O clima na Antártica tem um papel fundamental no balanço de energia global. Estudos sugerem que a atividade convectiva tropical e a circulação estratosférica exercem um papel importante sobre a circulação atmosférica nos extratrópicos. A temperatura do ar é uma variável sensível às mudanças na circulação, no entanto, ainda não foi investigada a importância da escala intra-sazonal na sua variabilidade sobre a Antártica. Neste trabalho estudou-se a variabilidade intra-sazonal da temperatura do ar a superfície na região da Península Antártica enfocando as interações trópicos-extratrópicos e troposfera-estratosfera na modulação de eventos extremos de temperatura naquela região. Foram utilizados dados diários de estações localizadas nos setores leste e oeste da Península Antártica no período de 1986-2002. A análise espectral dos dados ressaltou a importância da escala intra-sazonal na variabilidade da temperatura na Península Antártica, principalmente no período de inverno, primavera e verão. Baseado nestes resultados, os dados foram filtrados na escala intra-sazonal (banda de 20-100 dias) e posteriormente, obteve-se os extremos intra-sazonais frios e quentes para as três estações do ano, através dos quartis da distribuição dos dados. Os eventos extremos intra-sazonais de temperatura (EIT) foram mais intensos no inverno e mais fracos no verão. As características da circulação atmosférica intra-sazonal associada aos EIT foram obtidas através de composições defasadas das anomalias intra-sazonais da altura geopotencial em 200 hPa, vento zonal em 200 hPa e vento meridional em 850 hPa. Nas três estações do ano, observou-se nos eventos extremos intra-sazonais frios (EIF) a persistência de anomalias ciclônicas em altos níveis, a diminuição da intensidade do jato polar e uma advecção de ar frio em baixos níveis sobre a região de estudo. Uma situação oposta foi verificada nos eventos extremos intra-sazonais quentes (EIQ). De forma geral, observou-se um trem de ondas entre latitudes médias e altas no Hemisfério Sul (HS) durante os EIT, particularmente no inverno e primavera. Esta configuração mostrou-se semelhante a tele-conexão conhecida como Pacífico-Sul Americano (PSA). O papel do modo anular do HS sobre os EIT foi analisado através do cálculo de Funções Ortogonais Empíricas das anomalias intra-sazonais da altura geopotencial em 700 hPa ao sul de 20ºS. Sua estrutura foi mais intensa (mais fraca) nos EIF (EIQ) de inverno sobre a região de estudo. A interação troposfera-estratosfera no controle dos EIT foi investigada através do Fluxo Eliassen-Palm. Nas composições das anomalias intra-sazonais deste fluxo (EPIS), observou-se durante os EIF (EIQ) de inverno, um aumento da atividade de onda da baixa estratosfera (alta troposfera) para a alta troposfera (baixa estratosfera) sobre a região de estudo, associado à diminuição (aumento) da intensidade do jato polar. Na primavera, a atividade de onda foi mais intensa e verificou-se uma mudança na direção do fluxo EPIS quando comparado com os EIT de inverno. O fluxo EPIS e as anomalias intra-sazonais do vento zonal foram mais fracos no verão. As anomalias intra-sazonais da circulação atmosférica e da atividade de onda na troposfera e estratosfera foram observadas por cerca de 10 dias antes da observação dos EIT de inverno. Portanto, a atividade intra-sazonal nos extratrópicos e as interações troposfera-estratosfera são fatores relevantes para um melhor entendimento da variabilidade da temperatura sobre a Península Antártica. / The Antarctic climate plays a significant role for the global energy budget. Previous studies suggest that interactions tropics-extratropics and the dynamics of the stratosphere are important factors to understand climate variations in the extratropics. The air temperature near surface responds to changes in circulation in low and upper levels. However, no previous studies have objectively investigated the importance of intraseasonal variations in modulating temperature around the Antarctica Peninsula. The present study examines intraseasonal extreme anomalies of near surface air temperature in the Antarctica Peninsula, and investigates interactions tropics-extratropics and troposphere-stratosphere. Daily temperature data from stations located east and west of the Antarctica Peninsula during 1986-2002 are investigated. Spectral analyses indicate that intraseasonal anomalies in temperature records are statistically significant during summer, winter and spring in all stations. Based on these results, temperatures are band-filtered on intraseasonal timescales (20-100 days) and extreme anomalies are investigated in each season (spring, summer and winter) based on the quartiles of the distributions. Intraseasonal extreme temperature (IET) anomalies are more intense during winter than during summer. Variations in the atmospheric circulation during IET are investigated by performing composites of intraseasonal anomalies of the geopotential height in 200hPa, zonal wind in 200hPa and meridional wind in 850hPa. During the three seasons, cold IET are associated with persistent upper level cyclonic anomalies, easterly anomalies of the polar jet and cold advection in low levels over the Peninsula. Opposite features are observed during warm IET. An extratropical wave-train is observed during all IET with stronger intensity during winter and spring. This feature resembles the Pacific South American (PSA) teleconnection pattern. The Southern Hemisphere Annular mode during the IET, identified as the first Empirical Orthogonal Function (EOF) of the intraseasonal 700hPa geopotential height anomalies poleward of 20oS, is more intense (weak) during cold (warm) IET events during winter. The stratosphere-troposphere interaction during IET events was examined with composites of the Eliassen-Palm Flux intraseasonal anomalies (EPIS). During spring, the wave activity is more intense and the EPIS direction is opposite to winter. During summer, EPIS are weak. Intraseasonal anomalies in the circulation and the wave activity in the troposphere and stratosphere lead the IET during winter in about 10 days. Therefore, the intraseasonal activity in the extratropics and the interactions stratosphere-troposphere are important factors for a complete understanding of the temperature variability over the Antarctica Peninsula.

Le cycle hydrologique est une composante clef du climat de la Terre et sa compréhension repose à la fois sur les observations et sur les simulations de ses différents aspects, tels le transport, les changements de phase ou encore ses interactions avec le rayonnement. Les satellites géostationnaires METEOSAT ont, à leur bord, des radiomètres qui observent, dans l'infrarouge, la vapeur d'eau d'une large couche de la troposphère des régions tropicales et subtropicales de la région Afrique / Océan Atlantique. Disponibles depuis les années 80, ces observations dites "Vapeur d'Eau" donnent ainsi la possibilité d'étudier la distribution de la vapeur d'eau de la troposphère libre tropicale et sa variabilité depuis des échelles de temps journalières jusqu'à des échelles décennales. Dans cette thèse, une archive d'humidité de la troposphère libre (Free Tropospheric Humidity -FTH-), de haute résolution spatiale (0,625°x0,625°) et temporelle (3h), est élaborée à partir des observations IR de la succession des satellites METEOSAT (MET-2 à MET-5), dont l'étalonnage est ajusté sur celui du canal 12 du sondeur HIRS (NOAA-12) pris comme référence. En ciel clair, nous montrons que les mesures "VE" des régions tropicales et subtropicales s'interprètent en terme d'humidité relative moyenne d'une couche variable de l'atmosphère, définie de façon précise par le jacobien d'humidité relative, décrivant la sensibilité de la mesure à des perturbations locales relatives du profil d'humidité relative. Les nuages de basse altitude affectant la mesure "VE" de façon négligeable, ceux-ci sont échantillonnés, en plus du ciel clair, à partir des informations sur la nébulosité issues de l'analyse multi-spectrale ISCCP. Cette sélection des nuages bas amène une meilleure représentation des régions subtropicales et du proche environnement convectif. Des analyses de la distribution de la vapeur d'eau troposphérique sont menées et révèlent l'importance de la variabilité relative de la FTH des zones sèches subtropicales, notamment pour la région de l'Est de la Méditerranée. A l'échelle intrasaisonnière, l'utilisation d'un modèle de transport lagrangien permet de montrer que l'humidité relative à 500hPa de cette région de subsidence est caractérisée par un mélange de masses d'air tropicales et extra-tropicales, provenant de zones plus ou moins froides de la troposphère. La base de données est également utilisée dans le but d'évaluer les simulations de modèles de climat, dans le cadre d'un exercice international d'intercomparaison, montrant la difficulté des modèles à reproduire la variabilité interannuelle de la FTH des régions sèches subtropicales.

Los sistemas de posicionamiento global GNSS (GPS y GLONASS) se han convertido en una herramienta básica para obtener medidas geodésicas de la Tierra y en una fuente de datos para el estudio atmosférico. Proporcionan cobertura global y permanente y por la precisión, exactitud y densidad de datos, las señales radio transmitidas pueden ser usadas para la representación espacio-temporal de la atmósfera.La tecnología de los receptores GPS ha evolucionado con una sorprendente rapidez, resultando en instrumentos con suficiente calidad de medida para ser utilizados en estudios geodésicos, comparables a los resultados de técnicas como la interferometría de muy larga base (VLBI), y estudios atmosféricos cuyos resultados pueden ser usados en meteorología.En la tesis Tomografía Atmosférica utilizando Señales Radio de Satélites nos hemos centrado en el uso del sistema GPS por disponer mayor cantidad y calidad de referencias y herramientas para el procesado de los datos. No obstante, se ha demostrado la posibilidad de extender el concepto a cualquier sistema de transmisión radio desde satélite como sondeador atmosférico. La estructura de la tesis se ha dividido en dos áreas: el procesado de datos GPS para extraer información referente a los parámetros atmosféricos de interés, y la aplicación de técnicas tomográficas para la resolución de problemas inversos. En particular, la tomografía se ha aplicado a la ionosfera y la atmósfera neutra. En ambos casos, los resultados tienen un innegable impacto socio-económico: a) la monitorización del estado ionosférico es fundamental por las perturbaciones que la ionosfera provoca en las transmisiones radio que la atraviesan, y b) la estimación del contenido de vapor de agua de la troposfera es de utilidad en la predicción meteorológica y climática.La tomografía ionosférica se empezó a desarrollar usando únicamente datos de la red global IGS. A continuación se mejoró la resolución vertical mediante la utilización de datos de ocultaciones del experimento GPS/MET. La mejora de la resolución se ve limitada a la región en la que estos datos existen. Finalmente, se utilizaron datos de altimetría del satélite TOPEX/POSEIDON para mejorar los mapas y para demostrar la posibilidad de calibración instrumental de los altímetros radar usando técnicas tomográficas.La aplicación a la troposfera se obtuvo tras la mejora y refinamiento tanto del procesado de datos GPS como del proceso de inversión tomográfica. Los primeros resultados se obtuvieron mediante los datos experimentales de la red permanente en Kilauea, Hawaii, por la configuración particular de los receptores. Estos resultados demostraban la capacidad de obtener representaciones espacio-temporales de la troposfera mediante datos GPS. El análisis de los datos de la campaña REGINA, realizada en el Onsala Space Observatory, nos permitió la descripción de un fenómeno meteorológico complejo mediante la tomografía troposférica usando datos GPS y su verificación por comparación directa con medidas realizadas por radiosondeo.En conclusión, se ha demostrado la posibilidad de aplicar tomografía a la atmósfera utilizando señales radio de satélites y, en particular, la constelación GPS. / The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere.GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis.In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecastFor the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique.The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data.Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.

Biogenic isoprene plays an important role in tropospheric chemistry. We use HCHO column measurements by the Global Ozone Monitoring Experiment (GOME) to constrain isoprene emissions. Using the global Goddrad Earth Observing SystemChemistry (GEOS-Chem) as the forward model, a Bayesian inversion of GOME HCHO observations from September 1996 to August 1997 is conducted. Column contributions to HCHO from 12 sources including 10 terrestrial ecosystem groups, biomass burning, and industry are considered and inverted for 8 geographical regions globally. The a posteriori solution reduces the model biases for all regions, and estimates the annual global isoprene emissions of 566 Tg C yr-1, ~50% larger than the a priori estimate. Compared to the Global Emissions Inventory Activity (GEIA) inventory (~500 Tg C yr-1), the a posteriori isoprene emissions are generally higher at mid latitudes and lower in the tropics. This increase of global isoprene emissions significantly affects tropospheric chemistry, decreasing the global mean OH concentration by 10.8% to 0.95106 molecules/cm3. The atmospheric lifetime of CH3CCl3 increases from 5.2 to 5.7 years. Positive matrix factorization (PMF), an advanced method for source apportionment, is applied to TRAnsport of Chemical Evolution over the Pacific (TRACE-P) measurements and it is found that cyanogenesis in plants over Asia is likely an important emission process for CH3COCH3 and HCN. This approach also is applied to estimate source contributions to the tropospheric ozone (O3) with Tropospheric Ozone Production about the Spring Equinox (TOPSE) and TRACE-P measurements. The corresponding GEOS-Chem simulations are applied to the same factor-projected space in order to evaluate the model simulations. Intercontinental transport of pollutants is most responsible for increasing trend of springtime O3, while stratospheric influence is the largest contributions to troposperic O3 variability at northern middle and high latitudes. On the other hand, the overall tropospheric contributions to O3 variability are more important at northern low latitudes by long-range transport, biomass burning, and industry/urban emissions. In general, the simulated O3 variabilities are comparable with those of observations. However, the model underestimates the trends of and the contributions to O3 variability by long-range transport of O3 and its precursors at northern middle and high latitudes.

Several studies suggest that deep convection that penetrates the tropical tropopause layer may influence the long-term trends in lower stratospheric water vapor. This thesis investigates the relationship between penetrating deep convection and lower stratospheric water vapor variability using historical infrared (IR) observations. However, since infrared observations do not directly resolve cloud vertical structure and cloud top height, and there has been some debate on their usefulness to characterize penetrating deep convective clouds, CloudSat/Calipso and Aqua MODIS observations are first combined to understand how to best interpret IR observations of penetrating tops. The major findings of the combined CloudSat/Calipso and Aqua MODIS analysis show that penetrating deep convection predominantly occur in the western tropical Pacific Ocean. This finding is consistent with IR studies but is in contrast to previous radar studies where penetrating deep convective clouds predominantly occur over land regions such as equatorial Africa. Estimates on the areal extent of penetrating deep convection show that when using IR observations with a horizontal resolution of 10 km, about two thirds of the events are large enough to be detected. Evaluation of two different IR detection schemes, which includes cold cloud features/pixels and positive brightness temperature differences (+BTD), show that neither schemes completely separate between penetrating deep convection and other types of high clouds. However, the predominant fraction of +BTD distributions and cold cloud features/pixels ≤ 210 K is due to the coldest and highest penetrating tops as inferred from collocated IR and radar/lidar observations. This result is in contrast to previous studies that suggest the majority of cold cloud features/pixels ≤ 210 K are cirrus/anvil cloud fractions that coexist with deep convective clouds. Observations also show that a sufficient fraction of penetrating deep convective cloud tops occur in the extratropics. This provides evidence that penetrating deep convection should be documented as a pathway of stratospheric-tropospheric exchange within the extratropical region. Since the cold cloud feature/pixel ≤ 210 K approach was found to be a sufficient method to detect penetrating deep convection it was used to develop a climatology of the coldest penetrating deep convective clouds from GridSat observations covering years 1998-2008. The highest frequencies of the coldest penetrating deep convective clouds consistently occur in the western-central Pacific and Indian Ocean. Monthly frequency anomalies in penetrating deep convection were evaluated against monthly anomalies in lower stratospheric water vapor at 82 mb and show higher correlations for the western-central Pacific regions in comparison to the tropics. At a lag of 3 months, the combined western-central Pacific had a small but significant anticorrelation, where the largest amount of variance explained by the combined western-central Pacific region was 8.25%. In conjunction with anomalies in the 82 mb water vapor mixing ratios, decreasing trends for the 1998-2008 period were also observed for tropics, the western Pacific and Indian Ocean. Although none of these trends were significant at the 95% confidence level, decreases in the frequency of penetrating deep convection over the 1998-2008 shows evidence that could explain in part some of the 82 mb lower stratospheric water vapor variability.

The aim of this thesis is to examine the nature and characteristics of tropospheric ozone over Johannesburg, South Africa. Ozone, water vapour and meteorological profile data, which form part of the MOZAIC (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft) database for the period 1995 to 2000 were utilized in this study. The thesis is divided into two main parts. The first part deals with the computation of total tropospheric ozone. A clear seasonal cycle, with ozone peaking in September and October is found. It is suggested that the main reason for the spring maximum is biomass burning, combined with prevailing anticyclonic circulation patterns, which facilitate the build-up of ozone over the region. Variability in TTO is greatest in January, September and November and least during autumn and winter (April to July). The lower day-to-day variability in autumn and winter is a reflection of the more settled weather at this time. Interannual variability is least in January and April to June. The autumn and winter ozone values are more consistent and appear to represent background tropospheric ozone loadings on which the dynamic and photochemical influences of other months are superimposed. High TTO events (>30 DU) occurred predominantly during September and October. Enhancements in the lower troposphere occurred mostly in September and seldom lasted for more than 1-2 consecutive days. It is suggested that these events are most likely due to effects of local surface pollution sources, either localised biomass burning or urban-industrial effects. An extended period of enhancement in the 7-12 km layer occurred from 14-17 September 1998 and again on 20 September 1998. The extended duration of this event suggests that it is due to an STE event. Confirmation of this was given in a case study of a particular MOZAIC flight on 16 September 1998 from Johannesburg to Cape Town. The second part of the thesis deals with the classification of ozone profiles and is used to find pattern and order within the profiles. TWINSPAN (Two-Way INdicator SPecies ANalysis), a cluster analysis technique, was used to classify the profiles according to the magnitude and altitude of ozone concentration. Six distinct groups of profiles have been identified and their characteristics described. The HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) trajectory model was used to relate the profiles to the origin of air masses, revealing clearly defined source regions. The mid-tropospheric peak in summer and the low to mid-tropospheric enhancement in spring is attributed to continental areas over central Africa and long-range transport while local sources are responsible for the winter low tropospheric enhancement. Reduced ozone values are due to westerlies bringing in clean maritime air. The classification has highlighted three important findings. Firstly, it has emphasized the pronounced seasonality of ozone profiles. It is evident that seasons are dominated by particular patterns and by inference, the processes and transport patterns that shape individual profiles are seasonally dependent. Secondly, the widely recognized spring maximum in tropospheric ozone has been confirmed in this classification, but a new and equally high summer mid-tropospheric enhancement due to the penetration of tropical air masses from continental regions in central Africa has been identified. Thirdly, it is suggested that the computation of a mean profile and furthermore, extrapolation of trends based on a mean profile is meaningless, particularly for a location on the boundaries of zonally defined meteorological regimes. / Thesis (M.A.)-University of Natal, Durban, 2002.

To understand the contribution of aerosol particles to radiative forcing and heterogeneous chemical processes in the upper troposphere and lowermost stratosphere (UT/LMS), the knowledge of the particle size distribution is mandatory. Unfortunately, measurements in the UT/LMS are costly. Research aircrafts are expensive and thus their application is limited in time and space. Satellite remote sensing measurements provide a good temporal and spatial (horizontal) coverage, but only a limited vertical resolution and currently cannot resolve the particle size distribution. Therefore, within this thesis an optical particle counter (OPC) unit was modified for the application onboard a passenger long-haul aircraft within the CARIBIC project (www.caribic-atmospheric.com). The CARIBIC OPC unit provides regular and cost-efficient particle size distribution measurements of accumulation mode particles in the UT/LMS. In April 2010, the new OPC unit was installed for the first time onboard the Lufthansa Airbus A340 600 (D-AIHE) for the measurement of the volcanic ash cloud from the Eyjafjallajökull eruption (April to May 2010). Since June 2010 the OPC unit measures on usually four intercontinental flights per month the UT/LMS particle size distribution in the particle size range 125 to 1300 nm particle diameter. As the data acquisition stores the scattering raw signal and all housekeeping data as well, during the post flight data analysis the temporal- and size channel resolution can be flexible set. Within this work the data were analyzed with 32 size channels and 300 seconds. As aircraft-borne measurements are always time-consuming, the development of the OPC unit and the analysis routine, as well as its characterization and certification took more than two thirds of the total working time of this thesis. Therefore, the analysis of the data is limited to the first year of regular measurements until May 2011. Nevertheless, this dataset is sufficient to demonstrate the scientific relevance of these measurements. To validate the OPC data, a comparison to particle size distributions measured from board research aircraft was carried out. The analysis of the volcanic ash flights in April and May 2010 showed strongly enhanced particle mass concentrations inside the plumes and agreed in some regions very well to the particle mass concentration predicted by a dispersion model. A further case study shows the occurrence of a surprising large (1000 km) and high concentrated pollution plume over eastern Asia close to Osaka (Japan). Inside the plume the highest particle number- and mass concentrations measured with the OPC unit in the analysis period were observed (except volcanic ash flights). A detailed analysis of the in parallel measured trace gasses as well as meteorological- and LIDAR data showed, the observed plume originate from biomass burning and industrial emissions in eastern China. A third case study gives a first attempt of a mass closure/validation between the particle masses derived by the CARIBIC OPC unit and the CARIBIC impactor particle samples. First statistical analyses to the vertical, meridional, and seasonal variation of the accumulation mode particle size distribution and therefrom derived parameter indicate a stratospheric vertical increasing gradient for the particle number- and mass concentration. In general in the mid-latitude LMS the concentration of accumulation mode particles was found to be on average 120% higher than in the mid-latitude UT. The mid-latitude LMS particle size distribution shows a seasonal variation with on average 120% higher concentrations during spring compared to fall. This results can be explained with general dynamics in the stratosphere (Brewer-Dobson Circulation) and in the tropopause region (stratosphere-troposphere-exchange, STE). An anti-correlation of gaseous mercury to the stratospheric particle surface area concentration (R²=0.97) indicates that most likely stratospheric aerosol particles do act as a sink for gaseous mercury. Finally, two comparisons of the OPC data to data from satellite remote sensing and a global aerosol model underline the OPC potential and the benefits of creating an in situ measured reference dataset. / Um die Rolle von Aerosolpartikeln beim Strahlungsantrieb und der heterogenen chemischen Prozessen in der oberen Troposphäre und untersten Stratosphäre (OT/US) verstehen zu können, ist es unabdingbar die Partikelgrößenverteilung zu kennen. Messungen der Partikelgrößenverteilung in dieser Region sind allerdings aufwendig. Der Einsatz von Forschungsflugzeugen ist teuer und deshalb zeitlich und räumlich nur begrenzt. Satellitenmessungen bieten zwar eine gute zeitliche und räumliche (horizontal) Abdeckung, aber nur eine begrenzte vertikale Auflösung. Weiterhin können bisherige Satellitenmessungen die Partikelgrößenverteilung nicht auflösen. Im Rahmen dieser Arbeit wurde deshalb ein optischer Partikelzähler (OPC) Messeinschub für den Einsatz an Bord eines Langstrecken-Passagierflugzeugs aufgebaut (CARIBIC Projekt, www.caribic-atmospheric.com). Mit diesem Messeinschub kann regelmäßig und kosteneffizient die Partikelgrößenverteilung des Akkumulationsmodes in der OT/US gemessen werden. Im April 2010 wurde der neue OPC Einschub erstmals an Bord des Lufthansa Airbus A340-600 (D-AIHE) installiert um die Vulkanasche der Eyjafjallajökull Eruption (April bis Mai 2010) zu messen. Seit Juni 2010 misst der OPC Einschub auf durchschnittlich vier Interkontinentalflügen pro Monat die Partikelgrößenverteilung der OT/US im Größenbereich zwischen 125 und 1300 nm Partikeldurchmesser. Während des Fluges speichert die Datenerfassung alle Rohsignale ab und ermöglicht dadurch eine nutzerspezifische Datenauswertung nach dem Flug (z. B. Anzahl der Größenkanäle oder Zeitauflösung). Im Rahmen dieser Arbeit wurden die Daten mit 32 Größenkanälen und 300 Sekunden analysiert. Da fluggetragene Messungen immer sehr aufwendig sind, beanspruchte die Entwicklung des OPC Einschubs und des Analysealgorithmus, sowie die Charakterisierung und Zertifizierung mehr als zwei Drittel der Gesamtarbeitszeit dieser Arbeit. Daher ist die Analyse der Messdaten auf das erste Jahr der regulären Messungen bis Mai 2011 beschränkt. Dennoch ist dieser Datensatz geeignet um die wissenschaftliche Relevanz dieser Messungen zu demonstrieren. Um die OPC-Daten zu validieren, wurde ein Vergleich mit bisherigen OPC Messungen von Bord Forschungsflugzeugen durchgeführt. Die Analyse der Vulkanascheflüge im April und Mai 2010 zeigte in der Abluftfahne stark erhöhte Partikelmassekonzentrationen, welche in einigen Vergleichsregionen sehr gut mit der Vorhersage eines Disperionsmodells übereinstimmten. Eine weitere Fallstudie zeigt das Auftreten einer überraschend großen (1000 km) und hoch konzentrierten Abluftfahne über Ostasien nahe Osaka (Japan). In der Abluftfahne wurde die im Analysezeitraum höchste mit dem CARIBIC OPC gemessene Partikelanzahl- und Massenkonzentration beobachtet (ausgenommen Vulkanascheflüge). Eine detaillierte Analyse der parallel gemessenen Spurengase, sowie meteorologischer Daten und LIDAR Profile zeigte, dass die beobachtete Abluftfahne eine Mischung aus Biomasseverbrennungs- und Industrieabgasen aus Ost-China war. Eine dritte Fallstudie stellt einen ersten Versuch einer Massenschließung/Validierung zwischen der aus den CARIBIC OPC-Daten abgeleiteten Partikelmasse und der Partikelmasse aus CARIBIC Impaktorproben dar. Erste statistische Analysen zur vertikalen, meridionalen und saisonalen Variabilität der Partikelgrößenverteilung im Akkumulationsmode und daraus abgeleiteten Parametern zeigen einen vertikal ansteigenden Gradienten für die Partikelanzahl- und Massenkonzentration. Generell war in der US der mittleren Breiten die Konzentration von Akkumulationsmode Partikeln im Mittel um 120% höher als in der OT der mittleren Breiten. Weiterhin wurde in der US der mittleren Breiten eine jahreszeitliche Schwankung gefunden. Im Frühling war die mit dem OPC gemessene Partikelkonzentrationen im Mittel um 120% höher als im Herbst. Diese Befunde lassen sich mit der atmosphärischen Dynamik in der Stratosphäre (Brewer-Dobson Zirkulation) und in der Tropopausenregion (Stratosphäre-Troposphäre-Austauschprozesse) erklären. Eine gefundene negative Korrelation von gasförmigen Quecksilber mit der stratosphärischen Partikeloberflächenkonzentration (R²=0.97) ist ein starker Indikator dafür, dass in der US Aerosolpartikel eine Senke für gasförmiges Quecksilber darstellen. Zum Abschluss unterstreichen zwei Vergleiche der OPC-Daten mit Satellitenmessungen und Ergebnissen eines globalen Aerosolmodels das Potential und den Nutzen der CARIBIC OPC Daten als in-situ gemessenen Referenzdatensatz.

A lack of quality data on high clouds has led to inadequate representations within global weather and climate models. Recent advances in spaceborne measurements of the Earth’s atmosphere have provided complementary information on the interior of these clouds. This study demonstrate how an array of space-borne measurements can be used and combined, by close co-located comparisons in space and time, to form a more complete representation of high cloud processes and properties. High clouds are found in the upper atmosphere, where sub-zero temperatures frequently result in the formation of cloud particles that are composed of ice. Weather and climate models characterise the bulk properties of these ice particles to describe the current state of the cloud-sky atmosphere. By directly comparing measurements with simulations undertaken at the same place and time, this study demonstrates how improvements can be made to the representation of cloud properties. The results from this study will assist in the design of future cloud missions to provide a better quality input. These improvements will also help improve weather predictions and lower the uncertainty in cloud feedback response to increasing atmospheric temperature. Most clouds are difficult to monitor by more than one instrument due to continuous changes in: large-scale and sub-cloud scale circulation features, microphysical properties and processes and characteristic chemical signatures. This study undertakes co-located comparisons of high cloud data with a cloud ice dataset reported from the Microwave Limb Sounder (MLS) instrument onboard the Aura satellite that forms part of the A-train constellation. Data from the MLS science team include vertical profiles of temperature, ice water content (IWC) and the mixing ratios of several trace gases. Their vertical resolutions are 3 to 6 km. Initial investigations explore the link between cloud-top properties and the longwave radiation budget, developing methods for estimating cloud top heights using; longwave radiative fluxes, and IWC profiles. Synergistic trios of direct and indirect high cloud measurements were used to validate detections from the MLS by direct comparisons with two different A-train instruments; the NASA Moderate-resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth’s Radiant Energy System (CERES) onboard on the Aqua satellite. This finding focuses later studies on two high cloud scene types that are well detected by the MLS; deep convective plumes that form from moist ascent, and their adjacent outflows that emanate outwards several hundred kilometres. The second part of the thesis identifies and characterises two different high cloud scenes in the tropics. Direct observational data is used to refine calculations of the climate sensitivity to upper tropospheric humidity and high cloud in different conditions. The data reveals several discernible features of convective outflows are identified using a large sample of MLS data. The key finding, facilitated by the use of co-location, reveals that deep convective plumes exert a large longwave warming effect on the local climate of 52 ± 28Wm−2, with their adjacent outflows presenting a more modest warming of 33 ± 20Wm−2.

The atmospheric drivers of winter and summer surface climate in western Canada are evaluated using a synoptic climatological approach. Winter snow accumulation provides the largest contribution to annual streamflow of the north-flowing Mackenzie and east-flowing Saskatchewan Rivers, while summer water availability is primarily a product of basin-wide precipitation and evapotranspiration. A catalogue of dominant synoptic types is produced for winter (Nov-Apr) and summer (May-Oct) using the method of Self-Organizing Maps. Water availability, quantified through high-resolution gridded temperature and precipitation data, associated with these synoptic types is then determined. The frequency of dominant types during positive/negative phases of the Southern Oscillation Index, Pacific Decadal Oscillation, and Arctic Oscillation reveal the atmospheric processes through which these teleconnections influence surface climate. Results from the winter analysis are more coherent than summer, with strong relationships found between synoptic types, teleconnections, and surface climate. Although not as strong, links between summer synoptic types and water availability also exist. Additionally, time-series analysis of synoptic type frequencies indicates a trend toward circulation patterns that produce warmer, drier winters as well as an earlier onset and extension of the summer season. This study increases our understanding of the atmospheric processes controlling the distribution of water resources in western Canada. / Graduate / 0388 / 0725 / 0368 / bwnewton@uvic.ca

A method of inferring tropospheric gravity wave source characteristics from middle atmosphere observations has been adapted from previous studies for use with MF radar observations of the equatorial mesosphere-lower thermosphere at Christmas Island in the central Pacific. The nature of the techniques applied also permitted an analysis of the momentum flux associated with the characterised sources and its effects on the equatorial mean flow and diurnal solar thermal tide. An anisotropic function of gravity wave horizontal phase speed was identified as being characteristic of convectively generated source spectra. This was applied stochastically to a ray-tracing model to isolate numerical estimates of the function parameters. The inferred spectral characteristics were found to be consistent with current theories relating convective gravity wave spectra to tropospheric conditions and parameters characterising tropical deep convection. The results obtained provide observational constraints on the model spectra used in gravity wave parameterisations in numerical weather prediction and general circulation models. The interaction of gravity waves with the diurnal solar thermal tide was found to cause an amplification of the tide in the vicinity of the mesopause. The gravity wave-tidal interactions were highly sensitive to spectral width and amplitude. Estimates were made of the high frequency gravity wave contribution to forcing the MSAO with variable results. The data used in the analysis are part of a large archive which now has the potential to provide tighter constraints on wave spectra through the use of the methods developed here. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1352362 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2009