The MIUU meso-scale model has been used to evaluate a new lateral boundary condition. The new lateral boundary condition is a combination of two lateral boundary conditions used in regional models, the flow relaxation scheme and the tendency modification scheme. The impact of different lateral boundary formulations on meso-scale phenomena, such as convective boundary layers, nocturnal jets, sea breezes and mountain waves (Bora winds) has been studied. When, for instance, stably stratified air with a constant wind speed is advected through the lateral boundaries into a meso-scale model with a flat and homogenous land surface, the convective boundary layer is reduced in height and the nocturnal jet is reduced in magnitude up to a distance of 750 km from the inflow lateral boundary. This is the case, when the most common lateral boundary condition is used, namely the flow relaxation scheme, where the flow relaxation parameter is constant with height and a function of the horizontal grid points only. In the other tests a flow relaxation parameter is used that is very small up to a certain level above ground, increasing with height to a maximum value higher up, and being constant above this upper level. Then, the convective boundary layer and the nocturnal jet are fully developed already at 23 km from the inflow lateral boundary. When, for instance, islands are not represented in the large-scale model, due to the coarse grid resolution, but well represented in the meso-scale model, stably stratified air can be advected into the meso-scale model even during daytime. Then, artificial thermal circulations can arise at the lateral boundaries of the meso-scale model, and collide with a real sea-breeze circulation that develops at the coast-line. These artificial thermal circulations disappear only when the flow relaxation parameter is very small in the lowest levels. When mountain waves (Bora winds) are simulated in a relatively small model domain, the critical layer, i.e. the layer where the nonlinear large-amplitude mountain wave is generated and broken, is surprisingly displaced irrespective of the tested lateral boundary formulations. In many simulations large-scale fields have to be introduced into meso-scale models. If only the flow relaxation scheme is used, the flow relaxation parameter has to be “constant-in-height” and relatively large in order to introduce large-scale temperature and wind changes with the right time-scale at all levels. However, with the new lateral boundary condition, the flow relaxation parameter can be kept very small in the lowest kilometers above ground. A small value of the flow relaxation parameter means that the convective boundary layer and the nocturnal jet at the lateral boundaries are not affected by the boundary conditions, and furthermore, no artificial thermal circulations are created. At the same time, large-scale temperature and wind changes are correctly introduced at all heights during the prescribed time into the meso-scale model through the tendency modification scheme. / Den mesoskaliga MIUU modellen har använts för test av olika laterala gränsvillkor. Ett nytt lateralt gränsvillkor har konstruerats. Detta nya gränsvillkor är en kombination av två gränsvillkor, nämligen ’the flow relaxation scheme’ och ’the tendency modification scheme’. Inverkan av olika gänsvillkorsformuleringar på mesoskaliga fenomen som konvektiva gränsskikt, ’nocturnal’ jets, sjöbrisar och bergsvågor (Boravindar) har studerats. När stabilt skiktad luft med konstant vindhastighet advekteras in genom de laterala ränderna in till en mesoskalig modelldomän, som har en slät och homogen landyta, kommer det konvektiva gränsskiktets höjd och styrkan på ’nocturnal’ jeten att påverkas av gränsvillkoret. Randvillkoret kan påverka temperatur och hastighetsfältet upp till 750 km:s avstånd från inflödesranden. Detta sker när det vanligaste laterala gränsvillkoret används, nämligen, ’the flow relaxation scheme’. I detta schema är ’flow relaxation’-parametern konstant med höjden, dvs endast en funktion av de horisontella gridpunkterna. Sensivitetsstudier på värdet och formen av ’flow relaxation’-parametern har utförts. En ’flow relaxation’-parameter, som är mycket liten upp till en viss nivå och sedan ökar med höjden påverkar temperatur- och hastighetsfältet mycket mindre. Randvillkorets påverkan är då minimal redan på 23 km:s avstånd från inflödesranden och det konvektiva gränsskiktet och ’nocturnal’ jeten kan bli fullt utvecklade. Om till exempel öar, som är väl representerade i den mesoskaliga modellen, inte är representerade i den storskaliga modellen pga dess grova upplösning, kan stabilt skiktad luft advekteras in till den mesoskaliga modelldomänen till och med under dagtid. Det kan då uppstå en artificiell termisk cirkulation vid de laterala ränderna hos den mesoskaliga modellen. Denna artificiella termiska cirkulation kan sedan kollidera med en verklig sjöbriscirkulation. Detta kan förstöra den mesoskaliga modellösningen totalt. Denna artificiella termiska cirkulation försvinner endast då ’flow relaxation’-parametern är väldigt liten i de lägsta nivåerna. När bergsvågor (Boravindar) simuleras i en relativt liten modelldomän så är det kritiska skiktet, dvs det skikt där de icke-linjära vågorna med stor amplitud bryts och genereras, förflyttat jämfört med referensfallet där de laterala ränderna var långt borta från det studerade området. Detta sker förvånansvärt oberoenda av vilken lateral gränsvillkorsformulering som används. I många simuleringar ska storskaliga processer såsom fronter och geostrofiska vindänd-ringar införas till den mesoskaliga modellen. Om endast ’the flow relaxation scheme’ används måste ’flow relaxation’-parametern vara konstant med höjden och relativt stor. Detta för att storskaliga temperatur- och vindändringar skall kunna introduceras till den mesoskaliga modellen med rätt tidskonstant och på alla höjder. I det nya laterala gränsvillkoret behöver ’flow relaxation’-parametern inte vara lika stor och inte heller konstant med höjden. Temperatur- och vindändringar är ändå korrekt introducerade med exakt tidsskala i alla nivåer in till den mesoskaliga modellen. Detta sker genom användandet av det s.k. ’tendency modification’-schemat. Dessutom kan det konvektiva gränsskikt, ’nocturnal’ jeten och sjöbrisar utveklas korrekt i närheten av de laterala ränderna.

A spectral cloud model is developed for a 3-dimensional mesoscale model considering only the microphysical conversion processes of the warm cloud. Because of the expected computation requirements, which are strongly increased in relation to the bulk-parameterization, we develop concepts for the parallelization of the module, explain their applicability and present first results. / Für ein 3-dimensionales Mesoskalenmodell wird ein spektrales Wolkenmodul entwickelt, das zunächst nur die mikrophysikalischen Umwandlungsprozesse der warmen Wolke berücksichtigt. Aufgrund des zu erwartenden, im Vergleich zur bulk-Parametrisierung stark erhöhten Rechenzeitbedarfs entwickeln wir Konzepte zur Parallelisierung des Moduls, erläutern deren Anwendbarkeit und stellen erste Ergebnisse vor.

A spectral cloud model is developed for a 3-dimensional mesoscale model considering only the microphysical conversion processes of the warm cloud. Because of the expected computation requirements, which are strongly increased in relation to the bulk-parameterization, we develop concepts for the parallelization of the module, explain their applicability and present first results. / Für ein 3-dimensionales Mesoskalenmodell wird ein spektrales Wolkenmodul entwickelt, das zunächst nur die mikrophysikalischen Umwandlungsprozesse der warmen Wolke berücksichtigt. Aufgrund des zu erwartenden, im Vergleich zur bulk-Parametrisierung stark erhöhten Rechenzeitbedarfs entwickeln wir Konzepte zur Parallelisierung des Moduls, erläutern deren Anwendbarkeit und stellen erste Ergebnisse vor.

No description available.

L'objectif majeur de ce travail est d'étudier le climat urbain, principalement en mettant l'accent sur les tendances de la température. Il s’agit principalement de l’augmentation des températures grâce à des techniques d'observation et de modélisation. A cet effet, des données températures de 1950 à 2004 ont étudiées sur plusieurs stations de mesure au Pakistan. Les données de températures annuelles et saisonnières moyennes quotidiennes minimales (Tmin) et maximales (Tmax) de 37 observatoires météorologiques du Pakistan (17 urbain, 7 petite ville et 13 rurale) pour la période 1950-2004 ont d'abord été homogénéisées, puis analysées. Les résultats montrent qu’après les années 1980, Tmin et Tmax tendent à augmenter plus vite que la période d'avant 1980 sur les zones urbaines. Au cours de la période 1980-2004, l'augmentation annuelle de Tmin sur les stations urbaines est observée plus élevée que sur les stations des petites villes et les stations rurales. Pour comprendre l’effet de la taille de la ville, le changement du l’utilisation des sols et la hauteur du bâtiment sur l'évolution des températures minimales et maximales des zones urbaines a été étudié en utilisant le model FVM (Finite Volume Model) et des simulations ont faites pour trois jours à partir de 00:00 (GMT) le 19e jour de chaque mois et se terminant à 00:00 (GMT) le 22e jour de chaque mois. Pour chaque mois, 48 combinaisons possibles de scénarios de simulation sont exécutés (4*4*3) et au total, 576 simulations (48*12) sont exécutés pendant un an. Les résultats centre montrent que Tmin et Tmax augmente lorsque fraction urbaine u, taille de la ville r et hauteur du bâtiment h augmente. Mais on remarque que Tmax augmente plus que le Tmin quand u augmente, Tmin augmente plus que Tmax lorsque r augmente et Tmin augmente plus que Tmax lorsque h augmente. Parmi tous les facteurs urbains (fraction urbaine u, taille de la ville r et hauteur du bâtiment h), la taille de la ville est le facteur majeur qui contribue principalement à augmenter la température minimale plus que température maximale dans les zones urbaines. / The objective of this work is to study the urban climate, mainly by focusing on urban temperature trends. The specific focus is to understand the reasons of increase in minimum temperature through observational and modelling techniques. For this purpose, the temperatures data from 1950 to 2004 measured on several meteorological stations of Pakistan is studied and analyzed. Daily averaged annual and seasonal minimum (Tmin) and maximum (Tmax) temperature data of 37 meteorological observatories of Pakistan (17 urban, 7 town and 13 rural) from 1950 to 2004 is first homogenized and then analyzed. The results show that after 1980s Tmin and Tmax increase faster than the period before 1980s at urban areas. During 1980–2004, the increase in Tmin at major urban stations is observed higher than the smaller towns and rural stations. To understand, the effect of the size of the city, changing land use and the building height on the evolution of minimum and maximum temperatures in urban areas has been studied by using the FVM (Finite Volume Model) model and the simulations are run for three days starting at 00:00 (GMT) on 19th day of each month and ending at 00:00 (GMT) on 22nd day of each month. For each month, 48 possible combinations of simulation scenarios are run (4*4*3) and in total, 576 simulations (48*12) are run for a year. The main results show that Tmin and Tmax increase when urban fraction u, city size r and building height h increase. But it is noticed that Tmax increases more than the Tmin when u increases, Tmin increases more than the Tmax when r increases and Tmin increases more than the Tmax when h increases. Among all urban factors (urban fraction u, city size r and building’s height h), city size is the major factor that mainly contributes to increase the minimum temperature more than the maximum temperature in urban areas.

<p>The boreal forests represent 8 % of all forested areas on the earth and have a significant role in the control of greenhouse gases and an impact on global climate change. The main objective of this thesis is to increase the understanding of how evaporation and heat-flux processes in the boreal forest zone are affecting the regional and global climate.</p><p>A meteorological mesoscale model with an advanced land-surface parameterization has been utilized to study aggregation of fluxes of water vapour and heat. The model has been compared against four other methods for flux estimation in a southern boreal landscape. The results show that the mesoscale model is successfully reproducing 24-hour averages of fractionally weighted mast measurements of sensible and latent heat flux.</p><p>The model was also evaluated against in-situ observations of surface fluxes and other meteorological variables. The results reveal that a correct initialization of soil moisture is crucial to simulate a realistic partitioning of the sensible and latent heat fluxes. Significant differences in surface fluxes and friction velocities between two apparently similar forest sites indicate the need for careful assessment of areal representativity when comparing mesoscale model results with in-situ observations.</p><p>A parameterization for the absorption of solar radiation of high-latitude sparse forests was implemented and tested in the model that significantly improved the simulation of high wintertime midday sensible heat fluxes. A scheme for heat storage in vegetation was also implemented which improved the results, but the scheme needs further evaluation for high latitude forests.</p><p>Two commonly used strategies for the description of land-surface heterogeneity, the effective parameter approach and the mosaic approach, were tested in the mesoscale model against airborne observations of sensible and latent heat fluxes. The results show that the mosaic approach produces better results especially when small lakes are present in model grid-squares.</p> / <p>Norra halvklotets barrskogsbälte representerar 8 % av all skogsbeklädd mark på jorden och har stor betydelse för kontrollen av växthusgaser och påverkan på globala klimatförändringar. Syftet med denna avhandling är att öka förståelsen av hur avdunstning och värmeflöden i den boreala skogszonen påverkar klimatet regionalt och globalt.</p><p>En meteorologisk mesoskalemodell med en avancerad landyteparameterisering har använts för att studera aggregering av avdunstning och värmeflöden. Modellen jämfördes med fyra andra metoder för uppskattning av värmeflöden i den boreala skogszonens södra delar. Resultaten visade att mesoskalemodellen reproducerar 24-timmarsmedelvärden av sensibelt och latent värmeflöde från areellt viktade mastmätningar med bra resultat.</p><p>Modellen utvärderades även mot markbaserade mätningar av sensibelt och latent värme och andra meteorologiska variabler. Resultaten visar att en korrekt initialisering av markvatteninnehållet är avgörande för att simulera en realistisk uppdelning av de sensibla och latenta värmeflödena. Markanta skillnader i markyteflöden och friktionshastigheter mellan två liknande skogsmätstationer påvisar nödvändigheten av en noggrann bedömning av den areella representativiteten när man jämför resultat från mesoskalemodellen med markbaserade mätningar.</p><p>En parameterisering för absorption av solstrålning i glesa skogsbestånd på höga breddgrader infördes och testades i modellen vilket markant förbättrade simuleringen av de höga sensibla värmeflöden som observerats vid middagstid på vintern. Ett uttryck för att beskriva värmelagring i vegetationen infördes också vilket förbättrade resultaten, men uttrycket behöver vidare utvärdering för skogsbestånd på höga breddgrader.</p><p>Två ofta använda strategier för att beskriva markytans heterogenitet, effektiva parametermetoden och mosaikmetoden, testades i mesoskalemodellen mot flygburna observationer av sensibla och latenta värmeflöden. Resultaten visar att mosaikmetoden ger bättre resultat särskilt när mindre sjöar förekommer i modellrutorna.</p>

The boreal forests represent 8 % of all forested areas on the earth and have a significant role in the control of greenhouse gases and an impact on global climate change. The main objective of this thesis is to increase the understanding of how evaporation and heat-flux processes in the boreal forest zone are affecting the regional and global climate. A meteorological mesoscale model with an advanced land-surface parameterization has been utilized to study aggregation of fluxes of water vapour and heat. The model has been compared against four other methods for flux estimation in a southern boreal landscape. The results show that the mesoscale model is successfully reproducing 24-hour averages of fractionally weighted mast measurements of sensible and latent heat flux. The model was also evaluated against in-situ observations of surface fluxes and other meteorological variables. The results reveal that a correct initialization of soil moisture is crucial to simulate a realistic partitioning of the sensible and latent heat fluxes. Significant differences in surface fluxes and friction velocities between two apparently similar forest sites indicate the need for careful assessment of areal representativity when comparing mesoscale model results with in-situ observations. A parameterization for the absorption of solar radiation of high-latitude sparse forests was implemented and tested in the model that significantly improved the simulation of high wintertime midday sensible heat fluxes. A scheme for heat storage in vegetation was also implemented which improved the results, but the scheme needs further evaluation for high latitude forests. Two commonly used strategies for the description of land-surface heterogeneity, the effective parameter approach and the mosaic approach, were tested in the mesoscale model against airborne observations of sensible and latent heat fluxes. The results show that the mosaic approach produces better results especially when small lakes are present in model grid-squares. / Norra halvklotets barrskogsbälte representerar 8 % av all skogsbeklädd mark på jorden och har stor betydelse för kontrollen av växthusgaser och påverkan på globala klimatförändringar. Syftet med denna avhandling är att öka förståelsen av hur avdunstning och värmeflöden i den boreala skogszonen påverkar klimatet regionalt och globalt. En meteorologisk mesoskalemodell med en avancerad landyteparameterisering har använts för att studera aggregering av avdunstning och värmeflöden. Modellen jämfördes med fyra andra metoder för uppskattning av värmeflöden i den boreala skogszonens södra delar. Resultaten visade att mesoskalemodellen reproducerar 24-timmarsmedelvärden av sensibelt och latent värmeflöde från areellt viktade mastmätningar med bra resultat. Modellen utvärderades även mot markbaserade mätningar av sensibelt och latent värme och andra meteorologiska variabler. Resultaten visar att en korrekt initialisering av markvatteninnehållet är avgörande för att simulera en realistisk uppdelning av de sensibla och latenta värmeflödena. Markanta skillnader i markyteflöden och friktionshastigheter mellan två liknande skogsmätstationer påvisar nödvändigheten av en noggrann bedömning av den areella representativiteten när man jämför resultat från mesoskalemodellen med markbaserade mätningar. En parameterisering för absorption av solstrålning i glesa skogsbestånd på höga breddgrader infördes och testades i modellen vilket markant förbättrade simuleringen av de höga sensibla värmeflöden som observerats vid middagstid på vintern. Ett uttryck för att beskriva värmelagring i vegetationen infördes också vilket förbättrade resultaten, men uttrycket behöver vidare utvärdering för skogsbestånd på höga breddgrader. Två ofta använda strategier för att beskriva markytans heterogenitet, effektiva parametermetoden och mosaikmetoden, testades i mesoskalemodellen mot flygburna observationer av sensibla och latenta värmeflöden. Resultaten visar att mosaikmetoden ger bättre resultat särskilt när mindre sjöar förekommer i modellrutorna.

The objective of this work is to study the urban climate, mainly by focusing on urban temperature trends. The specific focus is to understand the reasons of increase in minimum temperature through observational and modelling techniques. For this purpose, the temperatures data from 1950 to 2004 measured on several meteorological stations of Pakistan is studied and analyzed. Daily averaged annual and seasonal minimum (Tmin) and maximum (Tmax) temperature data of 37 meteorological observatories of Pakistan (17 urban, 7 town and 13 rural) from 1950 to 2004 is first homogenized and then analyzed. The results show that after 1980s Tmin and Tmax increase faster than the period before 1980s at urban areas. During 1980-2004, the increase in Tmin at major urban stations is observed higher than the smaller towns and rural stations. To understand, the effect of the size of the city, changing land use and the building height on the evolution of minimum and maximum temperatures in urban areas has been studied by using the FVM (Finite Volume Model) model and the simulations are run for three days starting at 00:00 (GMT) on 19th day of each month and ending at 00:00 (GMT) on 22nd day of each month. For each month, 48 possible combinations of simulation scenarios are run (4*4*3) and in total, 576 simulations (48*12) are run for a year. The main results show that Tmin and Tmax increase when urban fraction u, city size r and building height h increase. But it is noticed that Tmax increases more than the Tmin when u increases, Tmin increases more than the Tmax when r increases and Tmin increases more than the Tmax when h increases. Among all urban factors (urban fraction u, city size r and building's height h), city size is the major factor that mainly contributes to increase the minimum temperature more than the maximum temperature in urban areas.

In some species, including humans, red blood cells (RBCs) under low shear stress tend to clump together and form into regular stacks called rouleaux. These stacks are not static, and constantly move and break apart. This phenomenon is referred to as red blood cell aggregation and disaggregation. When modelled as a single liquid, blood behaves as a non-Newtonian fluid. Its viscosity varies, mainly due to the aggregation of RBCs. The aim of this research is to develop a mesoscale computational model for the simulation of RBCs in plasma. This model considers RBC interaction and aggregation to predict blood-flow characteristics such as viscosity, rouleaux size and velocity distribution. In this work, the population-balance modelling (PBM) approach is utilized to model the RBC aggregation process. The PBM approach is a known method that is used for modelling agglomeration and breakage in two-phase flow fluid mechanics to find aggregate size. The PBM model is coupled to the incompressible Navier-Stokes equations for the plasma. Both models are numerically solved simultaneously. The population-balance equation has been used previously in a more restricted form, the Smoluchowski equation, to model blood viscosity, but it has never been fully coupled with the Navier-Stokes equation directly for the numerical modelling of blood flow. This approach results in a comprehensive model which aims to predict RBC aggregate size and their velocities for different flow configurations, as well as their effects on the apparent macro-scale viscosity. The PBM approach does not treat the microscopic physics of aggregation directly but rather uses experimental correlations for aggregation and disaggregation rates to account for the effects of aggregation on the bulk. To find the aggregation rate, a series of experiments on RBC sedimentation due to gravity is designed. In these tests, aggregated RBCs (rouleaux) tend to settle faster than single RBCs and, due to low shear stresses, disaggregation is very low and can be neglected. A high-speed camera is used to acquire video-microscopic pictures of the process. The size of the aggregates and their velocities are extracted using image processing techniques. For image processing, a general Matlab program is developed which can analyze all the images and report the velocity and size distribution of rouleaux. An experimental correlation for disaggregation rate is found using results from a previous steady-state Couette flow experiment. Aggregation and disaggregation rates from these experiments are used to complete the PBM model. Pressure-driven channel flow experiments are then used for the final validation of the model. Comparisons of the apparent viscosity of whole blood in previous experiments show reasonable agreement with the developed model. This model fills a gap between micro-scale and macro-scale treatments and should be more accurate than traditional macro-scale models while being cheaper than direct treatment of RBCs at the micro-scale.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2005. / Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-20T21:03:34Z No. of bitstreams: 1 Estudo para o desenvolvimento de um previsor descargas elétricas atmosféricas aplicado à região costeira do estado do Rio de Janeiro.pdf: 5929611 bytes, checksum: 6d12186a0ae17fe81eca3382c1b88f42 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-04T16:31:08Z (GMT) No. of bitstreams: 1 Estudo para o desenvolvimento de um previsor descargas elétricas atmosféricas aplicado à região costeira do estado do Rio de Janeiro.pdf: 5929611 bytes, checksum: 6d12186a0ae17fe81eca3382c1b88f42 (MD5) / Made available in DSpace on 2013-06-04T16:31:08Z (GMT). No. of bitstreams: 1 Estudo para o desenvolvimento de um previsor descargas elétricas atmosféricas aplicado à região costeira do estado do Rio de Janeiro.pdf: 5929611 bytes, checksum: 6d12186a0ae17fe81eca3382c1b88f42 (MD5) Previous issue date: 2005 / The atmospheric dynamics evidently is very complex. There are many macro and micron scales processes and meteorological variables involved in the atmospheric physical phenomena. The storms with electrical dischargesare distinguished, among these phenomena, by the damage consequences to the human beings, directly or indirectly. Many researchers have pursued the possibility of forecasting the occurrence of a storm with electrical discharges, principally in the last three decades. However, there are not improvements in forecast performance, mainly due to phenomenon complexity. The main objective of the present dissertation was to accomplish a study to determine the viability or not of constructing a forecast system of atmospheric electrical discharges from artificial intelligence techniques, specifically artificial neural networks (NN). The base of the system was constituted of numerical simulations results of the atmospheric dynamics obtained from the mesoscale model MM5. It was identified meteorological variables (outputs of MM5) that would have some correlation with the electrical discharges. These variables act as input in the NN, which generate the forecast, consisting in the number of electrical discharges that will reach the ground some posterior time to the relative time of the simulated atmospheric fields. The region chosen for this study includes the state of Rio de Janeiro, the south of Espírito Santo, the southeast of Minas Gerais and the AtlanticOcean. Besides possessing a detection system of electrical discharges, this region contains the most important concentration of oil platforms of Brazil, being strategic to better know the atmospheric behavior in this place. Before developing the forecast system based on NN, some comparative tests were made using the MM5 simulation results and GOES infrared imagery, in order to survey the model prognostic capability. The forecast system showed reasonable results, indicating that the NN application may be a promising way to the electrical discharge forecast. However, it is necessary a better investigation, mainly with relation to the accomplishment of others tests with a bigger set of electrical discharges real data. / A dinâmica da atmosfera é evidentemente bastante complexa. Muitos são os processos físicos de macro e micro escalas e as variáveis meteorológicas envolvidos nos fenômenos atmosféricos. As tempestades com descargas elétricas destacam-se, dentre estes fenômenos, pelas conseqüências danosas causadas aos seres humanos, direta ou indiretamente. Diversos pesquisadores têm procurado investigar a possibilidade de prever a ocorrência de tempestades com descargas elétricas, principalmente nas úl timas três décadas, entretanto, progressos na performance da previsão ainda não foram alcançados devido à complexidade do fenômeno. O principal objetivo da presente dissertação foi realizar um estudo para determinar a viabilidade ou não de construir um sistema de previsão de descargas elétricas atmosféricas a partir de técnicas de inteligência artificial, mais precisamente redes neurais artificiais (RNA). A base do sistema constituiu-se de resultados de simulações numéricas da dinâmica atmosférica obtidos com o modelo de mesoescala MM5. Variáveis meteorológicas (saídas do MM5), que teriam alguma correlação com as descargas elétricas, foram identificadas e selecionadas como entradas na RNA, a qual gera a previsão, isto é, o número de descargas elétricas que atingirá o solo algum tempo posterior ao tempo relativo dos campos atmosféricos simulados. A região escolhida para este estudo, abrangendo o Estado do Rio de Janeiro, o sul do Estado do Espírito Santo, o sudeste do Estado de Minas Gerais e o Oceano Atlântico, além de possuir um sistema de detecção e monitoramento de descargas elétricas, contém a mais importante concentração de plataformas de petróleo do Brasil, sendo, portanto, estratégico conhecer melhor o seu comportamento atmosférico. Antes de desenvolver o sistema de previsão baseado em RNA, alguns testes comparativ os foram realizados usando resultados de simulação do MM5 e imagens infravermelhas de satélite geoestacionário, a fim de aferir a capacidade preditiva do modelo. O sistema de previsão apresentou resultados razoáveis, indicando que a aplicação da RNA é um cami nho promissor na previsão de descargas elétricas. Contudo, faz-se necessária uma mel hor investigação, principalmente quanto à realização de outros testes com um conjunto maior de dados reais de descargas elétricas.