The effect of flow anisotropy and three dimensional separation on the turbulent structure and radiated turbulence ingestion noise of a rotor in two experimental configurations is studied. The first consists of a non-axisymmetric boundary layer wake ingested by a rotor mounted at the aft of a body of revolution inclined at 5 degree angle of attack. In the second configuration a transient disturbance is generated by an upstream wing body junction pitching from zero to 20 degree angle of attack . This disturbance is convected downstream and ingested into a rotor immersed in a wall boundary layer. In both cases flow velocimetry at the rotor inflow is done and the far field sound is measured. The flow velocimetry in the wake of the inclined body of revolution shows evidence of three dimensional separation and vortex rollup between the lee and body sides. A boundary layer embedded shear layer develops as the turbulent kinetic energy is pulled off the wall by the flow separation and is visible in the port side velocimetry. The turbulent structure of this shear layer and the boundary layer on the lee of the body is visualized using compact eddy structure representation and the modes on the port side are shown to be stretched versions of similar modes seen in an equilibrium, zero pressure gradient boundary layer. The effect these structures had on the radiated sound served to both increase blade to blade correlation and the overall broadband levels of the sound. Measurements of the sound using an acoustic array showed directivity effects that resulted from the location of the embedded shear layer and rollup vortices. Although the vortices likely have some effect on the spectra, most of the noise is dominated by the turbulence ingestion of the embedded shear layer. For the second experimental configuration the transient motion was documented through repeated measurements of the flow field and sound, and an ensemble average of the measurements taken. Overall the flow was unsteady, particularly in the outer region of the boundary layer. The sound radiated was shown to be tonal during the first half of the interaction, where the flow is dominated by a deterministic mean flow change, and attributed to a form of periodic unsteady loading. During the latter half of the disturbance the broadband and overall sound levels increased significantly and are associated with the interaction of the rotor with flow separation over the wing body junction when it reached a critical, 16 degree angle of attack. / Doctor of Philosophy / The interaction of rotors and propellers with turbulence is commonly encountered when vehicles transit fluid mediums. In vehicles with aft mounted propellers, such as pusher type aircraft or underwater vehicles, turbulent boundary layers developed over the vehicle surface are ingested by the propeller. The size or scale of the average turbulent eddy greatly affects the type of sound generated by the interaction. For eddies that are small enough to only interact with one blade, the blade angle of attack varies randomly as it rotates through the turbulence and this radiates broadband sound. However, if the blade encounters eddies that are large or long enough to interact with multiple blades then the angle of attack, and thus the fluctuating lift force, begins to be correlated for each passage of the blade. This is known as blade to blade correlation and produces energy and sound concentration around the frequencies that correspond to the blade passage. This phenomenon is fairly well understood and many attempts have been made to model and predict the sound spectra from a rotor encountering turbulence in this manner. However these models often assume isotropic and homogenous turbulence when making predictions. This assumption works well in many applications, however, often the turbulence the rotor encounters is anisotropic with significant flow inhomogeneities. Thus, experimental investigations into the mechanisms and sources of sound in inhomogenous and anisotropic flows is necessary in an attempt to inform further flow and acoustic models. In this dissertation the inflow and acoustic response of a rotor ingesting significantly complex and anisotropic flows is characterized. It focuses on two commonly encountered flow arrangements; a rotor mounted at the stern of a body of revolution at an angle of attack, and a rotor ingesting a turbulent wall boundary layer with transient disturbances introduced by an upstream wing body junction. In both cases the flow is three dimensional and the rotor encounters significant circumferential turbulence variation during its rotation through the resultant turbulent flow field. For the flow about the body of revolution the flow and noise appear to be driven by the rotor interaction with an embedded shear layer that results from three dimensional separation between the lee and windward sides of the body. For the transient disturbance interaction the rotor noise response shows two separate noise sources. During the first half of the disturbance the blade response is tonal and associated with a deterministic blade angle of attack change as the rotor interacts with the transient. In the latter half of the disturbance the rotor broadband noise is significantly increased due to flow separation over the wing body junction.

Sea turtles face numerous threats on their nesting beaches, including habitat degradation, artificial lighting, and human interventions like beach nourishment projects. These factors can disrupt nesting behavior and reduce overall reproductive success. This study examined the impact of anthropogenic disturbances, specifically artificial lighting and beach nourishment projects, on the nesting success (quantified as portion of adult female emergences resulting in a nest) of loggerhead (Caretta caretta) and green turtles (Chelonia mydas) in southern Brevard County, Florida. Utilizing a long-term dataset (1989-2023) from the UCF Marine Turtle Research Group, the research focused on the Archie Carr National Wildlife Refuge (ACNWR), a site with minimal lighting and development, and the Brevard County Mid Reach, an area characterized by high levels of artificial lighting and development. I aimed to: (1) evaluate the effects of artificial lighting on nesting success by comparing 1989-2023 data from ACNWR and Mid Reach; (2) assess the impact of beach nourishment projects by analyzing nesting success before and after nourishment events, which began in 2005; and (3) explore the interaction between artificial lighting and beach nourishment by comparing nesting success in areas with varying levels of lighting and development. The study found that both loggerhead and green turtle nesting success were lower in areas with high-lighting compared to more natural, low-lighting areas, as well as following more frequent, larger-scale nourishment projects. This research provides new insights into how these human activities influence sea turtle nesting behaviors and the effectiveness of conservation measures like the establishment of the ACNWR in mitigating these impacts. Findings can contribute to the development of strategies to enhance sea turtle conservation efforts in regions experiencing similar pressures.

This thesis examined vegetation change over the last 43 years in Australia's largest contiguous alpine area, the Kosciuszko alpine zone in south-eastern Australia. Using historical and current data about the state of the most common vegetation community, tall alpine herbfield, this thesis addressed the questions: (1) what were the patterns of change at the species/genera and life form levels during this time period; (2) what were the patterns of recovery, if recovery occurred, from anthropogenic disturbances such as livestock grazing or trampling by tourists; (3) what impacts did natural disturbances such as drought have on the vegetation and how does it compare to anthropogenic disturbances; and (4) What are the benefits, limitations and management considerations when using long-term data for assessing vegetation changes at the species/genera, life form and community levels? The Kosciuszko alpine zone has important economic, cultural and ecological values. It is of great scientific and biological importance, maintaining an assemblage of vegetation communities found nowhere else in the world. It is one of the few alpine regions in the world with deep loamy soils, and contains endemic flora and fauna and some of the few periglacial and glacial features in Australia. The area also forms the core of the Australian mainland's most important water catchment and is a popular tourist destination, offering a range of recreational opportunities. The vegetation of the Kosciuszko alpine zone is recovering from impacts of livestock grazing and is increasingly exposed to pressures from tourism and anthropogenic climate change. At the same time, natural disturbances such as drought and fire can influence the distribution, composition and diversity of plants. Thus, there is a need for detailed environmental data on this area in order to: (1) better understand ecological relationships; (2) understand existing and potential effects of recreational and management pressures on the region; (3) provide data against which future changes can be assessed; and (4) provide better information on many features of this area, including vegetation, for interpretation, education and management. The research in this thesis utilised three types of ecological information: (1) scientific long-term datasets; (2) photographic records; and (3) a comparison of disturbed and undisturbed vegetation. This research analysed data from one of the longest ongoing monitoring programs in the Australian Alps established by Alec Costin and Dane Wimbush in 1959. Permanent plots (6 transects and 30 photoquadrats) were established at two locations that differed in the time since grazing and have been repeatedly surveyed. Plots near Mt Kosciuszko had not been grazed for 15 years and had nearly complete vegetation cover in 1959, while plots near Mt Gungartan showed extensive impacts of grazing and associated activities which only ceased in 1958. Some transect data from 1959 to 1978 have been analysed by the original researchers. The research presented in this thesis extends this monitoring program with data from additional surveys in 1990, 1999 and 2002 and applies current methods of statistical evaluation, such as ordination techniques, to the whole data set for the first time. Results indicated that the recovery from livestock grazing and the effects of drought have been the main factors affecting vegetation. Recovery from livestock grazing at the three transects at Gungartan was slow and involved: (1) increasing genera diversity; (2) increasing vegetation cover; (3) decreasing amounts of bare ground; and (4) a directional change over time in species composition. Patterns of colonisation and species succession were also documented. In 2002, 44 years after the cessation of grazing, transects near Mt Gungartan had similar vegetation cover and genera diversity to the transects near Mt Kosciuszko, but cover by exposed rock remained higher. A drought in the 1960s resulted in a temporary increase of litter and a shift in the proportional cover of life forms, as grasses died and herb cover increased at both locations. Proportions of cover for life forms reverted to pre-drought levels within a few years. The results also highlighted the spatial variability of tall alpine herbfield. The photoquadrats were surveyed in the years 1959, 1964, 1968, 1978 and 2001 and are analysed for the first time in this thesis. After comparing a range of methods, visual assessment using a 130 point grid was found to be the most suitable technique to measure vegetation cover and genera diversity. At the 18 quadrats near Mt Gungartan, there was a pattern of increasing vegetation cover as bare areas were colonised by native cudweeds and the naturalized herb Acetosella vulgaris. Revegetation from within bare areas largely occurred by herb species, while graminoids and shrub species predominately colonised bare ground by lateral expansion from the edges, eventually replacing the colonising herbs. At the 12 quadrats near Mt Kosciuszko, vegetation cover was almost complete in all years surveyed except 1968, which was at the end of a six year drought. Similar to the results from the transect study, the drought caused an increase in litter at both locations as graminoid cover declined. Initially herb cover increased, potentially as a result of decreased competition from the graminoids and a nutrient spike from decaying litter, but as the drought became more severe, herb cover also declined. Graminoid cover rapidly recovered after the drought, reaching pre-drought levels by 1978, and was at similar levels in 2001. Herb cover continued to decline after peaking in 1964. The photoquadrat study also documented the longevity and growth rates of several species indicating that many taxa may persist for several decades. It further provided insights into replacement patterns amongst life forms. In addition to assessing vegetation change following livestock grazing and drought at the long-term plots, recovery from tourism impacts was examined by comparing vegetation and soils on a closed walking track, with that of adjacent undisturbed tall alpine herbfield at a series of 22 paired quadrats. Fifteen years after the track was closed there was limited success in restoration. Over a quarter of the closed track was still bare ground with non-native species the dominant vegetation. Plant species composition differed and vegetation height, soil nutrients and soil moisture were lower on the track which had a higher compaction level than adjacent natural vegetation. The results presented in this thesis highlight that tall alpine herbfield is characterised by nearly entire vegetation cover which is dominated by graminoids, followed by herbs and shrubs in the absence of disturbance by livestock grazing, trampling or drought. The studies also showed that under quot;average" conditions, the relative cover of herbs and graminoids remained fairly stable even though there can be considerable cycling between them. Spatial variability in terms of taxa composition was high. The only common introduced species in unrehabilitated sites was Acetosella vulgaris, which was effective at colonising bare ground but was eventually replaced by other native species. However, in areas actively rehabilitated, such as on the closed track, non-native species introduced during revegetation efforts still persist with high cover 15 years after their introduction. Monitoring of vegetation change is also important at the landscape scale. This thesis provides a review of the potential use, the limitations and the benefits of aerial photography to examine vegetation change in the Kosciuszko alpine zone. Numerous aerial photography runs have been flown over the area since the 1930s for government agencies, industry and the military. Some of these records have been used to map vegetation communities and eroding areas at a point in time. Other studies compared different types and scales of photographs, highlighting in particular the benefits and potential of large scale colour aerial photography to map alpine vegetation. However, despite their potential to assess vegetation change over time, a temporal comparison of vegetation in the Kosciuszko alpine zone from aerial photographs has not been completed to this date. Historical photographs may not be easy to locate or access and difficulties with vegetation classification may restrict the practicality of using historical aerial photographs to assess vegetation change. Despite these issues, aerial photography may provide a very useful and efficient tool to assess changes over time when applied appropriately, even in alpine environments. The development of digital classification techniques, the application of statistical measures of error to both methodology and data, and the application of geographic information systems are likely to further improve the practicality of historical aerial photographs for the detection of vegetation change and assist in overcoming some of the limitations. The results presented in this thesis highlight the need for limiting disturbance, for ongoing rehabilitation of disturbed areas and for long-term monitoring in the Kosciuszko alpine zone. The results contribute to our understanding of how vegetation may change in the future and may be affected by new land use activities and climate change. This type of information, which otherwise would require the establishment of long-term studies and years of monitoring, can assist land managers of this and other important protected areas. The study highlights how the use and expansion of already existing datasets to gather ecological information can save considerable money and time, providing valuable data for current and emerging issues.

Se ha estudiado una muestra de 130 niños , internados en una Institución por problemáticas sociofamiliuares, a los cuales se dividió en dos grupos según su rendimiento académico, aceptable o deficiente.Analizadas las variables individuales y socioambientales que diferenciaban ambos grupos, mediante análisis estadísticos multivariantes, los resultados evidenciaron que los trastornos conductuales, la conducta antisocial y los trastornos psicoafectivos, están relacionados cn un rendimiento escolar deficiente. También se observó que un buen nivel de adaptación y una relación familiar favorableestán relacionados con un rendimiento escolar aceptable y por último, los resultados reflejaron una mayor vulnerabilidad en las niñas que en los niños al estrés psicosocial / We have studied a sample of children living in a institution because of social and family problems, who were divided into two groups according to their academic performance acceptable and deficient.After we have analysed both the individual and the social and environmental variants which differentiated both groups through multivariates statistical analysis, the results showed that the disturbances of behaviour, the nos social behaviour and the emotional disturbances, has bearing on an deficient school performance.And also the results showed that a good adaptation level and a favourable family relationship has a bearing on an acceptable schol performance. The findings show a greater vulnerability of girls to psicosocial stress.

xii, 64 p. : ill. (some col.), maps / Salmon habitat restoration is ongoing at a Nature Conservancy preserve on the Middle Fork John Day River in the Columbia River Basin in north-central Oregon. The site has a long history of disturbance including dredge mining upstream, channelization, grazing, logging, fire, and floods. Using historic aerial photos, habitat unit surveys, and cross sectional profiles, this thesis shows how the channel morphology, particularly habitat unit diversity, has changed since 1939, just before placer mining began. Results show that the dominant influence on present day channel morphology is channelization from the 1930's. Other changes including dredge mining in the late 1930's to early 1940's, cessation of cattle grazing in 1991, and a fire followed by a flood in the winter of 1996-1997, had less impact because of the straightened, stabilized channel morphology. / Committee in charge: Patricia McDowell, Chairperson; W. Andrew Marcus, Member / 10000-01-01

Les perturbations sont des événements séparés dans le temps qui modifient une population, un écosystème ou un paysage, en changent la structure, le milieu physique et le fonctionnement. Ces événements font partie intégrante de la dynamique des écosystèmes, mais les hommes en ont changé le régime par l’agriculture, les travaux de génie civil, etc. Elles sont devenues une menace pour la biodiversité. C’est ainsi qu’une étude a été menée pour évaluer l’influence du projet de pipeline Tchad-Cameroun sur les assemblages de termites, cinq ans après son achèvement.<p>Les recherches ont été menées dans les écosystèmes de savane et de forêts camerounaises via deux méthodes d’échantillonnage. La méthode des transects belts d’Eggleton et Jones (2000) a permis de collecter 99 espèces de termites (36 transects dans 4 écosystèmes) ;en complément à celle-ci, la méthode quantitative des carottages de Wood et Sands (1978) a permis de récolter 70 espèces de termites (480 carottes). La différence de richesse spécifique résulte du sous échantillonnage par la méthode des carottages parce que certains habitats susceptibles d’abriter des termites ne sont pas explorés.<p>Les résultats obtenus montrent que l’infrastructure a perturbé sensiblement les paramètres texturaux, la densité apparente, les propriétés hydriques et la matière organique du sol. Il a diminué la richesse spécifique globale des termites, et essentiellement celle des humivores. Il a augmenté la densité des termites du groupe II et diminué celle des termites du groupe IV mais la densité globale des termites n’a pas été modifiée. En fait, les milieux témoins que nous avons échantillonnés étaient déjà moyennement dégradés avant la pose de l’oléoduc.<p>L’étude de l’évolution de la litière de Milicia excelsa en litter bags a permis de montrer que ni le l’infrastructure ni la variabilité des écosystèmes n’exercent un effet sur la vitesse de décomposition de cette litière ;en revanche, la dimension de la maille, autorisant ou non le passage des termites, a montré que ceux-ci interviennent pour environ 20 % dans la perte de masse de la litière.<p>L’apport expérimental d’infusions à base de Chromolaena odorata et d’Alchornea cordifolia a sensiblement abaissé le rapport C/N du sol mais n’a eu qu’un effet très limité sur les assemblages de termites.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Ziel der Untersuchung war die Ermittlung der Prävalenz schlafbezogener Atmungsstörungen (SBAS) in einer Gruppe von Herzschrittmacherpatienten. Durch Gegenüberstellung mit der in der Literatur angegebenen Prävalenz SBAS in vergleichbaren Patientengruppen ohne Herzschrittmacher sollte eine Aussage über einen möglichen Zusammenhang zwischen SBAS und schrittmacherbedürftigen Herzrhythmusstörungen getroffen werden. Dieser Zusammenhang könnte indirekt über die bekannte Koinzidenz zwischen SBAS und arterieller Hypertonie bzw. KHK bestehen. Es wurden 192 Patienten (100 Männer, 92 Frauen) der Rhythmussprechstunde des Universitätsklinikums Charité in Berlin mit einem Durchschnittsalter von 62,2 +/- 12,2 Jahren ambulant für eine Nacht untersucht. Zum Einsatz kam das tragbare Schlafapnoe-Monitoring-Gerät MESAM IV. Schlafbezogene Atmungsstörungen lagen dann vor, wenn der respiratorische Gesamtindex (RDI = respiratory disturbance index) als Summe der Apnoen und Hypopnoen pro Stunde Schlaf größer oder gleich 10 war. Anhand des RDI erfolgte eine Einteilung der Patienten in Diagnosegruppen: Gruppe A (RDI < 5, kein Vorliegen SBAS), Gruppe B (RDI >= 5 und < 10, Grenzbefund) und Gruppe C (RDI >= 10, Vorliegen SBAS). Ergebnisse (Gesamtkollektiv / Männer / Frauen): Gruppe A: 100 / 44 / 56 Patienten (52,1 / 44,0 / 60,9 %) Gruppe B: 30 / 16 / 14 Patienten (15,6 / 16,0 / 15,2 %) Gruppe C: 62 / 40 / 22 Patienten (32,3 / 40,0 / 23,9 %). Signifikant häufiger wurden SBAS (Gruppe C) bei Männern als bei Frauen nachgewiesen. Ebenso liegen das Durchschnittsalter (Gruppe A: 58,5 +/- 14,5 Jahre, Gruppe C 67,3 +/- 6,8 Jahre) sowie der durchschnittliche Body-Mass-Index (Gruppe A: 24,8 +/- 3,4 kg/m2, Gruppe C 27,1 +/- 3,3 kg/m2) bei Patienten mit SBAS signifikant höher als bei Patienten ohne SBAS. Patienten mit unterschiedlichen, der Schrittmacherimplantation zugrundeliegenden, Herzerkrankungen (z. B. Sick-Sinus-Syndrom, AV-Block, Bradyarrhythmia absoluta) wiesen keine signifikanten Differenzen in der Häufigkeit SBAS auf. Gleichermaßen konnte das Vorliegen zusätzlicher kardiovaskulärer Erkrankungen und Risikofaktoren (z. B. KHK, arterielle Hypertonie, Rauchen) nicht als Einflußfaktor für das gehäufte Auftreten SBAS nachgewiesen werden. Angaben zur Prävalenz SBAS in der Literatur schwanken für die entsprechende Altersgruppe von Patienten ohne Herzschrittmacher zwischen 24 % und 73 %. Die für die Herzschrittmacherpatienten ermittelte Prävalenz der SBAS mit 32,3 % liegt innerhalb dieser großen Spannbreite. Die Untersuchungsergebnisse ergaben daher keinen Zusammenhang zwischen SBAS und schrittmacherbedürftigen Herzrhythmusstörungen. Auch konnte kein Unterschied im Auftreten SBAS in Abhängigkeit von der Art der Herzrhythmusstörung nachgewiesen werden. Weiterführende Untersuchungen (z. B. in Form einer Fall-Kontroll-Studie) erscheinen notwendig. / The study was aimed to determine prevalence of sleep-related respiratory disturbances (SRRD) in a group of pacemaker patients. It was investigated if SRRD are more prevalent in pacemaker patients compared to corresponding patients without pacemaker. This question was raised in background of the wellknown coincidence of SRRD and arterial hypertension respectively coronary heart disease. References about the prevalence of SRRD in corresponding elderly people served as standard of comparison. 192 hospital outpatients (100 men and 92 women) from rhythmological ambulance of university hospital "Charité" in Berlin were randomly selected and examined for one night by means of MESAM IV device, a Non-laboratory-monitoring-system". The mean age of these patients was 62,2 +/- 12,2 years. A respiratory disturbance index (RDI; the sum of apneas and hypopneas per hour of sleep) equal or greater than 10 was laid down for the existence of SRRD. The RDI built the basis for dividing the patients into three groups: Group A (RDI < 5, no SRRD), Group B (RDI >= 5 and < 10, borderline SRRD) an Group C (RDI >= 10, SRRD). Results (all patients / men / women): Group A: 100 / 44 / 56 patients (52,1 / 44,0 / 60,9 %) Group B: 30 / 16 / 14 patients (15,6 / 16,0 / 15,2 %) Group C: 62 / 40 / 22 patients (32,3 / 40,0 / 23,9 %). Significant differences occured in the frequency of SRRD (Group C) between men and women. Apart from that the mean age (Group A: 58,5 +/- 14,5 years, Group C: 67,3 +/- 6,8 years) as well as the Body-Mass-Index (Group A: 24,8 +/- 3,4 kg/m2, Group C: 27,1 +/. 3,3 kg/m2) were significantly higher in patients with SRRD than in patients without SRRD. No significant differences in the frequency of SRRD could be demonstrated in dependence on underlying rhythm disturbances (e. g. Sick-Sinus-Syndrom, atrioventricular block, Bradyarrhythmia absoluta). In the same manner no evidences regarding significant influences of additionally existing cardiovascular diseases or risk factors (e. g. coronary heart disease, arterial hypertension, smoking) on the appearance of SRRD were shown. References about the prevalence of SRRD in corresponding elderly people without pacemaker vary from 24 % to 73 %. The prevalence of SRRD in pacemaker patients (32,3 %) fits right in the frame of this great variety. A more frequent appearance of SRRD in patients with pacemaker than in patients without could not be proved. Equally, the underlying rhythm disturbance has apparently no correlation to SRRD. Extended studies are necessary.

No description available.

Sleep disturbances and insomnia are prevalent, with around 33% of adults indicating that they experience at least one main symptom of insomnia, and bidirectional relationships exist with common psychopathology, particularly major depressive disorder (MDD). However, genetic and environmental (e.g., traumatic event exposure) contributions to the etiology of these phenotypes are not yet well understood. A genetically informative sample of approximately 12,000 Han Chinese women aged 30-60 (50% with recurrent MDD) was used to address several gaps within the sleep literature. Sleep disturbances were assessed in all individuals using a general item addressing sleeplessness (GS). A sleep within depression sum score (SDS) was also created in MDD cases, combining information from the GS and two insomnia items within MDD. A total of 11 traumatic events were assessed and additional information on childhood sexual abuse (CSA) was also obtained. First, factor analyses were conducted to determine trauma factor structure. The best-fit solution included 3 factors: interpersonal, child interpersonal, and non-assaultive, and composite variables were constructed accordingly. A series of hierarchical regressions were run to examine differential effects of trauma type and timing on sleeplessness. All traumatic events predicted sleeplessness at similar magnitudes, although population models indicated that childhood interpersonal trauma may be particularly potent. An association between CSA and sleeplessness was also replicated. A series of genetic analyses demonstrated that the single nucleotide polymorphism-based heritability of sleep phenotypes did not differ significantly from zero. Further, association analyses did not identify any genome-wide significant loci. However, using a liberal false discovery rate threshold of 0.5, two genes of interest, KCNK9 and ALDH1A2, emerged for the SDS. Polygenic risk score (PRS) analyses demonstrated genetic overlap between the SDS in MDD cases and GS in MDD controls, with PRSs explaining 0.2-0.3% of the variance. A final combined model of both genetic and environmental risk indicated that both PRS and traumatic events were significant predictors of sleeplessness. While genetic results should be interpreted with caution given the lack of heritability, additional research into the genetic and environmental contributions to insomnia, utilizing more standardized phenotypes and properly ascertained samples, is clearly warranted.

Uma climatologia de 21 anos dos Distúrbios Ondulatórios de Leste (DOLs) sobre a região NEB foi realizada com o intuito de obter um melhor entendimento dos processos dinâmicos e sinóticos do ciclo de vida destes sistemas, incluindo gênese, crescimento/decaimento, trajetória e dissipação. Adicionalmente, foi avaliada a eficiência do modelo de mesoescala WRF em simular este tipo de sistema. A identificação dos DOLs foi obtida de forma subjetiva através de imagens de satélite no canal infravermelho e campos de linhas de corrente e vorticidade relativa nos níveis de 1000, 850, 700, 500 e 200 hPa da reanálise do ERA-Interim. Neste período foram identificados 518 eventos de DOLs, onde 97% (3%) dessas ondas atingiram (não atingiram) a região do NEB, 64% (36%) foram convectivas (não convectivas) e 14% (86%) atingiram a região da Amazônia. Os principais sistemas que deram origem aos DOLs foram: Zona de Convergência Intertropical (ZCIT), Vórtice Ciclônico de Altos Níveis (VCAN), Frentes Frias (FF) e conglomerados convectivos provenientes da costa oeste da África (AF). Além destes, a interação entre os sistemas AF/FF, AF/ZCIT, AF/VCAN e ZCIT/FF estiveram associadas a sua formação. Em média, foram observadas aproximadamente 25 ondas por ano, com máxima (mínima) frequência compreendida entre os meses de Março a Agosto (Setembro a Fevereiro) e, com pronunciada variabilidade interanual. O ciclo de vida dos DOLs foi avaliado de forma objetiva a partir de um método automático de identificação e rastreio (TracKH), onde dos 518 eventos identificados na análise subjetiva, conseguiu capturar 342 ondas ( ~ 66%). A partir desta detecção, uma análise foi feita no nível 850 hPa para determinar as características típicas do seu ciclo de vida, que mostra um pico proeminente entre as longitudes de 35°W e 15°W e latitudes de 20°S e 5°N associado a densidade de gênese. A trajetória e dissipação se concentraram sobre a costa leste do NEB, entre os estados de Alagoas e Rio Grande do Norte, porém a dissipação diminuía a medida que adentrava ao continente. Os padrões sinóticos associados aos DOLs foram analisados através da anomalia de composição durante o período de máxima (úmido) e mínima (seco) frequência desde 3 dias antes até um dia após os DOLs atingirem a costa do NEB. Durante o período úmido, a circulação associada aos DOLs apresentou anomalia ciclônica e confluente, vorticidade negativa e convergência até médios níveis, enquanto que em 200 hPa apresentou apenas a característica do cavado. Por outro lado, para o período seco, estas características foram observadas somente em baixos níveis. Anomalias negativas de movimentos verticais e temperatura e positivas de umidade foram observadas associadas aos DOLs nas duas estações, porém atingindo maiores altitudes durante o período seco. A composição de precipitação indicou que os DOLs são responsáveis por um acréscimo de 16% (4%) durante a estação úmida (seca). As características típicas dessas ondas foram: período médio de 8 (73) dias, comprimento de onda de aproximadamente 4500 (5500) km e velocidade de fase da ordem de 6,5 (0,9) m.s-1, para o período úmido (seco). O modelo WRF simulou os padrões sinóticos, a precipitação e as características típicas associadas aos DOLs de forma coerente, sendo comparado aos resultados do Climate Forecast System Reanalysis (CFSR), porém com maior intensidade, para os eventos de 11 e 17 de junho de 2006. / A 21-year climatology of Easterly Wave Disturbances (EWDs) over NEB region was constructed in order to obtain a better understanding of dynamic and synoptic processes life cycle of these systems, including genesis, growth / decay, trajectory and dissipation. Moreover, we evaluated the efficiency of WRF mesoscale model to simulate this type of system. The identification of EWDs was obtained subjectively through satellite images in infrared channel and fields of streamlines and relative vorticity at the levels 1000, 850, 700, 500 and 200 hPa from ERA-Interim reanalysis. During this period, 518 EWDs were identified, where 97% (3%) of these waves hit (not hit) the NEB region, 64% (36%) were convective (non-convective) and 14% (86%) reached the Amazon region. The main systems that gave rise to DOLs were: Intertropical Convergence Zone (ITCZ), Upper-Tropospheric Cyclonic Vortices (UTCV), Cold Fronts (FF) and convective clusters from the west coast of Africa (AF). In addition, the interaction between systems AF/FF, AF/ITCZ, AF/UTCV and ITCZ/FF were associated with their formation. On average, we observed approximately 25 waves per year, with maximum (minimum) frequency between the months of March to August (September to February) and, with pronounced interannual variability. The life cycle of EWDs was evaluated objectively using an automatic method for the identification and tracking (TracKH). From the 518 events identified in the subjective analysis, TracKH was able to capture 342 waves (~ 66%). From this detection, an analysis was made at 850 hPa level to determine the characteristics of their life cycle, which shows a prominent peak around of 35°W-15°W and 20°S-5°N associated with density genesis. The trajectory and dissipation have concentrated over east coast of the NEB, between the states of Alagoas and Rio Grande do Norte, but the dissipation decreased once the systems enter the continent. The synoptic patterns associated with EWDs were analyzed by composing anomaly during the period of maximum (wet) and minimum (dry) frequency from 3 days before until one day after the EWDs reaching the NEB coast. During the wet period, the circulation presented cyclonic and confluent anomaly, negative vorticity and convergence at all levels except at 200 hPa which only showed a trough characteristic while for the dry season, this feature was only observed at low levels. Negative anomalies of vertical movements and temperature and positive humidity associated with EWDs were observed in both seasons, but reaching higher elevations during the dry period. The precipitation composition indicated that the EWDs are responsible for an increase of 16% (4%) during the wet season (dry). Typical characteristics of these waves were: mean period of 8 (73) days, wavelength of about 4500 (5500) km and phase velocity of about 6.5 (0.9) m.s-1 for the wet period (dry). The WRF model simulated the synoptic patterns, precipitation and the typical features associated with EWDs in a coherently manner when compared to the results of the Climate Forecast System Reanalysis (CFSR), but with greater intensity to the events of 11 and 17 June 2006.