Magaly de Fatima Correia

Descargas atmosféricas e interrupções de energia elétrica na área da CHESF: relação com variáveis atmosféricas em anos de El Niño e La Niña

Climatic and environmental conditions directly influence the development and the intensification of storms followed by atmospheric discharges and they are responsible for interruptions in the electric energy supply in the Northeast of Brazil. This study has as objective to establish relations between meteorological variables that allow formulating the influence of environmental conditions to the intensification of convective activity responsible for interruptions of the electric energy supply during years of El Nino and La Nina. The analyses are restricted to the CHESF (Companhia Hidro Eletrica do Sao Francisco) activity areas having most of its energy Transmission Lines installed in the semi-arid of Northeastern Brazil. The method of principal component analysis chosen as main analysis tool, allowed isolating significant atmospheric patters of moisture, wind and air temperature over the analyzed domain. Upper Tropospheric Cyclonic Vortices (UTCV) had been responsible for the development of intense precipitation systems and occurrences of transient failures in the CHESF transmission system.

Precipitação na Cidade de Salvador: Variabilidade Temporal e Classificação em Quantis

Este trabalho tem como objetivo contribuir com o estudo da precipitacao na cidade de Salvador–BA. Os totais mensais de precipitacao obtidos pelo Instituto Nacional de Meteorologia no periodo de 51 anos (1961-2011) fundamentaram esta pesquisa. A variabilidade pluviometrica foi analisada com enfase na determinacao das classes da precipitacao nas escalas anual, quadrimestral e mensal. Foram utilizados os testes de significância nao parametricos de Mann-Kendall e as estimativas de inclinacao pelo metodo da Curvatura de Sen. Na classificacao pluviometrica foi utilizado o Metodo dos Percentis (Quantis). Para a analise anual, os resultados mostraram que 1964 (1961) foi um ano classificado como “muito chuvoso” (“muito seco”). Na analise do quadrimestre mais chuvoso AMJJ (mais seco ASON), o ano de 1971 (1980) foi o mais extremo “muito chuvoso” (“muito seco”). Na analise mensal, o evento que obteve maior volume pluviometrico ocorreu em abril de 1984 com registros de 889,8 mm. A analise da tendencia mostrou uma reducao no volume de chuva na escala anual, entretanto, sem significância estatistica. Grande parte dos eventos analisados ocorreram com condicoes oceânicas no Pacifico equatorial e/ou Atlântico Sul Tropical favoraveis (desfavoraveis) ao aumento (diminuicao) do volume de chuva na area em estudo, tendo por base uma analise qualitativa.

Aspectos da Variabilidade Sazonal da Radiação, Fluxos de Energia e CO2 em Área de Caatinga (Seasonal Variability Aspects of Radiation and Fluxes of Energy and CO2 in a Caatinga Area)

Regioes semiaridas sao particularmente sensiveis a variabilidade pluviometrica com respostas imediatas da superficie ao aumento ou reducao no teor de umidade do solo e processos de evapotranspiracao. Mudancas no padrao espacial e temporal das chuvas representam um fator determinante nas trocas de calor, vapor d’agua e CO 2 entre o ecossistema e a atmosfera. Nesse contexto, este trabalho tem como objetivo analisar o comportamento sazonal da radiacao, dos fluxos de energia e CO 2 em area de caatinga. Mudancas na disponibilidade de umidade sao determinantes para as alteracoes no regime de cobertura do dossel e impoem multiplas adaptacoes a vegetacao da caatinga. A reducao na cobertura vegetal acarreta uma maior susceptibilidade do ambiente aos efeitos da radiacao e insolacao. Variacoes diarias da temperatura aceleram a atividade microbiana do solo e liberacao de CO 2 . As analises foram concentradas no periodo de julho de 2004 a julho de 2005. Os resultados mostram que a maior parte da energia absorvida pela superficie foi liberada na forma de calor sensivel, refletindo a resposta da vegetacao a insuficiencia hidrica da regiao. Os resultados obtidos com a analise da evolucao do fluxo de carbono possibilitam concluir que no periodo de estiagem, embora com taxas minimas, o bioma atua como emissor de CO 2 . Valores substancialmente mais elevados (negativos) observados no periodo chuvoso indicam um comportamento inverso no qual o bioma atua como sumidouro de carbono da atmosfera (sequestro de CO 2 ). Esse resultado indica a importância da conservacao do bioma caatinga no controle do efeito estufa e, consequentemente, do aquecimento global. Palavras - chave: caatinga, CO 2 , semiarido Seasonal Variability Aspects of Radiation and Fluxes of Energy and CO 2 in a Caatinga Area ABSTRACT Semiarid regions are particularly sensitive to rainfall variability with quick surface responses to an increase or decrease in soil moisture content and evapotranspiration processes. Changes in spatial and temporal rainfall patterns are a determining factor in heat, water vapor and CO2 exchanges between the ecosystem and the atmosphere. In this context, the objective in this work is to analyze the seasonal behavior of the radiation and of the energy and CO2 fluxes in a caatinga area. Changes in moisture availability dictate alterations in the canopy cover regime and lead to multiple adaptations of the caatinga vegetation. The reduction in vegetation cover causes a higher environmental susceptibility to the radiation and insolation effects. Daily temperature variations accelerate the microbial activity in the soil and the CO2 loss. Analyses were concentrated in the period from July 2004 to July 2005. The results show that most of the energy absorbed by the surface is released as sensible heat, which reflects the vegetation response to the hydrological deficiency in the region. The results obtained by analyzing the evolution of the CO2 flux allow to conclude that during the dry season the biome acts as CO2 source, although with minima rates. Substantially higher (negative) values observed during the rainy season indicate an opposite behavior in which the biome acts as a sink of atmospheric carbon (CO2 sequestration). This result indicates the importance of the caatinga biome conservation in the control of greenhouse gases increase and hence global warming. Keywords: caatinga, CO 2 , semiarid

Distúrbio Ondulatório de Leste e seus impactos na cidade de Salvador

WAVELIKE EASTERLY DISTURBANCE AND ITS IMPACTS ON SALVADOR CITY: An extreme rainfall event registered in the city of Salvador, Bahia, is investigated in this work. Observational surface and upper air data, gridpoint data, meteorological satellite images and disasters information provided by the Civil Defense of Salvador (CODESAL) were used in the analysis. During the period from midnight to 3 A.M. on 12 June 2006 51 mm accumulated rainfall was registered. A high number of disasters were registered by CODESAL, particularly landslides. Weak winds throughout the troposphere and maximum convective available potential energy of 3,233 J kg -1 were identified in Salvador on June 11th, fifteen hours before the heavy rainfall. Areas of deep convection characterized this event, favored by a wave that reached the eastern coast of Northeast Brazil after moving westward over the South Atlantic with an estimated phase speed of 10 m s -1 , as seen on the

CONVECÇÃO LINEARMENTE ORGANIZADA NA ÁREA DE PETROLINA, SEMI-ÁRIDO DO NORDESTE DO BRASIL: ASPECTOS EM MESO E GRANDE ESCALA

A study on linearly organized convective systems observed by a C-band meteorological radar in the semi-arid area of Northeast Brazil is presented. The convective activity during three selected days of 1985 March (27 to 29) was analyzed emphasizing the role played by local and large-scale factors on the development of rain systems. On the large-scale scenario, the covered radar area was influenced by an austral upper-level air trough on March 27th and by an upper-level cyclonic vortex on the 29th. Near-surface moisture convergence favored convective activity on days 27 and 29, while near-surface moisture divergence inhibited convective activity on day 28. On the mesoscale, it was found that diurnal heating was an important factor influencing the formation of the convective cells, while their location was determined mainly by the orography. In general, the radar images show the linearly-organized convective systems over elevated terrain and intense convective cells embedded by a stratiform rain area. The results indicate that large-scale convergence of the moisture flux and radiative heating are determinant factors on the evolution and development of the echoes in the area of study.

TROPOSPHERIC DUCTS AND PLANETARY BOUNDARY LAYER STRUCTURE IN THE PETROLINA REGION

The planetary boundary layer (PBL) structure is investigated focusing on days with low-tropospheric ducts occurrence in the Petrolina-PE region, in the period from 1 to 29 April 2014. Ducts identification and the estimative of the PBL top/height and its dynamic and thermodynamic characterization is based on 12 UTC upper-air soundings launched at the altitude station of Petrolina. Surface ducts are associated with high instability and wind speed intensification in the surface layer. Ducts at the PBL top (elevated ducts) are associated with a decrease in the moisture content of the air and a wind speed maximum, above the PBL, in the low-troposphere.

INFLUENCE OF LOCAL CIRCULATIONS IN AREAS OF WIND POWER DEVELOPMENT IN THE SOBRADINHO LAKE REGION

In this work local circulation patterns are investigated for the year of 2010 in the Sobradinho Lake region, at the 25 m and 50 m levels. The hodographs illustrate the local wind variation in the four quadrants of the wind rose, in the majority of the months. The local time (LT) and magnitude of the maxima and minima intensities depend on the time of the year. A negative vertical shear in the local wind during the late night-early morning (night) is more evident in the period from May to September (October to February). The local wind, at times of maximum intensity, represents up to 60% of the observed wind speed and, in the remaining of the twenty four hours of the day, between 10 and 30%. This ratio decreases with height in the twelve months of 2010, and is more evident in the periods 4-6 LT and 17-20 LT, with exception of March and June, respectively. The local circulations may be associated with coupling between the land (lake) breeze and the catabatic (anabatic) winds during the late night-early morning (late afternoon-early night). The months of June, July and August show less variability in wind direction, favoring a better use of the wind turbines.

Regimes do vento à superfície na área de Petrolina, submédio São Francisco

In this work the daily surface wind cycle is investigated focusing on the seasonal variation and the local circulations. The data collected by the automatic station located 25-30 km far from Petrolina and by the conventional station located in the city are used. The results show that the hourly mean wind speeds increase (decrease) during April-May-June (October-November-December) due to the intensification (weakening) of the South Atlantic subtropical high. During the three-month period July-August-September the hourly wind speeds are very close and have their highest intensities, with wind direction in the interval 120-130 degrees. In general, the daily cycle gives evidence of a maximum at 8-9 LT (local time) and two minima, one at 5-6 LT and another at 17-18 LT, in every month. The hodographs of the local wind at both stations show weak local circulations from January to May, a characteristic that may be related to a higher soil moisture content and, as a consequence, to lower values of the sensible heat flux gradient. During the remaining of the year, the dry period, the local circulations are comparatively stronger. The hodographs are irregularly drawn suggesting one local wind regime, in the southeast-northwest direction. The local circulations are stronger at 9 and 18 LT, the times of maximum and minimum wind speeds during the daily cycle, respectively.

Mudanças na Estrutura Termodinâmica da Atmosfera na Presença de Vórtices Ciclônicos de Altos Níveis: Um Episódio de Precipitação Extrema no Semiárido Brasileiro (Changes in the Atmospheric Thermodynamic Structure in the Presence of Upper Level...)

The nature of the relationship between convective potential energy (CAPE), the instability index K and high rainfall rates under the influence of upper level cyclonic vortices is investigated. Upper air sounding data collected in Petrolina – PE, Brazil, were used to diagnose changes in the thermodynamic structure of the atmosphere. Daily precipitation totals observed at the surface meteorological station allowed evaluation of the K and CAPE efficiency in the determination of the degree of atmospheric instability and prediction of extreme rainfall. The relationship between high CAPE values and precipitation is evident in the period of study. However, high CAPE values may not lead to rainfall. The large rainfall totals and flooding registered in the Petrolina region were a result of the combined action of local and synoptic scale atmospheric systems. Dynamical mechanisms associated with VCAN played a major role in the enhancement or inhibition of convective activity.