The use of numerical weather prediction (NWP) has brought significant improvements to severe weather outbreak forecasting; however, determination of the primary mode of severe weather (in particular tornadic and nontornadic outbreaks) continues to be a challenge. Uncertainty in model runs contributes to forecasting difficulty; therefore it is beneficial to a forecaster to understand the sources and magnitude of uncertainty in a severe weather forecast. This research examines the impact of data assimilation, microphysics parameterizations, and planetary boundary layer (PBL) physics parameterizations on severe weather forecast accuracy and model variability, both at a mesoscale and synoptic-scale level. NWP model simulations of twenty United States tornadic and twenty nontornadic outbreaks are generated. In the first research phase, each case is modeled with three different modes of data assimilation and a control. In the second phase, each event is modeled with 15 combinations of physics parameterizations: five microphysics and three PBL, all of which were designed to perform well in convective weather situations. A learning machine technique known as a support vector machine (SVM) is used to predict outbreak mode for each run for both the data assimilated model simulations and the different parameterization simulations. Parameters determined to be significant for outbreak discrimination are extracted from the model simulations and input to the SVM, which issues a diagnosis of outbreak type (tornadic or nontornadic) for each model run. In the third phase, standard synoptic parameters are extracted from the model simulations and a k-means cluster analysis is performed on tornadic and nontornadic outbreak data sets to generate synoptically distinct clusters representing atmospheric conditions found in each type of outbreak. Variations among the synoptic features in each cluster are examined across the varied physics parameterization and data assimilation runs. Phase I found that conventional and HIRS-4 radiance assimilation performs best of all examined assimilation variations by lowering false alarm ratios relative to other runs. Phase II found that the selection of PBL physics produces greater spread in the SVM classification ability. Phase III found that data assimilation generates greater model changes in the strength of synoptic-scale features than either microphysics or PBL physics parameterization.

L'influence des paramétrisations chimiques et météorologiques sur les concentrations de polluants calculées avec un modèle de qualité de l'air est étudiée. L'influence des différences entre deux mécanismes chimiques de la phase gazeuse sur la formation d'ozone et d'aérosols en Europe est faible en moyenne. Pour l'ozone, les fortes différences observées localement proviennent principalement de l'incertitude associée à la cinétique des réactions d'oxydation du monoxyde d'azote (NO) d'une part et de la représentation des différents chemins d'oxydation des composés aromatiques d'autre part. Les concentrations d'aérosols sont surtout influencées par la prise en compte des précurseurs majeurs d'aérosols secondaires et le traitement explicite des régimes chimiques correspondant au niveau d'oxydes d'azote (NOx). L'influence des paramétrisations météorologiques sur les concentrations d'aérosols et leur répartition verticale est évaluée sur l'Île de France par comparaison à des données lidar. L'influence de la paramétrisation de la dynamique de la couche limite atmosphérique est importante ; cependant, c'est l'utilisation d'un modèle de canopée urbaine qui permet d'améliorer considérablement la modélisation de la répartition verticale des polluants / The influence of chemical mechanisms and meteorological parameterizations on pollutant concentrations calculated with an air quality model is studied. The influence of the differences between two gas-phase chemical mechanisms on the formation of ozone and aerosols in Europe is low on average. For ozone, the large local differences are mainly due to the uncertainty associated with the kinetics of nitrogen monoxide (NO) oxidation reactions on the one hand and the representation of different pathways for the oxidation of aromatic compounds on the other hand. The aerosol concentrations are mainly influenced by the selection of all major precursors of secondary aerosols and the explicit treatment of chemical regimes corresponding to the nitrogen oxides (NOx) levels. The influence of the meteorological parameterizations on the concentrations of aerosols and their vertical distribution is evaluated over the Paris region in France by comparison to lidar data. The influence of the parameterization of the dynamics in the atmospheric boundary layer is important ; however, it is the use of an urban canopy model that improves significantly the modeling of the pollutant vertical distribution

The influence of chemical mechanisms and meteorological parameterizations on pollutant concentrations calculated with an air quality model is studied. The influence of the differences between two gas-phase chemical mechanisms on the formation of ozone and aerosols in Europe is low on average. For ozone, the large local differences are mainly due to the uncertainty associated with the kinetics of nitrogen monoxide (NO) oxidation reactions on the one hand and the representation of different pathways for the oxidation of aromatic compounds on the other hand. The aerosol concentrations are mainly influenced by the selection of all major precursors of secondary aerosols and the explicit treatment of chemical regimes corresponding to the nitrogen oxides (NOx) levels. The influence of the meteorological parameterizations on the concentrations of aerosols and their vertical distribution is evaluated over the Paris region in France by comparison to lidar data. The influence of the parameterization of the dynamics in the atmospheric boundary layer is important ; however, it is the use of an urban canopy model that improves significantly the modeling of the pollutant vertical distribution

No description available.

Este trabalho investiga a evolução espacial da Camada Limite Planetária (CLP) na região do Canal de São Sebastião (CSS) - SP, uma das áreas mais impactadas por derramamentos acidentais de óleo das regiões sul e sudeste do Brasil. Para tanto, foi feito levantamento da topografia e cobertura do solo para uma região de 12 km x 12 km no CSS com o intuito de levantar parâmetros essenciais para a estimativa do balanço de energia sobre o continente. Foram utilizados dados médios horários de vento, temperatura e umidade específica do ar coletados pelo Centro de Biologia Marinha (CEBIMar), e temperatura do oceano obtida de um fundeio ancorado próximo ao centro do canal. Os dados médios foram utilizados para estimar o balanço de energia sobre o continente, utilizando o método proposto por Deardorff (1978), e sobre o oceano através de parametrização do tipo bulk para as condições de verão e inverno. Com os resultados obtidos foi determinada a altura da CLP para ambas as superfícies e, em seguida, aplicada uma média móvel com advecção destas alturas no sentido do vento zonal - a componente mais intensa do vento ao longo do dia segundo análise de dados para ambas estações estudadas - para investigar sua evolução espacial ao longo de duas linhas de latitude: uma interceptando o CEBIMar e outra, mais ao sul, numa região composta por água e continente em igual proporção. / This work investigates the spatial evolution of the Planetary Boundary Layer in the region of São Sebastião Channel (SSC) - SP, one of the most impacted area by accidental oil spilling in the South and Southeast regions of Brazil. It was performed a topographic and soil cover survey for a region of 12 km x 12 km in the SSC region in order to obtain the essential parameters to estimate the energy balance over the continent. Hourly averaged data of wind, air temperature and specific humidity collected by the Marine Biologic Center (CEBIMar) and ocean temperature obtained by a mooring near the center of the channel were used in this work to estimate the energy balance over the continent using the routine proposed by Deardorff (1978) and over the ocean using bulk parameterizations for winter and summer conditions. The obtained results were used to determine the PBL height for both surfaces. To investigate the PBL spatial evolution in the transition continent-water-continent it was applied a movable average with advection of the PBL height in the zonal wind direction the wind component more intense during winter and summer, according to the data analysis- to investigate the PBL spatial evolution through two latitude lines: one intercepting the CEBIMar and another in an region southward with equal water and continent proportion.

Este trabalho investiga a evolução espacial da Camada Limite Planetária (CLP) na região do Canal de São Sebastião (CSS) - SP, uma das áreas mais impactadas por derramamentos acidentais de óleo das regiões sul e sudeste do Brasil. Para tanto, foi feito levantamento da topografia e cobertura do solo para uma região de 12 km x 12 km no CSS com o intuito de levantar parâmetros essenciais para a estimativa do balanço de energia sobre o continente. Foram utilizados dados médios horários de vento, temperatura e umidade específica do ar coletados pelo Centro de Biologia Marinha (CEBIMar), e temperatura do oceano obtida de um fundeio ancorado próximo ao centro do canal. Os dados médios foram utilizados para estimar o balanço de energia sobre o continente, utilizando o método proposto por Deardorff (1978), e sobre o oceano através de parametrização do tipo bulk para as condições de verão e inverno. Com os resultados obtidos foi determinada a altura da CLP para ambas as superfícies e, em seguida, aplicada uma média móvel com advecção destas alturas no sentido do vento zonal - a componente mais intensa do vento ao longo do dia segundo análise de dados para ambas estações estudadas - para investigar sua evolução espacial ao longo de duas linhas de latitude: uma interceptando o CEBIMar e outra, mais ao sul, numa região composta por água e continente em igual proporção. / This work investigates the spatial evolution of the Planetary Boundary Layer in the region of São Sebastião Channel (SSC) - SP, one of the most impacted area by accidental oil spilling in the South and Southeast regions of Brazil. It was performed a topographic and soil cover survey for a region of 12 km x 12 km in the SSC region in order to obtain the essential parameters to estimate the energy balance over the continent. Hourly averaged data of wind, air temperature and specific humidity collected by the Marine Biologic Center (CEBIMar) and ocean temperature obtained by a mooring near the center of the channel were used in this work to estimate the energy balance over the continent using the routine proposed by Deardorff (1978) and over the ocean using bulk parameterizations for winter and summer conditions. The obtained results were used to determine the PBL height for both surfaces. To investigate the PBL spatial evolution in the transition continent-water-continent it was applied a movable average with advection of the PBL height in the zonal wind direction the wind component more intense during winter and summer, according to the data analysis- to investigate the PBL spatial evolution through two latitude lines: one intercepting the CEBIMar and another in an region southward with equal water and continent proportion.

The atmospheric boundary layer (ABL) is the lowest layer of the atmosphere where surface effects are felt on time scales of about an hour. While its properties are determined by the surface characteristics, season and synoptic conditions, they in turn determine convective cloud properties and are required for the representation of cloud processes in atmospheric models. Further, interaction of the ABL with the surface layer of the ocean is a key component of ocean-atmosphere coupling. ABL characteristics over ocean surrounding the sub-continent become very important for understanding the monsoon processes during the monsoon season because the roots of many monsoon systems, that give rain to India, are over there. In this thesis data used are from three major field experiments namely the Bay of Bengal Monsoon Experiment (BOBMEX, 1999), Arabian Sea Monsoon Experiment (ARMEX, in two phases, ARMEX-I during 2002 and ARMEX-II in 2003), and Continental Tropical Convergence Zone (CTCZ) experiment (Pilot in 2009) which were carried out under the Indian Climate Research Programme (ICRP). While there have been few studies on ABL characteristics for individual cruises, a comprehensive study considering all available radiosonde data from the above cruises has been missing. This study fills this gap and focuses on the vertical structure of ABL using more than 400 high resolution Vaisala GPS radiosonde data collected over Bay of Bengal and Arabian Sea. The study attempts at first to look at the ABL characteristics of individual cruises and then compare and contrast them over the Bay of Bengal and Arabian Sea. ABL height Hm, estimated by using virtual potential temperature (θv) profile, shows diurnal variation during weak phase of convection while maximum in early morning during active phase of convection. Different variables i.e. moist static energy (h), specific humidity (q), convective available potential energy (CAPE), virtual potential temperature (θv) and equivalent potential temperature (θe) also differ during weak and active convection periods. Conserved variables mixing line approach gives the height up to which ground thermals penetrate in the vertical. This height, denoted by MH that represents the actual ABL height, is 2-3 times larger than Hm when shallow convective clouds are present. In general both Hm and MH are 20-30% larger over Arabian Sea compares to that over Bay of Bengal. Comparison of surface convective available potential energy (CAPE) and equivalent potential temperature (θe) between normal and deficit monsoon years shows that convective instability was as large in deficit years. This means that dynamic and not thermodynamics, controlled the occurrence of convection.

Abstract in English, Afrikaans and Zulu / The aim of the study was to develop a critical posthumanist and democratic theory that may be applied in the teaching and learning of Life Sciences in South Africa in order to achieve an expanded form of democracy that would not discriminate between human and nonhuman. Though both critical posthumanist and democratic theories have been used in pedagogical studies separately, this study focused on the development of a merged and broader theory that has elements of both of the theories. The term nonhuman, as used here, does not specifically refer to non-person individuals only. Rather, it also refers to people who are regarded by the dominant humans as nonhumans – inferiors and subalterns. The latter group of people include the poor, women, children, people of colour and the disabled. Owing to this binarisation characteristic of the Life Sciences as a subject – which it adopts from the nature of science, its curriculum, and pedagogical approaches – the impression is given that as the master of the universe, the human has unlimited power over all other entities. These other nonhuman entities are then regarded as resources for the use of humans. Yet, it is this attitude which has caused humans to abuse nonhumans to the extent that the earth is facing the catastrophe of the Anthropocene. The adoption of a critical education approach characterised by the development of a critical posthumanist and democratic theory that may be applied in the teaching and learning of Life Sciences is essential in dealing with the issue of the Anthropocene that is threatening the earth currently. This study thus seeks to adopt a critical education approach through the introduction of democracy into the teaching and learning of Life Sciences, specifically so that humans would get to a position where they would consider nonhumans as entities with which they co-exist, and entities with equal agency within the environment. The recognition of the need for democracy would allow the humans to treat the nonhumans (such as the environment and ‘subalterns’) with respect, as their compatriots; and by doing that, the harrowing issues leading to the catastrophe of the Anthropocene could be either avoided or averted. / Die doel van die studie was om ’n kritiese posthumanistiese en demokratiese teorie te ontwikkel wat op die onderrig en leer van Lewenswetenskappe in Suid-Afrika toegepas kan word om ’n uitgebreide vorm van demokrasie daar te stel wat nie tussen menslik en niemenslik sal diskrimineer nie. Hoewel kritiese posthumanistiese sowel as demokratiese teorieë apart in pedagogiese studies gebruik word, het hierdie studie op die ontwikkeling van ’n saamgesmelte en breër teorie wat elemente van beide teorieë bevat, gefokus. Die term niemenslik soos wat dit hier gebruik word, verwys nie spesifiek net na niepersoon-individue nie. Dit verwys eerder ook na mense wat deur die dominante mense as niemense – minderes en ondergeskiktes – beskou word. Die laasgenoemde groep mense sluit die armes, vroue, kinders, mense van kleur en gestremde mense in. Vanweë hierdie binêre eienskap van die Lewenswetenskappe as ’n vak – wat dit as gevolg van die aard van wetenskap, sy kurrikulum en pedagogiese benaderings aanvaar het – word die indruk geskep dat die mens as heerser van die heelal onbeperkte mag oor al die ander entiteite het. Hierdie ander niemenslike entiteite word dan as hulpbronne vir gebruik deur mense gesien. Dit is egter hierdie houding wat veroorsaak het dat mense niemense misbruik, in so ’n mate dat die aarde die katastrofe van die Antroposeen in die gesig staar. Die aanneem van ’n kritiese onderrigbenadering wat gekenmerk word deur die ontwikkeling van ’n kritiese posthumanistiese en demokratiese teorie wat by die onderrig en leer van Lewenswetenskappe gebruik kan word, is noodsaaklik om die kwessie van die Antroposeen wat die aarde tans bedreig, te hanteer. Hierdie studie wil dus ’n kritiese onderrigbenadering volg deur middel van die bekendstelling van demokrasie by die onderrig en leer van Lewenswetenskappe, in die besonder sodat mense in ’n posisie sal wees waar hulle niemense as entiteite saam met wie hulle ’n bestaan moet voer, en entiteite met gelyke verteenwoordiging in die omgewing, sal beskou. Om die behoefte aan demokrasie te erken, sal die mense toelaat om die niemense (soos die omgewing en “ondergeskiktes”) as hulle landgenote met respek te behandel; en deur dit te doen, kan die pynlike kwessies wat tot die katastrofe van die Antroposeen sal lei, moontlik vermy of afgeweer word. / Inhloso yalolu cwaningo kwakungukusungula umbono obucayi owenziwa ngemuva kokuphila komuntu nentando yeningi engasetshenziswa ekufundisweni nasekufundeni kwesayensi yezempilo eNingizimu Afrika ukuze kuzuzwe uhlobo olwandisiwe lwentando yeningi olungeke lubandlulule phakathi kwabantu kanye nokungebona abantu. Yize zombili izinkolelo ezibucayi ezenziwa ngemuva kokuphila komuntu nezentando yeningi zisetshenzisiwe ezifundweni zokufundisa ngokwehlukana, lolu cwaningo lugxile ekuthuthukiseni kombono ohlanganisiwe futhi obanzi onezici zombili zale mibono. Igama elithi okungebona abantu njengoba lisetshenziswa lapha, alibhekiseli ngqo kubantu abangebona abantu kuphela. Esikhundleni salokho, libhekise nakubantu ababhekwa ngabantu abaphezulu njengabantu abangebona abantu – abaphansi nabasezingeni eliphansi. Iqembu lokugcina labantu lifaka phakathi abampofu, abesifazane, izingane, abantu bebala nabakhubazekile. Ngenxa yalesi sici sokuhlukaniswa kwesayensi yezempilo njengesifundo – emukela emvelweni yesayensi, ikharikhulamu yayo, kanye nezindlela zokufundisa - kunikezwa umbono wokuthi njengomphathi wendawo yonke, umuntu unamandla angenamkhawulo kuzo zonke ezinye izinhlangano. Lezi ezinye izinto ezingezona abantu zithathwa njengezinsiza ukusetshenziswa abantu. Kodwa-ke, yilesi simo sengqondo esidale ukuthi abantu bahlukumeze abantu abangebona abantu kuze kufike lapho umhlaba ubhekene nenhlekelele yokwakhiwa nokuthuthukiswa komhlaba. Ukwamukelwa kwendlela ebucayi yezemfundo ebonakala ngokuthuthukiswa kombono obucayi owenziwa ngemuva kokuphila komuntu kanye nentando yeningi engasetshenziswa ekufundisweni nasekufundeni kwesayenzi yezempilo kubalulekile ekubhekaneni nodaba lokwakhiwa nokuthuthukiswa komhlaba olusongela umhlaba njengamanje. Lolu cwaningo-ke lufuna ukwamukela indlela yezemfundo ebucayi ngokwethulwa kwentando yeningi ekufundisweni nasekufundeni kwesayensi yezempilo, ikakhulukazi ukuze abantu bafike esikhundeni lapho bezobheka khona abantu abangebona abantu njengezinhlangano abaphila nazo, nezinhlangano ezinokumela ngokulinganayo ngaphakathi kwemvelo. Ukwamukelwa kwesidingo sentando yeningi kuzovumela abantu ukuthi baphathe abantu abangebona abantu (njengemvelo kanye nabasezingeni eliphansi) ngenhlonipho, njengabantu bakubo; futhi ngokwenza lokho, izingqinamba ezihlasimulisayo eziholela enhlekeleleni yokwakhiwa nokuthuthukiswa komhlaba zingagwenywa noma zivinjelwe. / Educational Foundations / Ph. D. (Philosophy of Education)