The Quasi-Biennial Oscillation (QBO) is the dominant pattern of variability in the tropical stratosphere. Despite a well established theory regarding its generation in the atmosphere, the simulation in global climate models remains difficult. A set of metrics assessing the quality of model simulations is presented in this study. The QBO simulations in models submitted to the CMIP5 and CCMVal-2 intercomparison projects are characterised and compared to radiosonde observations and reanalysis datasets. Common model biases and their potential causes are addressed. As the QBO has a long intrinsic period, knowing its influences on other parts of the climate system can be used to improve long range forecasts. These teleconnections of the QBO in observations are investigated using composite analysis, multilinear regression and a novel approach called causal effect networks (CEN). Findings from these analyses confirm previous results of the QBO modulating the stratospheric polar vortex and subsequently the North Atlantic Oscillation (NAO). They also suggest that it is important to take the equatorial zonal mean zonal wind vertical profile into account when studying teleconnections, rather than the more traditional method of using just one single level. While QBO influences on the Northern Hemisphere winter polar vortex and the NAO are more clearly established, interactions within the tropics remain inconclusive. Regression analysis does not show a connection between the QBO and the MJO, whereas the CEN analysis does. Further studies are needed to understand the interaction mechanisms near the equator. Finally, following the unprecedented disruption of the QBO cycle in the winter 2015/16, the event is described and a model analogue from the MPI-ESM-MR historical simulation is presented. Future implications are unclear, although model projections indicate more frequent QBO irregularities in a warming climate.

Dans un contexte actuel préoccupé par la couche d’ozone et son recouvrement ainsi que par le réchauffement global, comprendre, représenter et modéliser la dynamique stratosphérique sont des enjeux majeurs. Une question récurrente est de pouvoir évaluer les biais des modèles à haute altitude dans la stratosphère. Or la stratosphère est une couche de l’atmosphère difficilement accessible à la mesure. Une solution est d’extraire des informations en analysant les trajectoires des ballons qui sont essentiellement conditionnées par les mouvements des masses d’air. Ces travaux de thèse ont donné naissance à une banque de données rassemblant des mesures de vent, de température et de pression issues des vols de ballons stratosphériques sur une période de plus de 20 ans à des régions variées (région polaire arctique, à moyenne latitude et en régions intertropicales) et à différentes saisons. Une méthode d’analyse des biais mesures/modèle a été mise en place et appliquée aux réanalyses ERA-Interim. Par comparaison avec une précédente étude faite dans des conditions de vortex polaire, les mesures ainsi que la méthode d’analyse des biais ont été validées. Enfin, une analyse systématique des biais sur le vent à haute altitude dans la stratosphère considérant plusieurs régions à différentes saisons a été implémentée. Les résultats montrent que les biais dans les réanalyses ERA-Interim varient et augmentent en fonction de l’altitude. Les régions associées à des régimes bien établis sont plutôt bien représentées alors que les zones de transition ou de changement de circulation présentent plus de difficultés. D’une manière générale, les résultats de biais rapportent que les réanalyses ERA-Interim sous-estiment la vitesse du vent dans la stratosphère. / In a current context focused on the ozone layer recovery and on the global warming, understand, represent and model the stratospheric dynamic became major issues. Realism of these models needs to be assessed. Unfortunately the stratosphere is an atmospheric layer hardly accessible to measurements. Balloons trajectories are mainly depending on the air masses displacements. Extract measurements from balloon trajectories is a solution. These works led to the creation of a database which contains winds, temperature and pressure measurements from stratospheric balloons flights data collected over a time period of more 20 years at several locations (arctic polar region, at mid-latitude and in tropics) and at different seasons. A methodology of winds biases analysis has been developed and has been applied to the ERA-Interim reanalysis data. By comparing our results with a previous study, we have been able to validate the database and the winds biases analyse methodology. A systematic analyse of winds biases at high altitude in the stratosphere considering several locations/seasons has been implemented. The results show the biases in ERA-Interim reanalyses vary and rise as function of the altitude. The locations which are associated to well established circulations are rather well represented while the locations where the variability is higher present more difficulty. Globally biases results report ERA-Interim reanalyses underestimate wind speed in the stratosphere.

L'ion nitrate (NO3-) présent dans les neiges Antarctiques est issus de l'oxydation des oxydes d'azote (NOx = NO + NO2) dans l'atmosphère. Aux sites de faible accumulation de neige tels que Vostok et Dôme C sur le plateau de l'Est de l'Antarctique, le nitrate n'est pas piégé de manière ultime dans la neige, ce qui limite fortement l'interprétation des enregistrements en nitrate dans les carottes de glace. Des mesures récentes de la composition isotopique en azote du nitrate (δ15N) montrent des valeurs extrêmement élevées (+339‰) dans les premiers décimètres de la neige de Dôme C. Ces valeurs ont été attribuées à la photolyse du nitrate et au recyclage important qui en résulte. Le nitrate possède, par ailleurs, une anomalie isotopique en oxygène (Δ17O) qui permet de tracer l'activité de l'ozone (O3) au cours de sa formation. Ce travail de thèse présente le premier enregistrement de la composition isotopique complète du nitrate (δ15N, Δ17O et δ18O) dans une carotte de glace : la carotte de glace de Vostok dont les 64 échantillons analysés couvrent une période de 150 000 ans. Ce jeu de données a été complété par 313 échantillons collectés entre 2007 et 2010 dans le continuum atmosphère/givre/neige au Dôme C ainsi que dans 21 puits de neige prélevés dans une zone couvrant l'essentiel de l'Est de l'Antarctique. L'analyse isotopique de ces échantillons modernes a permis de contraindre le modèle conceptuel TRANSITS développé au cours de cette thèse et dont le but est de représenter le recyclage du nitrate à l'interface entre l'atmosphère et la neige ainsi que son impact sur la composition isotopique du nitrate archivé. Les valeurs positives et élevées du δ15N du nitrate piégé dans la carotte de glace de Vostok montrent que le recyclage du nitrate a toujours eu lieu sur le plateau Antarctique au cours de la période étudiée. Les variations du flux primaire de nitrate reçu au site de Vostok estimées à l'aide du modèle TRANSITS montrent, en périodes glaciaires, un flux primaire plus important qui pourrait être lié à une dénitrification stratosphérique plus conséquente. Les valeurs de Δ17O du nitrate montrent que l'incursion d'ozone d'origine stratosphérique dans la troposphère était plus fréquente en périodes glaciaires. Nous proposons enfin que les résultats acquis dans le cadre de cette thèse pourraient permettre de mieux contraindre le cycle de l'azote sur la côte Antarctique et d'apporter des éléments d'interprétation des enregistrements en nitrate dans les carottes de glace de sites de plus forte accumulation de neige (au Groenland par exemple). / Nitrate ions (NO3-) found in Antarctic snows stem from the degradation of nitrogen oxydes (NOx = NO + NO2) in the atmosphere. At sites with low snow accumulation rates such as Vostok or Dome C (East Antarctic plateau), nitrate deposition to the snow is not irreversible and this strongly hampers the interpretation of nitrate concentration records in ice cores. Nitrogen stable isotopic (δ15N) as high as +339‰ were measured in nitrate in the upper firn at Dome C and have been attributed to nitrate photolysis initiating a strong recycling at the snow surface. The oxygen isotopic anomaly (Δ17O) reflects the activity of ozone (O3) in nitrate formation. We present the first comprehensive isotopic analysis of nitrate (δ15N, Δ17O and δ18O) in a deep ice core. 64 samples of nitrate from the Vostok ice core have been analyzed and cover the last 150 000 years. This dataset has been completed with 313 samples recently collected in the atmosphere/surface hoar/snow continuum at Dome C as well as in several snowpits from various sites covering most of the East Antarctica. Those present-day samples are used to evaluate a conceptual model (named TRANSITS) developped during this PhD and which aims at representing nitrate recycling at the snow/atmosphere interface and at modelling its impact on the isotopic composition of the archived nitrate. High positive δ15N values measured in the Vostok ice core reveal that nitrate recycling has always occurred at the surface of the Antarctic plateau over this period. Past variations of the primary flux of nitrate to the Vostok site have been estimated using the TRANSITS model. They show that glacials are characterized by higher inputs which may be linked to a greater stratospheric denitrification. The Δ17O values indicate that intrusions of stratospheric air masses to the troposphere may have been more frequent in glacials thus incorporating significant amounts of stratospheric ozone to the lower atmosphere. Last, we suggest that this study may have some relevance to the coastal nitrogen budget in Antarctica and to the interpretation of ice cores retrieved from high accumulation sites (e.g. in Greenland).

Made available in DSpace on 2015-09-25T12:19:46Z (GMT). No. of bitstreams: 1 Marcia Figueiredo Leite.pdf: 1188074 bytes, checksum: 604cf56aebeabeee9a6405b49c1c86fc (MD5) Previous issue date: 2012-05-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / During the northern hemisphere winter the stratospheric polar temperature increases abruptly. On some occasions, the stratospheric polar region experience more intense heating, which are accompanied by a reversal in the zonal mean circulation. These events are classified as sudden stratospheric warming. Some studies showed intense connection between the events of abrupt warming of the Northern Hemisphere polar stratosphere and mesospheric cooling of the region, as well as between these events and disturbances in the mesosphere and the ionosphere at middle and low latitudes, including the equatorial region. The objective of this study was to investigate possible effects of sudden warming event in stratospheric polar temperature behavior of the equatorial region near the menopause. In this sense, temperature data estimated from meteor radar measurements obtained at São João do Cariri-PB (7.4°S, 36.5°W) were analyzed together with data from the polar stratosphere, provided by National Centre for Environmental Prediction (NCEP). Analyzing the results it was found that during the sudden stratospheric warming major the mesopause temperatures on the São João do Cariri are lower than during the stratospheric warming events considered minor. Also was verified an anti-correlation between the equatorial mean mesopause temperature and the temperature in the polar cap (poleward of 60 N) at 10 hPa, during Sudden Stratospheric Warming Major events. / Durante o inverno do hemisfério norte a temperatura da estratosfera polar aumenta de forma brusca. Em algumas ocasiões, a estratosfera polar experimenta aquecimentos mais intensos, os quais são acompanhados de uma inversão na circulação zonal média. Estes eventos são classificados como aquecimentos abruptos estratosféricos (Sudden Stratospheric Warming). Alguns estudos evidenciaram conexão entre os eventos intensos de aquecimento abrupto da estratosfera polar do hemisfério norte e o esfriamento da região mesosférica, assim como entre os eventos e perturbações presentes na mesosfera e na ionosfera em médias e baixas latitudes, incluindo a região equatorial. O objetivo deste trabalho foi investigar possíveis efeitos de evento de aquecimento abrupto da estratosfera polar no comportamento da temperatura da região próxima à mesopausa equatorial. Neste sentido, dados de temperaturas estimados a partir de medidas obtidas com radar meteórico em São João do Cariri-PB (7,4°S, 36,5°O) foram analisados juntamente com dados da estratosfera polar, fornecidos pelo National Centre for Environmental Prediction (NCEP). Analisados os resultados, verificou-se que durante evento intenso de aquecimento abrupto da estratosfera polar, as temperaturas da mesopausa sobre São João do Cariri são mais baixas do que durante os eventos de aquecimento estratosféricos considerados fracos. Também foram verificadas anticorrelações entre a temperatura próxima a região da mesopausa equatorial e a média zonal da temperatura da estratosfera polar durante eventos intensos de aquecimento abrupto da estratosfera.

LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work

Several phenomena in the middle latitude stratosphere are studied in the thesis. The reanalyses are utilized as a source of data for our study. Different reanalyses are compared each other and with observations and problems of reanalyses are shown. We are interested in connection between ozone, dynamics and other phenomena (Sudden Stratospheric Warmings, solar cycle, NAO etc.) in the stratosphere, mainly from 1979 to present using ERA-Interim, NCEP/NCAR reanalyses or satellite observations. The linear connection between total ozone difference and 100 hPa eddy heat flux is found in winter middle latitudes. Ozone trends in Europe and China are analysed. The meridional and zonal wind is also studied using MERRA reanalysis and model output (CCM SOCOL v3.0). The comparison of geographical distribution of geopotential height and meridional wind is done. Differences between MERRA and CCM SOCOL v3.0 has been observed for geopotential hight and meridional wind for winter season.

In der oberen Troposphäre und untersten Stratosphäre (OT/US) beeinflussen Aerosolpartikel im Submikrometerbereich den Strahlungshaushalt der Erde direkt und, was noch wichtiger ist, indirekt, da sie als Kondensationskern für Wolken dienen und somit die Spurengaskonzentrationen durch heterogene chemische Prozesse ändern können. Seit 1997 gibt es regelmäßige in situ Messungen der OT/US Partikel durch das Leibniz-Institut für Troposphärenforschung in Leipzig, Deutschland. Diese Messungen werden an Bord eines Passagierflugzeugs mit dem weltweit einzigartigen IAGOS-CARIBIC Messcontainer durchgeführt (www.iagos.org/iagos-caribic). In der vorliegenden Arbeit wurden die Partikelanzahlkonzentration und die Partikelgrößenverteilung im Submikrometerbereich der vergangenen Jahre ausgewertet. Dafür wurden die Daten von drei Kondensationspartikelzählern (CPC, Condensation Particle Counter) und einem optischen Partikelgrößenspektrometer (OPSS, Optical Particle Size Spectrometer) verwendet. Zunächst wurde im Labor eine umfangreiche Charakterisierung des IAGOS-CARIBIC OPSS hinsichtlich der Zähleffizienz durchgeführt. Weiterhin wurde eine Kalibrierung mit Polystyrol-Latex im geräterelevanten Bereich von 140 nm bis 1050 nm vorgenommen und daraus mit Hilfe der Mie-Streuung eine Funktion zur Datenauswertung für die OT/US entwickelt. Die statistische Analyse der IAGOS-CARIBIC OPSS und CPC Daten gibt einen guten Überblick über die in der OT/US vorkommenden Partikelanzahlkonzentrationen und stellt sicher, dass ein statistisch fundierter Datensatz für die Analyse zur Verfügung steht. Auf dieser Grundlage wurde zum ersten Mal eine detaillierte Analyse der raumzeitlichen Verteilung der Aitkenmode- und Akkumulationsmode-Partikelanzahlgrößenverteilung in der OT/US vorgenommen. Diese Analyse beinhaltet Weltkarten mit Medianwerten, Wahrscheinlichkeitsdichtefunktionen für spezielle Flugrouten und Partikelgrößenverteilungen entlang der Längengrade. Außerdem wurden die Partikelanzahlkonzentrationen zum ersten Mal mit dem globalen Klimamodell ECHAM-HAM verglichen. Dabei ergab sich, dass die Partikelanzahlkonzentration hauptsächlich von großräumigen Strömungsverhältnissen beeinflusst wird, was im Großen und Ganzen gut vom Modell wiedergegeben wird. Für die einzelnen Jahreszeiten wurden mit Hilfe der potentiellen Temperatur und äquivalenten Breitengrade die vertikalen Profile ausgewertet. Für die Analyse in Bezug auf die Aerosol-Mikrophysik und den Transport durch die Tropopause wurden auch die in IAGOS-CARIBIC gemessenen Spurengase, wie z.B. Ozon und Wasserdampf, hinzugezogen. Die Auswertung zeigt ebenfalls deutlich den Einfluss von Wolken in der oberen Troposphäre und verschiedene Austauschprozesse zwischen der Stratosphäre und Troposphäre. Außerdem wurde der Einfluss verschiedener Austauschprozesse auf die Partikelanzahlkonzentration untersucht: die Brewer-Dobson Zirkulation, warm conveyor belts, Isentropentransport und der Transport durch tropische, hochreichende konvektive Bewölkung. In der Vergangenheit wurde diese Analyse nur für atmosphärische Spurengase durchgeführt, und nun zum ersten Mal auch für Aerosolpartikel. Die hier präsentierten Ergebnisse zeigen eine umfangreiche Charakterisierung der Aitken- und Akkumulationsmode-Partikelanzahlkonzentration in der OT/US und den Einfluss von Austauschprozessen der Stratosphäre und Troposphäre auf die Partikel. Die Auswertungen tragen maßgeblich zum Verständnis und zur Vorhersage der Partikelanzahlkonzentration in Klimamodellen und damit schlussendlich zur Berechnung des Strahlungshaushalts der Erde und dessen zeitlicher Veränderung bei. / Submicrometer aerosol particles in the upper troposphere and lowermost stratosphere (UT/LMS) influence the Earth's radiation budget directly and, more important, indirectly, by acting as cloud condensation nuclei and by changing trace gas concentrations through heterogeneous chemical processes. Since 1997, regular in situ measurements of UT/LMS particles have been conducted by the Leibniz Institute for Tropospheric Research, Leipzig, Germany, using the world-wide unique IAGOS-CARIBIC observatory (www.iagos.org/iagos-caribic) onboard a passenger aircraft. In this thesis, UT/LMS aerosol particle number concentrations and the submicrometer aerosol particle size distribution as measured by three condensation particle counters (CPCs) and one Optical Particle Size Spectrometer (OPSS) are discussed. Before analyzing the measurement data from the UT/LMS region a throughout characterization of the IAGOS-CARIBIC OPSS with respect to the counting efficiency was carried out in the laboratory for the OPSS-relevant particle size range of 140 nm to 1040 nm diameter. After calibration with polystyrene latex (PSL) particles a theoretical response function, representative for the UT/LMS, was calculated with Mie theory to ensure a correct data analysis. The statistical analysis of the IAGOS-CARIBIC OPSS and CPC data gives a good overview of existing particle number concentrations in the UT/LMS and ensures a statistically sound data analysis. On this basis a detailed characterization of the spatio-temporal distribution of Aitken and accumulation mode particle number concentrations in the UT/LMS was carried out for the first time. This analysis includes global maps with median values, probability density functions for specific flight routes, and longitudinal distributions of the particle size distribution. Also a first comparison with the global climate model ECHAM-HAM was conducted. The analysis showed that the aerosol distributions are mainly influenced by large-scale circulation patterns which were, in gererel terms, well reflected by the global climate model. Moreover, seasonal vertical cross-sections for particle number concentrations, the potential temperature, and the equivalent latitude were generated. The results are interpreted with respect to aerosol microphysics and cross-tropopause transport using IAGOS-CARIBIC trace gases like ozone and water vapor. The influence of clouds in the troposphere and the different stratosphere-troposphere exchange processes are clearly visible. Furthermore, the influence of the major transport processes into the UT/LMS region on the aerosol particle number concentrations was investigated: the Brewer-Dobson circulation, warm conveyor belts, isentropic transport, and tropical deep convective cloud outflow. In the past this was done only for atmospheric trace gases, but now for the first time for aerosol particles. The findings presented in this study represent a comprehensive characterization of the Aitken and accumulation mode particle number concentration in the UT/LMS and the influence of stratospheric-tropospheric exchange processes on these particles. These findings may help to evaluate and improve predictions of particle number concentrations by climate models and finally the calculation of the Earth's radiation budget and its change over the years.

The stratospheric and mesospheric wind field in winter is dominated by the stratospheric polar vortex, which reaches out up into the mesopause region and leads to strong westerlies there in winter. On the other hand, the tropospheric mean winter wind field is also connected with the polar vortex which thus can be considered as being extended from the surface up to the lower thermosphere. lt is found that the winter mesopause region zonal winds, as measured at the Collm Observatory of the University of Leipzig, are closely connected with the North Atlantic Oscillation (NAO) being an integrated measure for the northem hemispheric mean circulation. The NAO itself is found to be a measure for Central Europe winter temperatures. Thus also the mesopause region winds are closely correlated to the Central European winter surface temperatures. / Das stratosphärische und mesosphärische Windfeld wird im Winter wesentlich vom stratosphärischen Polarwirbel bestimmt, der von der Stratosphäre bis in die Mesopausenregion reicht und dort zu starken Westwinden führt. Auf der anderen Seite ist die mittlere troposphärische Zirkulation ebenfalls mit dem stratosphärischen Wirbel korreliert, so daß letzterer als von der Erdoberfläche bis in die untere Thermosphäre reichend betrachtet werden kann. Aus diesem Grund sind die mittleren Zonalwinde, gemessen am Observatorium Collm der Universität Leipzig, mit der Nordatlantikoszillation (NAO) korreliert. Andererseits hat die NAO einen starken Einfluß auf mitteleuropäische Wintertemperaturen, und damit ist der Wind im Mesopausenbereich ebenfalls mit den Wintertemperaturen korreliert.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1967. / Includes bibliographical references (leaves 167-170). / A monthly statistical analysis was made of the effects of large scale horizontal eddy transport processes on the zonal momentum, heat and energy budgets for three layers of the 1965 stratosphere. Geostrophic wind components were computed from IQSY data at 100, 50, 30 and 10 mb for use in calculating the statistical quantities -used in the analysis. It was found that temporal and spatial variances and covariances -computed from monthly means of temperature and geostrophic wind components give meaningful results when used in the computation of momentum, heat and energy balances. Monthly meridional distributions of eddy transports and energy conversions show large latitudinal and height variations. They also indicate a physically reasonable compatibility with month to month changes in zonal mean values of temperature, zonal wind and geo-potential. It was further determined that in the winter, the eddies in the middle stratosphere convert a self contained source of zonal available potential energy into eddy available potential energy. It is speculated that further conversion of this energy eventuates in its availability as a significant source for the mean zonal motions. / by Merwin Eugene Richards. / M.S.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography : leaves 62-65. / M.S.