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.

  3. 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 mechanisms thought to be responsible for ozone depletion in the Antarctic and the Arctic. Reactions on 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 I PCS's obtained in Antarctica in September 1987, using recently measured optical constraints of the various compounds that might be present in PSC's. We find that these PSC's were not composed of nitric acid trihydrate but instead had a more complex composition 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 PSC's 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.

  4. 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.

  5. 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

  6. Polar stratospheric cloud climatology based on Stratospheric Aerosol Measurement II observations from 1978 to 1989

    NASA Technical Reports Server (NTRS)

    Poole, Lamont R.; Pitts, Michael C.

    1994-01-01

    The probability of polar stratospheric cloud (PSC) occurrence in the Antarctic and Arctic has been estimated using Stratospheric Aerosol Measurement (SAM) II aerosol extinction data from 1978 to 1989. Antarctic PSCs are typically observed by SAM II from mid-May to early November, with a maximum zonal average probability of about 0.6 at 18-20 km in August. The typical Arctic PSC season extends only from late November to early March, with a peak zonal average probability of about 0.1 in early February at 20-22 km. There is considerable year-to-year variability in Arctic PSC sightings because of changes in the dynamics of the northern polar vortex. Year-to-year variability in Antarctic sightings is most prominent in the number of late season clouds. Maximum PSC sighting probabilities in both polar regions occur in the region from 90 deg W through the Greenwich meridian to 90 deg E, where temperatures are coldest on average. Arctic sighting probabilities approach zero outside this region, but clouds have been sighted in the Antarctic at all longitudes during most months. Inferred PSC formation temperatures remain constant throughout the Arctic winter and are similar to those in early Antarctic winter. PSC formation temperatures in the Antarctic drop markedly in the 15 to 20-km region by September, a pattern consistent with the irreversible loss of HNO3 and H2O vapor in sedimenting PSC particles.

  7. 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.

  8. 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

  9. 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.

  10. Reactions on sulphuric acid aerosol and on polar stratospheric clouds in the Antarctic stratosphere

    NASA Astrophysics Data System (ADS)

    Wolff, E. W.; Mulvaney, R.

    1991-06-01

    Ways that HCl could be present in sulphuric acid areosol that remains liquid even at the lowest stratospheric temperatures are examined in the light of new field data and of laboratory data. Evidence is gathered to show that reactions occurring on liquid sulphuric acid aerosol may be those that initially convert Cl to its active form. It is proposed that as the temperature falls, sulphuric acid aerosol absorbs water until about 198 K, where it contains only 50 percent H2SO4, so that HCl can be absorbed in appreciable quantities. It is suggested that the sulphuric acid aerosol may still be present with a surface area comparable to the polar stratospheric clouds. Only if sulphuric acid aerosol is frozen is it likely that reactions on PSCs will dominate.

  11. Polar stratospheric clouds: A high latitude warming mechanism in an ancient greenhouse world

    NASA Astrophysics Data System (ADS)

    Sloan, L. Cirbus; Pollard, D.

    The presence of water vapor clouds in the stratosphere produces warming in excess of tropospheric greenhouse warming, via radiative warming in the lower stratosphere. The stratospheric clouds form only in regions of very low temperature and so the warming produced by the clouds is concentrated in polar winter regions. Results from a paleoclimate modeling study that includes idealized, prescribed polar stratospheric clouds (PSCs) show that the clouds cause up to 20°C of warming at high latitude surfaces of the winter hemisphere, with greatest impact in oceanic regions where sea ice is reduced. The modeled temperature response suggests that PSCs may have been a significant climate forcing factor for past time intervals associated with high concentrations of atmospheric methane. The clouds and associated warming may help to explain long-standing discrepancies between model-produced paleotemperatures and geologic proxy temperature interpretations at high latitudes, a persistent problem in studies of ancient greenhouse climates.

  12. Modelling Liquid Particle Composition In Polar Stratospheric Clouds

    NASA Astrophysics Data System (ADS)

    Lowe, D.; MacKenzie, A. R.

    Polar Stratospheric Clouds (PSCs) are thought to be composed of solid ni- tric acid trihydrate (NAT) particles, water ice particles, or supercooled liquid HNO3/H2SO4/H2O particles under different conditions and depending on the ther- mal history of the air mass. The solid particles are believed to form by the freezing of the liquid particles, the rate of which depends on the composition and size of the liquid particles. Lagrangian-in-radius-space numerical schemes have been used be- fore to study particle composition across the PSC size spectrum, in simple box model runs and in domain-filling Lagrangian studies. However these models were not de- signed to be compatible with global chemistry and transport models (CTMs), which currently model PSCs by assuming equilibrium with the atmosphere.We report here on an adaptation of a continuous (Eulerian-in-radius) distribution scheme, modelling the evolution of liquid PSC particles in non-equilibrium conditions. It uses an effi- cient numerical scheme, designed to be compatible with CTMs. Results from the new scheme have been validated against analytical solutions, and corroborate the compo- sition gradients across the size distribution under rapid cooling conditions that were reported in earlier studies.

  13. A study of Type I polar stratospheric cloud formation

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Turco, R. P.; Drdla, K.; Jacobson, M. Z.; Toon, O. B.

    1994-01-01

    Mechanisms for the formation of Type I (nitric acid-based) polar stratospheric clouds (PSCs) are discussed. If the pre-existing sulfate aerosols are liquid prior to PSC formation, then nitric acid particles (Type Ib) form by HNO3 dissolution in aqueous H2SO4 solution droplets. This process does not require a nucleation step for the formation of HNO3 aerosols, so most pre-existing aerosols grow to become relatively small HNO3-containing particles. At significantly lower temperatures, the resulting supercooled solutions (Type Ib) may freeze to form HNO3 ice particles (Type Ia). If the pre-existing sulfate aerosols are initially solid before PSC formation, then HNO3 vapor can be deposited directly on the frozen sulfate particles. However, because an energy barrier to the condensation exists a nucleation mechanism is involved. Here, we suggest a unique nucleation mechanism that involves formation of HNO3/H20 solutions on the sulfate ice particles. These nucleation processes may be highly selective, resulting in the formation of relatively small number of large particles.

  14. 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.

  15. 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

  16. 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.; hide

    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.

  17. Characteristics of polar stratospheric clouds during the formation of the Antarctic ozone hole

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    Measured properties of Antarctic polar stratospheric clouds are described, and the possible relationship between the clouds and the formation of the ozone hole is considered. It is shown that the ozone hole develops and the clouds dissipate in the same place and at the same time. There may be a causal relationship between cloud particle evaporation and ozone depletion. A heterogeneous mechanism involving chemical reactions in the cloud droplets is suggested.

  18. 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.

  19. Temperature histories in liquid and solid polar stratospheric cloud formation

    NASA Astrophysics Data System (ADS)

    Larsen, Niels; Knudsen, Bjørn M.; Rosen, James M.; Kjome, Norman T.; Neuber, Roland; Kyrö, Esko

    1997-10-01

    Polar stratospheric clouds (PSCs) have been observed by balloonborne backscatter sondes from Alert, Thule, Heiss Island, Scoresbysund, Sodankylä, Søndre Strømfjord, and Ny Ȧlesund during winters 1989, 1990, 1995, and 1996 in 30 flights. The observations can be categorized into two main groups: type 1a and type 1b PSC particles. Type 1b PSCs show the characteristics expected from liquid ternary solution (HNO3/H2SO4/H2O) particles, consistent with model simulations. Type 1a PSCs are observed at all temperatures below the condensation temperature TNAT of nitric acid trihydrate (NAT), consistent with solid NAT composition. Air parcel trajectories have been calculated for all observations to provide synoptic temperature histories of the observed particles. A number of cases have been identified, where the particles have experienced temperatures close to or above the sulfuric acid tetrahydrate melting temperatures within 20 days prior to observation. This assures a knowledge of the physical phase (liquid) of the particles at this time, prior to observation. The subsequent synoptic temperature histories, between melting and the time of observation, show pronounced differences for type 1a and type 1b PSC particles, indicating the qualitative temperature conditions, necessary to generate solid type 1a PSCs. The temperature histories of type 1b particles show smoothly, in most cases monotonic, decreasing temperatures. The temperature can apparently decrease to the frost point without causing the particles to freeze. The type 1b PSC particles are mostly observed shortly after entering a cold region. The observed type 1a particles have spent several days at temperatures close to or below TNAT prior to observation, often associated with several synoptic temperature oscillations around TNAT, and the particles are observed in aged clouds. It appears that the PSC particles may freeze, if they experience synoptic temperatures below TNAT with a duration of at least 1 day

  20. 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.

  1. 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.

  2. Stratospheric water vapour and temperature variability and their effect on polar stratospheric cloud formation and existence in the Arctic

    NASA Astrophysics Data System (ADS)

    Khosrawi, Farahnaz; Urban, Joachim; Lossow, Stefan; Stiller, Gabriele; Weigel, Katja; Braesicke, Peter; Pitts, Michael C.; Murtagh, Donal

    2015-04-01

    Based on more than 10-years of satellite measurements from UARS/HALOE, Envisat/MIPAS, Odin/SMR, Aura/MLS and SciSat/ACE-FTS we investigate water vapour (H2O) variability in the northern hemisphere polar regions. We find from the observations a connection between cold winters and enhanced water vapour mixing ratios in the lower polar stratosphere (475 to 525 K). We perform a sensitivity study along air parcel trajectories to test how an increase of stratospheric water vapour of 1 ppmv or a temperature decrease of 1 K affects the time period during which polar stratospheric clouds (PSCs) can be formed and exist. Air parcel trajectories were calculated 6-days backward in time. The trajectories were started at the time and locations where PSCs were observed by CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder satellite observations) during the Arctic winter 2010/2011. We test the sensitivity of PSCs formation and existence to changes in H2O and temperature based on PSC observations during this winter since it was one of the coldest Arctic winters in the last decade. The polar vortex persisted over a period of four months, thus leading to extensive PSC formation. During this winter PSCs were detected by CALIPSO on 42 days. In total, 738 trajectories were calculated and analysed. The resulting statistic derived from the air parcel trajectories shows a clear prolongation of the time period where PSCs can be formed and exist when the temperature in the stratosphere is decreased by 1 K and H2O is increased by 1 ppmv. We derive an increase in time where the stratospheric air is exposed to temperatures below Tice and TNAT, respectively, by ~6000 h. Thus, changes in stratospheric water vapour and temperature can prolong PSC formation and existence and thus have a significant influence on the chemistry of the polar stratosphere.

  3. 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.

  4. Heterogeneous conversion of COF2 to HF in polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Wofsy, Steven C.; Yatteau, John H.; Salawitch, Ross J.; Mcelroy, Michael B.; Toon, Geoffrey C.

    1990-01-01

    It is argued that the reaction COF2 + H2O - 2HF + CO2 should proceed on surfaces of polar stratospheric clouds, based on laboratory evidence for this reaction in condensed phase and on analysis of column observations of HF during the Airborne Arctic Stratospheric Expedition. If the hypothesis is confirmed, observations of COF2 and HF could provide unambiguous indication of heterogeneous processing of polar air, and could help elucidate the influence of heterogeneous chemistry on concentrations of HCl, ClNO3, and chlorine oxide radicals.

  5. 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.

  6. Freezing of polar stratospheric clouds in orographically induced strong warming events

    NASA Astrophysics Data System (ADS)

    Tsias, A.; Prenni, A. J.; Carslaw, K. S.; Onasch, T. P.; Luo, B. P.; Tolbert, M. A.; Peter, Th.

    1997-09-01

    Results from laboratory experiments and microphysical modeling are presented that suggest a potential freezing nucleation mechanism for polar stratospheric cloud (PSC) particles above the water ice frost point (Tice). The mechanism requires very high HNO3 concentrations of about 58 wt% in the droplets, and leads to the freezing of nitric acid dihydrate (NAD) in a highly selective manner in the smallest droplets of an ensemble. In the stratosphere such liquid compositions are predicted to occur in aerosol droplets which are warmed adiabatically with rates of about +150 K/h from below 190 K to 194 K. Such rapid temperature changes have been observed in mountain leewaves that occur frequently in the stratosphere, clearly demonstrating the need for a stratospheric gravity wave climatology.

  7. The unsuitability of meteoritic and other nuclei for polar stratospheric cloud freezing

    NASA Astrophysics Data System (ADS)

    Biermann, U. M.; Presper, T.; Koop, T.; Mößinger, J.; Crutzen, P. J.; Peter, Th.

    Bulk freezing experiments have been performed with binary and ternary HNO3/H2SO4/H2O solutions containing original micrometeorites, ground samples of representative larger meteorites and other freezing nuclei of potential stratospheric importance. The experiments enable us to determine upper bounds for the heterogeneous freezing rates of sulfuric and nitric acid hydrates. Based on an analysis of the meteoritic mass flux from space and of the modifications meteorites undergo when entering the atmosphere, the resulting morphology and surface area of extraterrestrial material in the stratosphere are estimated. From this micrometeorites gained from Antarctica are shown to be a good proxy for meteoritic surfaces in the stratosphere. In combination with this analysis the freezing experiments suggest that heterogeneous nucleation rates on micrometeorites are too low to enhance freezing of polar stratospheric clouds above the frost point.

  8. Satellite Observations of Arctic and Antarctic Polar Stratospheric Clouds and Atmospheric Composition

    NASA Astrophysics Data System (ADS)

    Lambert, A.; Santee, M. L.; Wu, D. L.

    2012-12-01

    We present an overview of polar stratospheric clouds (PSCs) and atmospheric composition during the 2008-2012 Arctic and Antarctic seasons using A-Train measurements of lidar backscatter and gas phase concentrations of HNO3, H2O, HCl and ClO. The processes of denitrification, dehydration and chlorine activation are investigated. PSC types are classified using the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite which measures vertical profiles of aerosol and cloud backscatter at 532 nm (total and perpendicular polarization) and 1064 nm. Ambient temperature/pressure profiles and constituent gases are obtained from the Aura Microwave Limb Sounder (MLS). Since April 2008 these two instruments have flown in close formation in the A-Train, maintaining colocation across track to less than 10 km and with temporal sampling differences less than 30 seconds.

  9. 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.

  10. 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.

    2015-07-01

    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. Although in the polar regions no significant trend is found in the lower stratosphere, we found from the observations a correlation between cold winters and enhanced water vapour mixing ratios.

  11. 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.

  12. 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.

  13. 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.

  14. Polar stratospheric clouds at the South Pole in 1990: Lidar observations and analysis

    SciTech Connect

    Collins, R.L.; Bowman, K.P.; Gardner, C.S. )

    1993-01-20

    In December 1989 a Rayleigh/sodium lidar (589 nm) was installed at the Amundsen-Scott South Pole station, and was used to measure stratospheric aerosol, temperature, and mesospheric sodium profiles through October 1990. Observations of stratospheric aerosol and temperature are presented in this paper. Polar stratospheric clouds (PSCs) were first observed in late May at about 20 km. As the lower stratosphere cooled further, PSCs were observed throughout the 12-27 km altitude region, and remained there from mid-June until late August. Observations in early September detected no PSCs above 21 km. An isolated cloud was observed in mid-October. Throughout the winter the clouds had small backscatter ratios (< 10). Observations made at two wavelengths in July show that the clouds are predominately composed of nitric acid trihydrate with associated Angstrom coefficients between 0.2 and 3.7. Comparison of the lidar data and balloon borne frost point measurements in late August indicate that the nitric acid mixing ratio was less than 1.5 ppbv. Observations over periods of several hours show downward motions in the cloud layers similar to the phase progressions of upwardly-propagating gravity waves. The vertical phase velocities of these features ([approx] 4 cm/s) are significantly faster than the expected settling velocities of the cloud particles. Both the backscatter ratio profiles and the radiosonde horizontal wind profiles show 1-4 km vertical structures. This suggests that the kilometer-scale vertical structure of the PSCs is maintained by low frequency gravity waves propagating through the cloud layers. 24 refs., 9 figs., 4 tabs.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Lidar measurements of polar stratospheric clouds during the 1989 airborne Arctic stratospheric expedition

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Browell, Edward V.

    1991-01-01

    The Airborne Arctic Stratospheric Expedition (AASE) was conducted during January to February 1989 from the Sola Air Station, Norway. As part of this expedition, the NASA Langley Research Center's multiwavelength airborne lidar system was flown on the NASA Ames Research Center's DC-8 aircraft to measure ozone (O3) and aerosol profiles in the region of the polar vortex. The lidar system simultaneously transmitted laser beams at 1064, 603, 311, and 301.5 nm to measure atmospheric scattering, polarization and O3 profiles. Long range flights were made between Stavanger, Norway, and the North Pole, and between 40 deg W and 20 deg E meridians. Eleven flights were made, each flight lasting an average of 10 hours covering about 8000 km. Atmospheric scattering ratios, aerosol polarizations, and aerosol scattering ratio wavelength dependences were derived from the lidar measurements to altitudes above 27 km. The details of the aerosol scattering properties of lidar observations in the IR, VIS, and UV regions are presented along with correlations with the national meteorological Center's temperature profiles.

  5. An analysis of lidar observations of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Kinne, S.; Browell, E. V.; Jordan, J.

    1990-01-01

    Lidar observations by Browell et al. (1990) are interpreted using single scattering calculations for nonspherical particles and aerosol microphysical calculations. Many of the lidar observations are consistent with particles containing 10 ppbv of condensed nitric acid vapor and an equivalent mass of water. The lidar observations of these Type 1 clouds identify two subtypes, whose properties are deduced. Type 1b particles are spherical, or nearly spherical, and typically have radii near 0.5 micron; Type 1a particles are not spherical, and have a spherical volume equivalent radius exceeding 1.0 micron. Several factors may cause variations in the size of the particles. The most significant factors are the cooling rate and the degree to which the air parcels cool below the condensation point. Specific examples in which cooling rate and cooling point may have led to variations in particle size are found in the Browell et al. (1990) data set. Condensation of 1 ppmm of water or less is quantitatively sufficient to account for the magnitude of the lidar backscatter observed from water ice clouds. The ice particles are not spherical in shape. The sizes of particles in water ice clouds cannot be determined because they are much larger than the wavelength of the lidar.

  6. 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.

  7. 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.

  8. First temperature measurements within Polar Stratospheric Clouds with the Esrange lidar

    NASA Astrophysics Data System (ADS)

    Achtert, Peggy; Khaplanov, Mikhail; Khosrawi, Farahnaz; Gumbel, Jörg

    2013-04-01

    In the winter stratosphere polar stratospheric clouds (PSCs) provide the surface for heterogeneous reactions which transform stable chlorine and bromine species into their highly reactive ozone-destroying states. PSCs are classified into three types (PSC Ia: nitric acid di- or trihydrate crystals, NAD or NAT; PSC Ib: supercooled liquid ternary solutions, STS; PSC II: ice) according to their particle composition and to their physical phase. The formation of PSCs depends strongly on temperature. For a comprehensive understanding of such temperature-dependent processes in the lower stratosphere, lidar measurements using the rotational-Raman technique are most suitable. The rotational-Raman technique allows for temperature measurements without a priori assumptions of the state of the atmosphere. The technique is feasible in aerosol layers and clouds, such as PSCs. A rotational-Raman channel for temperature measurements in the upper troposphere and lower stratosphere was added to the Esrange lidar in late 2010. The Esrange lidar operates at Esrange (68°N, 21°E) near the Swedish city of Kiruna. By combining rotational-Raman measurements (4-35 km height) and the integration technique (30-80 km height), the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. Such measurements could be used to validate current lidar-based PSC classification schemes and the current understanding of PSC formation. The new capability of the instrument furthermore enables the studies of other clouds layers, temperature variations and exchange processes in the upper troposphere/lower stratosphere. These studies will take advantage of the geographical location of Esrange where mountain wave activity in the lee of the Scandinavian mountain range gives rise to a wide range of PSC growth conditions. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. Observations of ozone and polar stratospheric clouds at Heiss Island during winter 1988-1989

    NASA Astrophysics Data System (ADS)

    Rosen, J. M.; Kjome, N. T.; Khattatov, V. U.; Rudakov, V. V.; Iushkov, V. A.

    1992-05-01

    Simultaneous balloonborne measurements of ozone and polar stratospheric clouds (PSCs) were made over Heiss Island during the 1988-1989 winter. These soundings were supplemented with additional ozonesondes and meteorological information obtained from regular radiosondes and rocketsondes. The ozone measurements taken by themselves do not suggest a spring decrease in ozone over Heiss Island. However, a comparison with ozonesondes data from another location near the solar terminator can be interpreted as suggesting an approximately 20 percent ozone loss between 17.5 and 24 km in the outer vortex. This would roughly correspond to a loss of 10 Dobson units (DU) or 3-4 percent loss in total ozone column.

  15. 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.

  16. 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.

  17. The Arctic polar stratospheric cloud aerosol - Aircraft measurements of reactive nitrogen, total water, and particles

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    In situ aircraft measurements in the lower stratosphere are used to investigate the reactive nitrogen, NO(y), total water, and particle components of the polar stratospheric cloud (PSC) aerosol in the Arctic. The results are compared to findings from the Antarctic derived using similar measurements and interpretive techniques. The Arctic data show that particle volume well above background values is present at temperatures above the frostpoint, confirming the result from the Antarctic that the observed PSCs are not water ice particles. NO(y) measurements inside a PSC are enhanced above ambient values consistent with anisokinetic sampling of particles containing NO(y). In the Arctic data over long segments of several flights, calculations show saturation with respect to nitric acid trihydrate without significant PSC particle growth above background.

  18. 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.

  19. 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.

  20. Estimation of polar stratospheric cloud infrared extinction climatology using visible satellite observations

    NASA Technical Reports Server (NTRS)

    Pitts, Michael C.; Thomason, Larry W.

    1995-01-01

    Polar stratospheric clouds (PSC's) provide surfaces for heterogeneous processes which can dramatically alter the normal partitioning of odd nitrogen and chlorine families in the winter polar stratospheres, setting up conditions for significant ozone depletion as manifested in the springtime Antarctic ozone hole. The spatial and temporal distribution of PSC's is important for parameterizing PSC occurrence in multidimensional photochemical models whose use is essential for fully understanding observed Antarctic ozone losses as well as for accessing the possibility of a similar phemonenon occurring in the future in the Arctic. The Stratospheric Aerosol Measurement (SAM) 2 sensor, a single-channel (1mu m) photometer launched into a Sun-synchronous orbit aboard the Nimbus 7 satellite in October 1978, provided a unique database to establish the climatology of PSC's. Poole and Pitts (1994) used the record of high-latitude aerosol extinction obtained by SAM II from 1979-1989 to establish the climatology of PSC occurrences in the Arctic and Antarctic. Unfortunately, little information about PSC composition or type was detectable from the single-wavelength SAM II data.

  1. 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.

  2. 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.

  3. 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".

  4. 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.

  5. Freezing temperatures of H2SO4/HNO3/H2O mixtures: Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Song, Naihui

    1994-01-01

    The freezing temperatures of H2SO4/HNO3/H2O mixtures were systematically documented. Nitric acid was found to affect freezing significantly. Measurements show that nitric acid can cause substantial supercooling over a broad composition range. However, some ternary compositions, like to those in polar stratospheric clouds (PSCs), have high freezing temperatures. The freezing of PSC particles could be controlled by the temperature and vapor pressure of both nitric acid and water in a non-linear way. Formation of polar stratospheric clouds may be forecasted on the basic of conditions of temperature and vapor contents of water and nitric acid.

  6. Freezing temperatures of H2SO4/HNO3/H2O mixtures: Implications for polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Song, Naihui

    1994-01-01

    The freezing temperatures of H2SO4/HNO3/H2O mixtures were systematically documented. Nitric acid was found to affect freezing significantly. Measurements show that nitric acid can cause substantial supercooling over a broad composition range. However, some ternary compositions, like to those in polar stratospheric clouds (PSCs), have high freezing temperatures. The freezing of PSC particles could be controlled by the temperature and vapor pressure of both nitric acid and water in a non-linear way. Formation of polar stratospheric clouds may be forecasted on the basic of conditions of temperature and vapor contents of water and nitric acid.

  7. 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

  8. A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

    NASA Astrophysics Data System (ADS)

    Hoffmann, Lars; Spang, Reinhold; Orr, Andrew; Alexander, M. Joan; Holt, Laura A.; Stein, Olaf

    2017-02-01

    Atmospheric gravity waves yield substantial small-scale temperature fluctuations that can trigger the formation of polar stratospheric clouds (PSCs). This paper introduces a new satellite record of gravity wave activity in the polar lower stratosphere to investigate this process. The record is comprised of observations of the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite from January 2003 to December 2012. Gravity wave activity is measured in terms of detrended and noise-corrected 15 µm brightness temperature variances, which are calculated from AIRS channels that are the most sensitive to temperature fluctuations at about 17-32 km of altitude. The analysis of temporal patterns in the data set revealed a strong seasonal cycle in wave activity with wintertime maxima at mid- and high latitudes. The analysis of spatial patterns indicated that orography as well as jet and storm sources are the main causes of the observed waves. Wave activity is closely correlated with 30 hPa zonal winds, which is attributed to the AIRS observational filter. We used the new data set to evaluate explicitly resolved temperature fluctuations due to gravity waves in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis. It was found that the analysis reproduces orographic and non-orographic wave patterns in the right places, but that wave amplitudes are typically underestimated by a factor of 2-3. Furthermore, in a first survey of joint AIRS and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite observations, nearly 50 gravity-wave-induced PSC formation events were identified. The survey shows that the new AIRS data set can help to better identify such events and more generally highlights the importance of the process for polar ozone chemistry.

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

    NASA Astrophysics Data System (ADS)

    Khosrawi, F.; Urban, J.; Pitts, M. C.; Voelger, P.; Achtert, P.; Kaphlanov, M.; Murtagh, D.; Fricke, K.-H.

    2011-04-01

    The sedimentation of HNO3 containing Polar Stratospheric Cloud (PSC) particles leads to a permanent removal of HNO3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion. The polar vortex in the Arctic winter 2009/2010 was very cold and stable between end of December and end of January. Strong denitrification was observed in the Arctic in mid of January by the Odin Sub Millimetre Radiometer (Odin/SMR) which was the strongest denitrification that had been observed in the entire Odin/SMR measuring period (2001-2010). Lidar measurements of PSCs were performed in the area of Kiruna, Northern Sweden with the IRF (Institutet för Rymdfysik) lidar and with the Esrange lidar in January 2010. The measurements show that PSCs were present over the area of Kiruna during the entire period of observations. The formation of PSCs during the Arctic winter 2009/2010 is investigated using a microphysical box model. Box model simulations are performed along air parcel trajectories calculated six days backward according to the PSC measurements with the ground-based lidar in the Kiruna area. From the temperature history of the trajectories and the box model simulations we find two PSC regions, one over Kiruna according to the measurements made in Kiruna and one north of Scandinavia which is much colder, reaching also temperatures below Tice. Using the box model simulations along backward trajectories together with the observations of Odin/SMR, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and the ground-based lidar we investigate how and by which type of PSC particles the denitrification that was observed during the Arctic winter 2009/2010 was caused. From our analysis we find that due to an unusually strong synoptic cooling event in mid January, ice particle formation on NAT may be a possible mechanism that caused denitrification during the Arctic winter 2009/2010.

  10. Heterogeneous formation of polar stratospheric clouds-nucleation of nitric acid trihydrate (NAT) in the arctic stratosphere

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    Satellite based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current theory, 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 on the surface of dust or meteoritic particles. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along tens of thousands of trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarisation (CALIOP) observation points. Comparing the optical properties of the modelled NAT PSCs with these observations enables 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 and is simple to implement in models. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Optical effects of polar stratospheric clouds on the retrieval of TOMS total ozone

    NASA Technical Reports Server (NTRS)

    Torres, O.; Ahmad, Z.; Herman, J. R.

    1992-01-01

    Small areas of sharply reduced ozone density appear frequently in the maps produced from polar region total ozone mapping spectrometer (TOMS) data. These mini-holes are of the order of 1000 km in extent with a lifetime of a few days. On the basis of measurements from ground-based instruments, balloon-borne ozonesondes, and simultaneous measurements of aerosol and ozone concentrations during aircraft flights in the Arctic and Antarctic regions, the appearance of polar stratospheric clouds (PSCs) are frequently associated with false reductions in ozone derived from the TOMS albedo data. By combining radiative transfer calculations with the observed PSC and ozone data, it is shown that PSCs located near or above the ozone density maximum (with optical thickness greater than 0.1) can explain most of the differences between TOMS ozone data and ground or in situ ozone measurements. Several examples of real and false TOMS mini-hole phenomenon are investigated using data from the 1989 Airborne Arctic Stratospheric Expedition (AASE) and from balloon flights over Norway and Sweden.

  15. 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.

  16. Heterogeneous formation of polar stratospheric clouds - Part 2: Nucleation of ice on synoptic scales

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  17. Heterogeneous formation of polar stratospheric clouds - Part 2: Nucleation of ice on synoptic scales

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  18. Freezing of sulfuric and nitric acid solutions: Implications for polar stratospheric cloud formation

    NASA Astrophysics Data System (ADS)

    Salcedo Gonzalez, Dara

    2000-12-01

    Polar Stratospheric Clouds (PSCs) play an important role in ozone chemistry during the polar winter. The magnitude of their effect depends on their phase, composition and formation mechanism, which are not fully understood yet. In order to understand how liquid PSCs freeze, two apparatus were designed to study the freezing behavior of small drops using a Fourier transform infrared (FTIR) spectrometer and an optical microscope. Sulfuric acid aqueous drops with composition of 10 to 50 wt % were studied with the FTIR apparatus. The surface on which the drops stand caused heterogeneous nucleation of ice, but not of the sulfuric acid hydrates. The more concentrated solutions (>40 wt %) supercooled to 130 K without freezing. Below 150 K these solutions formed an amorphous solid, which liquefied upon warming. Drops with composition of 40 to 64 wt % HNO3 were prepared and their phase transitions were detected with the optical microscope apparatus. Freezing temperatures of the drops were determined and homogeneous nucleation rates of nitric acid dihydrate (JNAD) and nitric acid trihydrate (JNAT) between 170 and 190 K were calculated. JNAT and JNAD depend predominantly on the saturation of the solid in the liquid solution: higher saturation ratios correspond to higher nucleation rates. Classical nucleation theory was used to parameterize this relation. Since the saturation ratios of NAD and NAT vary with temperature and composition in different ways, NAT or NAD can form preferentially under different conditions. Evidence was found that NAD catalyzes the nucleation of NAT below ~183 K. Mullite, cristobalite and alumina were tested as possible heterogeneous nuclei of volcanic origin for PSCs. They catalyze freezing of NAD and NAT at temperatures below 179 K, which are too low to be stratospherically important. The results suggest that the largest drops in a PSC will freeze homogeneously if the stratospheric temperature remains below the NAT condensation temperature for more

  19. Formation of mixed-phase particles during the freezing of polar stratospheric ice clouds.

    PubMed

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki; Mayer, Erwin; Loerting, Thomas

    2010-03-01

    Polar stratospheric clouds (PSCs) are extremely efficient at catalysing the transformation of photostable chlorine reservoirs into photolabile species, which are actively involved in springtime ozone-depletion events. Why PSCs are such efficient catalysts, however, is not well understood. Here, we investigate the freezing behaviour of ternary HNO₃-H₂SO₄-H₂O droplets of micrometric size, which form type II PSC ice particles. We show that on freezing, a phase separation into pure ice and a residual solution coating occurs; this coating does not freeze but transforms into glass below ∼150 K. We find that the coating, which is thicker around young ice crystals, can still be approximately 30 nm around older ice crystals of diameter about 10 µm. These results affect our understanding of PSC microphysics and chemistry and suggest that chlorine-activation reactions are better studied on supercooled HNO₃-H₂SO₄-H₂O solutions rather than on a pure ice surface.

  20. 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.

  1. Simulation of polar stratospheric clouds in the chemistry-climate-model EMAC via the submodel PSC

    NASA Astrophysics Data System (ADS)

    Kirner, O.; Ruhnke, R.; Buchholz-Dietsch, J.; Jöckel, P.; Brühl, C.; Steil, B.

    2011-03-01

    The submodel PSC of the ECHAM5/MESSy Atmospheric Chemistry model (EMAC) has been developed to simulate the main types of polar stratospheric clouds (PSC). The parameterisation of the supercooled ternary solutions (STS, type 1b PSC) in the submodel is based on Carslaw et al. (1995b), the thermodynamic approach to simulate ice particles (type 2 PSC) on Marti and Mauersberger (1993). For the formation of nitric acid trihydrate (NAT) particles (type 1a PSC) two different parameterisations exist. The first is based on an instantaneous thermodynamic approach from Hanson and Mauersberger (1988), the second is new implemented and considers the growth of the NAT particles with the aid of a surface growth factor based on Carslaw et al. (2002). It is possible to choose one of this NAT parameterisation in the submodel. This publication explains the background of the submodel PSC and the use of the submodel with the goal of simulating realistic PSC in EMAC.

  2. 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.

  3. Long-term measurements of Polar Stratospheric Clouds with the Esrange lidar

    NASA Astrophysics Data System (ADS)

    Achtert, Peggy; Tesche, Matthias; Blum, Ulrich

    2014-05-01

    Polar Stratospheric Clouds (PSCs) play a key role for ozone depletion in the polar stratosphere whose magnitude depends on the type of PSC and its lifetime and extent. PSCs are classified into three types (PSC Ia: nitric acid di- or trihydrate crystals, NAD or NAT; PSC Ib: supercooled liquid ternary solutions, STS; PSC II: ice) according to their particle composition and to their physical phase. This study presents long-term statistics of PSC occurrence from measurements with the lidar system at the Esrange Space Centre (68°N, 21°E), northern Sweden. The study gives an overview of the occurrence frequency of different PSC types in connection to the prevailing meteorological conditions for the northern hemispheric winters from 1996/97 to 2013/14. During these 18 years, most of the measurements were conducted in January. The geographical location of Esrange in the lee of the Scandinavian mountain range allows for the observation of a wide range of PSC growth conditions due to mountain-wave activity. The Esrange lidar data set contains hourly mean values of the parallel and perpendicularly polarized backscatter ratio and the linear particle depolarization ratio - all measured at 532 nm. These parameters are used for PSC classification. The lowest occurrence frequency is found for PSCs of type II (6% for the entire period). This low occurrence rate is reasonable since PSCs of type II are formed at temperatures below the ice-frost point. Such temperatures are rarely reached in the Arctic polar vortex. Most of the observations between 1997 and 2014 showed low particle depolarization ratios and low backscatter ratios according to which observed PSCs were classified as type Ib (47%) or mixtures (33%). The remaining 13% of the observation were classified as type Ia PSCs (NAT particles).

  4. 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.

  5. 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.

    2016-12-01

    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 airmass 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Khosrawi, F.; Urban, J.; Pitts, M. C.; Voelger, P.; Achtert, P.; Kaphlanov, M.; Santee, M. L.; Manney, G. L.; Murtagh, D.; Fricke, K.-H.

    2011-08-01

    The sedimentation of HNO3 containing Polar Stratospheric Cloud (PSC) particles leads to a permanent removal of HNO3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion. The polar vortex in the Arctic winter 2009/2010 was very cold and stable between end of December and end of January. Strong denitrification between 475 to 525 K was observed in the Arctic in mid of January by the Odin Sub Millimetre Radiometer (Odin/SMR). This was the strongest denitrification that had been observed in the entire Odin/SMR measuring period (2001-2010). Lidar measurements of PSCs were performed in the area of Kiruna, Northern Sweden with the IRF (Institutet för Rymdfysik) lidar and with the Esrange lidar in January 2010. The measurements show that PSCs were present over the area of Kiruna during the entire period of observations. The formation of PSCs during the Arctic winter 2009/2010 is investigated using a microphysical box model. Box model simulations are performed along air parcel trajectories calculated six days backward according to the PSC measurements with the ground-based lidar in the Kiruna area. From the temperature history of the backward trajectories and the box model simulations we find two PSC regions, one over Kiruna according to the measurements made in Kiruna and one north of Scandinavia which is much colder, reaching also temperatures below Tice. Using the box model simulations along backward trajectories together with the observations of Odin/SMR, Aura/MLS (Microwave Limb Sounder), CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and the ground-based lidar we investigate how and by which type of PSC particles the denitrification that was observed during the Arctic winter 2009/2010 was caused. From our analysis we find that due to an unusually strong synoptic cooling event in mid January, ice particle formation on NAT may be a possible formation mechanism during

  8. 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

  9. A synopsis of CALIPSO Polar Stratospheric Cloud Observations from 2006-2014

    NASA Astrophysics Data System (ADS)

    Pitts, Michael C.; Poole, Lamont R.

    2014-10-01

    Polar stratospheric clouds (PSCs) are known to play key roles in the springtime chemical depletion of ozone at high latitudes. PSC particles 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, 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. CALIOP began data collection in mid-June 2006 and has since acquired, on average, over 300,000 backscatter profiles daily at latitudes between 55° and 82° in both hemispheres. PSCs are detected in the CALIOP backscatter profiles as enhancements above the background aerosol in either 532-nm scattering ratio (the ratio of total-to-molecular backscatter) or 532-nm perpendicular-polarized backscatter. CALIOP PSCs are separated into composition classes based on the ensemble 532- nm scattering ratio 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 provide an overview of the CALIOP PSC measurements 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 eight-year data record.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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%.

  16. New Insight into Polar Stratospheric Cloud Processes from A-Train Observations

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Polar stratospheric clouds (PSCs) play essential roles in the chemical depletion of stratospheric ozone at high latitudes. Heterogeneous reactions occurring on PSC particles, primarily supercooled ternary (H2SO4-H2O-HNO3) solution (STS) droplets, convert stable chlorine reservoir species to highly reactive ozone-destructive forms. Also, sedimentation and evaporation of large nitric acid trihydrate (NAT) particles irreversibly redistributes odd nitrogen and prolongs ozone depletion by slowing the reformation of stable chlorine reservoirs. Even after three decades of research, significant gaps in our understanding of PSC processes still exist, particularly concerning NAT nucleation and the extent to which chlorine is activated on cold background aerosol prior to PSC formation. These uncertainties limit our ability to represent PSCs accurately in global models and call into question predictions of ozone recovery in a changing climate. PSC observations from the A-Train satellite constellation have stimulated a number of new research activities that have both extended and challenged our knowledge of PSC processes and modeling capabilities. Specifically, the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite is providing information on PSC morphology and composition in unprecedented detail, while the Microwave Limb Sounder (MLS) on the Aura satellite is providing nearly coincident measurements of gas-phase HNO3 and H2O, the major constituents of all PSC particles. The combined analyses of these datasets enable better PSC composition discrimination and provide valuable new insight into processes such as PSC-catalyzed chlorine activation and PSC particle growth kinetics. The more than ten years of CALIOP and MLS measurements have uniquely captured the primary aspects of the seasonal and multi-year variability of PSCs in the Arctic and Antarctic and are enabling the

  17. 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.

  18. Effects of Polar Stratospheric Clouds in the Nimbus 7 LIMS Version 6 Data Set

    NASA Technical Reports Server (NTRS)

    Remsberg, Ellis; Harvey, V. Lynn

    2016-01-01

    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 1-2K 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 194K 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 550K surface. Seven-month time series of the distributions of LIMS O3 and HNO3 are shown based

  19. Effects of Polar Stratospheric Clouds in the Nimbus 7 LIMS Version 6 Data Set

    NASA Technical Reports Server (NTRS)

    Remsberg, Ellis; Harvey, V. Lynn

    2016-01-01

    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 1-2K 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 194K 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 550K surface. Seven-month time series of the distributions of LIMS O3 and HNO3 are shown based

  20. 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

  1. Heterogeneous chemistry on Antarctic polar stratospheric clouds - A microphysical estimate of the extent of chemical processing

    NASA Technical Reports Server (NTRS)

    Drdla, K.; Turco, R. P.; Elliott, S.

    1993-01-01

    A detailed model of polar stratospheric clouds (PSCs), which includes nucleation, condensational growth. and sedimentation processes, has been applied to the study of heterogeneous chemical reactions. For the first time, the extent of chemical processing during a polar winter has been estimated for an idealized air parcel in the Antarctic vortex by calculating in detail the rates of heterogeneous reactions on PSC particles. The resulting active chlorine and NO(x) concentrations at first sunrise are analyzed with respect to their influence upon the Antarctic ozone hole using a photochemical model. It is found that the species present at sunrise are primarily influenced by the relative values of the heterogeneous reaction rate constants and the initial gas concentrations. However, the extent of chlorine activation is also influenced by whether N2O5 is removed by reaction with HCl or H2O. The reaction of N2O5 with HCl, which occurs rapidly on type 1 PSCs, activates the chlorine contained in the reservoir species HCl. Hence the presence and surface area of type 1 PSCs early in the winter are crucial in determining ozone depletion.

  2. Heterogeneous chemistry on Antarctic polar stratospheric clouds - A microphysical estimate of the extent of chemical processing

    NASA Technical Reports Server (NTRS)

    Drdla, K.; Turco, R. P.; Elliott, S.

    1993-01-01

    A detailed model of polar stratospheric clouds (PSCs), which includes nucleation, condensational growth. and sedimentation processes, has been applied to the study of heterogeneous chemical reactions. For the first time, the extent of chemical processing during a polar winter has been estimated for an idealized air parcel in the Antarctic vortex by calculating in detail the rates of heterogeneous reactions on PSC particles. The resulting active chlorine and NO(x) concentrations at first sunrise are analyzed with respect to their influence upon the Antarctic ozone hole using a photochemical model. It is found that the species present at sunrise are primarily influenced by the relative values of the heterogeneous reaction rate constants and the initial gas concentrations. However, the extent of chlorine activation is also influenced by whether N2O5 is removed by reaction with HCl or H2O. The reaction of N2O5 with HCl, which occurs rapidly on type 1 PSCs, activates the chlorine contained in the reservoir species HCl. Hence the presence and surface area of type 1 PSCs early in the winter are crucial in determining ozone depletion.

  3. Gravity Waves in the Polar Stratosphere and Mesosphere and Their Relations with Ice Cloud Observed Sofie/AIM

    NASA Astrophysics Data System (ADS)

    Liu, X.; Yue, J.; Xu, J.; Wang, L.; Yuan, W.; Russell, J. M., III; Hervig, M. E.

    2014-12-01

    A six-years (2007-2013) temperature dataset from the Solar Occultation for Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite is used to extract gravity waves (GWs) in the polar stratosphere and mesosphere of both hemispheres. These data are continuous in the polar regions. The monthly mean GW potential energy (PE) increases exponentially with a scale height of ~13 km in the upper stratosphere and mesosphere. GWs are stronger in the winter than in the summer and exhibit strong annual variation. GWs are stronger in the southern polar region (SPR) than in the northern polar region (NPR) except in the summer months. This is likely because there are stronger and longer-lasting zonal wind jets in the SPR stratosphere, as revealed from Modern-Era Retrospective analysis for Research and Applications (MERRA) wind data. The longitudinal variations of PE in the winter polar stratosphere are consistent with the elevated regions. In the mesosphere, the longitudinal variations of PE do not vary with height significantly. The correlations between GW PE and the column ice water content (IWC, an indicator of the polar mesosphere cloud) exhibit longitudinal and annual variations.

  4. Microphysical Simulations of Polar Stratospheric Clouds Compared with Calipso and MLS Observations

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Toon, O. B.; Kinnison, D. E.; Lambert, A.; Brakebusch, M.

    2014-12-01

    Polar stratospheric clouds (PSCs) form in the lower stratosphere during the polar night due to the cold temperature inside the polar vortex. PSCs are important to understand because they are responsible for the formation of the Antarctic ozone hole and the ozone depletion over the Arctic. In this work, we explore the formation and evolution of STS particles (Super-cooled Ternary Solution) and NAT (Nitric-acid Trihydrate) particles using the SD-WACCM/CARMA model. SD-WACCM/CARMA couples the Whole Atmosphere Community Climate Model using Specific Dynamics with the microphysics model (CARMA). The 2010-2011 Arctic winter has been simulated because the Arctic vortex remained cold enough for PSCs from December until the end of March (Manney et al., 2011). The unusual length of this cold period and the presence of PSCs caused strong ozone depletion. This model simulates the growth and evaporation of the STS particles instead of considering them as being in equilibrium as other models do (Carslaw et al., 1995). This work also explores the homogeneous nucleation of NAT particles and derives a scheme for NAT formation based on the observed denitrification during the winter 2010-2011. The simulated microphysical features (particle volumes, size distributions, etc.) of both STS (Supercooled Ternary Solutions) and NAT particles show a consistent comparison with historical observations. The modeled evolution of PSCs and gas phase ozone related chemicals inside the vortex such as HCl and ClONO2 are compared with the observations from MLS, MIPAS and CALIPSO over this winter. The denitrification history indicate the surface nucleation rate from Tabazadeh et al. (2002) removes too much HNO3 over the winter. With a small modification of the free energy term of the equation, the denitification and the PSC backscattering features are much closer to the observations. H2O, HCl, O3 and ClONO2 are very close to MLS and MIPAS observations inside the vortex. The model underestimates ozone

  5. 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.

  6. Simulation of polar stratospheric clouds in the chemistry-climate-model EMAC via the submodel PSC

    NASA Astrophysics Data System (ADS)

    Kirner, O.; Ruhnke, R.; Buchholz-Dietsch, J.; Jöckel, P.; Brühl, C.; Steil, B.

    2010-11-01

    The submodel PSC of the ECHAM5/MESSy Atmospheric Chemistry model (EMAC) has been developed to simulate the main types of polar stratospheric clouds (PSC). The parameterisation of the supercooled ternary solutions (STS, type 1b PSC) in the submodel is based on Carslaw et al. (1995b), the thermodynamical approach to simulate ice particles (type 2 PSC) on Marti and Mauersberger (1993). For the formation of nitric acid trihydrate (NAT) particles (type 1a PSC) two different parameterisations exist. The first one is based on an instantaneous thermodynamical approach from Hanson and Mauersberger (1988), the second one (new implemented by Kirner, 2008) considers the growth of the NAT particles with aid of a surface growth factor based on Carslaw et al. (2002). Via namelist switches the NAT parameterisation, as well as some parameters for the NAT and ice formation can be chosen. This publication explains the background of the submodel PSC and the use of the submodel with the goal to simulate realistic PSC in EMAC.

  7. 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.

  8. 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

  9. Molecular activation by surface coordination: New model for HCl reactivity on water-ice polar stratospheric clouds

    SciTech Connect

    MacTaylor, R.S.; Gilligan, J.J.; Moody, D.J.; Castleman, A.W. Jr.

    1999-05-27

    The annual depletion of the ozone layer in the polar stratosphere has received considerable scrutiny, particularly in the area of conversion chemistry involving chlorine. Numerous studies have implicated polar stratospheric clouds (PSCs) as playing a fundamental role in the conversion of reservoir chlorine species, such as HCl and ClONO{sub 2}, into active forms of chlorine such as Cl{sub 2} Results of studies of the uptake of HCl by the deuterated analogue of protonated water clusters are reported. The successive uptake of nHCl n = 1--4 is observed, n = 2--4 appearing in a stepwise manner with a ratio of 6:1 D{sub 2}O/HCl for the bimolecular reaction products. This primary uptake scheme is observed over a range of pressures and temperatures. However, for increased flows of HCl, enhanced uptake is observed at a lower ratio of D{sub 2}O/HCl, a trend that is effected by an increased buffer gas pressure. Two distinctly dominant mechanisms of HCl uptake are operative: the bimolecular uptake of HCl in a 6:1 ratio with water and a subsequent association mechanism of HCl binding to water in a 3:1 ratio. The atmospheric implications are discussed along with a proposed molecular activation by surface coordination (MASC) model for HCl uptake and subsequent reactivity on polar stratospheric clouds.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1993-09-01

    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.

  12. 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.

  13. 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.

  14. Laboratory Growth of Ice Crystals Under Simulated Polar Stratospheric Cloud and High Altitude Cirrus Conditions at Temperatures Below -70 C

    NASA Astrophysics Data System (ADS)

    Bailey, M.; Hallett, J.; Peterson, H.; Petersen, D.

    2006-12-01

    A static diffusion chamber has been used to grow ice crystals at temperatures below -70 C under controlled conditions of temperature, pressure, and ice supersaturation. Type 1 polar stratospheric cloud (PSC) particle growth was performed with frozen nitric acid solution drops in the presence of nitric acid and water vapor at temperatures between -75 C and -85 C. Type 2 PSC particle growth was performed with predominantly pure water at temperatures below -85 C. Ice crystals were also grown from pure water vapor over the same range of temperatures for comparison, nucleating on frozen sulfuric acid solution drops and on mineral dust particles. Linear, projected area, and volume growth rates are presented.

  15. 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.

  16. 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.

  17. 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).

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

    DTIC Science & Technology

    2009-05-01

    September. The effects of denitrification and dehumidification in the polar airmass can be seen most clearly in Au- gust. At that time, saturation with...August at nearly all levels), we would be better positioned to correlate cloud measurements with denitrification and dehumidification processes at the

  19. Determination of polar stratospheric cloud particle refractive indices by use of in situ optical measurements and T-matrix calculations.

    PubMed

    Scarchilli, Claudio; Adriani, Alberto; Cairo, Francesco; Di Donfrancesco, Guido; Buontempo, Carlo; Snels, Marcel; Moriconi, Maria Luisa; Deshler, Terry; Larsen, Niels; Luo, Beiping; Mauersberger, Konrad; Ovarlez, Joelle; Rosen, Jim; Schreiner, Jochen

    2005-06-01

    A new algorithm to infer structural parameters such as refractive index and asphericity of cloud particles has been developed by use of in situ observations taken by a laser backscattersonde and an optical particle counter during balloon stratospheric flights. All three main particles, liquid, ice, and a no-ice solid (NAT, nitric acid trihydrate) of polar stratospheric clouds, were observed during two winter flights performed from Kiruna, Sweden. The technique is based on use of the T-matrix code developed for aspherical particles to calculate the backscattering coefficient and particle depolarizing properties on the basis of size distribution and concentration measurements. The results of the calculations are compared with observations to estimated refractive indices and particle asphericity. The method has also been used in cases when the liquid and solid phases coexist with comparable influence on the optical behavior of the cloud to estimate refractive indices. The main results prove that the index of refraction for NAT particles is in the range of 1.37-1.45 at 532 nm. Such particles would be slightly prolate spheroids. The calculated refractive indices for liquid and ice particles are 1.51-1.55 and 1.31-1.33, respectively. The results for solid particles confirm previous measurements taken in Antarctica during 1992 and obtained by a comparison of lidar and optical particle counter data.

  20. Determination of polar stratospheric cloud particle refractive indices by use of in situ optical measurements and T-matrix calculations

    NASA Astrophysics Data System (ADS)

    Scarchilli, Claudio; Adriani, Alberto; Cairo, Francesco; di Donfrancesco, Guido; Buontempo, Carlo; Snels, Marcel; Moriconi, Maria Luisa; Deshler, Terry; Larsen, Niels; Luo, Beiping; Mauersberger, Konrad; Ovarlez, Joelle; Rosen, Jim; Schreiner, Jochen

    2005-06-01

    A new algorithm to infer structural parameters such as refractive index and asphericity of cloud particles has been developed by use of in situ observations taken by a laser backscattersonde and an optical particle counter during balloon stratospheric flights. All three main particles, liquid, ice, and a no-ice solid (NAT, nitric acid trihydrate) of polar stratospheric clouds, were observed during two winter flights performed from Kiruna, Sweden. The technique is based on use of the T-matrix code developed for aspherical particles to calculate the backscattering coefficient and particle depolarizing properties on the basis of size distribution and concentration measurements. The results of the calculations are compared with observations to estimated refractive indices and particle asphericity. The method has also been used in cases when the liquid and solid phases coexist with comparable influence on the optical behavior of the cloud to estimate refractive indices. The main results prove that the index of refraction for NAT particles is in the range of 1.37-1.45 at 532 nm. Such particles would be slightly prolate spheroids. The calculated refractive indices for liquid and ice particles are 1.51-1.55 and 1.31-1.33, respectively. The results for solid particles confirm previous measurements taken in Antarctica during 1992 and obtained by a comparison of lidar and optical particle counter data.

  1. 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

  2. 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

  3. Polar Stratospheric Cloud formation and denitrification during the Arctic winter 2009/2010 and 2010/2011

    NASA Astrophysics Data System (ADS)

    Khosrawi, Farahnaz; Urban, Joachim; Pitts, Michael C.; Kirner, Oliver; Braesicke, Peter; Santee, Michelle L.; Manney, Gloria L.; Murtagh, Donal

    2015-04-01

    The sedimentation of HNO3 containing polar stratospheric cloud particles leads to a permanent removal of HNO3 from the stratosphere. The so-called denitrification is an effect that plays an important role in stratospheric ozone depletion. The Arctic winter 2009/2010 and 2010/2011 were both quite unique. The Arctic winter 2010/2011 was one of the coldest winters on record leading to the strongest depletion of ozone measured in the Arctic. Though the Arctic winter 2009/2010 was rather warm in the climatological sense it was distinguished by an exceptionally cold stratosphere from mid December 2009 to mid January 2010 leading to prolonged PSC formation and significant denitrification. Model simulations and space-borne observations are used to investigate PSC formation and denitrification during these two winters. Model simulations were performed with the atmospheric chemistry-climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) and compared to observations by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations Satellite (CALIPSO) and the Odin Sub-Millimetre Radiometer (Odin/SMR) as well as with observations from the Microwave Limb Sounder on Aura (Aura/MLS). While PSCs were present during the Arctic winter 2010/2011 over nearly four months, from mid December to end of March, they were not as persistent as the ones that occurred during the shorter (one month) cold period during the Arctic winter 2009/2010. Although the PSC season during the Arctic winter 2009/2010 was much shorter than in 2010/2011, denitrification during the Arctic winter 2009/2010 was similar in magnitude than during 2010/2011.

  4. 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).

  5. Detection of global tropospheric clouds and polar stratospheric clouds over Antarctica using thermal infrared spectral data observed by TANSO-FTS/GOSAT

    NASA Astrophysics Data System (ADS)

    Someya, Yu; Imasu, Ryoichi; Ota, Yoshifumi; Saitoh, Naoko

    2014-05-01

    Global tropospheric cloud distribution was derived from thermal infrared band data observed by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse gases Observation SATellite (GOSAT). It is expected that this band has ability to detect optically thin clouds compared with Cloud and Aerosol Imager (CAI) which is the other sensor on GOSAT. In addition, polar stratospheric clouds (PSCs) which can be harder to detect than the tropospheric clouds because of high reflectivity or low temperature of the surface and their low optical thickness were also detected. We have modified CO2 slicing method which was developed as one of the cirrus cloud detection techniques using thermal infrared band data to detect thin clouds more stably. The pseudo spectral channels were defined as sets of several actual spectral channels between 700cm-1 and 750cm-1 which have weighting function peak height in a same height range for each 0.5km. These pseudo channels were optimized with simulation studies using a multi-scattering radiative transfer code, Polarized radiance System for Transfer of Atmospheric Radiation (Pstar) 3 for several temperature profile patterns prepared based on latitudes and temperature at 500hPa. GOSAT data was analyzed with the combination of these pseudo channels determined for each of observation points from these simulations and the results were compared with the observational results from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) / Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The comparisons about global cloud are based on the coincident observations in 2010. Monthly occurrences of Antarctic PSCs were compared for each grid area from June to September in 2010. As a result, the correlation coefficients in each month are 0.76, 0.71, 0.75, and 0.61 relatively. Though that is low value in September, it can be explained by decrease of occurrences.

  6. 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

  7. Influence of Mountain Waves and NAT Nucleation Mechanisms on Polar Stratospheric Cloud Formation at Local and Synoptic Scales during the 1999-2000 Arctic Winter

    DTIC Science & Technology

    2005-03-07

    B., Dörnbrack, A., Leut - becher, M., Volkert, H., Renger, W., Bacmeister, J., and Peter, T.: Particle microphysics and chemistry in remotely...observed moun- tain polar stratospheric clouds, J. Geophys. Res., 103, 5785– 5796, 1998a. Carslaw, K. S., Wirth, M., Tsias, A., Luo, B., Dörnbrack, A., Leut

  8. 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.

  9. 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.

  10. Polar Clouds

    NASA Image and Video Library

    2012-02-27

    With the changing of seasons comes changes in weather. This image from NASA 2001 Mars Odyssey spacecraft shows clouds in the north polar region. The surface is just barely visible in part of the image.

  11. Impact of Gravity Wave events on the properties of Polar Stratospheric Clouds over Antarctica from spaceborne lidar observations

    NASA Astrophysics Data System (ADS)

    Noel, V.; Chepfer, H.; Hertzog, A.

    2010-12-01

    The formation and properties of Polar Stratospheric Clouds (PSCs) are extremely dependent on their formation temperature. Depending on the stratospheric concentrations of chemical species, various temperature thresholds define PSC composition: Nitric Acid Trihydrate (NAT) or Sulfuric Ternary Solutions (STS) particles, ice crystals, or a mixture thereof. Most notably, ice-based PSCs (Type II in lidar observation terminology) require colder temperatures than NAT- or STS-based PSCs (Type Ia and Ib). On the other hand, ice-based PSC form in a relatively short time, while other PSCs require temperature to stay below their formation threshold for a much longer period (days or weeks). During the Antarctic winter, stratospheric temperatures are generally in a range conducive to the formation of Type Ia and Ib PSCs, even if their dominant nucleation mechanisms are still not well understood. Type II PSCs are rarer overall, as temperatures cold enough for their formation is less frequent. This description based on temperature is generally considered sufficient to explain the spatial and temporal distribution of PSCs. A recent theory however suggests that ice-based PSCs might play a more substantial role in the formation of NAT- and STS-based PSCs. According to the mountain-wave seeding hypothesis, ice-based PSCs form quickly following intense temperature drops due to gravity wave events propagating in the mid-stratosphere ; melting ice crystals exiting the gravity wave region then act as the basis for fast NAT nucleation. NAT particles are then widely disseminated around the Antarctic continent by the strong winds of the polar vortex. We aim to study the validity of this hypothesis by evaluating the impact of gravity wave events on the population of PSCs. PSC observations will be presented from the spaceborne lidar CALIOP, which is able to identify PSC altitude and composition with high accuracy. These observations will be correlated with high-resolution mesoscale simulations

  12. Gravity wave events from mesoscale simulations, compared to polar stratospheric clouds observed from spaceborne lidar over the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Noel, V.; Pitts, M.

    2012-06-01

    We compare Gravity Waves (GW) and Polar Stratospheric Clouds (PSC) above the Antarctic Peninsula for winters (June to September) between 2006 and 2010. GW activity is inferred from stratospheric temperature and vertical winds from the Weather and Research Forecast mesoscale model (WRF), and documented as a function of time and geography for the studied period. Significant GW activity affects 36% of days and follows the Peninsula orography closely. Volumes of PSC, composed of ice and Nitric Acid Trihydrate (NAT), are retrieved using observations from the spaceborne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). They are documented against GW activity as a function of time and longitude. Sixty-three percent of ice PSC are observed during GW events, when the average volume of PSC per profile doubles. Maximum ice PSC volumes are seen directly over the Peninsula (65°W), while maximum NAT PSC volumes appear downstream further East (˜35°W). Effects of GW events on NAT PSC are felt as far East as 40°E. Our results support the importance of gravity waves as a major mechanism driving the evolution of ice PSC in the area, but the effects on NAT PSC are harder to detect. After a GW event ends, volumes of ice PSC get back to their usual levels in less than 24 h, while this process takes more than 48 h for NAT PSC. Daily profiles of H2O and HNO3 mixing ratios, retrieved from MLS observations, are used to derive ice and NAT frost points with altitude and time. Combining these frost points with modeled stratospheric temperatures, the volumes of air able to support ice and NAT crystals are quantified and compared with PSC volumes. Correlation is high for ice crystals, but not for NAT, consistent with their much slower nucleation mechanisms. Observations of ice PSC over the domain are followed by a strong increase (+50-100%) in NAT PSC formation efficiency 2 to 6 h later. This increase is followed by a steep drop (6-10 h later) and a longer period of slow

  13. Interannual variations of early winter Antarctic polar stratospheric cloud formation and nitric acid observed by CALIOP and MLS

    NASA Astrophysics Data System (ADS)

    Lambert, Alyn; Santee, Michelle L.; Livesey, Nathaniel J.

    2016-12-01

    We use satellite-borne measurements collected over the last decade (2006-2015) from the Aura Microwave Limb Sounder (MLS) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) to investigate the nitric acid distribution and the properties of polar stratospheric clouds (PSCs) in the early winter Antarctic vortex. Frequently, at the very start of the winter, we find that synoptic-scale depletion of HNO3 can be detected in the inner vortex before the first lidar detection of geophysically associated PSCs. The generation of "sub-visible" PSCs can be explained as arising from the development of a solid particle population with low number densities and large particle sizes. Assumed to be composed of nitric acid trihydrate (NAT), the sub-visible PSCs form at ambient temperatures well above the ice frost point, but also above the temperature at which supercooled ternary solution (STS) grows out of the background supercooled binary solution (SBS) distribution. The temperature regime of their formation, inferred from the simultaneous uptake of ambient HNO3 into NAT and their Lagrangian temperature histories, is at a depression of a few kelvin with respect to the NAT existence threshold, TNAT. Therefore, their nucleation requires a considerable supersaturation of HNO3 over NAT, and is consistent with a recently described heterogeneous nucleation process on solid foreign nuclei immersed in liquid aerosol. We make a detailed investigation of the comparative limits of detection of PSCs and the resulting sequestration of HNO3 imposed by lidar, mid-infrared, and microwave techniques. We find that the temperature history of air parcels, in addition to the local ambient temperature, is an important factor in the relative frequency of formation of liquid/solid PSCs. We conclude that the initiation of NAT nucleation and the subsequent development of large NAT particles capable of sedimentation and denitrification in the early winter do not emanate from an ice

  14. 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

  15. 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.

  16. Type I polar stratospheric cloud particles - Concentration, shape, size, light extinction

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Ferry, G. V.; Snetsinger, K. G.; Goodman, J.; Hamill, P.; Livingston, J. M.; Mccormick, M. P.

    1990-01-01

    Results from the flight on January 24, 1989 of the Airborne Arctic Stratospheric Experiment during which the ER-2 aircraft transitioned from unsaturated to ice saturated air at 20 km altitude are presented. Aerosol particles were sampled by wire impactors and examined for number density as a function of particle size by taking photomicrographs in a scanning electron microscope and visually sizing and counting the particles. Differences in the chemical, physical and optical properties of stratospheric aerosol between ice-saturated and nonsaturated air are described.

  17. The potential for ozone depletion in the arctic polar stratosphere.

    PubMed

    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(2)) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl(2)O(2) throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO(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.

  18. 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.

  19. 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.

  20. In situ measurements of total reactive nitrogen, total water, and aerosol in a Polar Stratospheric Cloud in the Antarctic

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. POST: Polar Stratospheric Telescope

    NASA Astrophysics Data System (ADS)

    Bely, Pierre Y.; Ford, Holland C.; Burg, Richard; Petro, Larry; White, Rick; Bally, John

    1995-10-01

    The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips to 8 km in the polar regions. This makes the cold, dry and nonturbulent lower stratosphere accessible to tethered aerostats. Tethered aerostats can fly as high as 12 km and are extremely reliable, lasting for many years. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first in the Arctic (near Fairbanks, Alaska) and, potentially, later in the Antarctic, to operate a new technology 6-meter, diluted aperture telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (220 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2 to 3 micron band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 microns, the combination of high resolution images and a very dark sky make it the spectral region of choice for observing the redshifted light from galaxies and clusters of galaxies at moderate to high redshifts.

  6. 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.

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1990-03-01

    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.

  10. 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.

  11. Laboratory studies of heterogeneous reactions on ice and nitric acid-doped ice surfaces representative of polar stratospheric clouds and cirrus clouds

    NASA Astrophysics Data System (ADS)

    Zondlo, Mark Andrew

    1999-10-01

    Heterogeneous reactions on ice particles play an important role in the formation of the Antarctic ozone hole and in the chemistry of cirrus clouds and airplane condensation trails. Nonetheless, the phase, composition, and state of adsorption of surface products are largely unknown. To this end, atmospherically relevant molecules were studied on thin ice and HNO3 /H2O films. FTIR reflection absorption infrared spectroscopy was used to probe the condensed phases, and a Knudsen cell reactor was used to measure heterogeneous reaction rates. N2O5 and ClONO2 reacted rapidly on ice at 185 K to form a supercooled ~3:1 H2O:HNO3 liquid layer over the ice surface. Reaction efficiencies over the supercooled liquid layer were γ = 0.0007 +/- 0.0003 for N2O5 and γ = 0.0003 +/- 0.002 for ClONO2. Although nitric acid trihydrate (NAT) was most thermodynamically stable, the supercooled H 2O/HNO3 liquid never crystallized to NAT when at the ice frost point. These results suggest that polar stratospheric cloud (PSC) ice particles may be coated with a supercooled H2O/HNO3 liquid layer over the surface. Therefore, water-ice PSCs may be most accurately modeled with reaction rates over supercooled H2O/HNO3 liquids. The reaction of ClONO2 on crystalline H2O/HNO 3 films was studied at 185 K. As the relative humidity increased from 5 to 130%, reaction efficiencies increased from 0.0004 to 0.007 and progressively water-rich surface layers formed. The availability of surface water largely controls the observed kinetics of this reaction. The interaction of HNO3 and HCl with ice showed a monolayer and a multilayer uptake regime from 180-205 K delineated by the ice/liquid coexistence curve for each species. HBr and HI showed continuous uptake on ice with the formation of amorphous H2O/HX layers. All species are expected to show monolayer uptake under cirrus cloud conditions. Finally, the uptake of methanol on ice was examined from 120-200 K. Methanol surface coverages at a partial pressure of 2

  12. 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.

  13. POST: a polar stratospheric telescope

    NASA Astrophysics Data System (ADS)

    Ford, Holland C.; Bely, Pierre Y.; Bally, John; Crocker, James H.; Dopita, Mike; Tilley, James N.; Allen, Ronald; Bartko, Frank; White, Richard L.; Burg, Richard; Burrows, Christopher J.; Clampin, Mark; Harper, Doyal A.; Illingworth, Garth; McCray, Richard; Meyer, Stephan; Mould, Jeremy; Norman, Colin

    1994-06-01

    The lower stratosphere in the polar regions offers conditions for observation in the near-infrared comparable to those obtained from space. We describe a concept for a 6-meter, diluted aperture, near-infrared telescope carried by a tethered aerostat flying at 12 km altitude, to serve as a testbed for future space astronomical observatories while producing frontier science.

  14. Polar stratospheric cloud microphysical properties measured by the microRADIBAL instrument on 25 January 2000 above Esrange and modeling interpretation

    NASA Astrophysics Data System (ADS)

    Brogniez, C.; Huret, N.; Eckermann, S.; RivièRe, E. D.; Pirre, M.; Herman, M.; Balois, J.-Y.; Verwaerde, C.; Larsen, N.; Knudsen, B.

    2003-03-01

    The balloonborne microRADIBAL instrument is a radiometer that measures the radiance and polarization of the sunlight scattered by the atmosphere, gas, and aerosols in a horizontal plane in the near-infrared range. It was launched from Esrange, Sweden, on 25 January 2000 in the framework of the Third European Stratospheric Experiment on Ozone (THESEO) 2000 campaign, and performed measurements in the vicinity of a large polar stratospheric cloud (PSC). The measurements provide diagrams of the radiance versus scattering angle at several altitudes. The aerosol signature, derived from the radiance measurements, has been modeled via Mie theory and the T-Matrix code. Three different size distributions of aerosols have been tested: monomodal and bimodal size distributions of spherical particles, and bimodal size distributions including a mode of spherical and a mode of nonspherical particles. The best agreement between the measured and modeled signatures is obtained considering a bimodal size distribution composed by a mode of medium spherical particles (median radius about 0.15 μm) and a second mode of larger nonspherical particles (median radius about 1.1 μm, aspect ratio about 0.6). Concentrations and surface densities of the PSC particles have been estimated. The existence of such particles has been tentatively explained using the Lagrangian Microphysical and Photochemical Lagrangian Stratospheric Model of Ozone (MiPLaSMO) model. On 25 January 2000 the polar stratospheric cloud detected by microRADIBAL is associated with a lee-wave event. Temperature perturbations due to lee-wave events were calculated using the National Research Laboratory Mountain Wave Forecast Model (MWFM) and have been included along trajectories. They are localized in a large region between the Norwegian mountains and Esrange. Their amplitude varies from 3 to 7 K. Detailed comparisons between measured and modeled surfaces and dimensional distributions of PSCs' particles are achieved. The two

  15. 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.

  16. 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.

  17. Titan's south polar stratospheric vortex evolution

    NASA Astrophysics Data System (ADS)

    Teanby, Nicholas A.; Vinatier, Sandrine; Sylvestre, Melody; de Kok, Remco; Nixon, Conor; Irwin, Patrick Gerard Joseph

    2016-10-01

    Titan experienced northern spring equinox in August 2009 when the south polar region was plunged into perpetual darkness. Following equinox, the south pole experienced the most extreme changes in stratospheric behaviour ever observed: the global stratospheric circulation cell reversed direction (Teanby et al 2012), HCN ice clouds (de Kok et al 2014) and other exotic condensates appeared over the south pole (Jennings et al 2015, West et al 2016), and significant composition and temperature changes occurred (Vinatier et al 2015, Teanby et al 2015, Coustenis et al 2016). Here we use Cassini CIRS limb and nadir observations from 2004-2016 to investigate the evolution of south polar stratospheric temperature and composition in the post-equinox period. Reversal following equinox was extremely rapid, taking less than 6 months (1/60th of a Titan year), which resulted in an initial adiabatic polar hot spot and increased trace gas abundances (Teanby et al 2012). However, rather than develop this trend further as winter progressed, Titan's polar hot spot subsequently disappeared, with the formation of a polar cold spot. Recently in late 2015 / early 2016 a more subdued hotspot began to return with associated extreme trace gas abundances. This talk will reveal the rapid and significant changes observed so far and discuss implications for possible polar feedback mechanisms and Titan's atmospheric dynamics.Coustenis et al (2016), Icarus, 270, 409-420.de Kok et al (2014), Nature, 514, 65-67.Jennings et al (2015), ApJL, 804, L34.Teanby et al (2012), Nature, 491, 732-735.Teanby et al (2015), DPS47, National Harbor, 205.02.Vinatier et al (2015), Icarus, 250, 95-115.West et al (2016), Icarus, 270, 399-408.

  18. 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.

  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.

    2014-07-01

    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.

  20. South Polar Clouds

    NASA Image and Video Library

    2011-04-06

    Polar surface winds can reach high velocities. These winds can cause clouds to form when the winds flow into troughs and become chaotic. This image from NASA Mars Odyssey shows trough clouds as linear bands.

  1. Mountain Wave-Induced Polar Stratospheric Cloud Forecasts for Aircraft Science Flights during SOLVE/THESEO 2000

    DTIC Science & Technology

    2005-08-08

    by the mountain wave models several days in advance, permitting coordinated quasi- Lagrangian flights that measured their composition and structure in...wave PSC forecasting campaigns, such as use of anelastic rather than Boussinesq linearized gridpoint models and a need to forecast stratospheric...prediction (NWP) models . NWP fields, once available, were postprocessed into specialized AAOE mission products, such as isentropic potential vorticity maps

  2. 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

  3. Seasonal variations of stratospheric gravity waves in Antarctica and correlations to polar mesospheric cloud brightness in summer

    NASA Astrophysics Data System (ADS)

    Yamashita, C.; Chu, X.; Huang, W.; Nott, G. J.; Espy, P. J.

    2007-12-01

    Gravity waves (GWs) play an important role in the dynamics of global middle and upper atmosphere. However, quantitative characterization of GWs in the upper stratosphere is still rare in Antarctica. Here we present a study of stratospheric GW parameters and seasonal variations using the data obtained with the University of Illinois Fe Boltzmann/Rayleigh lidar at the South Pole (90°S) from December 1999 to January 2001 and at Rothera (67.5°S, 68.0°W) from December 2002 to March 2005. Through analyzing the Rayleigh lidar density data in 30-60 km, GW parameters are derived for the South Pole and Rothera, and the results are comparable. The annual mean GW vertical wavelength is 4.3 +/- 1.5 km, vertical phase speed is 0.33 +/- 0.15 m/s, and the period is 245 +/- 110 min. We characterize the stratospheric GW strength with the root- mean-square (RMS) relative density perturbation. The seasonal variation of GW strength is clear at Rothera, with the maximum in winter and the minimum in summer. No significant seasonal variations are observed at the South Pole. The data also show that the GW period is shorter in summer than in winter at Rothera. In addition, the stratospheric GW strength is negatively correlated with PMC brightness at Rothera but no significant correlation at the South Pole. Two important factors, i.e., the wind filtering effect and topographical GW source difference, are investigated in order to explain the GW seasonal variations. We then apply a GW ray-tracing model to analyze the GW source and propagation. The correlation between GW strength and PMC brightness also provides a clue of GW propagation from the stratosphere to the mesosphere.

  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. 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.

  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. Free energy of formation of a crystal nucleus in incongruent solidification: Implication for modeling the crystallization of aqueous nitric acid droplets in polar stratospheric clouds.

    PubMed

    Djikaev, Yuri S; Ruckenstein, Eli

    2017-04-07

    Using the formalism of classical thermodynamics in the framework of the classical nucleation theory, we derive an expression for the reversible work W* of formation of a binary crystal nucleus in a liquid binary solution of non-stoichiometric composition (incongruent crystallization). Applied to the crystallization of aqueous nitric acid droplets, the new expression more adequately takes account of the effects of nitric acid vapor compared to the conventional expression of MacKenzie, Kulmala, Laaksonen, and Vesala (MKLV) [J. Geophys. Res.: Atmos. 102, 19729 (1997)]. The predictions of both MKLV and modified expressions for the average liquid-solid interfacial tension σ(ls) of nitric acid dihydrate (NAD) crystals are compared by using existing experimental data on the incongruent crystallization of aqueous nitric acid droplets of composition relevant to polar stratospheric clouds (PSCs). The predictions for σ(ls) based on the MKLV expression are higher by about 5% compared to predictions based on our modified expression. This results in similar differences between the predictions of both expressions for the solid-vapor interfacial tension σ(sv) of NAD crystal nuclei. The latter can be obtained by using the method based on the analysis of experimental data on crystal nucleation rates in aqueous nitric acid droplets; it exploits the dominance of the surface-stimulated mode of crystal nucleation in small droplets and its negligibility in large ones. Applying that method to existing experimental data, our expression for the free energy of formation provides an estimate for σ(sv) of NAD in the range ≈92 dyn/cm to ≈100 dyn/cm, while the MKLV expression predicts it in the range ≈95 dyn/cm to ≈105 dyn/cm. The predictions of both expressions for W* become identical for the case of congruent crystallization; this was also demonstrated by applying our method for determining σ(sv) to the nucleation of nitric acid trihydrate crystals in PSC droplets of

  9. Polar stratospheric clouds observed by the ILAS-II in the Antarctic region: Dual compositions and variation of compositions during June to August of 2003

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Choi, W.; Lee, K.-M.; Park, J. H.; Massie, S. T.; Sasano, Y.; Nakajima, H.; Yokota, T.

    2006-07-01

    Compositions and effective radii of polar stratospheric clouds (PSCs) in the Antarctic region from 5 June to 28 August of 2003 are determined using transmittance data from the Improved Limb Atmospheric Spectrometer-II (ILAS-II). Dual compositions are derived for 83 Antarctic cases. The primary components are β-NAT (β form of nitric acid trihydrate), NAW (nitric acid water, or SBS, supercooled binary solution), and ICE. Other minor composition components are LTA (liquid ternary aerosol, or STS, supercooled ternary solution), α-NAT (α form of NAT), NAD (nitric acid dihydrate), and SAW (sulfuric acid water). Three single compositions are found; that is, β-NAT particles were observed from 11 June to 12 August, NAW particles were observed from 28 June to 24 July, and ICE particles were observed from 28 July to 25 August. During this period, dual compositions are also found, i.e., NAW + β-NAT, β-NAT + ICE, NAW + ICE, β-NAT + NAD, β-NAT + LTA, and β-NAT + SAW. For this observation period, temperatures varied from 195 K to 180 K while measurements were made progressively in time as latitude varied from 65°S to 80°S. This mixture of compositions is assumed to be either two separate patches of PSCs or a mixture of two different types along the line of sight. The feasibility of the coexistence of dual compositions in a PSC and importance of determination of the PSC particle type for the study of heterogeneous chemistry for ozone are briefly discussed.

  10. Titan's South Polar Cloud

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; West, R. A.; Lavvas, P.; Del Genio, A. D.; Barbara, J. M.; Roy, M.; Turtle, E. P.

    2014-04-01

    Cassini/ISS cameras detected a newly formed large cloud in the south polar region of Titan on 2012-178 (June 27). Images of this cloud in the continuum filters at 889 nm (MT3) and 935 nm (CB3) clearly reveal different characteristics relative to the'detached haze' layer that extends over all south latitudes. Figure 1 shows I/F at 889 nm, where the cloud patch is observed beyond the latitude -77º and with values of the SZA higher than 90º. In this work, we analyze different MT3/CB3 images taken by ISS cameras, in order to characterize the optical properties of this cloud as well as its altitude. We first analyze images in the MT3 filter at different angles of observation in order to have some constraints on the altitude of the cloud, and subsequently the cloud optical properties are estimated by using radiative transfer simulations.

  11. The stratospheric polar vortex: evolving perspectives

    NASA Astrophysics Data System (ADS)

    Plumb, R. A.

    2005-12-01

    The discovery of dramatic Antarctic ozone depletion occurred at a time of rapid change in our understanding of stratospheric dynamics. The existence of the polar vortex, encircled by the polar night jet, had been well known for some time, as had the planetary scale Rossby waves that so dominate stratospheric meteorology. But, 25 years ago, the concepts of Rossby wave breaking, and of the "surf zone" and the sharpness of its boundaries at the vortex edge and in the subtropics, were relatively new, and the role of these waves in the driving of the mean diabatic circulation was not fully appreciated. While the local importance of gravity wave drag in the mesosphere was recognized by that time, its impact in the stratosphere was by no means clear. For a time, it was thought by many that the "ozone hole" was produced by anomalous polar upwelling, whose existence seemed to be demanded by observations of widespread, anomalously low temperatures in high southern latitudes in spring, which (at first) did not appear to be a consequence of depleted ozone. In the event, of course, chemical observations provided overwhelming support for the chemical depletion theory, while tracer observations, as well as revised radiative calculations, undermined the case for polar upwelling. The demands of stratospheric chemistry have always required that dynamical understanding of the stratosphere should extend beyond traditional meteorology to include questions of the transport of chemical species. Stratospheric transport has many facets, of which one - the impermeability of the vortex edge - was brought into focus by the appearance of the ozone hole and the need to understand the degree to which vortex air is isolated from its environment. The issue was controversial for a time, but analyses of tracer observations have confirmed expectations based on dynamical theory and on modeling studies that the isolation is strong, except during major vortex disturbances. Interest in polar vortex

  12. Update of the Polar SWIFT model for polar stratospheric ozone loss (Polar SWIFT version 2)

    NASA Astrophysics Data System (ADS)

    Wohltmann, Ingo; Lehmann, Ralph; Rex, Markus

    2017-07-01

    The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in polar winter. It is intended for use in global climate models (GCMs) and Earth system models (ESMs) to enable the simulation of mutual interactions between the ozone layer and climate. To date, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. Polar SWIFT is based on a set of coupled differential equations, which simulate the polar vortex-averaged mixing ratios of the key species involved in polar ozone depletion on a given vertical level. These species are O3, chemically active chlorine (ClOx), HCl, ClONO2 and HNO3. The only external input parameters that drive the model are the fraction of the polar vortex in sunlight and the fraction of the polar vortex below the temperatures necessary for the formation of polar stratospheric clouds. Here, we present an update of the Polar SWIFT model introducing several improvements over the original model formulation. In particular, the model is now trained on vortex-averaged reaction rates of the ATLAS Chemistry and Transport Model, which enables a detailed look at individual processes and an independent validation of the different parameterizations contained in the differential equations. The training of the original Polar SWIFT model was based on fitting complete model runs to satellite observations and did not allow for this. A revised formulation of the system of differential equations is developed, which closely fits vortex-averaged reaction rates from ATLAS that represent the main chemical processes influencing ozone. In addition, a parameterization for the HNO3 change by denitrification is included. The rates of change of the concentrations of the chemical species of the Polar SWIFT model are purely chemical rates of change in the new version, whereas in the original Polar SWIFT model, they included a transport effect caused by the

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. SAM 2 measurements of the polar stratospheric aerosol, volume 2

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Brandl, D.

    1986-01-01

    The Stratospheric Aerosol Measurement (SAM) 2 sensor aboard Nimbus 7 is providing 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 2 measurement (Oct. 1981 - Apr. 1982) 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 at 1.0 micron in the main lower stratospheric aerosol layer for this time period are 2 to 4 times 10 to the -4 power/km. for the Antarctic region and 0.5 to 1 times 10 to the -3 power/km. for the Arctic region. Stratospheric optical depths are about 0.001 to 0.004 for the Antarctic region and 0.003 to 0.004 at the beginning to about 0.006 at the end of the time period for the Arctic region. Polar stratospheric clouds (PSC's) were observed during the Arctic winter, as expected. This report provides, in a ready-to-use format, a representative sample of the seventh semester of data to be used in atmospheric and climatic studies.

  18. SAM 2 measurements of the polar stratospheric aerosol, volume 5

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Brandl, D.

    1985-01-01

    The Stratospheric Aerosol Measurement (SAM) 2 sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing 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 2 mesurement (Oct. 1980 through Apr. 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. Seasonal variations and variations in space (altitude and longitude) for both polar regions are easily seen. Stratospheric optical depths are 0.002 to 0.003 for the Antarctic region and 0.005 to 0.006 at the beginning to 0.002 to 0.003 at the end of the time period for the Arctic region. The Northern Hemisphere values are quite large due mainly to the eruption of Mount St. Helens (46.2 deg N, 122.2 deg W) in May 1980. Polar stratospheric clouds at altitudes of about 20 km were observed during the Arctic winter. A ready-to-use format containing a representative sample of the fifth 6 months of data to be used in atmospheric and climatic studies is presented.

  19. 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

  20. Polar stratospheric optical depth observed between 1978 and 1985

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.

    1987-01-01

    Observations of the stratospheric optical depth at 1.0 micron obtained for high latitudes are presented for a 7-year period. Weekly averaged data determined from measurements made by the Stratospheric Aerosol Measurement experiment from October 1978-1985 show that the overall yearly values in both polar regions are controlled by volcanic perturbations, with most volcanic effects being experienced in Arctic latitudes. Conservatively, peak values found in the Antarctic region were approximately 0.02 and in the Arctic region about 0.55. Probable values for these regions are estimated to be 0.26 and 0.11, respectively. The weekly averaged data also show the seasonal fluctuations due to microphysical and dynamical processes. Comparison of the optical depth record with a weekly averaged 50-mbar temperature record indicates that polar stratospheric clouds are present in the southern high latitudes each year near this level from early June to early September. A depression observed in the optical depth record each austral spring season is believed to be the result of the downward displacement of particles caused by subsidence and sedimentation during the course of winter. Following the breakup of the vortex, optical depth values increase as aerosol is transported poleward. These features are noted to be present in the Arctic region as well, but on a smaller scale because of the satellite sampling methodology and the averaging scheme employed.

  1. Polar stratospheric optical depth observed between 1978 and 1985

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.

    1987-01-01

    Observations of the stratospheric optical depth at 1.0 micron obtained for high latitudes are presented for a 7-year period. Weekly averaged data determined from measurements made by the Stratospheric Aerosol Measurement experiment from October 1978-1985 show that the overall yearly values in both polar regions are controlled by volcanic perturbations, with most volcanic effects being experienced in Arctic latitudes. Conservatively, peak values found in the Antarctic region were approximately 0.02 and in the Arctic region about 0.55. Probable values for these regions are estimated to be 0.26 and 0.11, respectively. The weekly averaged data also show the seasonal fluctuations due to microphysical and dynamical processes. Comparison of the optical depth record with a weekly averaged 50-mbar temperature record indicates that polar stratospheric clouds are present in the southern high latitudes each year near this level from early June to early September. A depression observed in the optical depth record each austral spring season is believed to be the result of the downward displacement of particles caused by subsidence and sedimentation during the course of winter. Following the breakup of the vortex, optical depth values increase as aerosol is transported poleward. These features are noted to be present in the Arctic region as well, but on a smaller scale because of the satellite sampling methodology and the averaging scheme employed.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Laser radar observation of the polar stratospheric aerosol layer

    NASA Technical Reports Server (NTRS)

    Iwasaka, Y.; Hirasawa, T.; Fukunishi, H.; Fujiwara, M.; Fujii, R.; Miyaoka, H.

    1985-01-01

    The polar stratosphere has been speculated to be an active sink region of various stratospheric materials; ozone, water vapor, NOX, aerosol particles and so on, but this process is not theoretically and/or observationally made clear. The observation of the polar stratospheric aerosol layer using laser radar certainly contributes to the study of the global transport of these stratospheric minor constituents. In addition to this, from the viewpoint of aerosol science, there may be many interesting phenomena which cannot be found in the stratosphere at mid and low latitudes; the effect of precipitation of high energy molecules and atoms, of very cold winter stratosphere, of very cold mesopause in summer. Laser radar observation is one of the main activities of the Antarctic Middle Atmosphere (AMA) project at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica since May 1983. Laser radar measurement at Syowa Station is discussed in detail.

  9. 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

  10. Stratospheric tropical warming event and its impact on the polar and tropical troposphere

    NASA Astrophysics Data System (ADS)

    Kodera, Kunihiko; Eguchi, Nawo; Mukougawa, Hitoshi; Nasuno, Tomoe; Hirooka, Toshihiko

    2017-01-01

    Stratosphere-troposphere coupling is investigated in relation to middle atmospheric subtropical jet (MASTJ) variations in boreal winter. An exceptional strengthening of the MASTJ occurred in association with a sudden equatorward shift of the stratospheric polar night jet (PNJ) in early December 2011. This abrupt transformation of the MASTJ and PNJ had no apparent relation to the upward propagation of planetary waves from the troposphere. The impact of this stratospheric event penetrated into the troposphere in two regions: in the northern polar region and the tropics. Due to the strong MASTJ, planetary waves at higher latitudes were deflected and trapped in the northern polar region. Trapping of the planetary waves resulted in amplification of zonal wave number 1 component, which appeared in the troposphere as the development of a trough over the Atlantic sector and a ridge over the Eurasian sector. A strong MASTJ also suppressed the equatorward propagation of planetary waves, which resulted in weaker tropical stratospheric upwelling and produced anomalous warming in the tropical stratosphere. In the tropical tropopause layer (TTL), however, sublimation of ice clouds kept the temperature change minor. In the troposphere, an abrupt termination of a Madden-Julian Oscillation (MJO) event occurred following the static stability increase in the TTL. This termination suggests that the stratospheric event affected the convective episode in the troposphere.

  11. SAM 2 measurements of the polar stratospheric aerosol. Volume 4: April 1980 to October 1980

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Brandl, D.

    1983-01-01

    The Stratospheric Aerosol Measurement (SAM) 2 sensor is aboard the 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 are presented. Contours of aerosols 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 and 0.002 to 0.003 at the beginning to 0.005 to 0.006 at the end of the time period for the Arctic. 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 fourth 6 months of data to be used in atmospheric and climatic studies is reported.

  12. Stratosphere aerosol and cloud measurements at McMurdo Station Antarctica during the spring of 1987

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Measurements of stratospheric aerosols with balloonborne optical particle counters on 6 occasions at McMurdo Station (78 deg S) in the spring of 1986 indicated subsidence of the stratospheric sulfate layer during the time that the ozone hole was forming (Hofmann et al., 1988). Since dynamic models of ozone depletion involving upwelling in the spring polar vortex would suggest the opposite, we repeated the measurements with an increased frequency (about one sounding per week) in 1987. During 3 of the aerosol soundings in 1986, temperatures in the 15 to 20 km range were low enough (less than 80 C) for HNO3 to co-condense with water according to several theories of polar stratospheric cloud formation. However, particles were not observed with the characteristic size suggested by theory (approx. 0.5 microns). For this reason, it was proposed that polar stratospheric clouds may predominantly consist of large (approx. 5 to 50 microns) ice crystals at very low (approx. 10 sup 4- 10 sup 3 cm cubed) concentrations (Rosen et al., 1988). The particle counter employed would be relatively insensitive to these low concentrations. With the increased frequency of soundings in 1987, and adding additional size discrimination in the 1 to 2 micron region, this hypothesis could be verified if suitably low temperatures were encountered.

  13. Polar Stratospheric Research Platforms -Ballooning in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Peterzen, Steven; Masi, Silvia; Debernardis, Paolo

    Tracing the history of ballooning in the Antarctic and Arctic, we can look at Nobile/Amundsen in the Arctic as well as Scott in Antarctica making use of balloons. Technological advances over the past few decades have lead to the development of relatively secure stratospheric research platforms that can not only lift 4 tons of instrumentation to over 38 kilometers into "near space", but can last at float altitudes for well over 30 days at float. This kind of performance comes at a relatively low cost compared to rocket propelled research. For the past 7 years the Italian Space Agency (ASI) has funded the development of the most northern launch facility for Long Duration Balloons from Longyearbyen, Svalbard, Norway. In 2009, the launch of the SORA experiment from Svalbard, suspended below an 800,000 m3 balloon proved concept of the feasibility of scientific heavy lift balloon launches from 79 deg N. From deep space observations to near space investigation, aerosols and Earth observations, polar stratospheric balloons offer the scientific investigators a stable platform to perform a wide range of research. This paper will discuss research opportunities, future scientific payloads scheduled for launching from Svalbard, and the development of Ultra Light Long Duration Balloon and the telemetry systems.

  14. Tropical stratospheric gravity wave activity and relationships to clouds

    NASA Astrophysics Data System (ADS)

    Alexander, M. Joan; Beres, Jadwiga H.; Pfister, Leonhard

    2000-09-01

    Wind measurements from NASA's ER-2 aircraft in the stratosphere are used to obtain information on the momentum flux carried by gravity waves with horizontal wavelengths between 5 and 150 km. Tropical data are compared with the cloud brightness temperature below the aircraft as an indicator of deep convective activity. A striking correlation between cold, high clouds and large gravity wave momentum flux is seen in data from the Stratosphere-Troposphere Exchange Project (STEP) tropical campaign during the monsoon season over northern Australia and Indonesia. There is an enhancement in the flux carried by waves propagating against the background wind in these observations. The same analysis was performed with data from more recent ER-2 flights over the tropical Pacific Ocean during the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA), Stratospheric Tracers of Atmospheric Transport (STRAT), and Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaigns which took place in 1994, 1995-1996, and 1997, respectively. These data also show a correlation between gravity wave momentum flux and deep convective clouds, but the relationship is much weaker, and the magnitudes of the momentum flux over the deepest clouds are about 7 times smaller than those seen in the STEP data. The reasons for these differences remain uncertain, but possibilities include both real geophysical differences and differences associated with the flight paths during the 1987 versus later campaigns.

  15. 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.

  16. Downward-Propagating Temperature Anomalies in the Preconditioned Polar Stratosphere.

    NASA Astrophysics Data System (ADS)

    Zhou, Shuntai; Miller, Alvin J.; Wang, Julian; Angell, James K.

    2002-04-01

    Dynamical links of the Northern Hemisphere stratosphere and troposphere are studied, with an emphasis on whether stratospheric changes have a direct effect on tropospheric weather and climate. In particular, downward propagation of stratospheric anomalies of polar temperature in the winter-spring season is examined based upon 22 years of NCEP-NCAR reanalysis data. It is found that the polar stratosphere is sometimes preconditioned, which allows a warm anomaly to propagate from the upper stratosphere to the troposphere, and sometimes it prohibits downward propagation. The Arctic Oscillation (AO) is more clearly seen in the former case. To understand what dynamical conditions dictate the stratospheric property of downward propagation, the upper-stratospheric warming episodes with very large anomalies (such as stratospheric sudden warming) are selected and divided into two categories according to their downward-propagating features. Eliassen-Palm (E-P) diagnostics and wave propagation theories are used to examine the characteristics of wave-mean flow interactions in the two different categories. It is found that in the propagating case the initial wave forcing is very large and the polar westerly wind is reversed. As a result, dynamically induced anomalies propagate down as the critical line descends. A positive feedback is that the dramatic change in zonal wind alters the refractive index in a way favorable for continuous poleward transport of wave energy. The second pulse of wave flux conducts polar warm anomalies farther down. Consequently, the upper-tropospheric circulations are changed, in particular, the subtropical North Atlantic jet stream shifts to the south by 5 degrees of latitude, and the alignment of the jet stream becomes more zonal, which is similar to the negative phase of the North Atlantic Oscillation (NAO).

  17. Titan South Polar Cloud Burst

    NASA Image and Video Library

    2009-06-03

    This infrared image of Saturn's moon Titan shows a large burst of clouds in the moon's south polar region. These clouds form and move much like those on Earth, but in a much slower, more lingering fashion, new results from NASA's Cassini Spacecraft show. This image is a color composite, with red shown at a 5-micron wavelength, green at 2.7 microns, and blue at 2 microns. An infrared color mosaic is also used as a background image (red at 5 microns, green at 2 microns, blue at 1.3 microns). The images were taken by Cassini's visual and infrared mapping spectrometer during a flyby of Titan on March 26, 2007, known as T27. For a similar view see PIA12004. Titan's southern hemisphere still shows a very active meteorology (the cloud appears in white-reddish tones) even in 2007. According to climate models, these clouds should have faded out since 2005. Scientists have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. The way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing—clouds are still noticeable in the southern hemisphere while fall is approaching. http://photojournal.jpl.nasa.gov/catalog/PIA12005

  18. How does downward planetary wave coupling affect polar stratospheric ozone in the Arctic winter stratosphere?

    NASA Astrophysics Data System (ADS)

    Lubis, Sandro W.; Silverman, Vered; Matthes, Katja; Harnik, Nili; Omrani, Nour-Eddine; Wahl, Sebastian

    2017-02-01

    It is well established that variable wintertime planetary wave forcing in the stratosphere controls the variability of Arctic stratospheric ozone through changes in the strength of the polar vortex and the residual circulation. While previous studies focused on the variations in upward wave flux entering the lower stratosphere, here the impact of downward planetary wave reflection on ozone is investigated for the first time. Utilizing the MERRA2 reanalysis and a fully coupled chemistry-climate simulation with the Community Earth System Model (CESM1(WACCM)) of the National Center for Atmospheric Research (NCAR), we find two downward wave reflection effects on ozone: (1) the direct effect in which the residual circulation is weakened during winter, reducing the typical increase of ozone due to upward planetary wave events and (2) the indirect effect in which the modification of polar temperature during winter affects the amount of ozone destruction in spring. Winter seasons dominated by downward wave reflection events (i.e., reflective winters) are characterized by lower Arctic ozone concentration, while seasons dominated by increased upward wave events (i.e., absorptive winters) are characterized by relatively higher ozone concentration. This behavior is consistent with the cumulative effects of downward and upward planetary wave events on polar stratospheric ozone via the residual circulation and the polar temperature in winter. The results establish a new perspective on dynamical processes controlling stratospheric ozone variability in the Arctic by highlighting the key role of wave reflection.

  19. 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.”

  20. The tropospheric-stratospheric polar vortex breakdown of January 1977

    NASA Technical Reports Server (NTRS)

    Quiroz, R. S.

    1977-01-01

    An extraordinary warming of the stratosphere in December-January 1976-77 was followed by tropospheric warming in the polar region and cooling in middle latitudes. During January 10-20, the associated polar anticyclone extended from the surface to 10 mb. Antecedents of the polar vortex breakdown are reviewed with the aid of results of zonal-harmonic analyses of planetary waves, for heights of the pressure surfaces (700-10 mb), temperature, and mean stratospheric temperature (the latter determined from satellite radiation measurements). Wave 1 in height and temperature played a dominant role in the stratosphere, attaining amplitudes of 1600 gpm and 25 C, respectively, at 10 mb. On the other hand, superposition of retrogressing wave 1 and quasi-stationary wave 2 in the height of the 300-mb surface, with individual amplitudes exceeding 300 gpm, is judged to have been an important factor in the overall development.

  1. The tropospheric-stratospheric polar vortex breakdown of January 1977

    NASA Technical Reports Server (NTRS)

    Quiroz, R. S.

    1977-01-01

    An extraordinary warming of the stratosphere in December-January 1976-77 was followed by tropospheric warming in the polar region and cooling in middle latitudes. During January 10-20, the associated polar anticyclone extended from the surface to 10 mb. Antecedents of the polar vortex breakdown are reviewed with the aid of results of zonal-harmonic analyses of planetary waves, for heights of the pressure surfaces (700-10 mb), temperature, and mean stratospheric temperature (the latter determined from satellite radiation measurements). Wave 1 in height and temperature played a dominant role in the stratosphere, attaining amplitudes of 1600 gpm and 25 C, respectively, at 10 mb. On the other hand, superposition of retrogressing wave 1 and quasi-stationary wave 2 in the height of the 300-mb surface, with individual amplitudes exceeding 300 gpm, is judged to have been an important factor in the overall development.

  2. Variation in the stratospheric aerosol associated with the North Cyclonic Polar Vortex as measured by the SAM II satellite sensor. [Stratospheric Aerosol Measurement

    NASA Technical Reports Server (NTRS)

    Kent, G. S.; Farrukh, U. O.; Trepte, C. R.; Mccormick, M. P.

    1985-01-01

    Optical depth data gathered by the stratospheric aerosol measurement (SAM II) satellite during the 1979-80 winter season are analyzed to study mean atmospheric motions. The spacecraft photometer yielded extinction rates over the Northern Hemisphere in the 8-30 km altitude interval. Filtering was performed to remove the effects of high clouds and polar stratospheric clouds. Free horizontal mixing was prevalent below 14 km, as was a systematic difference across the polar jet stream above that altitude. The aerosol declined in altitude as the winter progressed. The polar vortex is concluded to have a base at the 14 km altitude and an outer boundary which coincides with the jet stream axis. The model accords with atmospheric tracer measurements made during the open-air nuclear testing programs in the 1950s.

  3. 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.

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

    SciTech Connect

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

    1991-02-01

    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.

  5. 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.

  6. On the Motion of Air through the Stratospheric Polar Vortex.

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

    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. 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 the 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.

  7. 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.

  8. SAM 2 measurements of the polar stratospheric aerosol. Volume 3: October 1979 to April 1980

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Brandl, D.

    1983-01-01

    The Stratospheric Aerosol Measurement (SAM) II sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric 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 (Oct. 1979 through Apr. 1980) are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are 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 microns for this time period are 2 to 4 times .0001/km in the main stratospheric aerosol layer. Optical depths for the stratosphere are about 0.002 to 0.003, up slightly over normal background levels (due to the eruption of Sierra Negra, Nov. 1979). Polar stratospheric clouds at altitudes of about 22 km were observed during the Arctic winter. A ready-to-use format containing a representative sample of the third 6 months of data to be used in atmospheric and climatic studies is presented.

  9. 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.

  10. 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.

  11. 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.

  12. POLARIZATION STRUCTURE OF FILAMENTARY CLOUDS

    SciTech Connect

    Tomisaka, Kohji

    2015-07-01

    Filaments are considered to be basic structures, and molecular clouds consist of filaments. Filaments are often observed as extending in the direction perpendicular to the interstellar magnetic field. The structure of filaments has been studied based on a magnetohydrostatic equilibrium model. Here we simulate the expected polarization pattern for isothermal magnetohydrostatic filaments. The filament exhibits a polarization pattern in which the magnetic field is apparently perpendicular to the filament when observed from the direction perpendicular to the magnetic field. When the line of sight is parallel to the global magnetic field, the observed polarization pattern is dependent on the center-to-surface density ratio for the filament and the concentration of the gas mass toward the central magnetic flux tube. Filaments with low center-to-surface density ratios have an insignificant degree of polarization when observed from the direction parallel to the global magnetic field. However, models with a large center-to-surface density ratio have polarization patterns that indicate that the filament is perpendicularly threaded by the magnetic field. When mass is heavily concentrated at the central magnetic flux tube, which can be realized by the ambipolar diffusion process, the polarization pattern is similar to that expected for a low center-to-surface density contrast.

  13. Barotropic Decelerations of the Southern Stratospheric Polar Vortex

    NASA Astrophysics Data System (ADS)

    Castanheira, J. M.; Marques, C. A. F.

    2016-12-01

    The northern and southern polar vortices are subject to quite different dynamical forcings with the variability of the northern polar vortex much more dominated by baroclinic wave processes. Some recent works describe a barotropic structure in vortex splitting sudden stratospheric warming events (SSWs). Performing an analysis of the anomalies of the energy cycle we show that strong decelerations of the southern polar vortex are, in fact, dominated by transfer of kinetic energy between barotropic components. A major role is played by the barotropic zonal wavenumber n=3 in the energy transfer of kinetic energy. This result, conjugated with the fact that the stationary tropospheric waves in the southern mid-latitudes have an amplitude peak in the zonal wavenumber n=3, suggests that a barotropic mechanism of ''non-linear resonance tuning'' may be the cause of strong decelerations of the southern stratospheric polar vortex.

  14. 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.

  15. Winds analysis for polar and equatorial stratospheric balloons flights

    NASA Astrophysics Data System (ADS)

    Ivano, Musso; Cardillo, Andrea; Ibba, Roberto; Spoto, Domenico; Amaro, Francesco; Memmo, Adelaide

    Astrophysicists, meteorologists and biologists are only some of the scientists that are requiring stratospheric flights and in particular Long Duration Balloon Flights for their researches and experiments. The Italian Space Agency (ASI) is therefore coordinating an effort for the developing of stratospheric balloons' campaigns from North Pole, where ASI collaborates with Andoya Rocket Range preparing the Nobile/Amundsen Stratospheric Balloon Centre at Svalbard and from the ASI satellite receiving station in Malindi Kenya. Flights have been ongoing by other agencies in Antarctica. From the Northern Polar Region and Equatorial Africa similar flights will be possible without the logistical difficulties of that area. Answering to a specific scientific requirement, polar nocturnal and equatorial flights are now being investigated. Missions during polar winter are interesting because they provide regions of the sky where measurements are normally impossible. Trajectories are evaluated with a statistical wind analysis. Summer flights provide circular paths from Svalbard around the Pole and a safe recovery in Greenland after two weeks or more. The nocturnal flights do not have the same stability: isobaric lines are not centred above the Pole and trajectories around Svalbard involving Russia, Norway and Greenland are usual between December and February. For the equatorial missions we have analysed the statistical properties of trajectories considering the biennal oscillation and the seasonal effects of the stratospheric winds.

  16. 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.

  17. 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

  18. Balloon observations of stratospheric bromine and aerosols in the 2009 summer polar stratosphere

    NASA Astrophysics Data System (ADS)

    Berthet, Gwenael; Renard, Jean-Baptiste; Brogniez, Colette; Chartier, Michel; Gaubicher, Bertrand; Auriol, Frederique; Balois, Jean-Yves; Francois, Philippe; Verwaerde, Christian

    In the frame of the International Polar Year STRAPOLETE project, a balloon campaign op-erated by the French National Space Agency (CNES) was conducted in August 2009 from Kiruna (Sweden) to explore the rather poorly-documented summertime stratosphere. A set of various in situ and remote-sensing instruments was launched to derive the chemical and dy-namical characteristics inherent in the summer 2009 arctic stratosphere through observations of long-lived and short-lived compounds and of aerosols. Here we firstly focus on the study of stratospheric bromine from remote-sensing UV-visible spectrometry. The total inorganic bromine content computed by a 3-dimensional Chemistry-Transport Model is assessed using the total bromine content derived from the observations of BrO. These observations will be useful to continue the stratospheric bromine trend as shown in the last World Meteorological Organization assessment. We also present observations of the stratospheric aerosol content which, to our knowledge, has not been reported yet in the summer arctic stratosphere. Aerosol counting/sizing data, photo-polarimetry observations and measurements of the aerosol extinc-tion in the visible spectral domain are used jointly to try to distinguish between the various natures of aerosols and to determine the spatial variability of their size distributions. The most striking feature is the strong spatial variability of the stratospheric aerosol content in particular around an altitude of 30 km from the 8 flights of the aerosol counter/sizer. We will give an estimation of the liquid sulfate aerosol content which is of importance in chemistry models and will estimate the vertical distribution of solid particles.

  19. Optical extinction by upper tropospheric/stratospheric aerosols and clouds: GOMOS observations for the period 2002-2008

    NASA Astrophysics Data System (ADS)

    Vanhellemont, F.; Fussen, D.; Mateshvili, N.; Tétard, C.; Bingen, C.; Dekemper, E.; Loodts, N.; Kyrölä, E.; Sofieva, V.; Tamminen, J.; Hauchecorne, A.; Bertaux, J.-L.; Dalaudier, F.; Blanot, L.; Fanton D'Andon, O.; Barrot, G.; Guirlet, M.; Fehr, T.; Saavedra, L.

    2010-04-01

    Although the retrieval of aerosol extinction coefficients from satellite remote measurements is notoriously difficult (in comparison with gaseous species) due to the lack of typical spectral signatures, important information can be obtained. In this paper we present an overview of the current operational nighttime UV/Vis aerosol extinction profile results for the GOMOS star occultation instrument, spanning the period from August 2002 to May 2008. Some problems still remain, such as the ones associated with incomplete scintillation correction and the aerosol spectral law implementation, but good quality extinction values can be expected at a wavelength of 500 nm. Typical phenomena associated with atmospheric particulate matter in the Upper Troposphere/Lower Stratosphere (UTLS) are easily identified: Polar Stratospheric Clouds, tropical subvisual cirrus clouds, background stratospheric aerosols, and post-eruption volcanic aerosols (with their subsequent dispersion around the globe). In this overview paper we will give a summary of the current results.

  20. Interhemispheric comparison of the development of the stratospheric polar vortex during fall - A 3-dimensional perspective for 1991-1992

    NASA Technical Reports Server (NTRS)

    Manney, Gloria L.; Zurek, Richard W.

    1993-01-01

    The development of the stratospheric polar vortex during fall and early winter in the Northern Hemisphere (NH) during 1991-1992, and the Southern Hemisphere (SH) during 1992 is examined using National Meteorological Center data. Compared to the NH, the polar vortex in the SH developed with less variability on short time scales, deepened more rapidly and continued to expand well into winter. Daily minimum temperatures in the lower stratosphere were lowest at equivalent seasonal dates in both hemispheres, but values below the condensation temperatures of polar stratospheric clouds occurred earlier, persisted much longer, and occupied a larger volume of air in the SH. These interhemispheric meteorological differences can account for some of the key features of the chlorine monoxide distributions observed by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite.

  1. Interhemispheric comparison of the development of the stratospheric polar vortex during fall - A 3-dimensional perspective for 1991-1992

    NASA Technical Reports Server (NTRS)

    Manney, Gloria L.; Zurek, Richard W.

    1993-01-01

    The development of the stratospheric polar vortex during fall and early winter in the Northern Hemisphere (NH) during 1991-1992, and the Southern Hemisphere (SH) during 1992 is examined using National Meteorological Center data. Compared to the NH, the polar vortex in the SH developed with less variability on short time scales, deepened more rapidly and continued to expand well into winter. Daily minimum temperatures in the lower stratosphere were lowest at equivalent seasonal dates in both hemispheres, but values below the condensation temperatures of polar stratospheric clouds occurred earlier, persisted much longer, and occupied a larger volume of air in the SH. These interhemispheric meteorological differences can account for some of the key features of the chlorine monoxide distributions observed by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite.

  2. 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.

  3. Occurrence of Ice Supersaturations, Ice Clouds, and Ternary Aerosols in the Arctic Lowermost Stratosphere

    NASA Technical Reports Server (NTRS)

    Jensen, Eric; Selkirk, Henry; Pfister, Leonhard; Sachee, Glen; Podolske, James; Anderson, Bruce; Gore, Warren J. (Technical Monitor)

    2000-01-01

    Relative humidity, aerosol concentration, and ice crystals all have important impacts on chemistry and radiative transfer in the lowermost stratosphere. In this study, we have combined SOLVE measurements with meteorological analyses to investigate the statistics of humidity, aerosols, and clouds in the arctic lower stratosphere. First, we will present a statistical analysis of relative humidity with respect to ice in the lowermost stratosphere, used on the DC-8 in situ measurements. We will show examples of ice supersaturation well within the stratosphere. Generally, these cases were associated with extremely low temperatures near the tropopause. Next, we will discuss the climatological occurrence frequency of tropopause temperatures low enough for ice saturation even with typically low stratospheric water vapor mixing ratios. Really, we will examine case studies of ice clouds observed in the lowermost stratosphere during SOLVE. We will discuss the possible origin of these clouds (i.e., precipitation from higher type II PSCs, injection of tropospheric air into the lower stratosphere, etc.).

  4. 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

  5. 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

  6. Aircraft deployment, and airborne arctic stratospheric expedition

    NASA Technical Reports Server (NTRS)

    Condon, Estelle; Tuck, Adrian; Hipskind, Steve; Toon, Brian; Wegener, Steve

    1990-01-01

    The Airborne Arctic Stratospheric Expedition had two primary objectives: to study the production and loss mechanisms of ozone in the north polar stratosphere and to study the effect on ozone distribution of the Arctic Polar Vortex and of the cold temperatures associated with the formation of Polar Stratospheric Clouds. Two specially instrumented NASA aircraft were flown over the Arctic region. Each aircraft flew to acquire data on the meteorological, chemical and cloud physical phenomena that occur in the polar stratosphere during winter. The chemical processes which occur in the polar stratosphere during winter were also observed and studied. The data acquired are being analyzed.

  7. Studies of stratospheric particulates

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Turco, Richard; Hamill, Patrick; Thomas, Gary

    1990-01-01

    A sophisticated computer model of polar stratospheric clouds was developed and used to study the properties of ice clouds. The model has recently been extended to investigate nitric acid clouds and ice clouds as well as their interactions with stratospheric gases. The model is now being applied to interpret data collected during recent expeditions to the Antarctic and the Arctic. Some work has also been done to understand the properties of noctilucent clouds and their implications for the chemistry and dynamics of the upper stratosphere.

  8. 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.

  9. Clouds and Hazes in Saturn's Troposphere and Stratosphere

    NASA Astrophysics Data System (ADS)

    Merlet, Cecile; Irwin, P.; Fletcher, L.

    2012-10-01

    We present new results from the analysis of Saturn's near-infrared spectra measured with the Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini orbiter. VIMS near-infrared data are particularly relevant for the study of clouds and hazes in the troposphere and stratosphere of Saturn. Thermal emission in the 4.5-5.1 wavelength range is absorbed and scattered mainly by tropospheric clouds and radiatively active gases. The vertical structure as well as the optical and physical properties of tropospheric aerosols are obtained from Saturn's thermal emission spectra by using the retrieval algorithm Nemesis. The distribution of tropospheric phosphine and ammonia in gas phase will also be presented here. We managed to break the degeneracies inherent to the retrieval problem by analysing Saturn's thermal emission simultaneously at various viewing geometries. By using this method, we found that VIMS spectra at 4.5-5.1 microns are also sensitive to the hazes formed above the cloud layers. Saturn's reflected sunlight spectra at 0.8-3.5 microns measured with VIMS were also analysed in order to constrain the haze properties in the upper troposphere and lower stratosphere of the planet. Results from both the 0.8-3.5 and 4.5-5.1 wavelength ranges were combined to determine the cloud and haze model most consistent with VIMS spectroscopy over a wide range of viewing geometries and lighting conditions. An increase of temperature below the tropopause, often referred to as the temperature knee, was retrieved from Cassini/CIRS spectra. Seasonal variations of the knee and haze structure are compared, and as a result the assumption of local heating by the hazes to explain this feature will be discussed.

  10. Laboratory studies of the nitric acid trihydrate - Implications for the south polar stratosphere

    NASA Technical Reports Server (NTRS)

    Hanson, David; Mauersberger, Konrad

    1988-01-01

    Vapor pressures of HNO3 and H2O have been measured over the trihydrate crystal, formed by vapor deposit on a glass surface. In the temperature range 190 to 205 K the two phase-equilibrium trihydrate/vapor was studied by adding and removing H2O. Coexistence equilibria vapor pressures of trihydrate/solid solutions of HNO3 in ice and of mono-/trihydrate were also measured. Results show that for typical mixing ratios of H2O and HNO3 found in the lower stratosphere (3 ppm H2O, 5 ppb HNO3) the trihydrate would start to form at temperatures about 7 K higher than the ice point. The pressure of atmospheric HNO3 would rapidly decrease as the atmosphere cools without large changes in partial pressures of H2O. These laboratory results provide information on the formation of polar stratospheric clouds containing H2O and HNO3.

  11. Solid-State Photochemistry as a Formation Mechanism for Titan's Stratospheric C4N2 Ice Clouds

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    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 per centimeter 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.

  12. Solid-State Photochemistry as a Formation Mechanism for Titan's Stratospheric C4N2 Ice Clouds

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    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 per centimeter 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.

  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. 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.

  18. Deep optically thin cirrus clouds in the polar regions. I - Infrared extinction characteristics

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Yoo, Jung-Moon; Dalu, Giuseppe; Fraser, R. S.

    1990-01-01

    The spectral data obtained by the infrared interferometer Spectrometer (IRIS) flown on Nimbus 4 satellite in 1970 indicated the existence of optically thin ice clouds in the upper troposphere that probably extended into lower stratosphere, in the polar regions, during winter and early spring. The spectral features of these clouds differ somewhat from that of the optically thin cirrus clouds in the tropics. From theoretical simulation of the infrared spectra in the 8-25 micron region, it is inferred that these polar clouds have a vertical stratification in particle size, with larger particles (about 12 microns) in the bottom of the cloud and smaller ones (less than 1 micron) aloft. Radiative transfer calculations also suggest that the equivalent ice-water content of these polar clouds is of the order of 1 mg/sq cm.

  19. Deep optically thin cirrus clouds in the polar regions. I - Infrared extinction characteristics

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Yoo, Jung-Moon; Dalu, Giuseppe; Fraser, R. S.

    1990-01-01

    The spectral data obtained by the infrared interferometer Spectrometer (IRIS) flown on Nimbus 4 satellite in 1970 indicated the existence of optically thin ice clouds in the upper troposphere that probably extended into lower stratosphere, in the polar regions, during winter and early spring. The spectral features of these clouds differ somewhat from that of the optically thin cirrus clouds in the tropics. From theoretical simulation of the infrared spectra in the 8-25 micron region, it is inferred that these polar clouds have a vertical stratification in particle size, with larger particles (about 12 microns) in the bottom of the cloud and smaller ones (less than 1 micron) aloft. Radiative transfer calculations also suggest that the equivalent ice-water content of these polar clouds is of the order of 1 mg/sq cm.

  20. 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

  1. The impact of gravity waves and cloud nucleation threshold on stratospheric water and tropical tropospheric cloud fraction

    NASA Astrophysics Data System (ADS)

    Schoeberl, Mark; Dessler, Andrew; Ye, Hao; Wang, Tao; Avery, Melody; Jensen, Eric

    2016-08-01

    Using the Modern Era Retrospective-Analysis for Research and Applications (MERRA) and MERRA-2 reanalysis winds, temperatures, and anvil cloud ice, we explore the impact of varying the cloud nucleation threshold relative humidity (RH) and high-frequency gravity waves on stratospheric water vapor (H2O) and upper tropical tropopause cloud fraction (TCF). Our model results are compared to 2008/2009 winter TCF derived from Cloud-Aerosol Lidar with Orthogonal Polarization and H2O observations from the Microwave Limb Sounder (MLS). The RH threshold affects both model H2O and TCF, while high-frequency gravity waves mostly impact TCF. Adjusting the nucleation RH and the amplitude of high-frequency gravity waves allows us to tune the model to observations. Reasonable observational agreement is obtained with a nucleation threshold between 130% and 150% RH consistent with airborne observations. For the MERRA reanalysis, we lower the tropopause temperature by 0.5 K roughly consistent with GPS radio occultation measurements and include ~0.1 K high-frequency gravity wave temperature oscillations in order to match TCF and H2O observations. For MERRA-2 we do not need to adjust the tropopause temperature nor add gravity waves, because there are sufficient high-frequency temperature oscillations already present in the MERRA-2 reanalysis to reproduce the observed TCF.

  2. 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.

  3. The Influence of Planetary Waves on Polar Mesospheric Clouds

    NASA Astrophysics Data System (ADS)

    France, J. A.; Randall, C. E.; Harvey, L.; Siskind, D. E.; Lumpe, J. D.; Bailey, S. M.; Carstens, J. N.; Russell, J. M., III

    2016-12-01

    Polar mesospheric clouds (PMCs) form as a result of low temperatures and enhanced water vapor near the polar summer mesospause. These conditions occur as a result of upwelling associated with the upper branch of the gravity wave-driven global residual circulation, and are sensitive to changes in planetary wave breaking in the winter hemisphere through interhemispheric coupling (IHC). Observations by the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite show an anomalous decline in northern hemisphere PMCs in August 2014. The decline is attributed to IHC triggered by planetary wave activity in the Antarctic stratosphere. The results indicate that the IHC in 2014 occurred via a pathway that previous studies have not emphasized. Based on Aura Microwave Limb Sounder data, we suggest that shifts in zonal winds in the summer stratosphere triggered a circulation change that led to the observed PMC decline. We also show that the 5-day planetary wave modulates the response to IHC, in that PMCs persist in the trough when zonal mean temperatures are too high to support PMCs, and are absent in the ridge when mean temperatures are low enough to support PMCs.

  4. Possible effect of extreme solar energetic particle event of 20 January 2005 on polar stratospheric aerosols: direct observational evidence

    NASA Astrophysics Data System (ADS)

    Mironova, I. A.; Usoskin, I. G.; Kovaltsov, G. A.; Petelina, S. V.

    2012-01-01

    Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical influence of ionization on aerosol growth and facilitated formation of clouds, this may be an important indirect link relating solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still remain illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important questions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can form and grow, are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar stratospheric aerosols, based on a case study of an extreme solar energetic particle (SEP) event of 20 January 2005. Using aerosol data obtained over polar regions from different satellites with optical instruments that were operating during January 2005, such as the Stratospheric Aerosol and Gas Experiment III (SAGE III), and Optical Spectrograph and Infrared Imaging System (OSIRIS), we found a significant simultaneous change in aerosol properties in both the Southern and Northern Polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high in the lower stratosphere during the extreme SEP event, might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, a detailed interpretation of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to discuss possible production of stratospheric aerosols under the influence of cosmic ray induced ionization. The observed effect is marginally detectable for the analyzed severe SEP event and can be undetectable for the majority of weak-moderate events. The present

  5. 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.

  6. 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.

  7. Jupiter's UV Aurora:Energy Input to the Polar Stratosphere

    NASA Astrophysics Data System (ADS)

    Livengood, Timothy A.

    The proposed research will use IUE observations of electron-impact excited H2 emission from the Jovian aurora to investigate the energy input to the polar stratosphere by charged particle precipitation. The effects of the particle precipitation on thermal profile and chemical abundances will be measured using coordinated ground-based observations of polar infrared emissions from atmospheric hydrocarbons. Limb spectra will investigate the partitioning of energy deposition above and below the CH4 homopause at the time of the intensity measurements. A related proposal by Harris et al. will investigate possible localtime dependence which may affect the limb measurements. These observations will be coordinated with other ground-based observers and with HST observations through the International Jupiter Watch. Spectra acquired in this program will be included in our database of previous observations to contribute to investigations of long-term trends in auroral activity and investigations of magnetospheric phenomena controlling the aurora.

  8. 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.

  9. Likely seeding of cirrus clouds by stratospheric Kasatochi volcanic aerosol particles near a mid-latitude tropopause fold

    NASA Astrophysics Data System (ADS)

    Campbell, James R.; Welton, Ellsworth J.; Krotkov, Nickolay A.; Yang, Kai; Stewart, Sebastian A.; Fromm, Michael D.

    2012-01-01

    Following the explosive 7-8 August 2008 Mt. Kasatochi volcanic eruption in southwestern Alaska, a segment of the dispersing stratospheric aerosol layer was profiled beginning 16 August in continuous ground-based lidar measurements over the Mid-Atlantic coast of the eastern United States. On 17-18 August, the layer was displaced downward into the upper troposphere through turbulent mixing near a tropopause fold. Cirrus clouds and ice crystal fallstreaks were subsequently observed, having formed within the entrained layer. The likely seeding of these clouds by Kasatochi aerosol particles is discussed. Cloud formation is hypothesized as resulting from either preferential homogenous freezing of relatively large sulfate-based solution droplets deliquesced after mixing into the moist upper troposphere or through heterogeneous droplet activation by volcanic ash. Satellite-borne spectrometer measurements illustrate the evolution of elevated Kasatochi SO 2 mass concentrations regionally and the spatial extent of the cirrus cloud band induced by likely particle seeding. Satellite-borne polarization lidar observations confirm ice crystal presence within the clouds. Geostationary satellite-based water vapor channel imagery depicts strong regional subsidence, symptomatic of tropopause folding, along a deepening trough in the sub-tropical westerlies. Regional radiosonde profiling confirms both the position of the fold and depth of upper-tropospheric subsidence. These data represent the first unambiguous observations of likely cloud seeding by stratospheric volcanic aerosol particles after mixing back into the upper troposphere.

  10. 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.

  11. 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.

  12. 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.

  13. A consistent definition of the Arctic polar vortex breakup in both the lower and upper stratosphere

    NASA Astrophysics Data System (ADS)

    Choi, W.; Seo, J.

    2014-12-01

    Breakup of the polar vortex is a dominant feature of the seasonal transition from winter to summer in the stratosphere, which significantly affects stratospheric O3 concentration and tropospheric weather. Previously several criteria for the vortex breakup have been suggested based on the potential vorticity (PV) and wind speed, however, those mainly have focused on the lower stratospheric vortex of which spatiotemporal evolution and decay are more continuous than those of the upper stratospheric vortex. To find a consistent criterion for the vortex breakup in both the lower and upper stratosphere, the present study defined a polar vortex breakup day as when PV gradient at the polar vortex edge becomes lower than that at the subtropical edge on the area equivalent latitude based on PV. With applying the new definition to the UK Met Office reanalysis data, the breakup days of the Arctic polar vortices on 18 isentropic levels from 450 K to 1300 K were calculated for the period of 1993-2005. In comparison with CH4, N2O and O3 measured by the ILAS and POAM II/III satellite instruments, the breakup days are well consistent with changes in the distribution of such tracers as well as their zonal standard deviations associated with the vortex structure breaking and irreversible mixing. The vortex breakup in the upper stratosphere occurs more or less a month prior to that in the middle and lower stratosphere while the stratospheric final warming events occurs simultaneously in the upper and lower stratosphere.

  14. Effects of stratospheric lapse rate on numerically simulated thunderstorm cloud top structure

    NASA Technical Reports Server (NTRS)

    Schlesinger, Robert E.

    1985-01-01

    The three-dimensional anelastic model of Schlesinger (1975, 1978, 1984) is utilized to study the effects of stratospheric stability on thunderstorm cloud top structure. Three experiments were conducted; in the first the stratosphere is assumed isothermal, in the second test there is a temperature lapse of 3 K/km, and in the third case there is a 3 K/km inversion. Time variations of vertical velocity, mature storm structure, and cloud top are examined. It is observed that the cloud summit height is lowered as stratospheric stability increases, a cloud-top thermal couplet occurs in all cases, the cold region has a U or V shape, and there is a height minimum in the warm regions.

  15. The change of depolarization of backscattering light from the polar stratospheric aerosol layer

    NASA Technical Reports Server (NTRS)

    Iwasaka, Y.

    1985-01-01

    The change of polarization properties of scattered light strongly depends on the non-spherisity of target particles. It should be helpful information for the study of stratospheric aerosols to know the non-spherisity of stratospheric aerosol particles. The change of the total backscatter depolarization ratio of the stratospheric aerosol layer measured at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica is described.

  16. Lower Stratospheric Temperature Differences In Meteorological Analyses and Their Impact On Polar Processing Studies

    NASA Astrophysics Data System (ADS)

    Manney, G.; Sabutis, J.; Pawson, S.; Santee, M.; Naujokat, B.; Swinbank, R.; Gelman, M.; Ebisuzaki, W.

    Models - chemical transport models (CTMs), trajectory and Eulerian transport mod- els, microphysical models - used in polar processing studies typically rely on winds and/or temperatures from one of several meteorological analyses to drive the transport and control processes such as polar stratospheric cloud (PSC) formation and chemical reaction rates. Using different analyzed data sets to obtain temperatures and temper- ature histories can have significant consequences. A quantitative comparison of six meteorological analyses (UK Met Office, National Centers for Environmental Pre- diction/Climate Prediction Center (NCEP), NCEP/National Center for Atmospheric Research Reanalysis (REAN), Freie Universität Berlin, European Centre for Medium- Range Weather Forecasts (ECMWF), NASA Data Assimilation Office (DAO)) is pre- sented for the cold 1999-2000 and 1995-1996 Arctic winters, showing substantial dif- ferences in diagnostics related to polar processing between the different analyses. Bi- ases between analyses vary from year to year. Temperature history case studies show substantial differences using Met Office, NCEP, REAN, ECMWF, and DAO analyses. Different meteorological conditions in the comparably cold winters of 1995-1996 and 1999-2000 had a large impact on both expectations for PSC formation and on the ef- fects of discrepancies between different meteorological analyses. Met Office, NCEP, REAN, ECMWF, and DAO analyses are commonly used in modeling polar processes; the choice of analysis can strongly influence the results of such studies.

  17. 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.

  18. 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.

  19. Climatology of the stratospheric polar vortex and planetary wave breaking

    NASA Technical Reports Server (NTRS)

    Baldwin, Mark P.; Holton, James R.

    1988-01-01

    The distribution of Ertel's potential vorticity (PV) on the 850 K isentropic surface is used to establish a climatology for the transient evolution of the planetary scale circulation in the Northern Hemisphere winter midstratosphere. PV distributions are computed from gridded NMC daily temperature and height maps for the 10 and 30 mb levels, and show that a very good approximation for 850 K PV can be derived from 10 mb heights and temperatures alone. It is assumed that reversals of the latitudinal gradient of PV, localized in longitude and latitude may be regarded as signatures of planetary wave breaking. Wave breaking identified by such signatures tends to occur mainly in the vicinity of the Aleutian anticyclone, with a secondary maximum over Europe. The area of the polar vortex, defined as the area enclosed by PV contours greater than a certain critical value, is strongly influenced by wave breaking. Erosion of the polar vortex due to transport and mixing of PV leads to a preconditioned state, when defined in terms of vortex area, that always occurs prior to major stratospheric warmings. During winters with little PV transport or mixing, the vortex area evolves rather uniformly in response to radiative forcing. During winters with major sudden warmings, the wave breaking signature as defined here first appears at low values of PV, then rapidly moves toward higher values as the vortex area is reduced and the 'surf-zone' structure becomes well defined.

  20. Climatology of the stratospheric polar vortex and planetary wave breaking

    NASA Technical Reports Server (NTRS)

    Baldwin, Mark P.; Holton, James R.

    1988-01-01

    The distribution of Ertel's potential vorticity (PV) on the 850 K isentropic surface is used to establish a climatology for the transient evolution of the planetary scale circulation in the Northern Hemisphere winter midstratosphere. PV distributions are computed from gridded NMC daily temperature and height maps for the 10 and 30 mb levels, and show that a very good approximation for 850 K PV can be derived from 10 mb heights and temperatures alone. It is assumed that reversals of the latitudinal gradient of PV, localized in longitude and latitude may be regarded as signatures of planetary wave breaking. Wave breaking identified by such signatures tends to occur mainly in the vicinity of the Aleutian anticyclone, with a secondary maximum over Europe. The area of the polar vortex, defined as the area enclosed by PV contours greater than a certain critical value, is strongly influenced by wave breaking. Erosion of the polar vortex due to transport and mixing of PV leads to a preconditioned state, when defined in terms of vortex area, that always occurs prior to major stratospheric warmings. During winters with little PV transport or mixing, the vortex area evolves rather uniformly in response to radiative forcing. During winters with major sudden warmings, the wave breaking signature as defined here first appears at low values of PV, then rapidly moves toward higher values as the vortex area is reduced and the 'surf-zone' structure becomes well defined.

  1. 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.

  2. Five-day Waves in Polar Stratosphere and Mesosphere Temperature and Mesospheric Ice Water Measured by SOFIE/AIM

    NASA Astrophysics Data System (ADS)

    Yue, J.; Liu, X.

    2015-12-01

    The temperature and column ice water content (IWC) of polar mesospheric clouds (PMCs) have been simultaneously measured by the Solar Occultation for Ice Experiment (SOFIE) onboard NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite since April 2007. The 8-year (2007-2014) data of the temperature and IWC are used to extract the 5-day planetary waves (PWs) with zonal wavenumbers ranging from -1 to -3 (eastward propagating mode, E1-E3), 0 (stationary mode, W0), and 1 to 3 (westward propagating mode, W1-W3) in the polar stratosphere and mesosphere. The 5-day PWs in temperature are stronger in the polar winter stratosphere and mesosphere and exhibit substantial inter-hemispheric asymmetry. The date-height distributions of the 5-day waves coincide with those of the eastward jet in each hemisphere. This indicates that the 5-day PWs might be generated from barotropic/baroclinic instability in the polar stratosphere. The relative strengths of 5-day PWs decrease with increasing wavenumbers. The E1 (W1) 5-day PW is stronger than any other mode in the winter stratosphere and lower mesosphere (summer upper mesosphere). SOFIE temperature and IWC data are derived from simultaneous measurements in the same air column and thus provide a good opportunity to study the phase relationship between the 5-day PWs in temperature and IWC. Our analyses show that the phase shifts of W1 5-day PW in temperature relative to that in IWC have a mean of -2.0 h (0.3 h) with a standard deviation of 3.8 h (4.2 h) in the northern (southern) polar region. This indicates that the formation of the W1 5-day PW in PMCs is controlled mainly by the W1 5-day PW in temperature and influenced by other factors and is consistent with previous studies.

  3. Five-day waves in polar stratosphere and mesosphere temperature and mesospheric ice water measured by SOFIE/AIM

    NASA Astrophysics Data System (ADS)

    Liu, Xiao; Yue, Jia; Xu, Jiyao; Yuan, Wei; Russell, James M., III; Hervig, Mark E.

    2015-05-01

    The temperature and column ice water content (IWC) of polar mesospheric clouds (PMCs) have been simultaneously measured by the Solar Occultation for Ice Experiment (SOFIE) on board NASA's Aeronomy of Ice in the Mesosphere satellite since April 2007. The 8 year (2007-2014) data of the temperature and IWC are used to extract the 5 day planetary waves (PWs) with zonal wave numbers ranging from -1 to -3 (eastward propagating mode, E1-E3), 0 (stationary mode, W0), and 1 to 3 (westward propagating mode, W1-W3) in the polar stratosphere and mesosphere. The 5 day PWs in temperature are stronger in the polar winter stratosphere and mesosphere and exhibit substantial interhemispheric asymmetry. The date-height distributions of the 5 day waves coincide with those of the eastward jet in each hemisphere. This indicates that the 5 day PWs might be generated from barotropic/baroclinic instability in the polar stratosphere. The relative strengths of 5 day PWs decrease with increasing wave numbers. The E1 (W1) 5 day PW is stronger than any other mode in the winter stratosphere and lower mesosphere (summer upper mesosphere). SOFIE temperature and IWC data are derived from simultaneous measurements in the same air column and thus provide a good opportunity to study the phase relationship between the 5 day PWs in temperature and IWC. Our analyses show that the phase shifts of W1 5 day PW in temperature relative to that in IWC have a mean of -2.0 h (0.3 h) with a standard deviation of 3.8 h (4.2 h) in the northern (southern) polar region. This indicates that the formation of the W1 5 day PW in PMCs is controlled mainly by the W1 5 day PW in temperature and influenced by other factors and is consistent with previous studies.

  4. Using polar mesosphere summer echoes and stratospheric/mesospheric winds to explain summer mesopause jumps in Antarctica

    NASA Astrophysics Data System (ADS)

    Lübken, Franz-Josef; Latteck, Ralph; Becker, Erich; Höffner, Josef; Murphy, Damian

    2017-09-01

    Recent high resolution temperature measurements by resonance lidar occasionally showed a sudden mesopause altitude increase by ∼5 km and an associated mesopause temperature decrease by ∼10 K at Davis (69°S). In this paper we present further observations which are closely related to this 'mesopause jump', namely the increase of mean height of polar mesospheric summer echoes (PMSE) observed by a VHF radar, very strong westward winds in the upper mesosphere measured by an MF radar, and relatively large eastward winds in the stratosphere taken from reanalysis. We present a detailed explanation of mesopause jumps. They occur only when stratospheric winds are moderately eastward and mesospheric winds are strongly westward. Under these conditions, gravity waves with comparatively large eastward phase speeds can pass the stratosphere and propagate to the lower thermosphere because their vertical wavelengths in the mesosphere are rather large which implies enhanced dynamical stability. When finally breaking in the lower thermosphere, these waves drive an enhanced residual circulation that causes a cold and high-altitude mesopause. The conditions for a mesopause jump occur only in the Southern Hemisphere (SH) and are associated with the late breakdown of the polar vortex. Mesopause jumps are primarily, but not only, observed prior and close to solstice. Our study also shows that during the onset of PMSE in the SH, stratospheric zonal winds are still eastward (up to 30 m/s), and that the onset is not closely related to the transition of the stratospheric circulation. Unlike previously published results with polar mesospheric clouds, we find an overall poor correlation between PMSE onset and the date of the vortex breakdown.

  5. Determining the Polar Cosmic Ray Effect on Cloud Microphysics and the Earth's Ozone Layer

    NASA Astrophysics Data System (ADS)

    Beckie, Charlene Radons

    Earth’s changing climate is an important topic where atmospheric ozone plays a critical role. Ozone has a direct influence on the amount and type of solar radiation received by the Earth. This study addresses how cosmic rays may influence the ozone layer by ionizing Earth’s atmosphere and enhancing the growth of cloud condensation nuclei and rate of chemical reactions on polar ice cloud surfaces. This theory was largely based on the lifetime work by Lu [2010]. The region of interest was centered over the Thule, Greenland neutron monitor station. Using cosmic ray, satellite-based ISCCP and ICARE project cloud data along with TOMS-OMI-SBUV and TEMIS total column ozone data, data comparisons were done. Plots of cosmic rays versus Antarctic atmospheric ozone from Lu [2009] were reproduced using regional Arctic data and extended to include years from 1983 to 2011. Comparisons to the research by Harris et al. [2010] were made by substituting ice cloud optical thickness for the cloud parameter and seasonal total column ozone for winter stratospheric ozone loss. The results of these data evaluations showed that the regional Arctic view matched very closely to Lu’s work from the Antarctic. The ozone 3-point moving average case demonstrated a statistically significant correlation of -0.508. Extending the data duration exposed a cosmic ray data peak that was 14 percent larger than the two previous 11-year cycles. Ice cloud tau / ozone data comparisons did not produce the strong correlations from Harris et al. [2010]. Five years of low stratospheric temperatures and increased volumes of polar stratospheric clouds, identified by Rex et al. [2006], matched significant years of total column ozone minimums. Polar atmospheric CO2 trended along with ice cloud tau and oppositely to total column ozone, suggesting that lower stratospheric temperatures are instrumental in ozone reduction. Future work would involve using more extensive datasets, focusing on parameters such as ice

  6. Attenuation by clouds of UV radiation for low stratospheric ozone conditions

    NASA Astrophysics Data System (ADS)

    Orte, Facundo; Wolfram, Elian; Salvador, Jacobo; D'Elia, Raúl; Quiroga, Jonathan; Quel, Eduardo; Mizuno, Akira

    2017-02-01

    Stratospheric poor ozone air masses related to the polar ozone hole overpass subpolar regions in the Southern Hemisphere during spring and summer seasons, resulting in increases of surface Ultraviolet Index (UVI). The impact of these abnormal increases in the ultraviolet radiation could be overestimated if clouds are not taking into account. The aim of this work is to determine the percentage of cases in which cloudiness attenuates the high UV radiation that would reach the surface in low total ozone column situations and in clear sky hypothetical condition for Río Gallegos, Argentina. For this purpose, we analysed UVI data obtained from a multiband filter radiometer GUV-541 (Biospherical Inc.) installed in the Observatorio Atmosférico de la Patagonia Austral (OAPA-UNIDEF (MINDEF - CONICET)) (51 ° 33' S, 69 ° 19' W), Río Gallegos, since 2005. The database used covers the period 2005-2012 for spring seasons. Measured UVI values are compared with UVI calculated using a parametric UV model proposed by Madronich (2007), which is an approximation for the UVI for clear sky, unpolluted atmosphere and low surface albedo condition, using the total ozone column amount, obtained from the OMI database for our case, and the solar zenith angle. It is observed that ˜76% of the total low ozone amount cases, which would result in high and very high UVI categories for a hypothetical (modeled) clear sky condition, are attenuated by clouds, while 91% of hypothetical extremely high UVI category are also attenuated.

  7. 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

  8. A Twilight and Moonlight Model for Polar Stratospheric Telescope (POST)

    NASA Astrophysics Data System (ADS)

    Petro, L.; Bely, P.; White, R.

    1994-05-01

    We have modeled the run of brightness of the sky during twilight in order to estimate the yearly amount of nightime available for visual and infrared observations (0.55 - 8.0 microns ) with the Polar Stratospheric Telescope (POST). We have also applied the model to the estimation of the brightness of scattered moonlight. Our calculations were motivated by the sensitive dependence on solar depression angle of the duration of twilight for ground-based observers in the polar regions. The twilight model represents singly and doubly Rayleigh scattered sunlight and the full three-dimensional geometry of the earth's atmosphere and shadow. The onset of nightime was determined using an additional model of the brightness of the night sky which incorporates the thermal emission of the atmosphere, scattered and thermal emissivity of the zodiacal light, and the thermal emission of POST. We find at 0.55 microns for an observer at an altitude of 13 km that ZA_⊙ is 0.7 deg less than for a sea-level observer to attain the same twilight sky brightness. The difference decreases to zero at 6 - 8 microns . In itself this will have little effect on the available nightime for POST. However, the predicted brightness of the 2.5 microns sky as observed with POST is three orders of magnitude fainter than for a ground-based observer, and as a consequence the sensible twilight is prolonged to ZA_⊙=110 deg . In contrast, the great brightness of the sky (although less than for a ground-based observer) in the range 3.5 - 8.0 microns reduces the sensible duration of twilight. At the end of twilight ZA_⊙=101 deg at 3.5 microns , ZA_⊙=97 deg at 6.0 microns , and ZA_⊙=95 deg at 8.0 microns . The number of hours of darkness per year for an arctic site (latitude = 65 deg ) is 2000 at 0.55 microns , 1850 at 2.5 microns , 2700 at 3.5 microns , 3300 at 6.0 microns , and 3600 at 8.0 microns . Finally, we find the brightness of atmospherically scattered moonlight is six times less for a POST

  9. Optical extinction by upper tropospheric/stratospheric aerosols and clouds: GOMOS observations for the period 2002-2008

    NASA Astrophysics Data System (ADS)

    Vanhellemont, F.; Fussen, D.; Mateshvili, N.; Tétard, C.; Bingen, C.; Dekemper, E.; Loodts, N.; Kyrölä, E.; Sofieva, V.; Tamminen, J.; Hauchecorne, A.; Bertaux, J.-L.; Dalaudier, F.; Blanot, L.; Fanton D'Andon, O.; Barrot, G.; Guirlet, M.; Fehr, T.; Saavedra, L.

    2010-08-01

    Although the retrieval of aerosol extinction coefficients from satellite remote measurements is notoriously difficult (in comparison with gaseous species) due to the lack of typical spectral signatures, important information can be obtained. In this paper we present an overview of the current operational nighttime UV/Vis aerosol extinction profile results for the GOMOS star occultation instrument, spanning the period from August 2002 to May 2008. Some problems still remain, such as the ones associated with incomplete scintillation correction and the aerosol spectral law implementation, but good quality extinction values are obtained at a wavelength of 500 nm. Typical phenomena associated with atmospheric particulate matter in the Upper Troposphere/Lower Stratosphere (UTLS) are easily identified: Polar Stratospheric Clouds, tropical subvisual cirrus clouds, background stratospheric aerosols, and post-eruption volcanic aerosols (with their subsequent dispersion around the globe). For the first time, we show comparisons of GOMOS 500 nm particle extinction profiles with the ones of other satellite occultation instruments (SAGE II, SAGE III and POAM III), of which the good agreement lends credibility to the GOMOS data set. Yearly zonal statistics are presented for the entire period considered. Time series furthermore convincingly show an important new finding: the sensitivity of GOMOS to the sulfate input by moderate volcanic eruptions such as Manam (2005) and Soufrière Hills (2006). Finally, PSCs are well observed by GOMOS and a first qualitative analysis of the data agrees well with the theoretical PSC formation temperature. Therefore, the importance of the GOMOS aerosol/cloud extinction profile data set is clear: a long-term data record of PSCs, subvisual cirrus, and background and volcanic aerosols in the UTLS region, consisting of hundreds of thousands of altitude profiles with near-global coverage, with the potential to fill the aerosol/cloud extinction data gap

  10. POST: A polar stratospheric telescope for the Antarctic

    NASA Astrophysics Data System (ADS)

    Dopita, M. A.; Ford, H. C.; Bally, J.; Bely, P.

    1996-01-01

    The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips down to only 8 km in the polar regions, allowing access to the cold, dry and nonturbulent lower stratosphere by tethered aerostats. These can float as high as 12 km, have long operating lifetimes, and are extremely reliable. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first near Fairbanks, Alaska, and later in the Antarctic, to operate a new-technology 4 m telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (about 200 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2-3 micron band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 micron, the combination of high-resolution images and a very dark sky make it the spectral region of choice for observing galaxies, QSOs and clusters of galaxies at the formation epoch of galaxies.

  11. 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.

  12. 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

  13. 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

  14. The Impact of Polar Stratospheric Ozone Loss on Southern Hemisphere Climate and Stratosheric Circulation - A Chemistry Climate Model Study

    NASA Astrophysics Data System (ADS)

    Keeble, James; Braesicke, Peter; Roscoe, Howard; Pyle, John

    2013-04-01

    It is now well established that the large spring time stratospheric ozone loss which occurs in the Southern Hemisphere is the result of the liberation of chlorine from the reservoir species HCl and ClONO2 through heterogeneous reactions occurring on Polar Stratospheric Cloud (PSC) particles. Here we investigate the impact this ozone loss has on Southern Hemisphere climate and the Brewer Dobson Circulation (BDC) using a fully coupled chemistry climate model, UM-UKCA. Two, 20 year time slice integrations were run, the first a reference year 2000 integration, and the second an identical integration in which heterogeneous chemistry on PSCs is suppressed. In the model, chlorine activation through reactions occurring on PSC particles results in a 70% decrease of vortex averaged ozone from October to November at 20km. This ozone loss leads to a large cooling of the lower stratosphere from mid September to late February, with a maximum cooling of 12K from November to December. Associated with the cooling is a decrease in geopotential height of greater than 500m over the polar cap, and a strengthening and poleward shift of the polar jet. The temperature, geopotential height and zonal wind changes are significant at the 95% confidence level, and all three propagate down to the surface in December. The surface temperature response is highly asymmetric; while much of the polar cap cools by more than 1K, the Antarctic Peninsula warms by approximately 0.5K. The change in the strength and position of the polar jet alters the propagation and breaking of planetary and gravity waves. This results in changes to the BDC, particularly increased downwelling over the polar cap during Southern Hemisphere spring and summer, measured using changes to the residual mean vertical velocity. Increased downwelling causes the middle and upper polar stratosphere to warm due to dynamical heating and increases ozone concentrations between 25 and 30km in DJF. Changes in the amplitude and phase of

  15. 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

  16. Study of finely divided aqueous systems as an aid to understanding the formation mechanism of polar stratospheric clouds: Case of HNO3/H2O and H2SO4/H2O systems

    NASA Astrophysics Data System (ADS)

    Bogdan, A.; Molina, M. J.; Kulmala, M.; MacKenzie, A. R.; Laaksonen, A.

    2003-05-01

    The study of nanometer-scale aqueous systems (finely divided aqueous systems (FDAS)) can be achieved using the absorption of vapors on fumed silica (SiO2) powder. Being a product of flame synthesis technology, fumed silica particles (6-11 nm) can be considered to be analogous to the silica smoke particles of anthropogenic and extraterrestrial origin that are supposed to be widely present in the stratosphere and mesosphere. Here, we describe the freezing and melting behavior of nanometer-scale pure H2O and binary HNO3/H2O and H2SO4/H2O systems of varying acid content, using differential scanning calorimetry (DSC). Besides reductions of melting temperature, Tm, large reductions in freezing and melting enthalpies, with ΔHf < ΔHm, in comparison with bulk solutions have also been detected. Experiments showed that fumed silica can serve as a freezing nucleus for heterogeneous ice nucleation from dilute HNO3/H2O droplets. The onset of freezing of a silica/HNO3/H2O sample with HNO3/H2O stoichiometry close to that of NAT (53 ± 5 wt % HNO3) at temperatures ≈7 K warmer than the ice frost point suggests that silica particles can promote heterogeneous freezing of nitric acid hydrates in the stratosphere. Freezing of bulk droplets (53.2 wt % HNO3) supported on Al substrate at temperatures warmer than -73°C (200 K) suggests that in principle, Al2O3 surface may induce freezing of HNO3 hydrates as well. DSC measurements performed on the silica/H2SO4/H2O nanosystem showed that at stratospheric temperatures, silica particles cannot induce heterogeneous formation of sulfuric acid hydrates.

  17. 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.

  18. Possible effect of extreme solar energetic particle event of 20 January 2005 on polar stratospheric aerosols: direct observational evidence

    NASA Astrophysics Data System (ADS)

    Mironova, I. A.; Usoskin, I. G.; Kovaltsov, G. A.; Petelina, S. V.

    2011-05-01

    Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical influence of ionization on aerosol growth and facilitated formation of cloud condensation nuclei, this may be an important indirect link relating solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still remain illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important questions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can be formed and grow large enough to influence cloud condensation nuclei (CCN), are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar stratospheric aerosols, based on a case study of an extreme solar energetic particle (SEP) event of 20 January 2005. Using aerosol data obtained over polar regions from different satellites with optical instruments that were operating during January 2005, such as the Stratospheric Aerosol and Gas Experiment III (SAGE III), and Optical Spectrograph and Infrared Imaging System (OSIRIS), we found a significant simultaneous change in aerosol properties in both the southern and northern polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high during this extreme SEP event, might have led to formation of new particles and/or growth of preexisting ultrafine particles up to the size of CCN. However, a detailed interpretation of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to provide evidence for the probable production of stratospheric CCN from cosmic ray induced ionization.

  19. Ozone Depletion in the Arctic Lower Stratosphere; Timing and Impacts on the Polar Vortex.

    NASA Astrophysics Data System (ADS)

    Rae, Cameron; Pyle, John

    2017-04-01

    There a strong link between ozone depletion in the Antarctic lower stratosphere and the strength/duration of the southern hemisphere polar vortex. Ozone depletion arising from enhanced levels of ODS in the lower stratosphere during the last few decades of the 20th century has been accompanied by a delay in the final warming date in the southern hemisphere. The delay in final warming is associated with anomalous tropospheric conditions. The relationship in the Arctic, however, is less clear as the northern hemisphere experiences relatively less intense ozone destruction in the Arctic lower stratosphere and the polar vortex is generally less stable. This study investigates the impacts of imposed lower stratospheric ozone depletion on the evolution of the polar vortex, particularly in the late-spring towards the end of its lifetime. A perpetual-year integration is compared with a series of near-identical seasonal integrations which differ only by an imposed artificial ozone depletion event, occurring a fixed number of days before the polar vortex final warming date each year. Any differences between the seasonal forecasts and perpetual year simulation are due to the timely occurrence of a strong ozone depletion event in the late-spring Arctic polar vortex. This ensemble of seasonal forecasts demonstrates the impacts that a strong ozone depletion event in the Arctic lower stratosphere will have on the evolution of the polar vortex, and highlights tropospheric impacts associated with this phenomenon.

  20. How does stratospheric polar vortex variability affect European surface weather?

    NASA Astrophysics Data System (ADS)

    Baldwin, Mark

    2017-04-01

    Stratospheric variability and change has substantial effects on European surface weather and climate, especially on the Annular Modes, with shifts in the jet streams, storm tracks, precipitation, and likelihood of blocking events. Despite unambiguous observations of this phenomenon, as well as numerical simulations, a clear physical explanation of this downward coupling has been elusive. I will discuss recent advances in our understanding—how pressure changes (movement of mass) in the stratosphere affects surface pressure. However, movement of mass in the stratosphere is not sufficient to fully explain the magnitude of observed surface changes—surface effects are larger than would be expected theoretically, and are larger than at the tropopause. This "tropospheric amplification" is easily quantified, and appears to be caused by stratospheric mechanical forcing near the tropopause, which has a direct effect on baroclinic eddies and storm tracks. The tropospheric amplification mainly comes from enhanced movement of mass in the Atlantic and Pacific storm tracks.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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 ν4 band at 1306 cm-1 (7.7 μm) 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-1 (143 μm and 71 μm) 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 58°S, 15°S, 15°N, and 85°N. 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 HASI value of 70.5K by ~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.

  3. Stratospheric polar vortex splits and displacements in the high-top CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Seviour, William J. M.; Gray, Lesley J.; Mitchell, Daniel M.

    2016-02-01

    Sudden stratospheric warming (SSW) events can occur as either a split or a displacement of the stratospheric polar vortex. Recent observational studies have come to different conclusions about the relative impacts of these two types of SSW upon surface climate. A clearer understanding of their tropospheric impact would be beneficial for medium-range weather forecasts and could improve understanding of the physical mechanism for stratosphere-troposphere coupling. Here we perform the first multimodel comparison of stratospheric polar vortex splits and displacements, analyzing 13 stratosphere-resolving models from the fifth Coupled Model Intercomparison Project (CMIP5) ensemble. We find a wide range of biases among models in both the mean state of the vortex and the frequency of vortex splits and displacements, although these biases are closely related. Consistent with observational results, almost all models show vortex splits to occur barotropically throughout the depth of the stratosphere, while vortex displacements are more baroclinic. Vortex splits show a slightly stronger North Atlantic surface signal in the month following onset. However, the most significant difference in the surface response is that vortex displacements show stronger negative pressure anomalies over Siberia. This region is shown to be colocated with differences in tropopause height, suggestive of a localized response to lower stratospheric potential vorticity anomalies.

  4. The Airborne Arctic Stratospheric Expedition - Prologue

    NASA Technical Reports Server (NTRS)

    Turco, Richard; Plumb, Alan; Condon, Estelle

    1990-01-01

    This paper presents an introduction to the initial scientific results of the Airborne Arctic Stratospheric Expedition (AASE), as well as data from other atmospheric experiments and analyses carried out during the Arctic polar winter of 1989. Mission objectives of the AASE were to study the mechanisms of ozone depletion and redistribution in the northern polar stratosphere, including the influences of Arctic meteorology, and polar stratospheric clouds formed at low temperatures. Some major aspects of the AASE are described including: logistics and operations, meteorology, polar stratospheric clouds, trace composition and chemistry, and ozone depletion. It is concluded that the Arctic-89 experiments have provided the scientific community with a wealth of new information that will contribute to a better understanding of the polar winter stratosphere and the critical problem of global ozone depletion.

  5. The Airborne Arctic Stratospheric Expedition - Prologue

    NASA Technical Reports Server (NTRS)

    Turco, Richard; Plumb, Alan; Condon, Estelle

    1990-01-01

    This paper presents an introduction to the initial scientific results of the Airborne Arctic Stratospheric Expedition (AASE), as well as data from other atmospheric experiments and analyses carried out during the Arctic polar winter of 1989. Mission objectives of the AASE were to study the mechanisms of ozone depletion and redistribution in the northern polar stratosphere, including the influences of Arctic meteorology, and polar stratospheric clouds formed at low temperatures. Some major aspects of the AASE are described including: logistics and operations, meteorology, polar stratospheric clouds, trace composition and chemistry, and ozone depletion. It is concluded that the Arctic-89 experiments have provided the scientific community with a wealth of new information that will contribute to a better understanding of the polar winter stratosphere and the critical problem of global ozone depletion.

  6. The sensitivity to polarization in stratospheric aerosol retrievals from limb scattered sunlight measurements

    NASA Astrophysics Data System (ADS)

    Elash, B. J.; Bourassa, A. E.; Rieger, L. A.; Dueck, S. R.; Zawada, D. J.; Degenstein, D. A.

    2017-03-01

    Satellite measurements of limb scattered sunlight at visible and near infrared wavelengths have been used successfully for several years to retrieve the vertical profile of stratospheric aerosol extinction coefficient. The existing satellite measurements are of the total radiance, with very little knowledge or impact of the polarization state of the limb radiance. Recently proposed instrument concepts for stratospheric aerosol profiling have been designed to measure the linearly polarized radiance. Yet, to date, the impact of the polarized measurement on the retrievals has not been systematically studied. Here we use a fully spherical, multiple scattering radiative transfer model to perform a sensitivity study on the effects of the polarized measurement on stratospheric aerosol extinction retrievals through specific investigations of the aerosol signal fraction in polarized measurements, potential retrieval bias, and achievable precision. In this study,we simulate both total and linearly polarized measurements, for a wide range of limb viewing geometries that are encountered in typical low earth orbits and for various aerosol loading scenarios. The orientation of the linear polarization with respect to the horizon is also studied. Taking into account instrument signal to noise levels it is found that in general, the linear polarization can be used as effectively as the total radiance measurement, with consideration of instrument signal to noise capabilities; however the horizontal polarization is more promising in terms of signal magnitude.

  7. 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.

  8. 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.

  9. Stratospheric meteorological conditions in the Arctic polar vortex, 1991 to 1992

    NASA Technical Reports Server (NTRS)

    Newman, P.; Lait, L. R.; Schoeberl, M.; Nash, E. R.; Kelly, K.; Fahey, D. W.; Nagatani, R.; Toohey, D.; Avallone, L.; Anderson, J.

    1993-01-01

    Stratospheric meteorological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 K) should have formed over small regions in early December. The temperatures in the polar vortex warmed beyond NAT temperatures by late January (earlier than normal). Perturbed chemistry was found to be associated with these cold temperatures.

  10. Comparison of the Dispersion of the Mt. Pinatubo and El Chichon Stratospheric Aerosol Clouds

    NASA Technical Reports Server (NTRS)

    Young, R. E.; Houben, H.; Cuzzi, Jeffrey N. (Technical Monitor)

    1994-01-01

    Insights into stratospheric transport and the climatic effects of large volcanic eruptions can be obtained by studying the dispersion of two of the largest volcanic eruptions this century, Mt. Pinatubo and El Chichon. Although both eruptions were located between 15 and 20 N latitude, and occurred either in spring or early summer (April vs June), the two volcanic clouds evolved differently in terms of dispersion of the volcanic aerosols. The El Chichon cloud stayed essentially confined to between 30 N and the equator until fall season following the eruption, whereas the Mt. Pinatubo cloud spread more rapidly into the southern hemisphere. Three dimensional stratospheric interactive tracer simulations for the particular years of the eruptions are reported. Radiative heating of the volcanic clouds due to upwelling IR radiation from the troposphere is important for understanding the dispersion of the volcanic aerosols, especially for Mt. Pinatubo. However, radiative heating alone does not explain the qualitative difference in meridional dispersion of the two volcanic clouds. The rate at which the aerosol clouds are sheared apart by wind shear limits the effectiveness of the radiative heating in producing meridional dispersion, and the wind shear is a function of the particular year of each eruption.

  11. Polar mesosphere and lower thermosphere dynamics: 2. Response to sudden stratospheric warmings

    NASA Astrophysics Data System (ADS)

    Dowdy, Andrew J.; Vincent, Robert A.; Tsutsumi, Masaki; Igarashi, Kiyoshi; Murayama, Yasuhiro; Singer, Werner; Murphy, Damian J.; Riggin, D. M.

    2007-09-01

    The dynamical response of the polar mesosphere and lower thermosphere (MLT) to sudden stratospheric warmings is investigated using MF radars at Davis (69°S, 78°E), Syowa (69°S, 40°E) and Rothera (68°S, 68°W) in the Antarctic and Poker Flat (65°N, 147°W) and Andenes (69°N, 16°E) in the Arctic. Mean winds, gravity waves and planetary waves are investigated during sudden stratospheric warmings, and comparisons are made with climatological means. The available MF radar data set includes six major sudden stratospheric warmings in the Northern Hemisphere and the unprecedented 2002 Southern Hemisphere major stratospheric warming. Three of the six northern events are relatively weak and could almost be classed as minor warmings, while the larger three have similar characteristics to the event in the Southern Hemisphere. Zonal wind reversals associated with the major warmings in both hemispheres are generally weaker and earlier by several days in the mesosphere than in the stratosphere. There are, however, significant differences between locations in their response to stratospheric warmings. The zonal winds are remarkably weaker than average during both winter and spring around the time of the southern major warming of 2002, but these effects are not observed for the Northern Hemisphere events. Gravity wave activity is found to vary significantly between individual stratospheric warming events and also between individual locations.

  12. Exploring the Effects of Cloud Vertical Structure on Cloud Microphysical Retrievals based on Polarized Reflectances

    NASA Astrophysics Data System (ADS)

    Miller, D. J.; Zhang, Z.; Platnick, S. E.; Ackerman, A. S.; Cornet, C.; Baum, B. A.

    2013-12-01

    A polarized cloud reflectance simulator was developed by coupling an LES cloud model with a polarized radiative transfer model to assess the capabilities of polarimetric cloud retrievals. With future remote sensing campaigns like NASA's Aerosols/Clouds/Ecosystems (ACE) planning to feature advanced polarimetric instruments it is important for the cloud remote sensing community to understand the retrievable information available and the related systematic/methodical limitations. The cloud retrieval simulator we have developed allows us to probe these important questions in a realistically relevant test bed. Our simulator utilizes a polarized adding-doubling radiative transfer model and an LES cloud field from a DHARMA simulation (Ackerman et al. 2004) with cloud properties based on the stratocumulus clouds observed during the DYCOMS-II field campaign. In this study we will focus on how the vertical structure of cloud microphysics can influence polarized cloud effective radius retrievals. Numerous previous studies have explored how retrievals based on total reflectance are affected by cloud vertical structure (Platnick 2000, Chang and Li 2002) but no such studies about the effects of vertical structure on polarized retrievals exist. Unlike the total cloud reflectance, which is predominantly multiply scattered light, the polarized reflectance is primarily the result of singly scattered photons. Thus the polarized reflectance is sensitive to only the uppermost region of the cloud (tau~<1) where photons can scatter once and still escape before being scattered again. This means that retrievals based on polarized reflectance have the potential to reveal behaviors specific to the cloud top. For example cloud top entrainment of dry air, a major influencer on the microphysical development of cloud droplets, can be potentially studied with polarimetric retrievals.

  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. 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.

  15. Effects of stratospheric lapse rate on numerically simulated thunderstorm cloud top structure

    NASA Technical Reports Server (NTRS)

    Schlesinger, R. E.

    1985-01-01

    The study of overshooting midlatitude severe thunderstorm tops has led to the detection of some intriguing patterns. This paper provides a summary of an investigation of the effects of stratospheric stability on thunderstorm cloud top structure, taking into account the utilization of a fully three-dimensional (3D) anelastic model discussed by Schlesinger (1975, 1978, 1984). The layout of model experiments is discussed, giving attention to initial environmental soundings, and initial forcing. The time variation of the vertical velocity extreme is examined, and a description of the mature storm structure is presented. Constant-altitude plane views throughout storm depth are considered along with cloud top height fields. With the stratospheric lapse, the warm region is small and breaks down into separate spots with secondary cold spots downshear of them.

  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. Measurements of cloud condensation nuclei in the stratosphere around the plume of mount st. Helens.

    PubMed

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

    1981-02-20

    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.

  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. 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.

  20. 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.

  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. 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.

  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. 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.

  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.

    2009-01-01

    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.

  6. 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.

  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. Spatial changes in the stratospheric aerosol associated with the north polar vortex

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.; Kent, G. S.

    1983-01-01

    In late January and early February 1983, observations made by the Stratospheric Aerosol Measurement (SAM II) satellite system showed that aerosol extinction profiles measured within the northern polar vortex differed significantly above 18 km from those measured outside the vortex. Values of the calculated optical depths above 18 km for February 1, 1983, are lower by approximately one order of magnitude within the polar vortex than those outside. Similar differences were found in the aerosol back-scattering profiles obtained using an airborne lidar system when crossing the polar vortex. Since potential vorticity at a constant altitude is not conserved across the polar vortex, horizontal adiabatic transport does not occur.

  9. Detection of Stratospheric Sulfuric Acid Aerosols with Polarization Lidar: Theory, Simulations, and Observations

    NASA Astrophysics Data System (ADS)

    Beyerle, Georg

    2000-09-01

    The derivation of backscatter ratio profiles from polarization lidar measurements is discussed. The method is based on differences in depolarization between molecular backscattering and backscattering from spherical aerosol particles. Simulations show that the polarization algorithms yield backscatter ratios with uncertainties comparable with those obtained by Klett s method, provided that the backscattering process is dominated by molecular scattering. The technique could be utilized for monitoring the stratospheric sulfuric acid aerosol layer during periods of background conditions. The polarization analysis method is discussed in light of simulation results and is applied to polarization lidar profiles observed during the ALBATROSS 1996 field measurement campaign.

  10. Modern Day Re-analysis of Pinatubo SO2 Injection, Cloud dispersion and Stratospheric Aerosols

    NASA Astrophysics Data System (ADS)

    Bhartia, P. K.; Krotkov, N. A.; Aquila, V.; Hughes, E. J.; Li, C.; Fisher, B. L.

    2016-12-01

    Cataclysmic June 15 1991 eruption of Mt. Pinatubo injected largest amount of SO2 in the lower stratosphere during the satellite era. The resulting volcanic clouds were tracked by the NASA's Nimbus 7 TOMS sensor that provided first estimates of total emissions of SO2 gas ( 15+/-3 Mt). Over time SO2 converted to long-lasting sulfate aerosols affecting radiation balance and composition of the stratosphere. Large numbers of articles and papers published in the past 25 years make this the most well-studied volcanic eruption. Still, several unresolved scientific issues remain: SO2 injection height, subsequent lofting of SO2 and aerosols in the stratosphere, how much sulfate aerosols were produced in the eruption (i.e., initial sulfate to SO2 ratio), and impact on stratospheric ozone. To answer these questions we have re-analyzed past satellite measurements using modern day tools, such as re-analyzed wind data from Goddard Modeling and Assimilation Office (GMAO), improved trajectory analysis tools, better radiative transfer model to process backscatter UV data from N7/TOMS and two NOAA SBUV/2s sensors, which provided measurements at shorter UV wavelengths that are sensitive to aerosols and SO2 in the mid stratosphere ( 25 km). We have also re-analyzed aerosol data from SAGE, AVHRR, and several instruments on the UARS satellite. These data provide strong support for recent assessment by modelers that the bulk of SO2 mass injected by the volcano was well below the 25 km altitude, contrary to earlier estimates. We also find convincing evidence that there was significant amount of sulfate aerosols embedded even in the day-old SO2 cloud. These results strongly support the hypothesis that SO2 gas self-lofted to 25 km as seeen by UARS MLS several weeks after the eruption and aerosols to 35 km, as seen by the SAGE sensor several months later.

  11. 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.

  12. Increased polar stratospheric ozone losses and delayed eventual recovery owing to increasing greenhouse-gas concentrations

    NASA Astrophysics Data System (ADS)

    Shindell, Drew T.; Rind, David; Lonergan, Patrick

    1998-04-01

    The chemical reactions responsible for stratospheric ozone depletion are extremely sensitive to temperature. Greenhouse gases warm the Earth's surface but cool the stratosphere radiatively and therefore affect ozone depletion. Here we investigate the interplay between projected future emissions of greenhouse gases and levels of ozone-depleting halogen species using a global climate model that incorporates simplified ozone-depletion chemistry. Temperature and wind changes induced by the increasing greenhouse-gas concentrations alter planetary-wave propagation in our model, reducing the frequency of sudden stratospheric warmings in the Northern Hemisphere. This results in a more stable Arctic polar vortex, with significantly colder temperatures in the lower stratosphere and concomitantly increased ozone depletion. Increased concentrations of greenhouse gases might therefore be at least partly responsible for the very large Arctic ozone losses observed in recent winters. Arctic losses reach a maximum in the decade 2010 to 2019 in our model, roughly a decade after the maximum in stratospheric chlorine abundance. The mean losses are about the same as those over the Antarctic during the early 1990s, with geographically localized losses of up to two-thirds of the Arctic ozone column in the worst years. The severity and the duration of the Antarctic ozone hole are also predicted to increase because of greenhouse-gas-induced stratospheric cooling over the coming decades.

  13. 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.

  14. 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

  15. Denitrification mechanism of the polar winter stratosphere by major volcanic eruptions

    SciTech Connect

    Bekki, S.

    1994-09-20

    The author presents results from a one dimensional model simulation of the absorption of HNO{sub 3} on sulfuric acid aerosol particles resulting from volcanic eruptions. Uptake of HNO{sub 3} on such droplets, followed by sedimentation of the aerosols may result in a net transfer of HNO{sub 3} to lower altitudes in the polar stratospheric winter. The effectiveness of this process is found to be strongly dependent upon the ambient temperature, and density of aerosol in the stratosphere. 25 refs., 10 figs., 2 tabs.

  16. Troposphere-Stratosphere Dynamic Coupling Under Strong and Weak Polar Vortex Conditions

    NASA Technical Reports Server (NTRS)

    Perlwitz, Judith; Graf, Hans-F.; Hansen, James E. (Technical Monitor)

    2001-01-01

    The relationship between Northern Hemisphere (NH) tropospheric and stratospheric wave-like anomalies of spherical zonal wave number (ZWN) 1 is studied by applying Canonical Correlation Analysis (CCA). A lag-correlation technique is used with 10-day lowpass filtered daily time series of 50- and 500-hPa geopotential heights. Generally stratospheric circulation is determined by ultralong tropospheric planetary waves. During winter seasons characterized either by any anomalously strong or weak polar winter vortex different propagation characteristics for waves of ZWN 1 are observed. The non-linear perspective of the results have implications for medium range weather forecast and climate sensitivity experiments.

  17. In-Situ Measurements of Changes in Stratospheric Aerosol and the N2O - Aerosol Relationship inside and outside of the Polar Vortex

    NASA Technical Reports Server (NTRS)

    Borrmann, S.; Dye, J. E.; Baumgardner, D.; Wilson, J. C.; Jonsson, H. H.; Brock, C. A.; Loewenstein, M.; Podolske, J. R.; Ferry, G. V.; Barr, K. S.

    1993-01-01

    Two optical particle counters on the ER-2, together covering a particle size diameter range from 0.1 micrometers to 23 micrometers, were used to measure the aerosol bulk quantities integral number, aerosol surface and volume, as well as detailed size distributions inside and outside of the polar vortex in the lower stratosphere. While AASE I (Arctic Airborne Stratospheric Expedition, (Dec. 1988 - Feb. 1989) was conducted in a period of relative volcanic quiescence, enhancements in aerosol number, surface and volume of factors around 10, 25 and 100 were observed during AASE II (Aug. 1991 - Mar. 1992) due to the eruption of Mt. Pinatubo. The changes in these bulk quantities as well as in the size distributions measured both outside and inside the the polar vortex are presented and compared with those obtained in polar stratospheric cloud events (AASE I). Except for a shift towards larger aerosol mixing ratios the general shape of correlograms between the measured N2O and particle mixing ratios remain similar before and after the eruption. Similar correlograms are used to interpret data from vertical profiles inside and outside of the polar vortex.

  18. In-situ measurements of changes in stratospheric aerosol and the N2O-aerosol relationship inside and outside of the polar vortex

    NASA Technical Reports Server (NTRS)

    Borrmann, S.; Dye, J. E.; Baumgardner, D.; Wilson, J. C.; Jonsson, H. H.; Brock, C. A.; Loewenstein, M.; Podolske, J. R.; Ferry, G. V.; Barr, K. S.

    1993-01-01

    Two optical particle counters on the ER-2, together covering a particle size diameter range from 0.1 microns to 23 microns, were used to measure the aerosol bulk quantities integral number, aerosol surface and volume, as well as detailed size distributions inside and outside of the polar vortex in the lower stratosphere. While AAES I (Arctic Airborne Stratospheric Expedition, (Dec. 88 - Feb. 89) was conducted in a period of relative volcanic quiescence, enhancements in aerosol number, surface and volume of factors around 10, 25 and 100 were observed during AASE 2 (Aug. 91 - Mar. 92) due to the eruption of Mt. Pinatubo. The changes in these bulk quantities as well as in the size distributions measured both outside and inside the polar vortex are presented and compared with those obtained in polar stratospheric cloud events (AASE I). Except for a shift towards larger aerosol mixing ratios the general shape of correlograms between the measured N2O and particle mixing ratios remain similar before and after the eruption. Similar correlograms are used to interpret data from vertical profiles inside and outside of the polar vortex.

  19. In-Situ Measurements of Changes in Stratospheric Aerosol and the N2O - Aerosol Relationship inside and outside of the Polar Vortex

    NASA Technical Reports Server (NTRS)

    Borrmann, S.; Dye, J. E.; Baumgardner, D.; Wilson, J. C.; Jonsson, H. H.; Brock, C. A.; Loewenstein, M.; Podolske, J. R.; Ferry, G. V.; Barr, K. S.

    1993-01-01

    Two optical particle counters on the ER-2, together covering a particle size diameter range from 0.1 micrometers to 23 micrometers, were used to measure the aerosol bulk quantities integral number, aerosol surface and volume, as well as detailed size distributions inside and outside of the polar vortex in the lower stratosphere. While AASE I (Arctic Airborne Stratospheric Expedition, (Dec. 1988 - Feb. 1989) was conducted in a period of relative volcanic quiescence, enhancements in aerosol number, surface and volume of factors around 10, 25 and 100 were observed during AASE II (Aug. 1991 - Mar. 1992) due to the eruption of Mt. Pinatubo. The changes in these bulk quantities as well as in the size distributions measured both outside and inside the the polar vortex are presented and compared with those obtained in polar stratospheric cloud events (AASE I). Except for a shift towards larger aerosol mixing ratios the general shape of correlograms between the measured N2O and particle mixing ratios remain similar before and after the eruption. Similar correlograms are used to interpret data from vertical profiles inside and outside of the polar vortex.

  20. In-situ measurements of changes in stratospheric aerosol and the N2O-aerosol relationship inside and outside of the polar vortex

    NASA Technical Reports Server (NTRS)

    Borrmann, S.; Dye, J. E.; Baumgardner, D.; Wilson, J. C.; Jonsson, H. H.; Brock, C. A.; Loewenstein, M.; Podolske, J. R.; Ferry, G. V.; Barr, K. S.

    1993-01-01

    Two optical particle counters on the ER-2, together covering a particle size diameter range from 0.1 microns to 23 microns, were used to measure the aerosol bulk quantities integral number, aerosol surface and volume, as well as detailed size distributions inside and outside of the polar vortex in the lower stratosphere. While AAES I (Arctic Airborne Stratospheric Expedition, (Dec. 88 - Feb. 89) was conducted in a period of relative volcanic quiescence, enhancements in aerosol number, surface and volume of factors around 10, 25 and 100 were observed during AASE 2 (Aug. 91 - Mar. 92) due to the eruption of Mt. Pinatubo. The changes in these bulk quantities as well as in the size distributions measured both outside and inside the polar vortex are presented and compared with those obtained in polar stratospheric cloud events (AASE I). Except for a shift towards larger aerosol mixing ratios the general shape of correlograms between the measured N2O and particle mixing ratios remain similar before and after the eruption. Similar correlograms are used to interpret data from vertical profiles inside and outside of the polar vortex.

  1. Stochastic Radiative Transfer in Polar Mixed Phase Clouds

    NASA Astrophysics Data System (ADS)

    Brodie, J.; Veron, D. E.

    2004-12-01

    According to recent research, mixed phase clouds comprise one third of the overall annual cloud cover in the Arctic region. These clouds contain distinct regions of liquid water and ice, which have a different impact on radiation than single-phase clouds. Despite the prevalence of mixed phase clouds in the polar regions, many modern atmospheric general circulation models use single-phase clouds in their radiation routines. A stochastic approach to representating the transfer of shortwave radiation through a cloud layer where the distribution of the ice and liquid is governed by observed statistics is being assessed. Data from the Surface Heat Budget of the Arctic (SHEBA) program and the Atmospheric Radiation Measurement (ARM) program's North Slopes of Alaska Cloud and Radiation Testbed site will be used to determine the characteristic features of the cloud field and to evaluate the performance of this statistical model.

  2. Asymmetries in ozone depressions between the polar stratospheres following a solar proton event

    NASA Technical Reports Server (NTRS)

    Maeda, K.; Heath, D. F.

    1978-01-01

    Ozone depletions in the polar stratosphere during the energetic solar proton event on 4 August 1972 were observed by the backscattered ultraviolet (BUV) experiments on the Nimbus 4 satellite. The observed ozone contents, the ozone depressions and their temporal variations above the 4 mb level exhibited distinct asymmetries between the northern and southern hemispheres. Since the ozone destroying solar particles precipitate rather symmetrically into the two polar atmospheres, due to the geomagnetic dipole field, it is suggested that these asymmetries may be explained in terms of the differences in dynamics between the summer and the winter polar atmospheres. In the summer (northern) hemisphere, the stratospheric and mesospheric ozone depletion and recovery are smooth functions of time due to the preponderance of undistributed orderly flow in this region. On the other hand, the temporal variation of the upper stratospheric ozone in the winter polar atmosphere (southern hemisphere) exhibits large amplitude irregularities. These characteristic differences between the two polar atmospheres are also evident in the vertical distributions of temperatures and winds observed by balloons and rocket soundings.

  3. Detecting Super-Thin Clouds With Polarized Light

    NASA Technical Reports Server (NTRS)

    Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

    2014-01-01

    We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

  4. Detecting Super-Thin Clouds With Polarized Light

    NASA Technical Reports Server (NTRS)

    Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

    2014-01-01

    We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

  5. Detecting Super-Thin Clouds with Polarized Sunlight

    NASA Technical Reports Server (NTRS)

    Sun, Wenbo; Videen, Gorden; Mishchenko, Michael I.

    2014-01-01

    We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only 0.06 and super-thin liquid water clouds having an optical depth of only 0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

  6. Stratospheric chemistry

    NASA Astrophysics Data System (ADS)

    Brune, William H.

    Advances in stratospheric chemistry made by investigators in the United States from 1987 to 1990 are reviewed. Subject areas under consideration include photochemistry of the polar stratosphere, photochemistry of the global stratosphere, and assessments of inadvertent modification of the stratosphere by anthropogenic activity. Particular attention is given to early observations and theories, gas phase chemistry, Antarctic observations, Arctic observations, odd-oxygen, odd-hydrogen, odd-nitrogen, halogens, aerosols, modeling of stratospheric ozone, and reactive nitrogen effects.

  7. Stratospheric chemistry

    SciTech Connect

    Brune, W.H. )

    1991-01-01

    Advances in stratospheric chemistry made by investigators in the United States from 1987 to 1990 are reviewed. Subject areas under consideration include photochemistry of the polar stratosphere, photochemistry of the global stratosphere, and assessments of inadvertent modification of the stratosphere by anthropogenic activity. Particular attention is given to early observations and theories, gas phase chemistry, Antarctic observations, Arctic observations, odd-oxygen, odd-hydrogen, odd-nitrogen, halogens, aerosols, modeling of stratospheric ozone, and reactive nitrogen effects.

  8. 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: to develop suitable validation data sets to evaluate the effectiveness of the ISCCP operational algorithm for cloud retrieval in polar regions and to validate model simulations of polar cloud cover; to identify limitations of current procedures for varying atmospheric surface conditions, and to explore potential means to remedy them using textural classifiers: and to compare synoptic cloud data from a control run experiment of the Goddard Institute for Space Studies (GISS) climate model 2 with typical observed synoptic cloud patterns. Current investigations underway are listed and the progress made to date is summarized.

  9. Early evolution of a stratospheric volcanic eruption cloud as observed with TOMS and AVHRR

    USGS Publications Warehouse

    Schneider, D.J.; Rose, William I.; Coke, L.R.; Bluth, G.J.S.; Sprod, I.E.; Krueger, A.J.

    1999-01-01

    This paper is a detailed study of remote sensing data from the total ozone mapping spectrometer (TOMS) and the advanced very high resolution radiometer (AVHRR) satellite detectors, of the 1982 eruption of El Chichón, Mexico. The volcanic cloud/atmosphere interactions in the first four days of this eruption were investigated by combining ultraviolet retrievals to estimate the mass of sulfur dioxide in the volcanic cloud [Krueger et al., 1995] with thermal infrared retrievals of the size, optical depth, and mass of fine-grained (1–10 μm radius) volcanic ash [Wen and Rose, 1994]. Our study provides the first direct evidence of gravitational separation of ash from a stratospheric, gas-rich, plinian eruption column and documents the marked differences in residence times of volcanic ash and sulfur dioxide in volcanic clouds. The eruption column reached as high as 32 km [Carey and Sigurdsson, 1986] and was injected into an atmosphere with a strong wind shear, which allowed for an observation of the separation of sulfur dioxide and volcanic ash. The upper, more sulfur dioxide-rich part of the cloud was transported to the west in the stratosphere, while the fine-grained ash traveled to the south in the troposphere. The mass of sulfur dioxide released was estimated at 7.1 × 109 kg with the mass decreasing by approximately 4% 1 day after the peak. The mass of fine-grained volcanic ash detected was estimated at 6.5 × 109 kg, amounting to about 0.7% of the estimated mass of the ash which fell out in the mapped ash blanket close to the volcano. Over the following days, 98% of this remaining fine ash was removed from the volcanic cloud, and the effective radius of ash in the volcanic cloud decreased from about 8 μm to about 4 μm.

  10. Replicator for characterization of cirrus and polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hallett, John; Purcell, Richard G.

    1995-01-01

    A formvar replicator for installation in an aircraft pod has been designed, built, and flight tested on the NASA DC-8. The system incorporates a deicing capability (which can be pressure activated) to enable climb out through icing situations prior to deployment. The system can be operated at preselected speeds such that data can be recorded over a period of one to ten hours on 200 ft of 16mm film. A x2 speed control can be used during flight. Capability exists for detection of chemical constituents by appropriate doping of the formvar solution. An article entitled 'Measurements of ice particles in tropical cirrus anvils: importance in radiation balance' is attached as appendix A.

  11. Replicator for characterization of cirrus and polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hallett, John; Purcell, Richard G.

    1995-01-01

    A formvar replicator for installation in an aircraft pod has been designed, built, and flight tested on the NASA DC-8. The system incorporates a deicing capability (which can be pressure activated) to enable climb out through icing situations prior to deployment. The system can be operated at preselected speeds such that data can be recorded over a period of 1 to ten hours on 200 ft of 16mm film. A x2 speed control can be used during flight. Capability exists for detection of chemical constituents by appropriate doping of formvar solution.

  12. Evidence for a polar ethane cloud on Titan

    USGS Publications Warehouse

    Griffith, C.A.; Penteado, P.; Rannou, P.; Brown, R.; Boudon, V.; Baines, K.H.; Clark, R.; Drossart, P.; Buratti, B.; Nicholson, P.; McKay, C.P.; Coustenis, A.; Negrao, A.; Jaumann, R.

    2006-01-01

    Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal the presence of a vast tropospheric cloud on Titan at latitudes 51?? to 68?? north and all longitudes observed (10?? to 190?? west). The derived characteristics indicate that this cloud is composed of ethane and forms as a result of stratospheric subsidence and the particularly cool conditions near the moon's north pole. Preferential condensation of ethane, perhaps as ice, at Titan's poles during the winters may partially explain the lack of liquid ethane oceans on Titan's surface at middle and lower latitudes.

  13. 'Downward control' of the mean meridional circulation and temperature distribution of the polar winter stratosphere

    NASA Technical Reports Server (NTRS)

    Garcia, Rolando R.; Boville, Byron A.

    1994-01-01

    According to the 'downward control' principle, the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level. In this paper, a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere. The results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km. The effect is most important when planetary wave driving is relatively weak: that is, during southern winter and in early northern winter. In southern winter, downwelling weakens by a factor of 2 near the stratospause and by 20% at 30 km when gravity wave drag is not included in the calculations. As a consequence, temperatures decrease considerably throughout the polar winter stratosphere (over 20 K above 40 km and as much as 8 K at 30 km, where the effect is enhanced by the long radiative relaxation timescale). The polar winter states obtained when gravity wave drag is omitted in this simple model resemble the results of simulations with some general circulation models and suggest that some of the shortcomings of the latter may be due to a deficit in mesospheric momentum deposition by small-scale gravity waves.

  14. Tropical tropopause water isotopes in a GCM: Sensitivity to cloud processes and stratosphere-troposphere exchange

    NASA Astrophysics Data System (ADS)

    Schmidt, G. A.; Hoffmann, G.; Hu, Y.

    2004-05-01

    Water isotopes ratios (δ 18O, δ D) are very sensitive tracers of the history of the water in the atmosphere. For example, depletion of heavy isotopes in convective plumes can be extreme and thus isotope ratios can be used to discriminate between upwelled and in-situ condensation. We present results with state-of-the-art GCMs that include water isotopes in every aspect of the modelled water cycle, including the relatively sophisticated prognostic cloud water scheme. These models also have reasonable representations of the stratospheric circulation and so can be used to look at the processes involved in stratosphere-troposphere exchange. We demonstrate that the models show a similar range of variability near the tropical tropopause to that seen in recent data, and that the zonal mean values are less depleted than a simple Rayleigh distillation column would suggest. Importantly, we show that the isotopes can be sensitive to uncertain details of the cloud parameterizations and thus may help in improving and validating cloud schemes in models.

  15. Lidar observations of the El Chichon cloud in the stratosphere over Fukuoka

    NASA Technical Reports Server (NTRS)

    Fujiwara, M.; Shibata, T.; Hirono, M.

    1985-01-01

    A volcanic cloud in the stratosphere, originating from the March to April 1982 eruptions of El Chichon, has been observed for about 2.5 years at Fukuoka (33.5 degrees N, 130.4 degrees E) with two wavelengths of Nd-YAG lidar, 1.06 and 0.53 microns. Time and height variabilities of the cloud are described, using the 1.06 microns data, and some results of the two-wavelength measurements are presented. A sudden enormous increase in the total aerosol backscattering from the stratosphere (backscattering coefficient for 1.06 microns integrated over 13.5 to 28.5 km range) was followed by a decrease from late spring to summer with large fluctuations. The cloud initially appeared stratified into two layers: the upper one with fine structure and sharp edges in the easterly wind region and the lower dumpy one in the westerly wind region. Most of the aerosols were contained in the upper layer. The two layers merged into a broad, single-peaked layer as the easterly prevailed in the whole region in fall, when the total aerosol backscattering began to increase. The layer then decreased its peak height as it broadened. The difference in shape of both layers and the increase of total backscattering from fall can be interpreted by the difference in velocity of material transport in the easterly and the westerly wind region.

  16. Dependence of model-simulated response to ozone depletion on stratospheric polar vortex climatology

    NASA Astrophysics Data System (ADS)

    Lin, Pu; Paynter, David; Polvani, Lorenzo; Correa, Gustavo J. P.; Ming, Yi; Ramaswamy, V.

    2017-06-01

    We contrast the responses to ozone depletion in two climate models: Community Atmospheric Model version 3 (CAM3) and Geophysical Fuild Dynamics Laboratory (GFDL) AM3. Although both models are forced with identical ozone concentration changes, the stratospheric cooling simulated in CAM3 is 30% stronger than in AM3 in annual mean, and twice as strong in December. We find that this difference originates from the dynamical response to ozone depletion, and its strength can be linked to the timing of the climatological springtime polar vortex breakdown. This mechanism is further supported by a variant of the AM3 simulation in which the southern stratospheric zonal wind climatology is nudged to be CAM3-like. Given that the delayed breakdown of the southern polar vortex is a common bias among many climate models, previous model-based assessments of the forced responses to ozone depletion may have been somewhat overestimated.

  17. Polar Processes in a 50-year Simulation of Stratospheric Chemistry and Transport

    NASA Technical Reports Server (NTRS)

    Kawa, S.R.; Douglass, A. R.; Patrick, L. C.; Allen, D. R.; Randall, C. E.

    2004-01-01

    The unique chemical, dynamical, and microphysical processes that occur in the winter polar lower stratosphere are expected to interact strongly with changing climate and trace gas abundances. Significant changes in ozone have been observed and prediction of future ozone and climate interactions depends on modeling these processes successfully. We have conducted an off-line model simulation of the stratosphere for trace gas conditions representative of 1975-2025 using meteorology from the NASA finite-volume general circulation model. The objective of this simulation is to examine the sensitivity of stratospheric ozone and chemical change to varying meteorology and trace gas inputs. This presentation will examine the dependence of ozone and related processes in polar regions on the climatological and trace gas changes in the model. The model past performance is base-lined against available observations, and a future ozone recovery scenario is forecast. Overall the model ozone simulation is quite realistic, but initial analysis of the detailed evolution of some observable processes suggests systematic shortcomings in our description of the polar chemical rates and/or mechanisms. Model sensitivities, strengths, and weaknesses will be discussed with implications for uncertainty and confidence in coupled climate chemistry predictions.

  18. On connections between the stratospheric polar vortex and sea ice in the Arctic

    NASA Astrophysics Data System (ADS)

    Lukovich, J. V.; Barber, D. G.

    2009-12-01

    The unprecedented decline in sea ice extent and thickness in the Arctic in the early part of the 21st century establishes conditions conducive to increased communication between oceanic, sea-ice and atmospheric phenomena. In this study we explore the correspondence between stratospheric dynamic variability in winter and changes in sea ice in the Arctic. Investigated in particular are anomalies and trends in Eliassen-Palm flux components in the northern hemisphere to determine changes in upward wave propagation in response to an accelerated decline in Arctic ice cover in the early part of the 21st century. Connections between the strength and position of the polar vortex and changes in sea ice extent, concentration, and motion are examined in the context of sudden stratospheric warmings and vortex splitting and displacement events. Relative vorticity is used to study the permeability of the polar vortex in response to storm activity in the Arctic with reduced ice cover. Initial results from this analysis suggest a decline in upward wave propagation in winter and an increase in upward wave propagation in fall in recent decades. Spatial coincidence is observed between composites of surface winds for years associated with vortex displacement events and record lows in ice extent. The implications of a poleward increase in cyclonic activity from 70 °N - 80 °N during spring and summer for seasonal variations in the stratospheric polar vortex are also examined.

  19. Polar Processes in a 50-year Simulation of Stratospheric Chemistry and Transport

    NASA Technical Reports Server (NTRS)

    Kawa, S.R.; Douglass, A. R.; Patrick, L. C.; Allen, D. R.; Randall, C. E.

    2004-01-01

    The unique chemical, dynamical, and microphysical processes that occur in the winter polar lower stratosphere are expected to interact strongly with changing climate and trace gas abundances. Significant changes in ozone have been observed and prediction of future ozone and climate interactions depends on modeling these processes successfully. We have conducted an off-line model simulation of the stratosphere for trace gas conditions representative of 1975-2025 using meteorology from the NASA finite-volume general circulation model. The objective of this simulation is to examine the sensitivity of stratospheric ozone and chemical change to varying meteorology and trace gas inputs. This presentation will examine the dependence of ozone and related processes in polar regions on the climatological and trace gas changes in the model. The model past performance is base-lined against available observations, and a future ozone recovery scenario is forecast. Overall the model ozone simulation is quite realistic, but initial analysis of the detailed evolution of some observable processes suggests systematic shortcomings in our description of the polar chemical rates and/or mechanisms. Model sensitivities, strengths, and weaknesses will be discussed with implications for uncertainty and confidence in coupled climate chemistry predictions.

  20. A case study of formation and maintenance of a lower stratospheric cirrus cloud over the tropics

    NASA Astrophysics Data System (ADS)

    Sandhya, M.; Sridharan, S.; Indira Devi, M.; Niranjan, K.; Jayaraman, A.

    2015-05-01

    A rare occurrence of stratospheric cirrus at 18.6 km height persisting for about 5 days during 3-7 March 2014 is inferred from the ground-based Mie lidar observations over Gadanki (13.5° N, 79.2° E) and spaceborne observations. Due to the vertical transport by large updrafts on 3 March in the troposphere, triggered by a potential vorticity intrusion, the water vapour mixing ratio shows an increase around the height of 18.6 km. Relative humidity with respect to ice is ~ 150%, indicating that the cirrus cloud may be formed though homogeneous nucleation of sulfuric acid. The cirrus cloud persists due to the cold anomaly associated with the presence of a 4-day wave.

  1. Cloud Statistics and Discrimination in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Chan, M.; Comiso, J. C.

    2012-12-01

    Despite their important role in the climate system, cloud cover and their statistics are poorly known, especially in the polar regions, where clouds are difficult to discriminate from snow covered surfaces. The advent of the A-train, which included Aqua/MODIS, CALIPSO/CALIOP and CloudSat/CPR sensors has provided an opportunity to improve our ability to accurately characterize the cloud cover. MODIS provides global coverage at a relatively good temporal and spatial resolution while CALIOP and CPR provide limited nadir sampling but accurate characterization of the vertical structure and phase of the cloud cover. Over the polar regions, cloud detection from a passive sensors like MODIS is challenging because of the presence of cold and highly reflective surfaces such as snow, sea-ice, glaciers, and ice-sheet, which have surface signatures similar to those of clouds. On the other hand, active sensors such as CALIOP and CPR are not only very sensitive to the presence of clouds but can also provide information about its microphysical characteristics. However, these nadir-looking sensors have sparse spatial coverage and their global data can have data spatial gaps of up to 100 km. We developed a polar cloud detection system for MODIS that is trained using collocated data from CALIOP and CPR. In particular, we employ a machine learning system that reads the radiative profile observed by MODIS and determine whether the field of view is cloudy or clear. Results have shown that the improved cloud detection scheme performs better than typical cloud mask algorithms using a validation data set not used for training. A one-year data set was generated and results indicate that daytime cloud detection accuracies improved from 80.1% to 92.6% (over sea-ice) and 71.2% to 87.4% (over ice-sheet) with CALIOP data used as the baseline. Significant improvements are also observed during nighttime, where cloud detection accuracies increase by 19.8% (over sea-ice) and 11.6% (over ice

  2. Retrievals of Aerosol and Cloud Particle Microphysics Using Polarization and Depolarization Techniques

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael; Hansen, James E. (Technical Monitor)

    2001-01-01

    The recent availability of theoretical techniques for computing single and multiple scattering of light by realistic polydispersions of spherical and nonspherical particles and the strong dependence of the Stokes scattering matrix on particle size, shape, and refractive index make polarization and depolarization measurements a powerful particle characterization tool. In this presentation I will describe recent applications of photopolarimetric and lidar depolarization measurements to remote sensing characterization of tropospheric aerosols, polar stratospheric clouds (PSCs), and contrails. The talk will include (1) a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics; (2) the use of multi-angle multi-spectral photopolarimetry to retrieve the optical thickness, size distribution, refractive index, and number concentration of tropospheric aerosols over the ocean surface; and (3) the application of the T-matrix method to constraining the PSC and contrail particle microphysics using multi-spectral measurements of lidar backscatter and depolarization.

  3. Retrievals of Aerosol and Cloud Particle Microphysics Using Polarization and Depolarization Techniques

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael; Hansen, James E. (Technical Monitor)

    2001-01-01

    The recent availability of theoretical techniques for computing single and multiple scattering of light by realistic polydispersions of spherical and nonspherical particles and the strong dependence of the Stokes scattering matrix on particle size, shape, and refractive index make polarization and depolarization measurements a powerful particle characterization tool. In this presentation I will describe recent applications of photopolarimetric and lidar depolarization measurements to remote sensing characterization of tropospheric aerosols, polar stratospheric clouds (PSCs), and contrails. The talk will include (1) a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics; (2) the use of multi-angle multi-spectral photopolarimetry to retrieve the optical thickness, size distribution, refractive index, and number concentration of tropospheric aerosols over the ocean surface; and (3) the application of the T-matrix method to constraining the PSC and contrail particle microphysics using multi-spectral measurements of lidar backscatter and depolarization.

  4. Polar Mesospheric Clouds (PMCs) Observed by the Ozone Monitoring Instrument (OMI) on Aura

    NASA Technical Reports Server (NTRS)

    DeLand, Matthew T.; Shettle, Eric P.; Levelt, Pieternel F.; Kowalewski, Matthew G.

    2010-01-01

    Backscattered ultraviolet (BUV) instruments designed for measuring stratospheric ozone profiles have proven to be robust tools for observing polar mesospheric clouds (PMCs). These measurements are available for more than 30 years, and have been used to demonstrate the existence of long-term variations in PMC occurrence frequency and brightness. The Ozone Monitoring Instrument (OMI) on the EOS Aura satellite provides new and improved capabilities for PMC characterization. OMI uses smaller pixels than previous BUV instruments, which increases its ability to identify PMCs and discern more spatial structure, and its wide cross-track viewing swath provides full polar coverage up to 90 latitude every day in both hemispheres. This cross-track coverage allows the evolution of PMC regions to be followed over several consecutive orbits. Localized PMC variations determined from OMI measurements are consistent with coincident SBUV/2 measurements. Nine seasons of PMC observations from OMI are now available, and clearly demonstrate the advantages of these measurements for PMC analysis.

  5. A 6-year climatology of cloud occurrence frequency from Stratospheric Aerosol and Gas Experiment II observations (1985-1990)

    NASA Astrophysics Data System (ADS)

    Wang, Pi-Huan; Minnis, Patrick; McCormick, M. Patrick; Kent, Geoffrey S.; Skeens, Kristi M.

    1996-12-01

    A 6-year climatology of subvisual and opaque cloud occurrence frequencies is established using observations from the Stratospheric Aerosol and Gas Experiment (SAGE) II between 1985 and 1990. The subvisual clouds are observed mostly at high altitudes near the tropopause. The opaque clouds terminate the profiling, reducing the measurement frequency of the SAGE II instrument in the troposphere. With its 1-km vertical resolution, the climatology shows many interesting features, including (1) the seasonal expansion and migration behavior of the subvisual and opaque cloud systems; (2) the association of the zonal mean cloud frequency distributions with the tropospheric mean circulation (Hadley and Ferrel cells); (3) the tropical cloud occurrence that follows the equatorial circulation, including the Walker circulation over the Pacific Ocean; and (4) the overall higher cloud occurrence in the northern hemisphere than in the southern hemisphere. The radiative impact of subvisual clouds is estimated to be a 1-W m-2 reduction in outgoing longwave radiation. The maximum overall effect is a net positive cloud forcing of 0.5-1 W m-2 in the tropics. During the 1987 El Niño-Southern Oscillation (ENSO), cloud frequency was generally enhanced in the tropics and midlatitudes and reduced in the subtropics and high latitudes. The present study shows a distinct negative correlation between the high-altitude cloud occurrence and the lower stratospheric water vapor mixing ratio in the tropics, providing intrinsic evidence on the delicate connection between the stratospheric-tropospheric exchange and dehydration processes and the high-altitude cloud activities.

  6. A two micron polarization survey toward dark clouds

    NASA Technical Reports Server (NTRS)

    Tamura, M.; Sato, S.; Gatley, I.; Hough, J. H.

    1989-01-01

    A near infrared (2.2 micron) polarization survey of about 190 sources was conducted toward nearby dark clouds. The sample includes both background field stars and embedded young stellar objects. The aim is to determine the magnetic field structure in the densest regions of the dark clouds and study the role of magnetic fields in various phases of star formation processes, and to study the grain alignment efficiency in the dark cloud cores. From the polarization of background field stars and intrinsically unpolarized embedded sources, the magnetic field structure was determined in these clouds. From the intrinsic polarization of young stellar objects, the spatial distribution was determined of circumstellar dust around young stars. Combining the perpendicularity between the disks and magnetic fields with perpendicularity between the cloud elongation and magnetic fields, it is concluded that the magnetic fields might have dominated nearly all aspects of cloud dynamics, from the initial collapse of the clouds right through to the formation of disks/tori around young stars in these low to intermediate mass star forming clouds of the Taurus, Ophiuchus, and Perseus.

  7. Meteoric material and the behavior of upper stratospheric polar zone

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.; Mcpeters, R. D.

    1986-01-01

    Ozone mixing ratios as a function of pressure level and time are presented based on data obtained with the Nimbus-7 SBUV instrument between 1979 and 1984, and implications of this data for the explanations of the spring Antarctic ozone depletion are considered. It is suggested that meteoric atoms react with the atmosphere to bond to OH, and subsequently react with HCl to form salts, resulting in the accumulation of chlorine during polar winter. The sudden release of this chlorine from photodissociation of these salts during spring could account for the loss of ozone in the upper atmosphere.

  8. Seasonal predictability of stratospheric Polar Jet Oscillation Events and their surface impact

    NASA Astrophysics Data System (ADS)

    Domeisen, Daniela; Hitchcock, Peter; Dobrynin, Mikhail; Müller, Wolfgang; Baehr, Johanna

    2017-04-01

    The prediction of mid-winter stratospheric sudden warming (SSW) events tends to be limited to time scales of about two weeks. This renders their prediction difficult on seasonal time scales, which further limits the prediction of surface impacts of these events, although these tend to be long-lived, i.e. up to several weeks. SSW events can sometimes be followed by so-called Polar Jet Oscillation (PJO) events, which are characterized by an extended recovery of the stratospheric flow and long-lasting temperature anomalies in the lower stratosphere. These events may therefore lead to an extended duration of the surface impact of SSW events (though PJO events may also occur independently of SSW events). An improvement in the prediction of PJO events along with a better understanding of their surface impact could therefore significantly improve winter predictability in the extratropical troposphere. We here report on a 30-member ensemble of seasonal hindcasts initialized on November 1st of each year from 1979 to 2014 in the seasonal prediction system based on the Max Planck Institute Earth System Model (MPI-ESM) at MR resolution. Evidence is found that the ensemble provides improved statistical predictability for both SSW and PJO events. In addition, the surface impact of PJO events is well represented in the model as compared to reanalysis, and it is significantly stronger and longer-lived than for SSW events. These results suggest that stratospheric PJO events may add significant predictability to the tropospheric winter evolution.

  9. On the age of stratospheric air and ozone depletion potentials in polar regions

    NASA Technical Reports Server (NTRS)

    Pollock, W. H.; Heidt, L. E.; Lueb, R. A.; Vedder, J. F.; Mills, M. J.; Solomon, S.

    1992-01-01

    Observations of the nearly inert, man-made chlorofluorocarbon CFC-115 obtained during January 1989 are used to infer the age of air in the lower stratosphere. These observations together with estimated release rates suggest an average age of high-latitude air at pressure altitudes near 17-21 km of about 3 to 5 yr. This information is used together with direct measurements of HCFC-22, HCFC-142b, CH3Br, H-1301, H-1211, and H-2402 to examine the fractional dissociation of these species within the Arctic polar lower stratosphere compared to that of CFC-11 and hence to estimate their local ozone depletion potentials in this region. It is shown that these HCFCs are much less efficiently dissociated within the stratosphere than CFC-11, lowering their ozone depletion potentials to only about 30-40 percent of their chlorine loading potentials. In contrast, the observations of CH3Br and the Halons considered confirm that they are rapidly dissociated within the stratosphere, with important implications for their ozone depletion potentials.

  10. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Key, J.

    1989-01-01

    The objectives are to develop a suitable validation data set for evaluating the effectiveness of the International Satellite Cloud Climatology Project (ISCCP) algorithm for cloud retrieval in polar regions, to identify limitations of current procedures and to explore potential means to remedy them using textural classifiers, and to compare synoptic cloud data from model runs with observations. Toward the first goal, a polar data set consisting of visible, thermal, and passive microwave data was developed. The AVHRR and SMMR data were digitally merged to a polar stereographic projection with an effective pixel size of 5 sq km. With this data set, two unconventional methods of classifying the imagery for the analysis of polar clouds and surfaces were examined: one based on fuzzy sets theory and another based on a trained neural network. An algorithm for cloud detection was developed from an early test version of the ISCCP algorithm. This algorithm includes the identification of surface types with passive microwave, then temporal tests at each pixel location in the cloud detection phase. Cloud maps and clear sky radiance composites for 5 day periods are produced. Algorithm testing and validation was done with both actural AVHRR/SMMR data, and simulated imagery. From this point in the algorithm, groups of cloud pixels are examined for their spectral and textural characteristics, and a procedure is developed for the analysis of cloud patterns utilizing albedo, IR temperature, and texture. In a completion of earlier work, empirical analyses of arctic cloud cover were explored through manual interpretations of DMSP imagery and compared to U.S. Air Force 3D-nephanalysis. Comparisons of observed cloudiness from existing climatologies to patterns computed by the GISS climate model were also made.

  11. The relationship of satellite-inferred stratospheric aerosol extinction to the position of the 50-mb north polar jet stream

    NASA Technical Reports Server (NTRS)

    Livingston, John M.; Endlich, Roy M.

    1988-01-01

    The relationship between stratospheric aerosols and the location of the north polar night stratospheric jet stream was investigated for selected periods of four successive winters (1979-1982), using measurements from SAM II (Stratospheric Aerosol Measurement II) and SAGE I (Stratospheric Aerosol and Gas Experiment I) satellite-borne sun photometers and corresponding meteorological observations. Each period investigated included a polar stratospheric warming during which major dynamic meteorological changes are known to have perturbed the structure of the polar vortex. The analysis of variations in aerosol extinction mixing ratio patterns among winters and during major stratospheric warming events within separate winters showed a well-defined positive gradient in extinction mixing ratio and temperature across the jet stream from the cyclonic side to the anticyclonic side at altitudes between 20 and 30 km during each winter period. Estimates of extinction mixing ratio profiles measured near the center of the polar vortex suggest that a gradual subsidence took place within the polar vortex during at least three of the four winter periods.

  12. Intra-seasonal variability of extreme boreal stratospheric polar vortex events and their precursors

    NASA Astrophysics Data System (ADS)

    Díaz-Durán, Adelaida; Serrano, Encarna; Ayarzagüena, Blanca; Abalos, Marta; de la Cámara, Alvaro

    2017-01-01

    The dynamical variability of the boreal stratospheric polar vortex has been usually analysed considering the extended winter as a whole or only focusing on December, January and February. Yet recent studies have found intra-seasonal differences in the boreal stratospheric dynamics. In this study, the intra-seasonal variability of anomalous wave activity preceding polar vortex extremes in the Northern Hemisphere is examined using ERA-Interim reanalysis data. Weak (WPV) and strong (SPV) polar vortex events are grouped into early, mid- or late winter sub-periods depending on the onset date. Overall, the strongest (weakest) wave-activity anomalies preceding polar vortex extremes are found in mid- (early) winter. Most of WPV (SPV) events in early winter occur under the influence of east (west) phase of the Quasi-Biennial Oscillation (QBO) and an enhancement (inhibition) of wavenumber-1 wave activity (WN1). Mid- and late winter WPV events are preceded by a strong vortex and an enhancement of WN1 and WN2, but the spatial structure of the anomalous wave activity and the phase of the QBO are different. Prior to mid-winter WPVs the enhancement of WN2 is related to the predominance of La Niña and linked to blockings over Siberia. Mid-winter SPV events show a negative phase of the Pacific-North America pattern that inhibits WN1 injected into the stratosphere. This study suggests that dynamical features preceding extreme polar vortex events in mid-winter should not be generalized to other winter sub-periods.

  13. Laboratory studies of stratospheric aerosol chemistry

    NASA Technical Reports Server (NTRS)

    Molina, Mario J.

    1996-01-01

    In this report we summarize the results of the two sets of projects funded by the NASA grant NAG2-632, namely investigations of various thermodynamic and nucleation properties of the aqueous acid system which makes up stratospheric aerosols, and measurements of reaction probabilities directly on ice aerosols with sizes corresponding to those of polar stratospheric cloud particles. The results of these investigations are of importance for the assessment of the potential stratospheric effects of future fleets of supersonic aircraft. In particular, the results permit to better estimate the effects of increased amounts of water vapor and nitric acid (which forms from nitrogen oxides) on polar stratospheric clouds and on the chemistry induced by these clouds.

  14. Weakening and shift of the Arctic stratospheric polar vortex: Internal variability or forced response?

    NASA Astrophysics Data System (ADS)

    Seviour, William J. M.

    2017-04-01

    Recent studies have proposed that the Arctic stratospheric polar vortex has weakened and shifted away from the North Pole during the past three decades. Some of these studies suggest that this trend has been driven by a decline in Arctic sea ice leading to enhanced zonal wave number 1 waves propagating into the stratosphere and that it has in turn contributed to a recent wintertime surface cooling over North America and some parts of Eurasia. Here trends in several measures of the location and strength of the stratospheric polar vortex from 1980 to 2016 are examined in two reanalysis products. All measures show weakening and equatorward shift trends, but only one measure, the vortex centroid latitude, has a trend which is statistically significant at the 95% level in both reanalyses. By comparing large ensembles of historical simulations with preindustrial control simulations for two coupled climate models, the ensemble mean response of the vortex is found to be small relative to internal variability. There is also no relationship between sea ice decline and trends in either vortex location or strength. Despite this, individual ensemble members are found to have vortex trends similar to those observed, indicating that these trends may be primarily a result of natural internally generated climate variability.

  15. Intensified tropospheric-stratospheric interaction during events of strong boreal Polar-night Jet Oscillations

    NASA Astrophysics Data System (ADS)

    Peters, Dieter H. W.; Schneidereit, Andrea

    2017-04-01

    The middle atmosphere in winter shows a high variability in polar latitudes from year to year, which is primarily caused by counter acting forces of radiative cooling and of upward directed transport of zonal mean easterly angular momentum by planetary wave. The aim of this study is to examine both the annual variation of Northern Annular Modes (NAMs) of geopotential height anomalies north of 60° N and the variability of Polar night Jet Oscillations (PJOs) determined as the two leading Empirical Orthogonal Functions (EOFs) of polar cap temperature profiles from 1979 until 2013, in order to investigate the coupling between troposphere and stratosphere and vice versa. Based on ERA-Interim reanalysis data we determine 20 major sudden stratospheric warmings (MSSWs) by the use of a NAM threshold of -2.3 at the 10 hPa layer in agreement with former studies. With an extended definition of PJO events of Hitchcook et al. (2013) we identified 9 strong PJOs (larger than (3σ for 100 degree)) and 7 no PJO events (smaller than (2σ for 100 degree)) whereas 4 intermediate PJO events remain. In the composites analysis of strong PJOs the lag-evolution of NAM and the one of zonal mean zonal wind anomalies show a strong downward propagating signal into the middle troposphere after the central day (CD). The mean difference between strong PJOs and no PJOs is significant (95 % student-t test): (i) in the upper troposphere about 20 days before CD, (ii) in the stratosphere and troposphere after CD. Furthermore, a main finding is that in the middle troposphere the zonal mean zonal wind anomalies are significantly reduced for strong PJOs about 20 days and about 50 days after CD. The zonal mean wind reductions are in coherence with pulses of enhanced eddy heat transport by planetary waves and their induced convergence of EP fluxes. For strong PJOs, the reestablishment of a strong polar vortex with strong zonal mean zonal wind anomalies in the upper stratosphere about 10 days after CD is

  16. A quantitative analysis of the reactions involved in stratospheric ozone depletion in the polar vortex core

    NASA Astrophysics Data System (ADS)

    Wohltmann, Ingo; Lehmann, Ralph; Rex, Markus

    2017-09-01

    We present a quantitative analysis of the chemical reactions involved in polar ozone depletion in the stratosphere and of the relevant reaction pathways and cycles. While the reactions involved in polar ozone depletion are well known, quantitative estimates of the importance of individual reactions or reaction cycles are rare. In particular, there is no comprehensive and quantitative study of the reaction rates and cycles averaged over the polar vortex under conditions of heterogeneous chemistry so far. We show time series of reaction rates averaged over the core of the polar vortex in winter and spring for all relevant reactions and indicate which reaction pathways and cycles are responsible for the vortex-averaged net change of the key species involved in ozone depletion, i.e., ozone, chlorine species (ClOx, HCl, ClONO2), bromine species, nitrogen species (HNO3, NOx) and hydrogen species (HOx). For clarity, we focus on one Arctic winter (2004-2005) and one Antarctic winter (2006) in a layer in the lower stratosphere around 54 hPa and show results for additional pressure levels and winters in the Supplement. Mixing ratios and reaction rates are obtained from runs of the ATLAS Lagrangian chemistry and transport model (CTM) driven by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis data. An emphasis is put on the partitioning of the relevant chemical families (nitrogen, hydrogen, chlorine, bromine and odd oxygen) and activation and deactivation of chlorine.

  17. Weakening of the stratospheric polar vortex by Arctic sea-ice loss.

    PubMed

    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, enhances 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.

  18. On the longitudinal variability of the mean age of stratospheric air and the polar vortex preconditioning

    NASA Astrophysics Data System (ADS)

    Šácha, Petr; Añel, Juan; de la Torre, Laura; Pišoft, Petr; Kuchař, Aleš

    2017-04-01

    Using three-dimensional (3D) fields of the mean age of stratospheric air (AoA) from the Canadian Middle Atmosphere Model (CMAM) as a 3D transport diagnostic, we study a role of the spatiotemporal gravity wave activity distribution for the middle atmospheric circulation and longitudinal variability of the Brewer-Dobson circulation. Further we make use of the fact that AoA reflects the cumulative effect of transport processes and study its potential to act as a vortex preconditioning proxy with a possibility to enhance the predictability of polar vortex events. For this case we created composite analysis of sudden stratospheric warming events from the CMAM specific dynamics simulation and focus on the full 3D fields and AoA distribution anomalies. The dynamical origin of these anomalies is then analysed with respect to the anomalous planetary and gravity wave activity.

  19. CLOUD AND HAZE IN THE WINTER POLAR REGION OF TITAN OBSERVED WITH VISUAL AND INFRARED MAPPING SPECTROMETER ON BOARD CASSINI

    SciTech Connect

    Rannou, P.; Le Mouelic, S.; Sotin, C.; Brown, R. H.

    2012-03-20

    A large cloud in the north polar region of Titan was first observed by the Visual and Infrared Mapping Spectrometer (VIMS) in 2005 and then in 2006. This cloud, confined beyond the latitude 62 Degree-Sign N, is surrounded by a mixture of aerosol and mist probably lying in the low stratosphere and troposphere. Subsequent images of this region of Titan show a gradual vanishing of this cloud which was reported previously. In this paper, we characterize the physical properties of this cloud, haze, and mist as well as their time evolutions. We note several details on the images such as a secondary cloud above the main cloud and latitudes beyond 70 Degree-Sign N. We also show that the cloud disappearance leaves the polar region poorly loaded in aerosols, yielding an annular zone of aerosols between 50 Degree-Sign N and 65 Degree-Sign N. Our analysis suggests that this structure observed by VIMS in the near-IR is an annular structure observed by ISS on board Voyager one Titan year ago in 1980.

  20. What Controls the Arctic Lower Stratosphere Temperature?

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  1. Effects of stratospheric aerosols and thin cirrus clouds on the atmospheric correction of ocean color imagery: simulations.

    PubMed

    Gordon, H R; Zhang, T; He, F; Ding, K

    1997-01-20

    Using simulations, we determine the influence of stratospheric aerosol and thin cirrus clouds on the performance of the proposed atmospheric correction algorithm for the moderate resolution imaging spectroradiometer (MODIS) data over the oceans. Further, we investigate the possibility of using the radiance exiting the top of the atmosphere in the 1.38-microm water vapor absorption band to remove their effects prior to application of the algorithm. The computations suggest that for moderate optical thicknesses in the stratosphere, i.e., tau(s) < or approximately 0.15, the stratospheric aerosol-cirrus cloud contamination does not seriously degrade the MODIS except for the combination of large (approximately 60 degrees) solar zenith angles and large (approximately 45 degrees) viewing angles, for which multiple-scattering effects can be expected to be particularly severe. The performance of a hierarchy of stratospheric aerosol/cirrus cloud removal procedures for employing the 1.38-microm water vapor absorption band to correct for stratospheric aerosol/cirrus clouds, ranging from simply subtracting the reflectance at 1.38 microm from that in the visible bands, to assuming that their optical properties are known and carrying out multiple-scattering computations of their effect by the use of the 1.38-microm reflectance-derived concentration, are studied for stratospheric aerosol optical thicknesses at 865 nm as large as 0.15 and for cirrus cloud optical thicknesses at 865 nm as large as 1.0. Typically, those procedures requiring the most knowledge concerning the aerosol optical properties (and also the most complex) performed the best; however, for tau(s) < or approximately 0.15, their performance is usually not significantly better than that found by applying the simplest correction procedure. A semiempirical algorithm is presented that permits accurate correction for thin cirrus clouds with tau(s) as large as unity when an accurate estimate of the cirrus cloud

  2. Lower stratospheric temperature differences between meteorological analyses in two cold Arctic winters and their impact on polar processing studies

    NASA Astrophysics Data System (ADS)

    Manney, Gloria L.; Sabutis, Joseph L.; Pawson, Steven; Santee, Michelle L.; Naujokat, Barbara; Swinbank, Richard; Gelman, Melvyn E.; Ebisuzaki, Wesley

    2003-03-01

    A quantitative comparison of six meteorological analyses is presented for the cold 1999/2000 and 1995/1996 Arctic winters. Using different analyzed data sets to obtain temperatures and temperature histories can have significant consequences. The area with temperatures below a polar stratospheric cloud (PSC) formation threshold commonly varies by ˜25% between the analyses, with some differences over 50%. Biases between analyses vary from year to year; in January 2000, Met Office analyses were coldest and National Centers for Environmental Prediction (NCEP) analyses were warmest, while NCEP analyses were usually coldest in 1995/1996 and NCEP/National Center for Atmospheric Research Reanalysis (REAN) were usually warmest. Freie Universität Berlin analyses are often colder than others at T ≲ 205 K. European Centre for Medium-Range Weather Forecasts (ECMWF) temperatures agreed better with other analyses in 1999/2000, after improvements in the assimilation system, than in 1995/1996. Temperature history case studies show substantial differences using Met Office, NCEP, REAN, ECMWF, and NASA Data Assimilation Office (DAO) analyses. In January 2000 (when a large cold region was centered in the polar vortex), all analyses gave qualitatively similar results. However, in February 2000 (a much warmer period) and in January and February 1996 (comparably cold to January 2000 but with the cold region near the polar vortex edge), distributions of "potential PSC lifetimes" and total time spent below a PSC formation threshold varied significantly between the analyses. Largest peaks in "PSC lifetime" distributions in January 2000 were at 4-6 and 11-14 days, while in 1996 they were at 1-3 days. Different meteorological conditions in comparably cold winters have a large impact on expectations for PSC formation and on the effects of discrepancies between different meteorological analyses. Met Office, NCEP, REAN, ECMWF, and DAO analyses are commonly used in modeling polar processes

  3. Clouds

    NASA Image and Video Library

    2010-09-14

    Clouds are common near the north polar caps throughout the spring and summer. The clouds typically cause a haze over the extensive dune fields. This image from NASA Mars Odyssey shows the edge of the cloud front.

  4. Inverted Polarity Thunderstorms Linked with Elevated Cloud Base Height

    NASA Astrophysics Data System (ADS)

    Cummins, K. L.; Williams, E.

    2016-12-01

    The great majority of thunderstorms worldwide exhibit gross positive dipole structure, produce intracloud lightning that reduces this positive dipole (positive intracloud flashes), and produce negative cloud-to-ground lightning from the lower negative end of this dipole. During the STEPS experiment in 2000 much new evidence for thunderstorms (or cells within multi-cellular storms) with inverted polarity came to light, both from balloon soundings of electric field and from LMA analysis. Many of the storms with inverted polarity cells developed in eastern Colorado. Fleenor et al. (2009) followed up after STEPS to document a dominance of positive polarity CG lightning in many of these cases. In the present study, surface thermodynamic observations (temperature and dew point temperature) have been used to estimate the cloud base heights and temperatures at the time of the Fleenor et al. lightning observations. It was found that when more than 90% of the observed CG lightning polarity within a storm is negative, the cloud base heights were low (2000 m AGL or lower, and warmer, with T>10 C), and when more than 90% of the observed CG lightning within a storm was positive, the cloud base heights were high (3000 m AGL or higher, and colder, with T< 2 C). Multi-cellular storms or temporally-evolving storms with mixed polarity were generally associated with intermediate cloud base heights. These findings on inverted polarity thunderstorms are remarkably consistent with results in other parts of the world where strong instability prevails in the presence of high cloud base height: the plateau regions of China (Liu et al., 1989; Qie et al., 2005), and in pre-monsoon India (Pawar et al., 2016), particularly when mixed polarity cases are excluded. Calculations of adiabatic cloud water content for lifting from near 0 oC cast some doubt on earlier speculation (Williams et al., 2005) that the graupel particles in these inverted polarity storms attain a wet growth condition, and so

  5. Dissipation of Titans north polar cloud at northern spring equinox

    USGS Publications Warehouse

    Le, Mouelic S.; Rannou, P.; Rodriguez, S.; Sotin, Christophe; Griffith, C.A.; Le, Corre L.; Barnes, J.W.; Brown, R.H.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.; Tobie, G.

    2012-01-01

    Saturns Moon Titan has a thick atmosphere with a meteorological cycle. We report on the evolution of the giant cloud system covering its north pole using observations acquired by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. A radiative transfer model in spherical geometry shows that the clouds are found at an altitude between 30 and 65 km. We also show that the polar cloud system vanished progressively as Titan approached equinox in August 2009, revealing at optical wavelengths the underlying sea known as Kraken Mare. This decrease of activity suggests that the north-polar downwelling has begun to shut off. Such a scenario is compared with the Titan global circulation model of Rannou et al. (2006), which predicts a decrease of cloud coverage in northern latitudes at the same period of time. ?? 2011 Elsevier Ltd. All rights reserved.

  6. The Three-Dimensional Structure of Breaking Rossby Waves in the Polar Wintertime Stratosphere.

    NASA Astrophysics Data System (ADS)

    Polvani, L. M.; Saravanan, R.

    2000-11-01

    The three-dimensional nature of breaking Rossby waves in the polar wintertime stratosphere is studied using an idealized global primitive equation model. The model is initialized with a well-formed polar vortex, characterized by a latitudinal band of steep potential vorticity (PV) gradients. Planetary-scale Rossby waves are generated by varying the topography of the bottom boundary, corresponding to undulations of the tropopause. Such topographically forced Rossby waves then propagate up the edge of the vortex, and their amplification with height leads to irreversible wave breaking.These numerical experiments highlight several nonlinear aspects of stratospheric dynamics that are beyond the reach of both isentropic two-dimensional models and fully realistic GCM simulations. They also show that the polar vortex is contorted by the breaking Rossby waves in a surprisingly wide range of shapes.With zonal wavenumber-1 forcing, wave breaking usually initiates as a deep helical tongue of PV that is extruded from the polar vortex. This tongue is often observed to roll up into deep isolated columns, which, in turn, may be stretched and tilted by horizontal and vertical shears. The wave amplitude directly controls the depth of the wave breaking region and the amount of vortex erosion. At large forcing amplitudes, the wave breaking in the middle/lower portions of the vortex destroys the PV gradients essential for vertical propagation, thus shielding the top of the vortex from further wave breaking.The initial vertical structure of the polar vortex is shown to play an important role in determining the characteristics of the wave breaking. Perhaps surprisingly, initially steeper PV gradients allow for stronger vertical wave propagation and thus lead to stronger erosion. Vertical wind shear has the notable effect of tilting and stretching PV structures, and thus dramatically accelerating the downscale stirring. An initial decrease in vortex area with increasing height (i.e., a

  7. Modulation of Madden-Julian Oscillation on the polar mesospheric clouds

    NASA Astrophysics Data System (ADS)

    Li, T.; Yang, C.; Liu, X.; Yue, J.; Russell, J. M., III; Dou, X.

    2016-12-01

    The Madden-Julian Oscillation (MJO) is a dominant intra-seasonal variability in the equatorial troposphere, and is characterized by eastward propagation of tropical deep convection with a speed of 5 m/s from Indian ocean to central Pacific ocean, and with a intra-seasonal period of 30-90 days [Madden and Julian, 1994]. The MJO could significantly impact the global weather and climate [Zhang, 2005]. Recent studies also suggested that the Northern Hemisphere (NH) stratospheric polar vortex could be modulated by the MJO with strengthened (weakened) polar vortex during the enhanced (suppressed) convection in the tropical central Pacific Ocean [Garfinkel et al., 2014]. Using the Aura/Microwave Limb Sounder (MLS) and Aeronomy of Ice in the Mesosphere (AIM) observations, the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis interim dataset, and Specified Dynamics of Whole Atmosphere Community Climate Model (SD-WACCM) simulations, we study the influences of MJO in the mesosphere during the Northern winter and on the southern hemisphere summer polar mesospheric cloud (PMC). The anomalous PMC occurrence frequency is clearly correlated with anomalous water vapor and anti-correlated with anomalous temperature in the southern hemisphere polar mesosphere, suggesting that the MJO modulates the summer polar mesospheric temperature and water vapor and thus the formation of PMC. We will also discuss the possible mechanism of the mesosphere responses to MJO using SD-WACCM and ECMWF.

  8. Radiative-dynamical and microphysical processes of thin cirrus clouds controlling humidity of air entering the stratosphere

    NASA Astrophysics Data System (ADS)

    Dinh, Tra; Fueglistaler, Stephan

    2016-04-01

    Thin cirrus clouds in the tropical tropopause layer (TTL) are of great interest due to their role in the control of water vapor and temperature in the TTL. Previous research on TTL cirrus clouds has focussed mainly on microphysical processes, specifically the ice nucleation mechanism and dehydration efficiency. Here, we use a cloud resolving model to analyse the sensitivity of TTL cirrus characteristics and impacts with respect to microphysical and radiative processes. A steady-state TTL cirrus cloud field is obtained in the model forced with dynamical conditions typical for the TTL (2-dimensional setup with a Kelvin-wave temperature perturbation). Our model results show that the dehydration efficiency (as given by the domain average relative humidity in the layer of cloud occurrence) is relatively insensitive to the ice nucleation mechanism, i.e. homogeneous versus heterogeneous nucleation. Rather, TTL cirrus affect the water vapor entering the stratosphere via an indirect effect associated with the cloud radiative heating and dynamics. Resolving the cloud radiative heating and the radiatively induced circulations approximately doubles the domain average ice mass. The cloud radiative heating is proportional to the domain average ice mass, and the observed increase in domain average ice mass induces a domain average temperature increase of a few Kelvin. The corresponding increase in water vapor entering the stratosphere is estimated to be about 30 to 40%.

  9. Time-variability of Polar Winter Snow Clouds on Mars

    NASA Astrophysics Data System (ADS)

    Hayne, P. O.; Kass, D. M.; Kleinboehl, A.; Schofield, J. T.; McCleese, D. J.

    2015-12-01

    Carbon dioxide snow clouds are known to occur in the polar regions on Mars during the long polar night. Earlier studies have shown that a substantial fraction (up to ~20%) of the seasonal ice caps of Mars can be deposited as CO2 snowfall. The presence of optically thick clouds can also strongly influence the polar energy balance, by scattering thermal radiation emitted by the surface and lower atmosphere. Furthermore, snow deposition is likely to affect the surface morphology and subsequent evolution of the seasonal caps. Therefore, both the spatial distribution and time variability of polar snow clouds are important for understanding their influence on the Martian CO2cycle and climate. However, previous investigations have suffered from relatively coarse time resolution (typically days), coarse or incomplete spatial coverage, or both. Here we report results of a dedicated campaign by the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter, to observe polar CO2 clouds with an unprecedented time-resolution within the same spatial region. By scanning the MCS field of view, we acquired observations directly over the north pole for every ~2hr orbit over the course of several days. This was repeated during two separate periods in northern winter. The 2 hr sampling frequency enables the detailed study of cloud evolution. These observations were also compared to a cloud-free, control region just off the pole, which was sampled in the same way. Results from this experiment show that the north polar CO2 clouds are dynamic, and appear to follow a consistent pattern: Beginning with a relatively clear atmosphere, the cloud rapidly grows to ~25 - 30 km altitude in < 2 hr. Then, the altitude of the cloud tops diminishes slowly, reaching near the surface after ~6 - 10 hr. We interpret this slow decay as the precipitation of snow particles, which constrains their size to be ~10 - 100 μm. Also pervasive in this season are water ice clouds, which may provide

  10. Lessened response of boreal winter stratospheric polar vortex to El Niño in recent decades

    NASA Astrophysics Data System (ADS)

    Hu, Jinggao; Li, Tim; Xu, Haiming; Yang, Shuangyan

    2017-07-01

    The decadal change of El Niño teleconnection and the corresponding response of the boreal winter stratospheric polar vortex are investigated through the composite analysis of El Niño events during the two periods 1958-78 and 1979-2015. It is found that, during the period 1958-78, El Niño generates an anomalous Aleutian low in the mid troposphere extending from northeastern Eurasia to the northeastern Pacific with the most significant center in the northwestern Pacific. The anomalous Aleutian low results in a marked increase in planetary wavenumber 1 but a weak decrease in wavenumber 2 from the upper troposphere to lower stratosphere. The Eliassen-Palm (EP) flux of planetary waves converges at the high latitudes in the stratosphere and brings about a significantly weakened polar vortex. In contrast, during the period 1979-2015, the wintertime El Niño-related Aleutian low shifts eastward into the northeastern Pacific. This variation in tropospheric El Niño teleconnection leads to a dramatic decrease in planetary wavenumber 2 but a relatively weak increase in wavenumber 1. Furthermore, the magnitude of the decrease of wavenumber-2 EP flux is comparable to the increase of wavenumber-1 EP flux in the stratosphere. Consequently, the stratospheric response lessens dramatically, showing a less disturbed and slightly enhanced polar vortex. The lessened stratospheric response is quite obvious in the stratosphere below 10 hPa regardless of the long-term trend being removed or not, indicating a dominant role of El Niño in the wintertime variability of lower polar stratosphere.

  11. Lessened response of boreal winter stratospheric polar vortex to El Niño in recent decades

    NASA Astrophysics Data System (ADS)

    Hu, Jinggao; Li, Tim; Xu, Haiming; Yang, Shuangyan

    2016-09-01

    The decadal change of El Niño teleconnection and the corresponding response of the boreal winter stratospheric polar vortex are investigated through the composite analysis of El Niño events during the two periods 1958-78 and 1979-2015. It is found that, during the period 1958-78, El Niño generates an anomalous Aleutian low in the mid troposphere extending from northeastern Eurasia to the northeastern Pacific with the most significant center in the northwestern Pacific. The anomalous Aleutian low results in a marked increase in planetary wavenumber 1 but a weak decrease in wavenumber 2 from the upper troposphere to lower stratosphere. The Eliassen-Palm (EP) flux of planetary waves converges at the high latitudes in the stratosphere and brings about a significantly weakened polar vortex. In contrast, during the period 1979-2015, the wintertime El Niño-related Aleutian low shifts eastward into the northeastern Pacific. This variation in tropospheric El Niño teleconnection leads to a dramatic decrease in planetary wavenumber 2 but a relatively weak increase in wavenumber 1. Furthermore, the magnitude of the decrease of wavenumber-2 EP flux is comparable to the increase of wavenumber-1 EP flux in the stratosphere. Consequently, the stratospheric response lessens dramatically, showing a less disturbed and slightly enhanced polar vortex. The lessened stratospheric response is quite obvious in the stratosphere below 10 hPa regardless of the long-term trend being removed or not, indicating a dominant role of El Niño in the wintertime variability of lower polar stratosphere.

  12. Sensitivity of Polar Stratospheric Ozone Loss to Uncertainties in Chemical Reaction Kinetics

    NASA Technical Reports Server (NTRS)

    Kawa, S. Randolph; Stolarksi, Richard S.; Douglass, Anne R.; Newman, Paul A.

    2008-01-01

    Several recent observational and laboratory studies of processes involved in polar stratospheric ozone loss have prompted a reexamination of aspects of our understanding for this key indicator of global change. To a large extent, our confidence in understanding and projecting changes in polar and global ozone is based on our ability to simulate these processes in numerical models of chemistry and transport. The fidelity of the models is assessed in comparison with a wide range of observations. These models depend on laboratory-measured kinetic reaction rates and photolysis cross sections to simulate molecular interactions. A typical stratospheric chemistry mechanism has on the order of 50- 100 species undergoing over a hundred intermolecular reactions and several tens of photolysis reactions. The rates of all of these reactions are subject to uncertainty, some substantial. Given the complexity of the models, however, it is difficult to quantify uncertainties in many aspects of system. In this study we use a simple box-model scenario for Antarctic ozone to estimate the uncertainty in loss attributable to known reaction kinetic uncertainties. Following the method of earlier work, rates and uncertainties from the latest laboratory evaluations are applied in random combinations. We determine the key reactions and rates contributing the largest potential errors and compare the results to observations to evaluate which combinations are consistent with atmospheric data. Implications for our theoretical and practical understanding of polar ozone loss will be assessed.

  13. Optical imaging of cloud-to-stratosphere/mesosphere lightning over the Amazon Basin (CS/LAB)

    NASA Technical Reports Server (NTRS)

    Sentman, Davis D.; Wescott, Eugene M.

    1995-01-01

    The purpose of the CS/LAB project was to obtain images of cloud to stratosphere lightning discharges from aboard NASA's DC-8 Airborne Laboratory while flying in the vicinity of thunderstorms over the Amazon Basin. We devised a low light level imaging package as an add-on experiment to an airborne Laboratory deployment to South America during May-June, 1993. We were not successful in obtaining the desired images during the South American deployment. However, in a follow up flight over the American Midwest during the night of July 8-9, 1993 we recorded nineteen examples of the events over intense thunderstorms. From the observations were estimated absolute brightness, terminal altitudes, flash duration, horizontal extents, emission volumes, and frequencies relative to negative and positive ground strokes.

  14. Solar mesosphere explorer satellite measurements of el Chicon stratospheric aerosols. 1. Cloud morphology

    SciTech Connect

    Rusch D.W.; Clancy, R.T.; Eparvier, F.G.; Thomas, G.E.; Thomas, R.J.

    1994-10-20

    Data from the Solar Mesosphere Explorer (SME) is used to track the time, latitude, and altitude (above 18 km) development of the aerosol cloud injected into the stratosphere by the eruption of el Chichon. This unique data set, using scattering data from the near-infrared (1.27 and 1.87 {mu}m) and visible (440 nm) spectrometers on SME, covers the period from the initial injection in April 1982 through the end of 1986. Although the bulk of the mass is contained in the latitude band from 10{degrees}S to 30{degrees}N for the entire duration of the measurements, transport of material to high latitudes is apparent in the data in the post eruption period. The times of aerosol density maxima vary greatly as a function of altitude and latitude. 10 refs., 13 figs., 1 tab.

  15. Magnetic Field Structure in Molecular Clouds by Polarization Measurements

    NASA Astrophysics Data System (ADS)

    Chen, W. P.; Su, B. H.; Eswaraiah, C.; Pandey, A. K.; Wang, C. W.; Lai, S. P.; Tamura, M.; Sato, S.

    2015-03-01

    We report on a program to delineate magnetic field structure inside molecular clouds by optical and infrared polarization observations. An ordered magnetic field inside a dense cloud may efficiently align the spinning dust grains to cause a detectable level of optical and near-infrared polarization of otherwise unpolarized background starlight due to dichroic extinction. The near-infrared polarization data were taken by SIRPOL mounted on IRSF in SAAO. Here we present the SIRPOL results in RCW 57, for which the magnetic field is oriented along the cloud filaments, and in Carina Nebula, for which no intrinsic polarization is detected in the turbulent environment. We further describe TRIPOL, a compact and efficient polarimer to acquire polarized images simultaneously at g', r', and i' bands, which is recently developed at Nagoya University for adaption to small-aperture telescopes. We show how optical observations probe the translucent outer parts of a cloud, and when combining with infrared observations probing the dense parts, and with millimeter and submillimeter observations to sutdy the central embedded protostar, if there is one, would yield the magnetic field structure on different length scales in the star-formation process.

  16. Occurrence of ozone laminae near the boundary of the stratospheric polar vortex

    SciTech Connect

    Reid, S.J.; Vaughan, G. ); Kyro, E. )

    1993-05-20

    The authors report on observations of laminae in ozone distributions observed at high northern latitudes near the polar vortex. Regions of enhanced and depleted ozone density are observed. Data from ozonesonde collections and lidar measurements during the Airborne Arctic Stratosphere Expedition (AASE) are analyzed, and compared with earlier work. The ozonesonde archives of the World Meteorological Organization are also examined in this analysis. The laminae are observed to distribute differently as a function of season, and with the potential temperature. Transport of ozone equatorward is also found with a class of these laminae.

  17. Atmospheric Polarization Imaging with Variable Aerosols, Clouds, and Surface Albedo

    DTIC Science & Technology

    2013-07-01

    saddle” region between Mauna Loa and Mauna Kea in the background (home of the Keck and other astronomical telescopes). The frequently changing clouds...3. Mr. Andrew Dahlberg – graduate student working primarily on Mauna Loa polarization; 4. Mr. Michael Thomas – graduate student developing aerosol...fully on work supported by this grant: 1. Mr. Andrew Dahlberg – All-sky polarization imager deployment at Mauna Loa Observatory, Hawaii – M.S. Thesis

  18. How Model Differences in Stratospheric Transport can Influence Polar Ozone Recovery

    NASA Astrophysics Data System (ADS)

    Strahan, S. E.; Douglass, A. R.; Stolarski, R. S.

    2006-05-01

    We examine 3 Global Modeling Initiative (GMI) chemistry and transport simulations that have the same WMO A2 source gas boundary conditions for 1980-2025 but different stratospheric circulations and Arctic temperatures. We examine the evolution of Cly in each polar vortex and compare the models' ozone response. Two simulations of the GMI stratospheric model were run at 2ox2.5o resolution. One had a repeating cold Arctic winter with abundant PSCs; the other had a repeating dynamically active, warm winter with almost no PSCs. Maximum Cly in the cold simulation was 2.9 ppb in 2000 and was slightly lower in the warm simulation. The cold winter showed greater sensitivity to Cly and consequently recovered at a faster rate. Nevertheless, both are projected to recover at about the same time. The factors controlling recovery are the halogen boundary condition and mean stratospheric circulation (i.e., age of air), both of which are nearly the same in these simulations. The differences between these simulations demonstrate that interannual variation in transport will play a large role in the appearance of Arctic ozone recovery. Age of air is a diagnostic for stratospheric circulation, but it does not assess the credibility of specific model transport processes. We compare the two simulations above with a GMI simulation run at 4ox5o resolution. All 3 models compare extremely well with mean age determined from aircraft CO2, but the lower resolution model has considerably lower vortex Cly. The low Cly is caused by a leaky vortex which leads to two credibility problems: the leaky vortex can't produce near complete O3 loss because it doesn't maintain the necessary high levels of Cly, and the leakiness causes the model to respond faster to reductions in chlorine, allowing it return to 1980 levels sooner. Models used to predict ozone recovery need to demonstrate a strong Antarctic mixing barrier.

  19. On the connection between stratospheric water vapour changes and widespread severe denitrification in the Arctic

    NASA Astrophysics Data System (ADS)

    Khosrawi, Farahnaz; Urban, Jo; Lossow, Stefan; Stiller, Gabi; Murtagh, Donal

    2013-04-01

    Water vapour is one of the most important greenhouse gases and plays a key role in the chemistry of the upper troposphere and lower stratosphere (UT/LS). Any changes in atmospheric water vapour bring important implications for the global climate. Long-term ground-based and satellite measurements indicate an increase of stratospheric water vapour abundance by an average of 1 ppmv during the last 30 years (1980-2010). Increases in stratospheric water vapour cool the stratosphere but warm the troposphere. Both the cooling of the stratosphere and the increase in water vapour enhance the potential for the formation of polar stratospheric clouds. More than a decade ago it already was suggested that a cooling of stratospheric temperatures by 1 K or an increase of 1 ppmv of stratospheric water vapor could promote denitrification, the permanent removal of nitrogen species from the stratosphere by solid polar stratospheric cloud particles. In fact, during the two recent Arctic winter 2009/2010 and 2010/2011 the strongest denitrification in the recent decade was measured by Odin/SMR. In the latter winter denitrification lead also to severe ozone depletion with similar extensions as the Antarctic "ozone hole". In this study, the correlation between observed water vapour trends and the recent temperature evolution in the Arctic together with trace gas measurements and PSC observations are considered to investigate a possible connection between the increase in stratospheric water vapour and polar stratospheric cloud formation/denitrification.

  20. Toward autonomous surface-based infrared remote sensing of polar clouds: cloud-height retrievals

    NASA Astrophysics Data System (ADS)

    Rowe, Penny M.; Cox, Christopher J.; Walden, Von P.

    2016-08-01

    Polar regions are characterized by their remoteness, making measurements challenging, but an improved knowledge of clouds and radiation is necessary to understand polar climate change. Infrared radiance spectrometers can operate continuously from the surface and have low power requirements relative to active sensors. Here we explore the feasibility of retrieving cloud height with an infrared spectrometer that would be designed for use in remote polar locations. Using a wide variety of simulated spectra of mixed-phase polar clouds at varying instrument resolutions, retrieval accuracy is explored using the CO2 slicing/sorting and the minimum local emissivity variance (MLEV) methods. In the absence of imposed errors and for clouds with optical depths greater than ˜ 0.3, cloud-height retrievals from simulated spectra using CO2 slicing/sorting and MLEV are found to have roughly equivalent high accuracies: at an instrument resolution of 0.5 cm-1, mean biases are found to be ˜ 0.2 km for clouds with bases below 2 and -0.2 km for higher clouds. Accuracy is found to decrease with coarsening resolution and become worse overall for MLEV than for CO2 slicing/sorting; however, the two methods have differing sensitivity to different sources of error, suggesting an approach that combines them. For expected errors in the atmospheric state as well as both instrument noise and bias of 0.2 mW/(m2 sr cm-1), at a resolution of 4 cm-1, average retrieval errors are found to be less than ˜ 0.5 km for cloud bases within 1 km of the surface, increasing to ˜ 1.5 km at 4 km. This sensitivity indicates that a portable, surface-based infrared radiance spectrometer could provide an important complement in remote locations to satellite-based measurements, for which retrievals of low-level cloud are challenging.

  1. Theoretical Studies of Polar Stratospheric Clouds and the Background Stratospheric Sulfate Aerosol

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This report describes the work done with funding from NASA Grant NAGW 3525 during 1995. The grant was initiated in March, 1992 and has a planned duration of three years. This report covers the time period March 1995 to Present. In this report I present a short description of the projects carried out and documentation of the work done in terms of papers presented, etc.

  2. Polarization of far-infrared radiation from molecular clouds

    NASA Technical Reports Server (NTRS)

    Novak, G.; Gonatas, D. P.; Hildebrand, R. H.; Platt, S. R.; Dragovan, M.

    1989-01-01

    The paper reports measurements of the polarization of far-infrared emission from dust in nine molecular clouds. Detections were obtained in Mon R2, in the Kleinmann-Low (KL) nebula in Orion, and in Sgr A. Upper limits were set for six other clouds. A comparison of the 100 micron polarization of KL with that previously measured at 270 microns provides new evidence that the polarization is due to emission from magnetically aligned dust grains. Comparing the results for Orion with measurements at optical wavelengths, it is inferred that the magnetic field direction in the outer parts of the Orion cloud is the same as that in the dense core. This direction is nearly perpendicular to the ridge of molecular emission and is parallel to both the molecular outflow in KL and the axis of rotation of the cloud core. In Mon R2, the field direction which the measurements imply does not agree withthat derived from 0.9-2.2 micron polarimetry. The discrepancy is attributed to scattering in the near-infrared. In Orion and Sgr A, where comparisons are possible, the measurements are in good agreement with 10 micron polarization measurements.

  3. Seasonal transitions and possible polar mesospheric cloud regions calculated by a zonally averaged model of the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Memmesheimer, M.; Gaertner, V.; Blum, P. W.

    1986-12-01

    A global, zonally averaged dynamical model of the middle atmosphere is used to calculate the seasonal variations of winds and temperature from 10 to 110 km. The main purpose of the study is to search for the existence of regions where noctilucent or polar mesospheric clouds (NLC/PMC) may be formed. For this purpose the difference between the actual temperature and the frost point is calculated based on a fixed water vapor mixing ratio. A value of 10 ppmV is chosen, which is in the upper range of the data obtained by different measurement techniques. Possible cloud existence regions (PCR) are defined by the condition that the actual temperature is below the frost point inside the PCR. It is found that this is the case for the summer polar mesopause during May-August (in the northern hemisphere) and November-February (in the southern hemisphere). The PCR extends from the pole to approximately 60° latitude at a height of about 85 km. In addition, in the lower stratosphere during winter the temperature also falls below the frost point, approximately at an altitude where stratospheric clouds are observed. The time-dependent behaviour of the PCR is investigated and compared with the data of the ultraviolet spectrometer on board the SME satellite and with ground-based observations of noctilucent clouds. It can be shown that the time of the NLC/PMC season is in good agreement with the time span covered by the estimated possible cloud region. The fast changes in atmospheric circulation and temperatures at mesospheric heights during late spring/early summer and late summer/beginning of autumn are an interesting fact. This may be responsible for the sudden start/end of the cloud season. The study shows that two dimensional modeling may be a good approach to get more insight into the development of large-scale atmospheric background conditions necessary for PMC/NLC formation.

  4. Polarization Lidar Liquid Cloud Detection Algorithm for Winter Mountain Storms

    NASA Technical Reports Server (NTRS)

    Sassen, Kenneth; Zhao, Hongjie

    1992-01-01

    We have collected an extensive polarization lidar dataset from elevated sites in the Tushar Mountains of Utah in support of winter storm cloud seeding research and experiments. Our truck-mounted ruby lidar collected zenith, dual-polarization lidar data through a roof window equipped with a wiper system to prevent snowfall accumulation. Lidar returns were collected at a rate of one shot every 1 to 5 min during declared storm periods over the 1985 and 1987 mid-Jan. to mid-Mar. Field seasons. The mid-barrier remote sensor field site was located at 2.57 km MSL. Of chief interest to weather modification efforts are the heights of supercooled liquid water (SLW) clouds, which must be known to assess their 'seedability' (i.e., temperature and height suitability for artificially increasing snowfall). We are currently re-examining out entire dataset to determine the climatological properties of SLW clouds in winter storms using an autonomous computer algorithm.

  5. Quantification of the SF6 lifetime based on mesospheric loss measured in the stratospheric polar vortex

    NASA Astrophysics Data System (ADS)

    Ray, Eric A.; Moore, Fred L.; Elkins, James W.; Rosenlof, Karen H.; Laube, Johannes C.; Röckmann, Thomas; Marsh, Daniel R.; Andrews, Arlyn E.

    2017-04-01

    Sulfur hexafluoride (SF6) is a greenhouse gas with one of the highest radiative efficiencies in the atmosphere as well as an important indicator of transport time scales in the stratosphere. The current widely used estimate of the atmospheric lifetime of SF6 is 3200 years. In this study we use in situ measurements in the 2000 Arctic polar vortex that sampled air with up to 50% SF6 loss to calculate an SF6 lifetime. Comparison of these measurements with output from the Whole Atmosphere Community Climate Model (WACCM) shows that WACCM transport into the vortex is accurate and that an important SF6 loss mechanism, believed to be electron attachment, is missing in the model. Based on the measurements and estimates of the size of the vortex, we calculate an SF6 lifetime of 850 years with an uncertainty range of 580-1400 years. The amount of SF6 loss is shown to be consistent with that of HFC-227ea, which has a lifetime of 670-780 years, adding independent support to our new SF6 lifetime estimate. Based on the revised lifetime the global warming potential of SF6 will decrease only slightly for short time horizons (<100 years) but will decrease substantially for time horizons longer than 2000 years. Also, the use of SF6 measurements as an indicator of transport time scales in the stratosphere clearly must account for potential influence from polar vortex air.

  6. Polar Ozone Workshop. Abstracts

    NASA Technical Reports Server (NTRS)

    Aikin, Arthur C.

    1988-01-01

    Results of the proceedings of the Polar Ozone Workshop held in Snowmass, CO, on May 9 to 13, 1988 are given. Topics covered include ozone depletion, ozonometry, polar meteorology, polar stratospheric clouds, remote sensing of trace gases, atmospheric chemistry and dynamical simulations.

  7. The Structure of the Stratospheric Aerosol Layer in the Equatorial and South Polar Regions of Jupiter

    NASA Astrophysics Data System (ADS)

    Moreno, Fernando

    1996-12-01

    A one-dimensional code to study the microphysical processes affecting aerosol particles in the jovian stratosphere and upper troposphere has been developed. The algorithms are based on those developed by Turcoet al.(Turco, R. P., P. Hamill, O. B. Toon, R. C. Whitten, and C. S. Kiang 1979.J. Atmos. Sci.36, 699-717) and include the effects of particle sedimentation, coagulation, eddy diffusion, and growth by heteromolecular condensation. A set of Hubble Space Telescope images in the near-UV was used to retrieve the aerosol distribution in the equatorial and south polar regions of Jupiter. The results obtained are consistent with the picture in which in the polar regions the aerosols are formed from auroral-related phenomena, while in the equatorial region the largest component of the aerosols would be those particles formed after condensation of hydrazine onto condensation nuclei. Concerning the charge of the particles, the particles in the south polar region must be considerably more charged than at equatorial latitudes. The model solutions give particles smaller than about 0.05 μm in radius at the equator, and 0.07 μm at the polar regions, with total optical depths of 0.3 and 1.3 at the equator and the south polar region, respectively, at 410 nm wavelength. The differences in the derived imaginary refractive indices reflect a compositional change in the aerosols at low and high latitudes.

  8. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    A definition is undertaken of the spectral and spatial characteristics of clouds and surface conditions in the polar regions, and to the creation of calibrated, geometrically correct data sets suitable for quantitative analysis. Ways are explored in which this information can be applied to cloud classifications as new methods or as extensions to existing classification schemes. A methodology is developed that uses automated techniques to merge Advanced Very High Resolution Radiometer (AVHRR) and Scanning Multichannel Microwave Radiometer (SMMR) data, and to apply first-order calibration and zenith angle corrections to the AVHRR imagery. Cloud cover and surface types are manually interpreted, and manual methods are used to define relatively pure training areas to describe the textural and multispectral characteristics of clouds over several surface conditions. The effects of viewing angle and bidirectional reflectance differences are studied for several classes, and the effectiveness of some key components of existing classification schemes is tested.

  9. Cloud and surface textural features in polar regions

    NASA Technical Reports Server (NTRS)

    Welch, Ronald M.; Kuo, Kwo-Sen; Sengupta, Sailes K.

    1990-01-01

    The study examines the textural signatures of clouds, ice-covered mountains, solid and broken sea ice and floes, and open water. The textural features are computed from sum and difference histogram and gray-level difference vector statistics defined at various pixel displacement distances derived from Landsat multispectral scanner data. Polar cloudiness, snow-covered mountainous regions, solid sea ice, glaciers, and open water have distinguishable texture features. This suggests that textural measures can be successfully applied to the detection of clouds over snow-covered mountains, an ability of considerable importance for the modeling of snow-melt runoff. However, broken stratocumulus cloud decks and thin cirrus over broken sea ice remain difficult to distinguish texturally. It is concluded that even with high spatial resolution imagery, it may not be possible to distinguish broken stratocumulus and thin clouds from sea ice in the marginal ice zone using the visible channel textural features alone.

  10. Cloud Coverage and Height Distribution from the GLAS Polar Orbiting Lidar: Comparison to Passive Cloud Retrievals

    NASA Technical Reports Server (NTRS)

    Spinhime, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.

    2004-01-01

    The Geoscience Laser Altimeter System (GLAS) began full on orbit operations in September 2003. A main application of the two-wavelength GLAS lidar is highly accurate detection and profiling of global cloud cover. Initial analysis indicates that cloud and aerosol layers are consistently detected on a global basis to cross-sections down to 10(exp -6) per meter. Images of the lidar data dramatically and accurately show the vertical structure of cloud and aerosol to the limit of signal attenuation. The GLAS lidar has made the most accurate measurement of global cloud coverage and height to date. In addition to the calibrated lidar signal, GLAS data products include multi level boundaries and optical depth of all transmissive layers. Processing includes a multi-variable separation of cloud and aerosol layers. An initial application of the data results is to compare monthly cloud means from several months of GLAS observations in 2003 to existing cloud climatologies from other satellite measurement. In some cases direct comparison to passive cloud retrievals is possible. A limitation of the lidar measurements is nadir only sampling. However monthly means exhibit reasonably good global statistics and coverage results, at other than polar regions, compare well with other measurements but show significant differences in height distribution. For polar regions where passive cloud retrievals are problematic and where orbit track density is greatest, the GLAS results are particularly an advance in cloud cover information. Direct comparison to MODIS retrievals show a better than 90% agreement in cloud detection for daytime, but less than 60% at night. Height retrievals are in much less agreement. GLAS is a part of the NASA EOS project and data products are thus openly available to the science community (see http://glo.gsfc.nasa.gov).

  11. Cloud Coverage and Height Distribution from the GLAS Polar Orbiting Lidar: Comparison to Passive Cloud Retrievals

    NASA Technical Reports Server (NTRS)

    Spinhime, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.

    2004-01-01

    The Geoscience Laser Altimeter System (GLAS) began full on orbit operations in September 2003. A main application of the two-wavelength GLAS lidar is highly accurate detection and profiling of global cloud cover. Initial analysis indicates that cloud and aerosol layers are consistently detected on a global basis to cross-sections down to 10(exp -6) per meter. Images of the lidar data dramatically and accurately show the vertical structure of cloud and aerosol to the limit of signal attenuation. The GLAS lidar has made the most accurate measurement of global cloud coverage and height to date. In addition to the calibrated lidar signal, GLAS data products include multi level boundaries and optical depth of all transmissive layers. Processing includes a multi-variable separation of cloud and aerosol layers. An initial application of the data results is to compare monthly cloud means from several months of GLAS observations in 2003 to existing cloud climatologies from other satellite measurement. In some cases direct comparison to passive cloud retrievals is possible. A limitation of the lidar measurements is nadir only sampling. However monthly means exhibit reasonably good global statistics and coverage results, at other than polar regions, compare well with other measurements but show significant differences in height distribution. For polar regions where passive cloud retrievals are problematic and where orbit track density is greatest, the GLAS results are particularly an advance in cloud cover information. Direct comparison to MODIS retrievals show a better than 90% agreement in cloud detection for daytime, but less than 60% at night. Height retrievals are in much less agreement. GLAS is a part of the NASA EOS project and data products are thus openly available to the science community (see http://glo.gsfc.nasa.gov).

  12. On the growth of nitric and sulfuric acid aerosol particles under stratospheric conditions

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    A theory for the formation of frozen aerosol particles in the Antarctic stratosphere was developed and applied to the formation of polar stratospheric clouds. The theory suggests that the condensed ice particles are composed primarily of nitric acid and water, with small admixtures of sulfuric and hydrochloric acids in solid solution. The proposed particle formation mechanism is in agreement with the magnitude and seasonal behavior of the optical extinction observed in the winter polar stratosphere.

  13. The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Krüger, K.; Bittner, M.; Timmreck, C.; Schmidt, H.

    2014-06-01

    Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol-climate model simulations. For all forcings, we find that temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high latitude effects result from robust enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. While there is significant ensemble variability in the high latitude response to each aerosol forcing set, the mean response is sensitive to the forcing set used. Significant differences, for example, are found in the NH polar stratosphere temperature and zonal wind response to two different forcing data sets constructed from different versions of SAGE II aerosol observations. Significant strengthening of the polar vortex, in rough agreement with the expected response, is achieved only using aerosol forcing extracted from prior coupled aerosol-climate model simulations. Differences in the dynamical response to the different forcing sets used imply that reproducing

  14. Titan’s South Polar cloud optical properties modelization

    NASA Astrophysics Data System (ADS)

    Toledo, Daniel; Rannou, Pascal; West, Robert A.; Lavvas, Panayotis

    2014-11-01

    Cassini/ISS cameras detected, in june 2012, a newly formed large cloud in the south polar region of Titan. Images of this cloud in filters at 889 nm (MT3) and 935 nm (CB3) clearly reveal different important characteristics. The cloud patch is observed beyond the latitude -77 degrees and with values of the SZA higher than 90 degrees. In this work, we analyze the radiance factor I/F in the methane 890-nm (MT3) filter by using radiative transfer simulations in order to retrieve constraints on the cloud properties, as its opacity, the size of the droplets and the refractive index. The cloud simulation requires the use of a three-dimensional Monte-Carlo radiative transfer model in spherical geometry since the plane-parallel approximation breaks down for high solar zenith angle (SZA). To model the outgoing intensity and because the cloud is not spherically symmetric but has a finite size and is located near the pole, we first use the source function computed in the atmosphere including the effect of haze and methane, but without cloud. Then, we add the cloud as a lower boundary condition, with a specific term of scattered intensity. We then re-integrate the radiative transfer equation from the cloud level to the top of the atmosphere to obtain outgoing intensity in the presence of the cloud. Doing that, the cloud is treated as an additive term. The haze optical properties are taken from Tomasko et al. (2008), and the methane absorption is taken from the band model of Karkoschka and Tomasko (2012). The phase Function and single scattering albedo of the cloud are calculated by the Mie theory. The effective size of particles is allowed to vary between 3 µm and 5 µm, whereas the effective variance is fixed at 0.2. We use as optical constants for the cloud particles, the real refractive index of 1.4 , while the imaginary part k, is left as a free parameter between 10-5 and 10-3.We then find, with our analysis, that the optical depth of the cloud can only take values between

  15. Composite analysis of the temporal development of waves in the polar MLT region during stratospheric warmings

    NASA Astrophysics Data System (ADS)

    Matthias, Vivien; Hoffmann, Peter; Rapp, Markus; Baumgarten, Gerd

    2012-12-01

    During winter the wind field in the mesosphere/lower thermosphere (MLT) at middle and polar latitudes is characterized by a strong variability due to enhanced planetary wave activity and related stratospheric sudden warming (SSW) events. Such events are considered as distinct vertical coupling processes influencing the atmosphere below and above the stratosphere. In the last 12 years, an enhanced number of SSW, compared to the period from 1989 to 1998, has been observed in the northern hemisphere. Every SSW is connected with different effects in the MLT (strength and temporal development of wind reversals, temperature changes, wave activity, longitudinal dependence). To characterize the average behavior of the mesospheric response to strong SSWs, we combine high-resolution wind measurements from MF- and meteor radar at Andenes (69°N, 16°E) with global temperature observations from MLS aboard the Aura satellite for SSW events with a return to the middle atmosphere normal winter condition afterwards. Our aim is to identify characteristic wave patterns which are common to the majority of these events and to define the average characteristics of the SSW-related wave activity in the MLT. These will be compared to the relatively quiet winter 2011 with only a short minor warming without a wind reversal and to the wave activity in 2009 and 2010. The results show clear signatures of enhanced mesospheric planetary wave activity before and during the SSW and an earlier onset of the short term wind reversal in the mesosphere compared to wind and temperature changes in the stratosphere. The strong eastward winds at altitudes below 80 km after SSW are connected with an enhanced gravity wave activity caused by changed filter conditions. This provides evidence for a strong modulation of semidiurnal tidal amplitudes before and during SSW by planetary waves. However, no clear relation has been found in the temporal development of tides relative to the onset of the selected SSW

  16. Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes

    NASA Astrophysics Data System (ADS)

    Kahler, S. W.; Crooker, N. U.; Gosling, J. T.

    1999-06-01

    We have used solar wind electron heat fluxes to determine the magnetic polarities of the interplanetary magnetic fields (IMF) during the ISEE-3 observations in 1978-1982. That period included 14 magnetic clouds (MCs) identified by Zhang and Burlaga. The MCs have been modeled as single magnetic flux ropes, and it is generally assumed that they are magnetically closed structures with each end of the flux rope connected to the Sun. The flux rope model is valid only if the magnetic polarity of each MC does not change during the passage of ISEE-3 through the MC. We test this model with the heat flux data, using the dominant heat flux in bidirectional electron heat fluxes to determine the MC polarities. The polarity changes within at least 2, and possibly 6, of the 14 MCs, meaning that those MCs can not fit the model of a single flux rope.

  17. Stratospheric denitrification due to polar aerosol formation: Implications for a future atmosphere with increased CO2

    NASA Astrophysics Data System (ADS)

    Pitari, Giovanni; Ricciardulli, Lucrezia

    The amount of stratospheric denitrification produced by NAT aerosol formation is studied with a photochemical two-dimensional model which includes the effects of zonal asymmetries of the temperature field. The model photochemistry is coupled with a microphysical code for aerosol formation and growth, so that the permanent loss of stratospheric nitric acid and water vapor may be taken into account. The model results for nitric acid relative to the atmospheric chemical composition of 1980 are compared with LIMS data. We show that the level of denitrification may rise substantially if the polar vortex cools down, as it could be the case in a future atmosphere richer in carbon dioxide. A three-dimensional model is used to calculate the temperature perturbation due to an increase of CO2 from 335 ppmv of 1980 (baseline) up to 500 ppmv (predicted for 2050). The photochemical model adopting these new temperatures predicts an average 20% HNO3 column decrease poleward of 45N with respect to baseline. One consequence is that the relative weight of the NOx catalytic cycle for O3 destruction decreases with respect to the present atmosphere.

  18. A comparison of Arctic lower stratospheric winter temperatures for 1988-89 with temperatures since 1964

    NASA Technical Reports Server (NTRS)

    Nagatani, Ronald M.; Miller, Alvin J.; Gelman, Melvyn E.; Newman, Paul A.

    1990-01-01

    Lower stratospheric temperatures during the Airborne Arctic Stratospheric Expedition are compared with temperatures available since January, 1964. January, 1989, was the coldest averaged January in the last 26 years at high latitude, lower stratospheric levels. There have been other months with temperatures almost as low as the level of January, 1989, and localized temperatures (e.g., minimum polar vortex temperatures) have been lower than that encountered in January 1989. February, 1989, was warmer than average and March, 1989, had some of the highest polar vortex temperatures in the last 26 years. Conditions were therefore not very favorable for Polar Stratospheric Cloud (PSC) formation into early spring.

  19. A comparison of Arctic lower stratospheric winter temperatures for 1988-89 with temperatures since 1964

    NASA Technical Reports Server (NTRS)

    Nagatani, Ronald M.; Miller, Alvin J.; Gelman, Melvyn E.; Newman, Paul A.

    1990-01-01

    Lower stratospheric temperatures during the Airborne Arctic Stratospheric Expedition are compared with temperatures available since January, 1964. January, 1989, was the coldest averaged January in the last 26 years at high latitude, lower stratospheric levels. There have been other months with temperatures almost as low as the level of January, 1989, and localized temperatures (e.g., minimum polar vortex temperatures) have been lower than that encountered in January 1989. February, 1989, was warmer than average and March, 1989, had some of the highest polar vortex temperatures in the last 26 years. Conditions were therefore not very favorable for Polar Stratospheric Cloud (PSC) formation into early spring.

  20. Collision of two spin-polarized fermionic clouds

    SciTech Connect

    Goulko, O.; Chevy, F.; Lobo, C.

    2011-11-15

    We study the collision of two spin-polarized Fermi clouds in a harmonic trap using a simulation of the Boltzmann equation. As observed in recent experiments, we find three distinct regimes of behavior. For weak interactions the clouds pass through each other. If interactions are increased they approach each other exponentially and for strong interactions they bounce off each other several times. We thereby demonstrate that all these phenomena can be reproduced using a semiclassical collisional approach and that these changes in behavior are associated with an increasing collision rate. We then show that the oscillation of the clouds in the bounce regime is an example of an unusual case in quantum gases: a nonlinear coupling between collective modes, namely, the spin dipole mode and the axial breathing mode, which is enforced by collisions. We also determine the frequency of the bounce as a function of the final temperature of the equilibrated system.

  1. Titan's Stratospheric Aerosols and Condensate Clouds as Observed with Cassini CIRS

    NASA Astrophysics Data System (ADS)

    de Kok, Remco; Irwin, P. G.; Teanby, N. A.; Samuelson, R. E.; Nixon, C. A.; Jennings, D. E.; Fletcher, L.; Howett, C.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Taylor, F. W.; Cassini/CIRS Team

    2006-09-01

    Four broad spectral features were identified in far-infrared limb spectra from the Cassini Composite Infrared Spectrometer (CIRS). The features are broader than the spectral resolution, which suggests that they are caused by particulates in Titan's stratosphere. We derive here the spectral properties and variations with altitude and latitude for these four features. Titan's main aerosol is called Haze 0 here. It is present at all wavenumbers in the far-infrared and is found to have a fractional scale height between 1.6-1.7 with a small increase in opacity in the north. A second feature around 140 cm-1 (Haze A) has similar spatial properties to Haze 0, but has a smaller fractional scale height of 1.2-1.3. Both Haze 0 and Haze A show an increase in abundance below 100 km, perhaps indicative of a scattering cloud. Two other features (Haze B around 220 cm-1 and Haze C around 190 cm-1) have a large maximum in their density profiles at 140 km and 90 km respectively. Haze B is much more abundant in the northern hemisphere compared to the southern hemisphere. Haze C also shows a large increase towards the north, but then disappears at 85oN. This work is supported by the Prins Bernhard Cultuurfond and Pieter Beijer Fonds.

  2. Sensitivity of Polar Stratospheric Ozone Loss to Uncertainties in Chemical Reaction Kinetics

    NASA Technical Reports Server (NTRS)

    Kawa, S. Randolph; Stolarski, Richard S.; Douglass, Anne R.; Newman, Paul A.

    2008-01-01

    Several recent observational and laboratory studies of processes involved in polar stratospheric ozone loss have prompted a reexamination of aspect of out understanding for this key indicator of global change. To a large extent, our confidence in understanding and projecting changes in polar and global ozone is based on our ability to to simulate these process in numerical models of chemistry and transport. These models depend on laboratory-measured kinetic reaction rates and photlysis cross section to simulate molecular interactions. In this study we use a simple box-model scenario for Antarctic ozone to estimate the uncertainty in loss attributable to known reaction kinetic uncertainties. Following the method of earlier work, rates and uncertainties from the latest laboratory evaluation are applied in random combinations. We determine the key reaction and rates contributing the largest potential errors and compare the results to observations to evaluate which combinations are consistent with atmospheric data. Implications for our theoretical and practical understanding of polar ozone loss will be assessed.

  3. A Lidar and Backscatter Sonde Aerosol Measurement Campaign at Table Mountain During February-March 1997: Observations of Stratospheric Background Aerosols and Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Beyerle, G.; Gross, M.; Haner, D.; Kjome, N.; McDermid, I.; McGee, T.; Rosen, J.; Schafer, H. J.; Schrems, O.

    1999-01-01

    Altitude profiles of backscater ratio of the stratospheric background aerosol layer at altitudes between 15 and 25 km and high-altitude cirrus clouds at altitudes below 13 km are analyzed and discussed. Cirrus clouds were present on 16 of the 26 campaign nights.

  4. Variability of water vapour in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, L.; Backman, L.; Kivi, R.; Karpechko, A.

    2015-08-01

    This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry climate model simulation covering years 1990-2013 is compared to observations (satellite and frostpoint hygrometer soundings) and the sources of stratospheric water vapour are studied. According to observations and the simulations the water vapour concentration in the Arctic stratosphere started to increase after year 2006, but around 2011 the concentration started to decrease. Model calculations suggest that the increase in water vapour during 2006-2011 (at 56 hPa) is mostly explained by transport related processes, while the photochemically produced water vapour plays a relatively smaller role. The water vapour trend in the stratosphere may have contributed to increased ICE PSC occurrence. The increase of water vapour in the precense of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. The polar vortex was unusually cold in early 2010 and allowed large scale formation of the polar stratospheric clouds. The cold pool in the stratosphere over the Northern polar latitudes was large and stable and a large scale persistent dehydration was observed. Polar stratospheric ice clouds and dehydration were observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT atmospheric sounding campaign. The observed changes in water vapour were reproduced by the model. Both the observed and simulated decrease of the water vapour in the dehydration layer was up to 1.5 ppm.

  5. The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Krüger, K.; Bittner, M.; Timmreck, C.; Schmidt, H.

    2014-12-01

    Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol-climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space-time structure of the volcanic aerosol forcing.

  6. Observational constraints on the tropospheric and near-surface winter signature of the Northern Hemisphere stratospheric polar vortex

    NASA Astrophysics Data System (ADS)

    Graf, Hans-F.; Zanchettin, Davide; Timmreck, Claudia; Bittner, Matthias

    2014-12-01

    A composite analysis of Northern Hemisphere's mid-winter tropospheric anomalies under the conditions of strong and weak stratospheric polar vortex was performed on NCEP/NCAR reanalysis data from 1948 to 2013 considering, as additional grouping criteria, the coincidental states of major seasonally relevant climate phenomena, such as El Niño-Southern Oscillation (ENSO), Quasi Biennial Oscillation and strong volcanic eruptions. The analysis reveals that samples of strong polar vortex nearly exclusively occur during cold ENSO states, while a weak polar vortex is observed for both cold and warm ENSO. The strongest tropospheric and near-surface anomalies are found for warm ENSO and weak polar vortex conditions, suggesting that internal tropospheric circulation anomalies related to warm ENSO constructively superpose on dynamical effects from the stratosphere. Additionally, substantial differences are found between the continental winter warming patterns under strong polar vortex conditions in volcanically-disturbed and volcanically-undisturbed winters. However, the small-size samples obtained from the multi-compositing prevent conclusive statements about typical patterns, dominating effects and mechanisms of stratosphere-troposphere interaction on the seasonal time scale based on observational/reanalysis data alone. Hence, our analysis demonstrates that patterns derived from observational/reanalysis time series need to be taken with caution as they not always provide sufficiently robust constraints to the inferred mechanisms implicated with stratospheric polar vortex variability and its tropospheric and near-surface signature. Notwithstanding this argument, we propose a limited set of mechanisms that together may explain a relevant part of observed climate variability. These may serve to define future numerical model experiments minimizing the sample biases and, thus, improving process understanding.

  7. Analysis of isentropic potential vorticities for the relationship between stratospheric polar vortex and the cooling process in China

    NASA Astrophysics Data System (ADS)

    Lu, C.

    2015-12-01

    We analyze the relationships between stratospheric polar vortex anomalies and cooling events in eastern China using isentropic reanalysis data from the European Center for Medium-Range Weather Forecasts. Daily mean data from 2000 to 2011 are used to explore the effective stratospheric signals. First, diagnoses of the 2009/2010 winter show that after the stratospheric sudden warming (SSW) of the Atlantic-East Asian (AEA) pattern, the stratospheric high isentropic potential vorticity(IPV) center derived from the split polar vortex will move to the northeast of the Eurasian continent. The air mass, accompanied by some southward and eastward movements and characterized by high IPV values, will be stretched vertically, leading to apparent reinforcements of the positive vorticity and the development of a cold vortex system in the troposphere. The northerly wind on the western side of the cold vortex can transport cold air southward and downward, resulting in this distinct cooling process in eastern China. Secondly, the Empirical Orthogonal Function analyses of IPV anomalies on the 430 K isentropic surface during 2000-2011 winters indicate that the IPV distribution and time series of the first mode are able to represent the polar vortex variation features, which significantly influence cold-air activity in eastern China, especially in the AEA-type SSW winter. When the time series increases significantly, the polar vortex will be split and the high-IPV center will move to the northeast of the Eurasian continent with downward and southward developments, inducing obvious cooling in eastern China. Moreover, all the four times SSW events of AEA pattern from 2000 to 2011 are reflected in the first time series, and after the strong polar vortex disturbances, cooling processes of different intensities are observed in eastern China. The cooling can sustain at least one week. For this reason the first time series can be used as an available index of polar vortex oscillation and has

  8. Lower Stratospheric Temperature Differences Between Meteorological Analyses in two cold Arctic Winters and their Impact on Polar Processing Studies

    NASA Technical Reports Server (NTRS)

    Manney, Gloria L.; Sabutis, Joseph L.; Pawson, Steven; Santee, Michelle L.; Naujokat, Barbara; Swinbank, Richard; Gelman, Melvyn E.; Ebisuzaki, Wesley; Atlas, Robert (Technical Monitor)

    2001-01-01

    A quantitative intercomparison of six meteorological analyses is presented for the cold 1999-2000 and 1995-1996 Arctic winters. The impacts of using different analyzed temperatures in calculations of polar stratospheric cloud (PSC) formation potential, and of different winds in idealized trajectory-based temperature histories, are substantial. The area with temperatures below a PSC formation threshold commonly varies by approximately 25% among the analyses, with differences of over 50% at some times/locations. Freie University at Berlin analyses are often colder than others at T is less than or approximately 205 K. Biases between analyses vary from year to year; in January 2000. U.K. Met Office analyses were coldest and National Centers for Environmental Prediction (NCEP) analyses warmest. while NCEP analyses were usually coldest in 1995-1996 and Met Office or NCEP[National Center for Atmospheric Research Reanalysis (REAN) warmest. European Centre for Medium Range Weather Forecasting (ECMWF) temperatures agreed better with other analyses in 1999-2000, after improvements in the assimilation model. than in 1995-1996. Case-studies of temperature histories show substantial differences using Met Office, NCEP, REAN and NASA Data Assimilation Office (DAO) analyses. In January 2000 (when a large cold region was centered in the polar vortex), qualitatively similar results were obtained for all analyses. However, in February 2000 (a much warmer period) and in January and February 1996 (comparably cold to January 2000 but with large cold regions near the polar vortex edge), distributions of "potential PSC lifetimes" and total time spent below a PSC formation threshold varied significantly among the analyses. Largest peaks in "PSC lifetime" distributions in January 2000 were at 4-6 and 11-14 days. while in the 1996 periods, they were at 1-3 days. Thus different meteorological conditions in comparably cold winters had a large impact on expectations for PSC formation and on the

  9. Spring polar ozone behavior

    NASA Technical Reports Server (NTRS)

    Aikin, Arthur C.

    1992-01-01

    Understanding of the springtime behavior of polar stratospheric ozone as of mid 1990 is summarized. Heterogeneous reactions on polar stratospheric clouds as hypothesis for ozone loss are considered and a simplified description of the behavior of Antarctic ozone in winter and spring is given. Evidence that the situation is more complicated than described by the theory is produced. Many unresolved scientific issues remain and some of the most important problems are identified. Ozone changes each spring since 1979 have clearly established for the first time that man made chlorine compounds influence stratospheric ozone. Long before important advances in satellite and in situ investigations, it was Dobson's decision to place a total ozone measuring spectrometer at Halley Bay in Antarctica during the International Geophysical Year and subsequent continuous monitoring which led to the discovery that ozone was being destroyed each spring by chlorine processed by polar stratospheric clouds.

  10. Stratospheric Cooling and Arctic Ozone Recovery

    NASA Technical Reports Server (NTRS)

    Danilin, Michael Y.; Sze, Nien-Dak; Ko, Malcolm K. W.; Rodriquez, Jose M.

    1998-01-01

    We present sensitivity studies using the AER box model for an idealized parcel in the lower stratosphere at 70 deg N during winter/spring with different assumed stratospheric cooling and chlorine loadings. Our calculations show that stratospheric cooling could further deplete ozone via increased polar stratospheric cloud (PSC) formation and retard its expected recovery even with the projected chlorine loading decrease. We introduce the concept of chlorine-cooling equivalent and show that a 1 K Cooling could provide the same local ozone depletion as an increase of chlorine by 0.4-0.7 ppbv for the scenarios considered. Thus, sustained stratospheric cooling could further reduce Arctic ozone content and delay the anticipated ozone recovery in the Northern Hemisphere even with the realization of the Montreal Protocol and its Amendments.

  11. Stratospheric Cooling and Arctic Ozone Recovery

    NASA Technical Reports Server (NTRS)

    Danilin, Michael Y.; Sze, Nien-Dak; Ko, Malcolm K. W.; Rodriquez, Jose M.

    1998-01-01

    We present sensitivity studies using the AER( box model for an idealized parcel in the lower stratosphere at 70 N during winter/spring with different assumed stratospheric coolings and chlorine loadings. Our calculations show that stratospheric cooling could further deplete ozone via increased polar stratospheric cloud (PSC) formation and retard its expected recovery even with the projected chlorine loading decrease. We introduce the concept of chlorine-cooling equivalent and show that a 1 K cooling could provide the same local ozone depletion as an increase of chlorine by 0.4-0.7 ppbv for the scenarios considered. Thus, sustained stratospheric cooling could further reduce Arctic ozone content and delay the anticipated ozone recovery in the Northern Hemisphere even with the realization of the Montreal Protocol and its Amendments.

  12. Wave Driven Disturbances of the Thermal Structure in the Polar Winter Upper Stratosphere and Lower Mesosphere

    NASA Astrophysics Data System (ADS)

    Greer, Katelynn R.

    The polar winter middle atmosphere is a dynamically active region that is driven primarily by wave activity. Planetary waves intermittently disturbed the region at different levels and the most spectacular type of disturbance is a major Sudden Stratospheric Warming (SSW). However, other types of extreme disturbances occur on a more frequent, intraseasonal basis. One such disturbance is a synoptic-scale "weather event" observed in lidar and rocket soundings, soundings from the TIMED/SABER instrument and UK Meteorological Office (MetO) assimilated data. These disturbances are most easily identified near 42 km where temperatures are elevated over baseline conditions by a remarkable 50 K and an associated cooling is observed near 75 km. As these disturbances have a coupled vertical structure extending into the lower mesosphere, they are termed Upper Stratospheric/Lower Mesospheric (USLM) disturbances. This research begins with description of the phenomenology of USLM events in observations and the assimilated data set MetO, develops a description of the dynamics responsible for their development and places them in the context of the family of polar winter middle atmospheric disturbances. Climatologies indicates that USLM disturbances are commonly occurring polar wintertime disturbances of the middle atmosphere, have a remarkably repeating thermal structure, are located on the East side of the polar low and are related planetary wave activity. Using the same methodology for identifying USLM events and building climatologies of these events, the Whole Atmosphere Community Climate Model WACCM version 4 is established to spontaneously and internally generate USLM disturbances. Planetary waves are seen to break at a level just above the stratopause and convergence of the EP-flux vector is occurring in this region, decelerating the eastward zonal-mean wind and inducing ageostrophic vertical motion to maintain mass continuity. The descending air increases the horizontal

  13. Uranus’ Hemispheric Asymmetries in Polar Cloud and Circulation Structures

    NASA Astrophysics Data System (ADS)

    Hammel, Heidi B.; Sromovsky, Lawrence; Fry, Pat; de Pater, Imke

    2015-11-01

    We report on the north polar region of Uranus in the post-equinoctial era. Near-IR imaging with Keck 2 using NIRC2 in 2012-2014 revealed numerous small bright features, as well as small dark features, between 50 degrees N and the north pole. Tracking of these features yielded circulation patterns, with the remarkable result that the region from 60 degrees to at least 83 degrees rotates about the northern pole as a solid body, with a drift rate of 4.1 degrees/hour westward relative to the interior (Sromovsky et al. 2015, Icarus 258, 192-223). For the south pole, the same latitude region had dramatically different characteristics, as judged by 1986 Voyager and 2003 Keck observations. The southern region showed no discrete near-IR features; detailed circulation measurements in that region were based solely on low-contrast features in re-analyzed Voyager images (Karkoschka, 2015, Icarus 250, 294-307). They revealed a large gradient in drift rates, with values reaching twice that seen in the corresponding northern region.The north-south asymmetry in circulation and cloud structure/morphology is surprising because the distribution of upper tropospheric methane is relatively symmetric: roughly constant over a region from 30 S to 30 N, and then declining at higher latitudes in both hemispheres. The methane distribution suggests symmetric down-welling motion in both polar regions, which would inhibit formation of condensation clouds there, in contrast to the observed dichotomy. Some asymmetry may be an effect of seasonal forcing, since the north versus south polar measurements were made during different seasons. If so, then major changes can be expected in the north polar region as Uranus proceeds toward its 2030 northern summer solstice. Hubble STIS observations expected in October of 2015 will further examine the vertical distribution and stability of the polar methane abundances. Future high-resolution imaging with Earth-based facilities will be able to track circulation