A produção in vitro de embriões é uma biotecnologia bastante difundida mundialmente. O Brasil, em 2015, foi responsável por aproximadamente 67% dos embriões bovinos produzidos in vitro no mundo (PERRY, 2014). Embora essa tecnologia seja bastante utilizada, é de grande interesse para o mercado desenvolver estratégias que levem ao maior aproveitamento dos oócitos obtidos e compreender os mecanismos, dentro do ambiente folicular, que determinam a competência oocitária. O microambiente folicular é fundamental para o crescimento e a aquisição da competência oocitária, tornando o oócito apto a desenvolver-se e manter o embrião até a transição materno embrionária. Para tanto, os componentes foliculares - células da granulosa, células do cumulus, oócito e líquido folicular - precisam trabalhar em unidade, visto que possuem uma relação de interdependência. Dentro dos mecanismos de comunicação existentes no ambiente folicular estão as vesículas secretadas por células, chamadas vesículas extracelulares, que foram descritas no líquido folicular, contendo material bioativo como proteínas, lipídios e RNAs, incluindo os microRNAs. Contudo, os componentes do ambiente folicular podem refletir na qualidade do oócito que será produzido e a hipótese geral deste trabalho é de que os miRNAs presentes no ambiente folicular regulam vias de sinalização importantes para o desenvolvimento oocitário e que os miRNAs e ou RNAs mensageiros presentes nas células foliculares podem ser explorados como importantes ferramentas para o diagnóstico da qualidade oocitária. O primeiro estudo determinou perfis transcricionais de miRNAs em células da granulosa, em complexos cumulus-oócito e em vesículas extracelulares derivadas destas células e também do fluido folicular. Além de conhecer a origem e o papel dos miRNAs no ambiente folicular, estes perfis de expressão indicaram a regulação no ambiente folicular da via de sinalização da PI3K-Akt. No segundo estudo, componentes desta via de sinalização foram então determinados em células foliculares associadas a oócitos de alta ou baixa competência ao desenvolvimento. Os resultados demonstram que a ativação da via PI3K-Akt em células foliculares correlaciona-se à maior competência oocitária; de modo oposto, a menor atividade desta via nas células foliculares está relacionada à reduzida competência oocitária. Nos estudos três e quatro, um conjunto de experimentos foram realizados para determinar o perfil de microRNAs e RNAs mensageiros em células do cumulus associadas a oócitos de alta ou baixa competência ao desenvolvimento. Buscou-se esclarecer alguns dos mecanismos responsáveis pela melhor qualidade oocitária e levar a identificação de biomarcadores de qualidade oocitária permitindo o avanço e o desenvolvimento de novas ferramentas para intensificar a produção in vitro de embriões bovinos. Por fim, estes resultados demonstram respostas integradas entre oócitos e células foliculares durante o desenvolvimento folicular e o processo de aquisição de competência oocitária e identificaram marcadores de qualidade oocitária. / In vitro embryo production of is a widespread biotechnology worldwide. In 2015 Brazil was responsible for approximately 67% of bovine embryos produced in vitro in the world (PERRY, 2014). Although widely used, to develop strategies that lead to better use of oocytes and understand the mechanisms (in follicular microenvironment) that determine oocyte competence is of great interest to national market. The follicular microenvironment is fundamental for oocyte growth and acquisition of competence, making the oocyte able to develop and maintain the embryo until the embryonic maternal transition. For this end, the follicular components - granulosa cells, cumulus cells, oocytes and follicular fluid - need to work in unity, since they have arelation of interdependence. Within the mechanisms of communication existing within the follicular environment are vesicles secreted by cells, called extracellular vesicles, which were described in follicular fluid, containing bioactive material such as proteins, lipids and RNAs, including microRNAs. The components of follicular environment may reflect the quality of the oocyte that will be produced and the general hypothesis of this work is that the miRNAs present in the follicular environment regulate signaling pathways important for oocyte development and that the miRNAs and/or messenger RNAs present in the follicular cells can be explored as important tools for the diagnosis of oocyte quality. The first study determined profiles of miRNAs in granulosa cells, cumulus-oocyte complexes and extracellular vesicles derived from these cells and also in follicular fluid. In addition, by knowing the origin and role of miRNAs in the follicular environment, the expression profiles indicated the PI3K-Akt signaling pathway regulation in the follicular environment. In the second study, components of this signaling pathway were then determined in follicular cells associated with oocytes of high or low developmental competence. The results demonstrated that the activation of the PI3K-Akt pathway in follicular cells correlates with increased oocyte competence; conversely, the lower activity of this pathway in follicular cells is related to reduced oocyte competence. In studies three and four, experiments were performed to determine the profile of microRNAs and messenger RNAs in cumulus cells associated with oocytes of high or low developmental competence. Aiming to clarify some of the mechanisms responsible for the best oocyte quality that lead to the identification of oocyte quality biomarkers, allows the advancement and development of new tools to intensify the in vitro production of bovine embryos. Finally, results obtained demonstrate integrated responses between oocytes and follicular cells during follicular development and give new insights to the study of oocyte competence acquisition process and identified oocyte quality markers.

Os mecanismos pelos quais a produção in vitro de embriões (PIVE) bovinos gera embriões com excessivo acúmulo lipídico, com elevado estresse celular e com reduzida criotolerância ainda são desconhecidos. Também permanece desconhecido quando essas alterações acontecem, se acontecem desde a maturação oocitária e o papel que as células do cumulus possuem neste mecanismo. O objetivo do presente trabalho foi estudar e comparar o metabolismo lipídico e homeostase celular, além dos perfis de miRNAs, durante a maturação oocitária e o desenvolvimento embrionário inicial in vivo e in vitro em bovinos. Para isso, o trabalho foi dividido em 4 estudos. No Estudo 1, intitulado \"A maturação in vitro gera complexos cumulus-oócitos metabolicamente desregulados e estressados em bovinos\" foram analisadas as células do cumulus e oócitos de complexos cumulus-oócitos (COCs) imaturos e maturados in vivo e in vitro. Foram realizadas análises de quantificação de lipídeos, espécies reativas de oxigênio (EROs), glutationa reduzida (GSH), razão ATP/ADP assim como expressão de mRNAs e miRNAs relacionados com as vias de metabolismo e homeostase celular. A partir dos dados obtidos neste estudo, concluímos que a maturação in vitro (MIV) provoca aumento de lipídeos no COC, diminuição de GSH e da atividade mitocondrial nos oócitos, acompanhado por uma desregulação massiva das vias relacionadas a metabolismo e homeostase nas células do cumulus da MIV. No Estudo 2, intitulado \"A proteína ligadora de ácidos graxos 3 (Fatty Acid Binding Protein 3 - FABP3) e as projeções transzonais estão envolvidas no acúmulo lipídico durante a maturação in vitro em oócitos bovinos\" foi constatado aumento do conteúdo lipídico e da expressão da FABP3 nas células do cumulus da MIV, quando comparado ao sistema in vivo. Ainda, imunolocalizamos a FABP3 dentro das projeções transzonais (TZPs) e verificamos um aumento concomitante da FABP3 e dos lipídeos oocitários nas primeiras 9 horas da MIV. Mediante a remoção das TZPs às 9 horas da MIV e consequente diminuição lipídica observada no oócito, concluímos que existe um possível transporte de ácidos graxos a partir das células do cumulus até o oócito mediante FABP3 e TZPs. No Estudo 3, intitulado \"Alterações no metabolismo lipídico e homeostase celular entre embriões bovinos produzidos in vivo e in vitro\", verificamos que, mesmo utilizando um cultivo in vitro com baixa tensão de oxigênio e sem soro, os blastocistos da PIVE possuem maiores níveis de lipídeos e EROs que aqueles produzidos in vivo. Além disso, constatamos que essas alterações nos lipídeos durante a PIVE não estão acompanhadas de alterações de expressão, porém, existe um aumento na expressão de genes relacionados com estresse. No último estudo, \"O sistema in vitro altera o perfil de miRNAs durante a maturação oocitária e desenvolvimento embrionário inicial em bovino\", constatamos as diferenças no perfil de miRNAs e nas vias reguladas por estes nas células do cumulus e oócitos maturados in vivo e in vitro e em blastocistos produzidos in vivo e in vitro. Verificamos uma maior regulação por miRNAs durante a maturação nas células do cumulus comparado ao oócito. Além do mais, tanto no COC quanto nos blastocistos, os miRNAs mostraram regular vias importantes do metabolismo, comunicação celular e vias de sinalização importantes para a maturação e desenvolvimento embrionário inicial. Conjuntamente, este trabalho permitiu elucidar as diferenças que a PIVE provoca no metabolismo e homeostase celular e na expressão de miRNAs. / The mechanism through which in vitro embryo production (IVEP) generates embryos with higher lipid accumulation, overstressed and with reduced cryotolerance is unknown. It is also unknown when these alterations take place, if occurs since the oocyte maturation and the role of cumulus cells in this mechanism are also unknown. The aim of the present work was to study and compare the lipid metabolism and cellular homeostasis, as well as the miRNAs profile during oocyte maturation and early in vivo and in vitro embryo development in bovines. For that, the present work was divided in 4 studies. In Study 1, entitled \"in vitro maturation generates metabolically disrupted and overstressed cumulus-oocyte complexes in bovines\" cumulus cells and oocytes from immature and in vivo and in vitro matured cumulus-cells complexes (COC) were analyzed. Analysis of lipid stores, oxygen reactive species (ROS), reduced glutathione and ATP/ADP ratio quantification, as well as mRNAs and miRNAs involved with metabolism and cellular homeostasis pathways were performed. From the obtained data in this study, we concluded that in vitro maturation (IVM) leads to an increase of lipids in the COC, a decrease of oocyte GSH and mitochondrial activity, as well as a massive deregulation in metabolism and homeostasis related pathways in MIV cumuls cells. In Study 2, \"Fatty Acid Binding Protein 3 and transzonal projections are involved on lipid accumulation during in vitro maturation in bovine oocytes\" we observed an increase of lipid accumulation and FABP3 expression in MIV cumulus cells when compared to the in vivo system. Furthermore, we immunolocalized the FABP3 inside the transzonal projections (TZPs) and verified a concomitant increase of FABP3 and oocyte lipids on the first 9 hours of MIV. By removing the TZPs at 9 hours of MIV and by the consequent lipid decrease observed in the oocyte, we concluded that there is a possible traffic of fatty acids from the cumulus cells to the oocyte mediated by FABP3 and TZPs. In Study 3, entitled \"Alterations in lipid metabolism and cellular homeostasis between in vivo and in vitro produced bovine embryos\", we observed that, even though under serum free and low oxygen tension used during in vitro culture was used, IVP blastocysts had higher lipid and ROS levels than the counterparts produced in vivo. Moreover, we found that these lipid alterations during IVP are not followed by corresponding genes expression alterations, however, there is an increase of the expression of stress related genes. In the last study, \"in vitro system alters miRNAs profile during oocyte maturation and early embryo development in bovines\", we observed differences in miRNAs profiles and in pathways modulated by them in in vivo and in vitro matured cumulus cells and oocytes and in in vivo and in vitro produced blastocysts. We observed an intense miRNAs regulation during maturation in cumulus cells when compared to the oocyte. Furthermore, in both COC and blastocysts, miRNAs regulated important metabolism, cellular communication pathways, as well as important signaling pathways for maturation and early embryo development. Taken together, the findings of the present work allowed us to elucidate the differences caused by IVEP on cell metabolism and homeostasis as well as on miRNAs expression.

The North American monsoon (NAM) is the principal driver of summer severe weather in the Southwest U.S. With sufficient atmospheric instability and moisture, monsoon convection initiates during daytime in the mountains and later may organize, principally into mesoscale convective systems (MCSs). Most monsoon-related severe weather occurs in association with organized convection, including microbursts, dust storms, flash flooding and lightning. The overarching theme of this dissertation research is to investigate simulation of monsoon severe weather due to organized convection within the use of regional atmospheric modeling. A commonly used cumulus parameterization scheme has been modified to better account for dynamic pressure effects, resulting in an improved representation of a simulated MCS during the North American monsoon experiment and the climatology of warm season precipitation in a long-term regional climate model simulation. The effect of urbanization on organized convection occurring in Phoenix is evaluated in model sensitivity experiments using an urban canopy model (UCM) and urban land cover compared to pre-settlement natural desert land cover. The presence of vegetation and irrigation makes Phoenix a "heat sink" in comparison to its surrounding desert, and as a result the modeled precipitation in response to urbanization decreases within the Phoenix urban area and increase on its periphery. Finally, analysis of how monsoon severe weather is changing in association with observed global climate change is considered within the context of a series of retrospectively simulated severe weather events during the period 1948-2010 in a numerical weather prediction paradigm. The individual severe weather events are identified by favorable thermodynamic conditions of instability and atmospheric moisture (precipitable water). Changes in precipitation extremes are evaluated with extreme value statistics. During the last several decades, there has been intensification of organized convective precipitation, but these events occur with less frequency. A more favorable thermodynamic environment for monsoon thunderstorms is the driver of these changes, which is consistent with the broader notion that anthropogenic climate change is presently intensifying weather extremes worldwide.

The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters. Their majesty evolves from the significant range of spatial scales they operate over: from the mesoscale, to the larger synoptic-scale. Their associated violent winds and seas, however, are often the cause of damage and destruction for settlements in their path. Between 10/11/07 and 16/11/07, tropical cyclone Sidr formed and intensified into a category 5 hurricane over the southeast tropical waters of the northern Indian Ocean. Sidr tracked west, then north, during the course of its life, and eventually made landfall on 15/11/07, as a category 4 cyclone near the settlement of Barguna, Bangladesh. The storm affected approximately 2.7 million people in Bangladesh, and of that number 4234 were killed. In this study, the dynamics of tropical cyclone Sidr are simulated using version 2.2.1 of Advanced Weather Research and Forecasting — a non-hydrostatic, two-way interactive, triply-nested-grid mesoscale model. Three experiments were developed examining model sensitivity to ocean-atmosphere interaction; initialisation time; and choice of convective parameterisation scheme. All experiments were verified against analysed synoptic data. The ocean-atmosphere experiment involved one simulation of a cold sea surface temperature, fixed at 10 °C; and simulated using a 15 km grid resolution. The initialisation experiment involved three simulations of different model start time: 108-, 72-, and 48-hours before landfall respectively. These were simulated using a 15 km grid resolution. The convective experiment consisted of four simulations, with three of these using a different implicit convective scheme. The three schemes used were, the Kain-Fritsch, Betts-Miller-Janjic, and Grell-Devenyi ensemble. The fourth case simulated convection explicitly. A nested domain of 5km grid spacing was used in the convective experiment, for high resolution modelling. In all experiments, the Eta-Ferrier microphysics scheme, and the Mellor-Yamada-Janjic planetary boundary layer scheme were used. As verified against available observations, the model showed considerable sensitivity in each of the experiments. The model was found to be well suited for combining ocean-atmosphere interactions: a cool sea surface caused cyclone Sidr to dissipate within 24 hours. The initialisation simulations indicated moderate model sensitivity to initialisation time: variations were found for both cyclone track and intensity. Of the three simulations, an initialisation time 108 hours prior to landfall, was found to most accurately represent cyclone Sidr’s track and intensity. Finally, the convective simulations showed that considerable differences were found in cyclone track, intensity, and structure, when using different convective schemes. The Kain-Fritsch scheme produced the most accurate cyclone track and structure, but the rainfall rate was spurious on the sub-grid-scale. The Betts-Miller-Janjic scheme resolved realistic rainfall on both domains, but cyclone intensity was poor. Of particular significance, was that explicit convection produced a similar result to the Grell-Devenyi ensemble for both model domain resolutions. Overall, the results suggest that the modelled cyclone is highly sensitive to changes in initial conditions. In particular, in the context of other studies, it appears that the combination of convective scheme, microphysics scheme, and boundary layer scheme, are most significant for accurate track and intensity prediction.

Atmospheric aerosols are a highly relevant component of the climate system affecting atmospheric radiative transfer and the hydrological cycle. As opposed to other key atmospheric constituents with climatic relevance, atmospheric aerosol particles are highly heterogeneous in time and space with respect to their size, concentration, chemical composition and physical properties. Many aspects of their life cycle are not understood, making them difficult to represent in climate models and hard to control as a pollutant. Aerosol-cloud interactions in particular are infamous as a major source of uncertainty in future climate predictions. Field measurements are an important source of information for the modeling community and can lead to a better understanding of chemical and microphysical processes. In this study, field data from urban, marine, and arid settings are analyzed and the impact of meteorological conditions on the evolution of aerosol particles while in the atmosphere is investigated. Particular attention is given to organic aerosols, which are a poorly understood component of atmospheric aerosols. Local wind characteristics, solar radiation, relative humidity and the presence or absence of clouds and fog are found to be crucial factors in the transport and chemical evolution of aerosol particles. Organic aerosols in particular are found to be heavily impacted by processes in the liquid phase (cloud droplets and aerosol water). The reported measurements serve to improve the process-level understanding of aerosol evolution in different environments and to inform the modeling community by providing realistic values for input parameters and validation of model calculations.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

The gonadotropin-induced resumption of meiosis and cumulus expansion in preovulatory follicles is preceded by expression of epidermal growth factor (EGF)-like factors, amphiregulin (AREG) and epiregulin (EREG), in mural granulosa and cumulus cells. In vitro, the EGF-like peptides are also produced in cumulus cells upon stimulation by FSH. Both FSH and the EGF-like peptides stimulate resumption of meiosis and cumulus expansion in vitro via activation of a broad signaling network in cumulus cells. To define signaling pathways that drive FSH- and AREG-induced cumulus expansion and meiotic resumption, in vitro cultured pig cumulus-oocyte complexes (COCs) were treated with specific protein kinase inhibitors. The results document that FSH-stimulated, but not the AREG-stimulated resumption of meiosis, depends on the PKA and MAPK14 activities; both modes of stimulation require activation of EGFR and MAPK3/1. To characterize the effects of FSH and EGF-like peptides on gene expression in cumulus cells, transcriptomes of cumulus cells were analysed using microarray approach. Both FSH and AREG+EREG increased the expression of genes associated with regulation of cell proliferation, blood coagulation and extracellular matrix remodeling. In contrast to AREG+EREG, FSH also increased the expression of genes coding...

Uma das maiores dificuldades das terapias de reprodução assistida é a seleção de células germinativas de boa qualidade para posterior fertilização e implantação. Atualmente, a seleção de oócitos se dá basicamente por avaliação morfológica, que não reflete satisfatoriamente a competência oocitária. Assim, a busca por bioindicadores da qualidade oocitária é necessária. O cumulus oophorus forma um conjunto de células somáticas que circundam o oócito no folículo antral,mantendo uma relação íntima com a célula germinativa, com comunicação direta via junções tipo GAP. As células do cumulus oophorus são descartadas após técnicas de fertilização in vitro, o que as torna um material de fácil acesso, livre de conflitos éticos. Uma série de metodologias de análise das células do cumulus foram propostas para identificação de anormalidades no oócito. Porém, nenhuma delas é rotineiramente utilizada na clínica. Os processos celulares das células do cumulus refletem as condições do microambiente folicular, e podem, assim, trazer evidências das condições oocitárias. Nosso grupo analisou as células do cumulus primeiramente por meio de abordagens de bioinformática, que revelaram processos celulares relacionados ao desenvolvimento de embriões até o estágio de blastocisto. Com base nestes resultados, análises de parâmetros bioquímicos e expressão gênica das células do cumulus foram realizadas e permitiram a identificação de possíveis biomarcadores da qualidade do oócito que levam em consideração as características clínicas das pacientes. Estas análises indicaram que expressão do gene PTGS2 e a atividade da enzima Glutationa-S-Transferase como indicadores da formação de blastocistos em pacientes com diferentes variáveis clínicas (backgrounds) analisados. Se confirmados, estes parâmetros poderão ser utilizados como biomarcadores no ambiente clínico, elevando as taxas de sucesso em técnicas de reprodução assistida. / One of the great challenges in assisted reproduction techniques is the selection of appropriate germ cells for fertilization and implantation. Nowadays, oocyte selection occurs basically through morphological evaluation, which does not reflect satisfactorily the oocyte competence. Therefore, the search for bioindicators of oocyte quality is necessary. The cumulus oophorus forms a set of somatic cells that surround the oocyte in the antral follicle, participating in the processes of oocyte maturation and folliculogenesis. These cells maintain an intimate relationship with the germ cell, with direct communication via GAP junctions. Cumulus oophorus cells are discarded in in vitro fertilization techniques, which makes them an easy-access material that can be collected in a free-of-ethicalissues way. A series of cumulus cell analysis methodologies were proposed to identify abnormalities in the oocyte. However, none of them is routinely used in clinical environment. The cellular processes of cumulus cells reflect the conditions of the follicular microenvironment, and may thus bring evidences of oocyte conditions. Our group analyzed cumulus cells in search of predictors of oocyte quality primarily through bioinformatics approaches, which revealed cellular processes related to the development of embryos up to the blastocyst stage. Based on these results, analyzes of biochemical parameters and gene expression of cumulus cells were performed and allowed the identification of possible biomarkers of oocyte quality that takes into consideration patients clinical variables. These analysis indicated PTGS2 expression and Glutathione-S-Transferase activity as indicators of blastocyst formation in all patient profiles (backgrounds) analyzed. If confirmed, these parameters may be used as biomarkers in clinical environment, improving assisted reproduction success rates.

Tese (doutorado)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, 2016. / A criopreservação do ovócito bovino ainda é um desafio. O tamanho celular, a quantidade de água no citoplasma, a reserva de ácidos graxos, a composição da membrana plasmática, são alguns dos fatores responsáveis pela baixa eficiência da técnica. Entre as metodologias utilizadas para a criopreservação de ovócitos, a vitrificação ainda é considerado o método mais eficaz. O objetivo principal deste trabalho foi avaliar diferentes alternativas para minimizar os efeitos deletérios da vitrificação em ovócitos bovinos imaturos ou maturados. Entre as abordagens utilizadas estão (1) o uso de beta- metil- ciclodextrina (MβCD), como substância para alterar a membrana plasmática e aumentar a fluidez da mesma; (2) a associação de L-Carnitina e Resveratrol durante a maturação in vitro (MIV), para diminuir a reserva de gotículas lipídicas, aumentar a produção de ATP e proteger o ovócito contra o acúmulo de espécies reativas de oxigênio (EROs); (3) o uso da maturação in vivo para melhorar a qualidade do ovócito e, (4) o uso da transferência intrafolicular de ovócito imaturo, para proporcionar aos ovócitos vitrificados uma ambiente in vivo durante todos os passos da produção de embriões. Em cada experimento, diferentes avaliações foram utilizadas para identificar o sucesso ou insucesso das alternativas propostas. Apesar de alguns procedimentos como o uso de MβCD, terem melhorado a maturação nuclear, nenhum dos procedimentos utilizados aumentou a produção de blastocistos a partir de ovócito vitrificados. Os resultados obtidos mostraram que as lesões sofridas pelo ovócito bovino durante a vitrificação e aquecimento, o comprometem de forma muito severa e irreversível. / Cryopreservation of bovine oocyte is still a challenge. The cell size, the amount of water in the cytoplasm, the reservation of fatty acids, plasma membrane composition , are some of factors responsible for low efficiency of technique for bovine oocytes. Among the methodologies used for cryopreservation of oocytes, vitrification is the one that can minimize the effects of water flow. The main objective of present thesis was to prove different methodologies for vitrification of immature or matured bovine oocytes. For different alternatives were proved: (1) MβCD, a substance to alter the plasma membrane and increase membrane fluidity. (2) the combination of L-carnitine and resveratrol during IVM, to reduce reserves of lipid droplets, increase ATP production and protect against ROS aa. (3) in vivo maturation system where, after hormonal stimulation on bovine heifers, in vivo and theatrically better oocyte were produced. (4) intrafollicular transfer of immature oocyte, we adapted a methodology for immature oocytes could be injected into pre-ovulatory follicles, resulting in a in vivo system. For each experiment, different assessments were used to identify the successes or failures of our hypothesis. A common evaluation used for all experiments was the use of immature or for some experiments matured oocytes, destined for blastocyst development, after IVF. In none of proposed experiments, we have succeeded in increasing the production of blastocysts from vitrified oocytes. Likewise, the results, indicated that the injuries suffered by bovine oocyte during vitrification and thawing, compromise the oocyte at very severe intensity.

A well-represented description of convection in weather and climate models is essential since convective clouds strongly influence the climate system. Convective processes interact with radiation, redistribute sensible and latent heat and momentum, and impact hydrological processes through precipitation. Depending on the models’ horizontal resolution, the representation of convection may look very different. However, the convective scales not resolved by the model are traditionally parameterized by an ensemble of non-interacting convective plumes within some area of uniform forcing, representing the “large scale”. A bulk representation of the mass-flux associated with the individual plumes in the defined area provide the statistical effect of moist convection on the atmosphere. Studying the characteristics of the ECMWF ensemble prediction system it is found that the control forecast of the ensemble system is not variable enough in order to yield a sufficient spread using an initial perturbation technique alone. Such insufficient variability may be addressed in the parameterizations of, for instance, cumulus convection where the sub-grid variability in space and time is traditionally neglected. Furthermore, horizontal transport due to gravity waves can act to organize deep convection into larger scale structures which can contribute to an upscale energy cascade. However, horizontal advection and numerical diffusion are the only ways through which adjacent model grid-boxes interact in the models. The impact of flow dependent horizontal diffusion on resolved deep convection is studied, and the organization of convective clusters is found very sensitive to the method of imposing horizontal diffusion. However, using numerical diffusion in order to represent lateral effects is undesirable. To address the above issues, a scheme using cellular automata in order to introduce lateral communication, memory and a stochastic representation of the statistical effects of cumulus convection is implemented in two numerical weather models. The behaviour of the scheme is studied in cases of organized convective squall-lines, and initial model runs show promising improvements. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted. </p>