Située sur la rive Est de la mer méditerranéenne, la région de Beyrouth est soumise aux brises de mer et de terre en période estivale. En présence de ces circulations, la pollution atmosphérique devient complexe en raison des interrelations entre les phénomènes se produisant à plusieurs niveaux scalaires. Notre étude s'est appuyée sur des documents et données existant (dans le service de météorologie de l'aéroport de Beyrouth) et de notre propre base de données issues de nos propre campagnes de mesures. Les bases théoriques de ces types de circulation et la diversité géographique de notre milieu d'étude étaient l'objet de la première partie. La deuxième partie présente la démarche adoptée pour prendre en compte la relation entre l'atmosphère, les brises, la pollution et le milieu. Une troisième partie analyse les conditions favorables à l'apparition des brises aux échelles synoptique et régionale. Et une quatrième partie traite les variabilités spatio-temporelles des brises en relation avec la topographie et l'occupation du sol et leurs incidences sur le transport etles concentrations des polluants aux échelles fines. / Situated on the East the Mediterranean Sea, the region of Beirut is subjected to the sea and land breezes in summer. In the presence of these circulations, the atmospheric pollution becomes complex because of the interrelations between the phenomena occurring at several scalar levels. We used existing documents in our study and existing data (in the service department of meteorology of the airport of Beirut) and of our own base of data acquired during previous campaigns of measures.The theoretical bases of these types of circulation and the geographical diversity of our environment were the object of the first part. The second part presents the approach adopted to account the relation between the atmosphere, the breezes, the pollution and the environment. The third part analyzes the favorable conditions for the appearance of the breezes on synoptic and regional scales. And the fourth part treats the variability in space and in time of the breezes in relation of the topography and the land-use as well as their incidences on the pollutants concentrations and transportation on micro local scale.

This study investigated the influences of sea-land breezes (SLBs) and northeastern monsoon (NEM) on the transportation and dispersion of air pollutants over coastal region in southern Taiwan. The physicochemical properties of particulate matter (PM) was simultaneously sampled and analyzed at both inland and offshore sites during eight intensive sampling periods. This study further used a SURFER 2-D plotting software, a backward trajectory model, a 3-D meteorological model (MM5), and a comprehensive air quality model (CAMx) to simulate surface wind fields and spatial distribution of air pollutants over the coastal region during the intensive sampling periods of SLBs and NEM. According to the meteorological condition and the synoptic weather patterns of the observation data showed that the SLBs sampling periods commonly occurred the weather patterns were zone of low pressure, pacific high pressure, and west stretch of the pacific high pressure when the main prevailing wind direction were west wind and southwest wind. During the NEM sampling periods, the weather patterns were strong northeastern monsoon, standard northeastern monsoon, and outflow rebound with high pressure in southern Taiwan, and then the main prevailing wind direction were northwest wind and northeast wind. However, during the MIX sampling periods, the weather patterns were outflow circulation of typhoon, weak northeastern monsoon, and outflow rebound with high pressure, while the wind directions didn¡¦t change regular. Thus, at coastal sites, the sea-land breezes induce an inland transport of air pollutants during the daytime and a seaward return of air pollutants at nighttime, causing a recirculation of air pollutants back to inland regions each day during the SLBs sampling periods. During the NEM sampling period was mainly brought from the northeastern wind which transported air pollutants from the northern region to Kaohsiung metropolitan area. The results of PM concentration and size distribution indicated that the inland sites had a higher fraction of fine particles (PM2.5), whereas the offshore sites had a higher fraction of coarse particles (PM2.5-10). These phenomena were attributed to the fact that marine aerosols are generally abundant in the coarse particles. PM concentration is relatively higher during the NEM sampling periods than during the SLBs and MIX sampling periods. For PM concentration, the order of secondary inorganic aerosols (SIA) was NEM > MIX > SLBs, while the SIA/Ions ratio of PM2.5 were approximately 50% during sampling periods. The [NO3-]/[SO42-] ratios of PM2.5 and PM2.5-10 during the SLBs sampling periods were always lowest than those during the NEM and MIX sampling periods. It is suggested that the PM concentrations during the SLBs sampling periods were highly influenced by stationary sources emissions. The crustal elements indicated that the Al, Ca, Fe, and K contributed major composition of particles. Artificial metals, such as Mg, Pb, V, and Zn were also enriched in the atmospheric PM during the NEM sampling periods. In addition, the higher concentration of Fe was attributed to local anthropogenic emission and weak northeastern monsoon during the MIX sampling periods. Regardless of inland or offshore sites, a high concentration of secondary organic carbon (SOC) during the NEM and MIX sampling periods was consistent with OC/EC ratio higher than 2.2 indicates the potential formation of secondary aerosols. Chloride deficit of PM at inland sites were lost easily for approximately 40.28% during the NEM sampling periods. Moreover, the lowest [Cl-]/[Na+] ratio occurred during the sampling periods when the chloride deficit was relative high at inland sites. According to the results of neutralization ratio (NR), regardless of the periods (SLBs, NEM, and MIX), the particulates of inland and offshore sites were both acid. During the NEM and MIX sampling periods, sulphur oxidation ratio (SOR) of PM2.5 over coastal region in southern Taiwan were above 0.25. It is suggested that the results of SOR during those sampling periods were highly influenced by long transportation. In addition, the nitrogen oxidation ratio was lower influenced than SOR over coastal region in southern Taiwan. It is suggested that air quality of Kaohsiung metropolitan area were influenced by the industrial source emissions. During the SLBs sampling period, sea breezes blown in the morning transported the offshore PM10 back to the inland sites in the Kaohsiung metropolitan area. In contrast, the air mass observed during the NEM sampling period was brought to the Kaohsiung metropolitan area mainly by a northerly wind which transported air mass originating in the northern region (i.e. Chiayi counties). The backward trajectory modeling of the MIX sampling periods suggested that the winds were dominated by the Northeastern Monsoon, and as such, likely inhibited the influences of sea-land breezes. Local surface air mass circulation over southern Taiwan obtained from MM5 model influenced by the southwestern monsoon during the SLBs sampling period. The weather in southern Taiwan during the NEM intensive sampling period was occasionally influenced by the Northeastern Monsoon as well as by complex terrain. During the MIX sampling periods, air mass recirculation was frequently observed in the coastal region of southern Taiwan. The results of CAMx model showed that air pollutions were occurred apparent sea breezes in the afternoon and land breezes at night during the SLBs sampling period. During the NEM sampling period, a strong Northeastern Monsoon blew air pollutions from the north to the southern region. We have compared the model simulation with field measured O3 and PM10 concentrations for inland and offshore regions. The order of correlation coefficients of ¬the model simulation and the measurement for O3¬ and PM10 in sampling periods is SLBs>MIX>NEM and NEM>MIX>SLBs, respectively. Overall, the correlation coefficients of the model simulation and the measurement were middle and high correlation.

The eastern coast of the Northeast Brazil (NEB) is a region where transient weather systems interact with local systems, modulating their frequency and intensity. Understanding the mechanisms of such interactions may be instrumental in explaining the observed precipitation patterns in this region. The objective of this work is quite within this scope and takes a new approach, namely the study of time series using spectral decomposition. The wavelet transform was adopted for it has proven to be a very powerful tool in dealing with local data in many areas. It furnishes a hierarchical frame that allows the double location in time and frequency domains. The hourly averaged series of wind speed and direction, air temperature, humidity and precipitation were taken at an observing tower at the 12.40 high during the October, 2004 October 2005 period in the Santa Rita island (mangrove area) at 9° 42 18 S e 35° 48 32 W. Relevant characteristics of the seasonality, transport and intensity of the breeze systems were noted, showing a clear distinction among the rainy, dry and transitional periods. Mesoscale systems are more active during the dry period because they are quite dependent of the daily cycle of heating and cooling. Large scale transient systems are more prominent during the rainy season, being responsible for the highest observed precipitation rates. The local wind system of sea land breezes shows a predominant southeast (SE) direction, thus evidencing the sea breeze. It was also noted that the highest amplitudes and wind persistency from SE were reinforced by the SE Trade Winds, creating a constructive interference in the signal. The prevailing winds from northwest (NW) were only observed during the dawn, thus characterizing the land breeze branch of the local circulation. The sea/land breeze variability affected the precipitation regime, by forming a surface convergence zone (rising motions) in accord with the time of the precipitations. These also showed a conic multifractal pattern in the periodgram, typical of high space-time variability. / Fundação de Amparo a Pesquisa do Estado de Alagoas / A costa leste do NEB é palco da ação simultânea de fenômenos transientes que interagem com os sistemas locais, modificando sua freqüência e intensidade. O conhecimento destas interações pode revelar o padrão das precipitações junto à costa do NEB. O objetivo desta dissertação se encaixa neste contexto e aborda os dados sob uma perspectiva nova, que consiste no estudo das séries temporais através de decomposição espectral. Para este fim, adotou-se a Transformada em Ondeletas (TO), que nas ultimas décadas tem alcançado notável êxito em diversas áreas da ciência. Trata-se de uma ferramenta matemática poderosa na detecção das freqüências e intensidades das séries temporais. Esta técnica fornece uma moldura hierárquica que permite a dupla localização em tempo e freqüência. Os dados horários de velocidade e direção do vento, temperatura do ar, umidade e precipitação foram medidos numa torre ao nível de 12,40m acima do solo, durante o período (Outubro de 2004 Outubro de 2005) numa área de proteção ambiental da Ilha de Santa Rita, localizada no mangue natural a 9° 42 18 S e 35° 48 32 W. Foram patenteadas características relevantes de transporte, sazonalidade e intensidade dos sistemas de brisas. As características do sinal mostraram a distinção entre as quadras seca e chuvosa, bem como as respectivas transições. Os sistemas de mesoescala atuam com mais intensidade no período seco, pelo fato de se ajustar ao ciclo diário da forçante térmica (radiação solar). Para a quadra chuvosa, predominam os sistemas transientes de grande escala, que são os responsáveis pelos maiores índices pluviométricos. O regime de ventos locais, caracterizado pelos sistemas das brisas de terra e mar, assinala que a direção do vento predominante é de sudeste (SE), o que caracteriza a brisa marítima. Foi verificado que as maiores amplitudes e persistência dos ventos de SE foram incrementadas pelos ventos Alísios de SE, que sopraram o ano inteiro, criando uma interferência construtiva no sinal. Os ventos predominantes de noroeste (NW) só foram observados no período da madrugada, distintivos da brisa terrestre. A mudança das brisas terrestres/marítimas apresentou intervenção no sistema de precipitação, criando uma zona de convergência em superfície (movimentos ascendentes) corroborando com os horários em que ocorreram as precipitações. Estas exibiram uma configuração multifractal cônica no periodograma, típica da sua alta variabilidade espaço-temporal.

The United Arab Emirates is a new country that has had little time to accumulate a scientific heritage. Meteorologically researched and documented weather material for forecasters is virtually non-existent and that available is fragmented and anecdotal. The thesis tackles this problem by identifying weather phenomena significant to aviation in the Emirates and particularly at Abu Dhabi International Airport (ADIA). Mechanisms responsible for their development are described and applicable forecasting rules and principles are derived. Surface and upper air observation data at ADIA from 1983 to 2002 were analysed to identify the weather phenomena, their associated weather systems and for statistical analyses. When relevant, observation data at Al Ain was also used. Post-processed numerical weather prediction Global Forecast Service Eta model data are used and when and where possible radar and satellite imagery. A secondary aim is to provide information of the general seasonal climate. This was achieved by means of a literature study of the dominating weather systems and the presentation of surface and upper air mean circulation charts. Fog is the most important weather phenomenon and serious disrupter of aviation at ADIA throughout the year. It does not occur during Shamal conditions, but fog can form well inland on the edge of the Empty Quarter at the Liwa Oasis when the Shamal wind becomes light. Contrary to local belief, fog is unlikely to occur on two, or more, consecutive nights. The Shamal can last for several days and disrupt helicopter flights to the oil rigs, while anabatic and katabatic effects often make it gustier and stronger inland at Al Ain than ADIA. While dust storms occur in strong southerly winds off the desert, the Shamal can bring dust from further afield from the north as can the previously unreported Nashi wind. The sea breeze can extend about 150 km inland to Al Ain and the Liwa Oasis. Thunderstorms associated with winter upper air troughs from the west, are the main producers of rain, while occasional thunderstorms off the Hajar Mountains in the east bring some rain in summer. Tropical depressions are a rare event. / Thesis (PhD)--University of Pretoria, 2010. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

Although sea-breezes frequently initiate convection, it is oftentimes challenging to forecast the precise location of storm development. This research examines temporal and spatial characteristics of sea-breeze driven convection and environmental conditions that support convective or non-convective sea-breeze days along the Northern Gulf Coast. Base reflectivity products were used to identify the initial time of convection (values greater than 30 dBZs) along the sea-breeze front. It was found that convective sea-breezes initiated earlier in the day compared to non-convective sea-breezes. Mapping convective cells in ArcGIS revealed favored locations of thunderstorm development including the southeastern cusp of Mobile County, Alabama and convex coastlines. Meteorological variables from the North American Regional Reanalysis dataset were compared between convective and non-convective sea-breeze days via a bootstrap analysis to reveal environmental characteristics pertinent to forecasting sea-breeze driven convection. Lapse rates, CAPE, CIN, specific humidity, dew point temperature, relative humidity, and precipitable water values were statistically significant.

Dans le Sud-Est de la France, le département des Alpes-Maritimes, singulier du fait de son relief contrasté, est soumis au jeu des brises et inversions thermiques nocturnes. L’agglomération littorale contribue aux émissions de particules qui sont un des polluants les plus nocifs pour la santé humaine. La pollution de l’air n’est évidemment pas répartie de manière homogène dans le temps et dans l’espace. Les topoclimats sont un protagoniste de la pollution de l’air au sein de cet espace littoral montagneux. La problématique centrale de cette thèse consiste donc à comprendre pourquoi et comment les topoclimats influencent la variabilité spatio-temporelle des concentrations de particules dans le sud-ouest du département, tout en considérant qu’ils ne sont pas seuls à expliquer les concentrations. Afin de répondre à cette question, plusieurs objectifs privilégiant les mesures de terrain, et la modélisation ont été fixés :- exploiter des données de concentrations de particules et de variables météorologiques acquises à l’aide de plusieurs appareils de mesures, de manière fixe et itinérante, en plusieurs endroits et à différentes échelles spatio-temporelles ;- caractériser les écoulements d’air à faible altitude à l’aide de ballons équilibrés (dits CLB) et les mettre en relation avec les niveaux de PM10 mesurés ; - caractériser chimiquement les PM10 pour évaluer la contribution des principales sources d’émissions ;- tester la capacité d’un logiciel de dispersion atmosphérique à simuler en relief contrasté les effets des topoclimats sur la variabilité spatio-temporelle des PM10.L’influence des topoclimats sur la pollution de l’air particulaire a été établie. / In the Southeastern of France, the department of the Alpes-Maritimes is singular by contrasting terrain and is submitted to breezes and temperature inversions. The coastal urbanization contributes to the particulate matters emissions that are part of the most harmful substances to human health. Air pollution is not spread heavenly in time and space, of course. Topoclimates are one of the protagonists of air contamination within this mountainous coastal area. The focus of this thesis work is to understand why and how topoclimates have impact on the spatio-temporal variability of particle concentrations in the Southwest of the department, while considering that they are not alone to explain the concentrations. The researcher identified several objectives to answer this question and he gave priority to ground measures and modeling: - To explore data about the particulate matters and meteorological characteristics that were collected through the use of several measuring tools, in a fixed and travelling way, in different places and on various spatio-temporal scales;- To identify and characterize air flows at low altitude with CLB (Constant Level Balloon) and cross compare them with the measured levels PM10; - To chemically analyse PM10 to assess the contribution of the main sources of emission;- To test the capacity of an atmospheric dispersion software to simulate the impact of topoclimates on the spatio-temporal variety of PM10 on mountainous and uneven landscapes.The influence of topoclimates on the air pollution has been scientifically established.