Dissertations / Theses on the topic 'Covariance turbulente'
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Queiros-Condé, Diogo. "Covariance d'échelle et surface de flamme en combustion turbulente." Aix-Marseille 1, 1996. http://www.theses.fr/1996AIX11056.
Sa, Leonardo Deane de Abreu. "Les flux turbulents dans la couche limite de surface analysés à partir de mesures aéroportées : validation d'une méthode dissipative-inertielle et étude de variabilité." Toulouse 3, 1992. http://www.theses.fr/1992TOU30088.
Herig, Coimbra Pedro Henrique. "A whirlwind journey of wavelet turbulent flux mapping : estimation of spatialized turbulent flux on tall towers and its uncertainties." Electronic Thesis or Diss., université Paris-Saclay, 2024. https://theses.hal.science/tel-04637523.
Climate and human activity are closely linked. Greenhouse gas (GHGs) emissions impact climate dynamics and air quality, affecting millions globally. Effective GHG monitoring is essential for informed policy decisions, yet it is complex due to spatial and temporal variability of sources and sinks, and atmospheric transport. Monitoring networks address this variability by deploying sensors across diverse geographic locations sampling continuously over time.Urban areas are key emission points, driving climate change. However, monitoring direct GHG changes over >5 km2 with varied sources and vegetated areas lacks a standard method. Eddy Covariance (EC) offers direct, continuous GHG net flux monitoring. Wavelet-based EC operates on the same principles as the standard method but calculates covariance using frequency decomposed time series. This approach does not require stationarity, leaving more data available for analysis, particularly beneficial in complex urban environments where non-stationary fluxes are common.Disentangling anthropogenic and biogenic components of a net CO2 flux is recognised as a key issue yet to be resolved in urbanised areas. Conventional ecosystem models used to partition gross primary productivity (GPP) and ecosystem respiration (Reco) are not appropriate for urbanised areas. Direct partitioning using high-frequency correlations between tracer gases may help overcoming the limitations of standard partitioning methods.While Eddy Covariance remains standard for local studies, estimating larger-scale surface fluxes often involves assimilating background concentration measurements to prior estimations using transport models. The progress in satellite imagery and detailed inventories provides a new basis that helps improve these methods. However, inversion methods using tower flux data are still sparse and would be interesting to test in urbanised areas.The objective of this PhD was to evaluate wavelet-based EC combined with Bayesian inversion methods for CO2 flux mapping. During the course of the PhD I discovered a new direct partitioning method that was used with a combination of CH4 and CO to improve the overall inversion in the suburban area of the Saclay plateau.In the first paper of the PhD, we hypothesised that decomposing concentration and wind signals by frequency can capture individual gusts within each frequency, typically mixed in the original signal. We leveraged this feature to propose a new parameter-free direct partitioning method based on quadrant analysis of CO2 and water vapour frequency decomposed fluxes. We showed that this method could indeed provide unbiased estimates of GPP and Reco at a crop and a forest ecosystem site near Paris. We also found that wavelet eddy covariance further saved up to 30% of the non-stationary data in these sites.In the second paper, we proposed using tall towers equipped with high-precision but slow analysers for measuring fluxes. Despite slower acquisition frequencies, attenuation was limited to 20 % by a lower contribution of high frequencies at this height. Results encourage further collaboration between atmospheric and ecosystem networks for in-situ measurements.In the third paper, we combined the partitioning method proposed in the first paper with the flux from the second paper, including now more gases measured to partition CO2 fluxes in biogenic and anthropogenic components and assimilate them in previous spatially-explicit estimations of fluxes at few km2. The obtained flux maps offer the advantage of relying on direct flux measurements at the landscape scale and may be used to informing large-scale inversions at broader scales.Results focused on the Parisian region provide valuable insights for flux measurements at the landscape scale and beyond, and contributing to emission monitoring strategies. These advancements contribute to understanding and addressing environmental challenges at the temporal and spatial scales where decisions are made
Nilsson, Charlotta. "Beräkning av turbulenta flödenenligt inertial dissipationsmetodenmed mätdata från enspecialkonstrueradlättviktsanemometer samtjämförelsemed turbulenta utbytesmetoden." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303161.
In order to evaluate a combined cup anemometer/wind vane profile instrument, measurementsfrom the instrument has been used in the so called inertial-dissipation method to derive itsability to measure turbulent fluxes. The result was compared to data from a sonic anemometercalculated with eddy-correlation method, which is assumed to be correct. Analysis of theresult was made from measurements at levels 8, 16 and 20 m. The profile instrument (inertialdissipationmethod) agreed well with the sonic anemometer (eddy-correlation method) duringnear neutral conditions and at high wind speed. The profile instrument also proved to be mostaccurate at conditions of growing sea, otherwise the result was affected by waves. In thereport there is also a recommendation for specific corrections when the profile instrument isused for calculating turbulent fluxes according to the inertial-dissipation method.
Inubushi, Masanobu. "Covariant Lyapunov Analysis of Navier-Stokes Turbulence." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175095.
Vendrame, Nadia. "Study of vegetation-atmosphere interactions over vineyards: CO2 fluxes and turbulent transport mechanics." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3425729.
Lo studio delle interazioni tra vegetazione e atmosfera è oggi un tema di grande interesse nell’ottica di migliorare la comprensione della risposta delle piante alle variabili ambientali e la modellizzazione del loro ruolo nel cambiamento climatico globale. Particolare attenzione è di solito rivolta ai flussi di anidride carbonica (CO2) e, in genere, gli ecosistemi naturali come le foreste hanno ricevuto una maggiore attenzione. In questa ricerca sono state studiate le interazioni vegetatione-atmosfera su una coltura agraria importante per il bacino mediterraneo, quale il vigneto, focalizzandosi sul monitoraggio del bilancio annuale di carbonio e approfondendo lo studio della meccanica del trasporto turbulento che è alla base degli scambi di energia e materia. Il vigneto è un sistema complesso con diverse sorgenti e sink di scalari (vapore d’acqua, anidride carbonica, calore), in cui le due principali componenti, vite e suolo, compongono il flusso totale della canopy in un rapporto che varia nel corso dell’anno. Nei vigneti del Nord Italia, l’interfila è solitamente non lavorata e inerbita, giocando un ruolo importante nel bilancio del carbonio del sistema. In questo contesto, risulta cruciale la ripartizione dello scambio netto di CO2 dell’ecosistema (Net Ecosystem Exchange, NEE) nelle componenti suolo e vite. Nel corso di questa indagine, la NEE di un vigneto è stata monitorata per tre anni utilizzando la tecnica micrometeorologica dell’ eddy covariance (EC), mentre la misura dei flussi di CO2 al suolo è stata effettuata con camere (a cupola trasparente e oscura). Nel 2015, il bilancio annuale di carbonio del vigneto è stato di circa ‒ 80 g C m‒ 2 a‒ 1, dimostrando quindi la capacità di agire da sink, ma la maggior parte dell’assimilazione è risultata legata al suolo inerbito (‒ 60 g C m‒2 a‒1). In ogni caso, il sistema ha dimostrato un’elevata variabilità interannuale del bilancio del carbonio stagionale, in cui ondate di calore e periodi di siccità estivi hanno giocato un ruolo primario. Nella stagione 2014, caratterizzata da un regime di precipitazione abbondante, la NEE ha raggiunto il valore massimo di circa ‒ 250 g C m‒2. L’organizzazione del vigneto in filari determina una particolare dinamica del trasporto turbolento dentro canopy. Inoltre, la struttura morfologica del vigneto è altamente variabile durante il corso dell’anno, passando da una canopy praticamente vuota nel periodo di dormienza della vite a una situazione dove il fogliame è denso e concentrato nelle file al culmine della stagione vegetativa. L’influenza dello sviluppo della densità fogliare sulle statistiche della turbolenza è stato studiato installando un profilo verticale di anemometri ad ultrasuoni. Il flusso turbolento è risultato fortemente influenzato dalla struttura della canopy. Senza foglie, il regime turbolento è caratteristico di un flusso di parete, mentre con lo sviluppo completo del fogliame assume le proprietà tipiche di un flusso con mixing‒layer, sebbene il flesso al limite superiore della canopy sia poco accentuato, a causa della bassa densità fogliare del vigneto. Infine, è stata condotta un’analisi specifica delle strutture coerenti coinvolte nel trasporto di quantità di moto e sulle loro scale temporali. L’importanza di eventi discendenti che trasportano aria più veloce del flusso medio (sweeps) è aumentata nel corso della stagione. La durata media delle strutture coerenti dominanti è stato nell’ordine di 6 ‒ 10 s e, in questo caso, non è stata riscontrata nessuna chiara correlazione con lo sviluppo della struttura della canopy. Lo studio ha messo in evidenza l’importanza del monitoraggio a lungo termine degli scambi tra vegetazione e atmosfera, ma anche la complessità dei fenomeni di trasporto turbolento che li caratterizzano. Tuttavia, solo la piena comprensione della meccanica di questi processi può portare alla corretta interpretazione del ruolo della vegetazione nei cicli biogeochimici più fondamentali.
Carneiro, Janaína Viário. "Fluxos turbulentos de CO2 em uma área de arroz irrigado no RS." Universidade Federal de Santa Maria, 2007. http://repositorio.ufsm.br/handle/1/9185.
This thesis quantifies the net change of CO2 (NEE) in an irrigated rice crop cultivation in RS (Brazil). The research is part of the project CT-HIDRO, which presents as main purpose the description of surface conditions for different ecosystems in the country. Data were gathered during the cultivation period, from October 2003 to March 2004. During this time, the average air temperature and the incident radiation were suitable for the development of the culture in such an area. The turbulent flows, calculated by the eddy covariance method, overestimated the NEE value, probably due to the low estimate of breathing tax, because, during some night-times, sensor registered little turbulence. Moreover, other factor could have interfered in the result of the flows, for instance, the time in which the flows are calculated. The Webb correction was applied in the curve of NEE, and a value smaller than 1% was found. Such result didn't modify the previous result significantly. The behavior of CO2 flow during the whole analyzed period showed a maximum of -0,47mgCO2 m−2 s −1 in January 2004, what demonstrates the largest absorption of CO2 from the atmosphere by the plant during the day and a smaller liberation at night, due to the development phase in which the plant is. In this case, the Webb correction was also little emphasized, not interfering in the obtained result. The curves that demonstrate the three phases of development of the rice presented a larger absorption of CO 2 during the reproductive phase. The behavior of the flow of CO 2 showed a negative flow during the day, when the plant absorbs CO2 from the atmosphere, and a positive flow during the night, when the inverse process occurs, what was waited for. The latent heat flow presented larger diary average values from January to February, always with positive values, consequence of the rice crop irrigation. Two days with high values of flow of latent heat were obtained, what motivated the analysis of the energy balance. The closing of the energy balance was not reached in both days. A possible reason for that could be the low estimate of flows when the eddy covariance method was applied.
Este trabalho quantifica a troca líquida de CO2 (NEE) em uma área de cultivo de arroz irrigado no RS, como parte do projeto CT-HIDRO, projeto este que tem como finalidade descrever condições de superfície para diferentes ecossistemas do país. Os dados utilizados foram coletados durante o período de cultivo, entre outubro de 2003 e março de 2004. Neste período a temperatura média do ar e a radiação incidente são adequadas para o desenvolvimento da cultura nesta região. Os fluxos turbulentos, calculados pelo método de covariância de vórtices (eddy covariance), superestimaram o valor da NEE, provavelmente devido, a subestimativa da taxa de respiração, pois em alguns períodos noturnos os sensores registraram pouca turbulência. Além disso, outro fator que pode interferir no resultado dos fluxos, como por exemplo, o intervalo em que os fluxos são calculados. Foi aplicada a correção de Webb na curva de NEE e encontrou-se um valor menor que 1%, fato este que não modificou significativamente o resultado encontrado. O comportamento do fluxo de CO 2 durante todo o período analisado, mostrou um pico de -0,47mgCO2 m−2 s −1 , em janeiro de 2004, o que demonstra a maior captura de CO2 da atmosfera pela planta durante o dia e uma menor liberação à noite, devido a fase de desenvolvimento em que a planta se encontra. Neste caso, a correção de Webb também foi pouco acentuada, não interferindo no resultado obtido. As curvas que demonstram as três fases de desenvolvimento do arroz mostraram claramente uma maior absorção de CO 2 durante a fase reprodutiva. O comportamento do fluxo de CO 2 mostra um fluxo negativo durante à dia, quando a planta absorve CO2 da atmosfera e um fluxo positivo durante à noite quando ocorre o processo inverso, o que era esperado. O fluxo de calor latente apresentou maiores valores médios diários entre os meses de janeiro e fevereiro, apresentando sempre valores positivos, conseqüência da irrigação do campo de arroz. Obtivemos dois dias com valores elevados de fluxo de calor latente, o que fez com que analisássemos o balanço de energia. O fechamento do balanço de energia não foi alcançado em ambos os dias. Uma possível razão para isto pode ser o devido à subestimativa dos fluxos quando aplicado o método de covariância de vórtices.
Stauch, Vanessa Juliane. "Data-led methods for the analysis and interpretation of eddy covariance observations." Phd thesis, kostenfrei, 2006. http://opus.kobv.de/ubp/volltexte/2007/1238/.
Zimermann, Hans Rogério. "Diferentes técnicas de condicionamento em séries temporais turbulentas." Universidade Federal de Santa Maria, 2005. http://repositorio.ufsm.br/handle/1/9211.
The dynamics process of the atmosphere near Earth ground is controled by two main forcings, termical and machanics. These process are reponsible for the atmospheric flow variability in this layer, and this variability characterizes the atmospheric turbulence. The presence of turbulence phenomena drives to distinguish it from the rest of atmosphere, such layer is commom called Atmospheric Boundary Layer (ABL). So, the importance of studying ABL is the fact of that turbulence represents an effective transport process near the ground surface. Adequate treating of the experimental data gives more truthful so qualitative as quantitavie when we are interpreting and understading these transports. This is very impportant for suitable trustful charaterizing the turbulent fluxes. This dissertation shows an overview about some basics turbulent data treatment techics. The dataset, colected experimentaly and separed into 27 minutes window samples, were subjected to simple mean, running mean through digital recursive filter e and linear detrending. Our focus are the implications of applying this technics and how each of this acts in turbulent time series of temperature and vertical velocity of the wind data, showing and discussing about the results in the estimating fluxes of sensible heat by Eddy Covariance method and also spectral densities estimates of temperature and vertical wind velocity. The main goal of the study done in this dissertation, was identifying that applying corrections on fase lag, not considered in older digital recursive filter (FDR as proposed by McMillen 1988) and, present into the model (FFDR proposed by Franceschi e Zardi 2003) leads for trusties estimatives, mainly for turbulent temperature spectra, which are the hardest ones for minimizing the non statinarity effects. Clearly, observing the graphical results of temperature spectra, we see that those low frequencies were better removed than the others technics, giving to spectral shape the classics espected shape.
A dinâmica da atmosfera próxima á superfície é regida por dois forçantes principais, um mecânico e outro térmico. Esses processos são responsáveis pela variabilidade dos escoamentos na baixa atmosfera e, é essa variabilidade que caracteriza a turbulência atmosférica. A presença do fenômeno de turbulência, permite distinguir uma camada do restante da atmosfera, esta é chamada de Camada Limite Atmosférica ( CLA). A importância de estudos nessa camada, está relacionada com o fato da turbulência representar um processo efetivo de transporte próximo à superfície. O tratamento adequado dos dados experimentais permite maior contabilidade, tanto qualitativa quanto quantitativas, na interpretação e entendimento desse transporte, ou seja, é necessário para uma adequada caracterização dos fluxos turbulentos. Nesta dissertação são investigadas algumas, das principais técnicas básicas, no tratamento de dados e condicionamento em séries temporais turbulentas. Os dados, experimentalmente coletados e separados em conjuntos de amostras com 27 minutos, são submetidos aos tratamentos com técnicas de média simples, média instantânea através de filtros digitais recursivos e remoção linear de tendência. Obeserva-se as implicações da aplicação destas técnicas, como cada uma delas age nas séries temporais turbulentas de temperatura e velocidade vertical do vento, apresentando e discutindo os resultados dessa aplicação, nas estimativas dos fluxos turbulentos de calor sensível através do método de Covariância dos Vórtices (MCV), e também das densidades espectrais de temperatura e velocidade vertical. Um dos grandes benefícios do estudo feito nessa dissertação, foi identificar que a correção do atraso de fase, que não era levada em consideração nos modelos de filtros digitais anteriores (FDR proposto por McMillen 1988) e, presente no modelo (FFDR Franceschi e Zardi 2003) conduz à estimativas satisfatórias, principalmente para espectros de temperatura turbulenta, que são os mais difíceis de se minimizar os efeitos de não estacionariedade. Ficou claro, observando nos resultados gráficos dos espectros, que a remoção de baixas freqüências nos espectros de temperatura, os deixou com o perfil típico de especros clássicamente esperados.
Polito, Martina. "Mean flow and turbulent exchange characteristics in real urban street canyons: the Lazzaretto case study." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Stevens, Kurt Benedict. "Remote measurement of the atmospheric isoplanatic angle and determination of refractive turbulence profiles by direct inversion of the scintillation amplitude covariance function with Tikhonov regularization." Thesis, Monterey, California. Naval Postgraduate School, 1985. http://hdl.handle.net/10945/21528.
Sundkvist, David. "Space Plasma Dynamics : Instabilities, Coherent Vortices and Covariant Parametrization." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6051.
Cambra, Rémi. "Etude des flux turbulents à l'interface air-mer à partir de données de la plateforme OCARINA." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLV024.
Exchanges of heat and momentum at the air-sea interface play a major role in the formation and the dynamics of water and air masses. In spite of decades of research, we still need to improve our knowledge of these exchanges, and more specifically our knowledge of turbulent fluxes, which are key variables in meteorological and climate models. In these models, sub-grid turbulent processes, thus turbulent fluxes also have to be modeled, which is mostly done with the Monin-Obukhov (1954, MOS hereafter) similarity theory. However, on the one hand, the use of a model implies that coefficients have to be adjusted. On the other hand, the model itself may require improvements. Unfortunately, obtaining flux estimates that have a good accuracy is a challenging effort, because of the intrusive effect of the platform, the limited accuracy the instruments, and because the instruments have their own sampling volume.Our study focuses on the estimation of turbulent fluxes at sea from measurements made with the new OCARINA platform (autonomous trimaran) during two campaigns : STRASSE 2012 and AMOP 2014. We analyze the characteristics of turbulence in the surface boundary layer, we estimate the turbulent fluxes by different methods, and compare the values of fluxes depending on environmental conditions, taking into account the sea state
Cambra, Rémi. "Etude des flux turbulents à l'interface air-mer à partir de données de la plateforme OCARINA." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLV024/document.
Exchanges of heat and momentum at the air-sea interface play a major role in the formation and the dynamics of water and air masses. In spite of decades of research, we still need to improve our knowledge of these exchanges, and more specifically our knowledge of turbulent fluxes, which are key variables in meteorological and climate models. In these models, sub-grid turbulent processes, thus turbulent fluxes also have to be modeled, which is mostly done with the Monin-Obukhov (1954, MOS hereafter) similarity theory. However, on the one hand, the use of a model implies that coefficients have to be adjusted. On the other hand, the model itself may require improvements. Unfortunately, obtaining flux estimates that have a good accuracy is a challenging effort, because of the intrusive effect of the platform, the limited accuracy the instruments, and because the instruments have their own sampling volume.Our study focuses on the estimation of turbulent fluxes at sea from measurements made with the new OCARINA platform (autonomous trimaran) during two campaigns : STRASSE 2012 and AMOP 2014. We analyze the characteristics of turbulence in the surface boundary layer, we estimate the turbulent fluxes by different methods, and compare the values of fluxes depending on environmental conditions, taking into account the sea state
Eshonkulov, Ravshan [Verfasser], and Thilo [Akademischer Betreuer] Streck. "Turbulent exchange of energy, water and carbon between crop canopies and the atmosphere : an evaluation of multi-year, multi-site eddy covariance data / Ravshan Eshonkulov ; Betreuer: Thilo Streck." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2019. http://d-nb.info/1184384584/34.
Connell, R. J. "Unstable equilibrium : modelling waves and turbulence in water flow." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/592.
Le, Thai Hoa. "UNSTEADY BUFFETING FORCES AND GUST RESPONSE OF BRIDGES WITH PROPER ORTHOGONAL DECOMPOSITION APPLICATIONS." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/49126.
The unsteady buffeting forces and the gust response prediction of bridges in the atmospheric turbulent flows is recently attracted more attention due to uncertainties in both experiment and analytical theory. The correction functions such as the aerodynamic admittance function and the spatial coherence function have been supplemented to cope with limitations of the quasi-steady theory and strip one so far. Concretely, so-called single-variate quasi-steady aerodynamic admittance functions as the transfer functions between the wind turbulence and induced buffeting forces, as well as coherence of wind turbulence has been widely applied for the gust response prediction. Recent literatures, however, pointed out that the coherence of force exhibits higher than that of turbulence. These correction functions, in the other words, contain their uncertainties which are required to be more understanding. Proper orthogonal decomposition (POD), known as the Karhunen-Loeve decomposition has been applied popularly in many engineering fields. Main advantage of the POD is that the multi-variate correlated random fields/processes can be decomposed and described in such simplified way as a combination of limited number of orthogonally low-order dominant eigenvectors (or turbulent modes) which is convenient and applicable for order-reduced representation, simulation of the random fields/processes such as the turbulent fields, turbulent-induced force fields and stochastic response prediction as well. The POD and its proper transformations based on either zero-time-lag covariance matrix or cross spectral one of random fields/processes have been branched by either the covariance proper transformation (CPT) in the time domain or the spectral proper transformation (SPT) in the frequency domain. So far, the covariance matrix-based POD and its covariance proper transformation in the time domain has been used almost in the wind engineering topics due to its simplification in computation and interpretation. In this research, the unsteady buffeting forces and the gust response prediction of bridges with emphasis on the POD applications have been discussed. Investigations on the admittance function of turbulent-induced buffeting forces and the coherence one of the surface pressure as well as the spatial distribution and correlation of the unsteady pressure fields around some typically rectangular cylinders in the different unsteady flows have been carried out thanks to physical measurements in the wind tunnel. This research indicated effect of the bluff body flow and the wind-structure interaction on the higher coherence of buffeting forces than the coherence of turbulence, thus this effect should be accounted and undated for recent empirical formulae of the coherence function of the unsteady buffeting forces. Especially, the multi-variate nonlinear aerodynamic admittance function has been proposed in this research, as well as the temporo-spectral structure of the coherence functions of the wind turbulence and the buffeting forces has been firstly here using the wavelet transform-based coherence in order to detect intermittent characteristics and temporal correspondence of these coherence functions. In POD applications, three potential topics in the wind engineering field have been discussed in the research: (i) analysis and identification, modeling of unsteady pressure fields around model sections; (ii) representation and simulation of multi-variate correlated turbulent fields and (iii) stochastic response prediction of structures and bridges. Especially, both POD branches and their proper transformations in the time domain and the frequency one have been used in these applications. It found from these studies that only few low-order orthogonal dominant modes are enough accuracy for representing, modeling, simulating the correlated random fields (turbulence and unsteady surface pressure, unsteady buffeting forces), as well as predicting stochastic response of bridges in the time and frequency domains. The gust response prediction of bridges has been formulated in the time domain at the first time in this research using the covariance matrix-based POD and its covariance proper transformation which is very promising to solve the problems of the nonlinear and unsteady aerodynamics. Furthermore, the physical linkage between these low-order modes and physical causes occurring on physical models has been interpreted in some investigated cases.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13372号
工博第2843号
新制||工||1418(附属図書館)
25528
UT51-2007-Q773
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授 松本 勝, 教授 河井 宏允, 准教授 白土 博通
学位規則第4条第1項該当
Zitouna-Chebbi, Rim. "Observations et caractérisation des échanges d'eau et d'énergie dans le continuum sol-plante-atmosphère en condition de relief collinaire : cas du bassin versant Kamech, Cap Bon, Tunisie." Montpellier SupAgro, 2009. http://www.theses.fr/2009NSAM0027.
GISOLO, DAVIDE. "Water, carbon and energy fluxes on grasslands of Western Alps: methodological issues, experimental data, hydrological modelling and atmospheric boundary layer phenomena." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2957761.
ARTHUR, FRANK. "CARBONDIOXIDE FLUXES FROM A CONTROLLED BOREAL RIVER." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-34353.
2018-07-09
Bureau, Jordan. "Nitrous oxide emissions by agricultural soils : effect of temperature dynamics ; up-scaling measurements from the plot to the landscape." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2003/document.
The greenhouse gas N₂O is mainly emitted by soils. Soil emissions are characterized by considerable spatial and temporal variabilities that make their quantification very difficult. While soil N₂O emissions are studied on an agricultural area in the Central France by the UR SOLS since 2008, we specifically studied in the laboratory the effect of temperature on these emissions and also developed a method for upscaling N₂O emissions from the plot to the landscape scales. Surprisingly, N₂O emissions were observed not to increase with temperature. Q₁₀ values, describing N₂O emission sensitivity to temperature, were observed to change over time. The use of acetylene for inhibiting N₂O reduction has revealed that the biological processes involved in the N₂O production and its consumption respond differently to temperature variations. N2O fluxes measured in the field using several methods covering different scales of the landscape gave consistent results. The mean measured N₂O fluxes were 43 μg N- N₂O m⁻² h⁻¹ for the eddy covariance mast, 37 μg N- N₂O m⁻² h⁻¹ for the fast-box over a similar area, while it was 71 μg N- N₂O m⁻² h⁻¹ by the automatic chambers over a fertilized wheat field. Flux attribution methods were developed to determine both the spatial and temporal variability of the N₂O flux over a 1-km landscape, resulting in original maps of N₂O emissions at the landscape scale. All these results could be further used for developing ecosystem models. Both these ecosystems models and the methodologies hereby proposed for upscaling N₂O emissions will help in soil N₂O emission quantification at large scales, relevant to the inventories and mitigation strategies
Valente, Fabíola Carolina Pereira. "SENSIBILIDADE DO FECHAMENTO DO BALANÇO DE ENERGIA A MÉTODOS DE PROCESSAMENTO DE DADOS DE FLUXOS SUPERFICIAIS SOBRE O BIOMA PAMPA." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/10291.
Neste trabalho realizou-se um procedimento para o processamento dos dados de fluxos medidos por um sistema de covariância dos vórtices turbulentos em um sítio experimental com vegetação representativa do bioma Pampa, em conjunto com medidas de uma estação meteorológica para o período de 20/11/2013 a 07/09/2015. A partir deste conjunto de dados foi realizada uma análise da sazonalidade dos fluxos superficiais de energia e das variáveis meteorológicas. Os resultados mostraram que a aplicação de diferentes métodos de correções para o cálculo dos fluxos de energia produz fluxos com diferentes níveis de qualidade em relação ao fechamento do balanço de energia (FBE). O coeficiente angular (CA) variou até 20% em razão das diferentes combinações de correções aplicadas no processamento dos dados para o cálculo das médias num intervalo de 30 minutos. As opções de correção que mostraram maior sensibilidade foram a constante de tempo e o método de remoção das flutuações turbulentas. Pelo diagnóstico do FBE constatou-se que a mudança de IRGA caminho fechado para caminho aberto melhorou cerca de 12% o FBE, indicando alguma deficiência do IRGA caminho fechado. Também foi verificado que o termo de solo (fluxo e armazenamento) aumentou ~4% o FBE, indicando sua importância para o balanço de energia de pastagem natural. Em virtude do não fechamento do balanço de energia observado na maioria dos estudos, e neste também, foi proposto um novo método de pós-fechamento do balanço de energia, simples, mas criterioso, pois se baseia na classificação de qualidade dos fluxos de energia (H e LE). O objetivo do método é gerar uma série de fluxos corrigidas, importante para a calibração e validação de modelos de superfície. Em relação à partição da energia, a evapotranspiração (ET) foi a componente predominante, com uma Fev = 61% da radiação disponível e β = 51%. Ela variou de ~4 mm d-1 no verão para ~1 mm d-1 no inverno, sendo controlada principalmente pelas forçantes atmosféricas (Rn, DPV, Tar) que determinaram a sua variação sazonal. No inverno, a sua redução foi associada também a baixa atividade fotossintética da vegetação. O albedo médio diurno da pastagem natural do Rio Grande do Sul foi 18%, com pouca variação sazonal. Por fim, fica sugerido aqui a inserção dos procedimentos realizados neste trabalho para o processamento de dados dos sítios experimentais da SULFLUX.
Lu, Po-Sheng, and 盧伯勝. "A study of Turbulent Heat Flux Measurements using Eddy Covariance System." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/71278130979227267912.
國立中興大學
環境工程學系
93
The Eddy Covariance System (EC) is now generally acknowledged that can used routinely for direct measurements of fluxes of momentum, heat, and trace gases in the Atmosphere Surface Layer (ASL). In this study we done an experiment on rice paddy at Wufong (24°01´ N, 120°41´ E) for one month (2005/4/4 to 2005/5/4) with EC. We also made vertical temperature and relative humidity profiles in the daytime during experiment period with the tethersonde. Then we compare with latent heat and sensible heat flux with different method, EC, Bowen Ratio Method, and Integral Businger Equation (IBE) Method. We found that the energy was imbalanced with EC. The energy gaps (1- [(LE +H) /(Rn-G-S) ]) are about 35.2 % during daytime and 28.0 % full-time. Using corrections, including with WPL term (Webb, 1980) and Double / Triple Rotation (Aubinet et al., 2000), for reducing the imbalance. After corrections the energy gaps in the daytime were became 27.4 % after correcting, and 20.1 % full-time. When we collect enough data about the real energy balance between the ecosystem on land and ASL with EC routinely. We can use these data to research, proof and improve the simulations of atmosphere, environment, ecosystem, etc. in the future. According to these data, we can have good applications of climate changes, hydrology circulation, remote sensing technology, etc. And we can increase the accuracy of regional weather forecast in the future.
Yu, Ssu-Ying, and 余思穎. "Turbulent Heat Flux Measurements Using Eddy Covariance System in an Urban Area." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/23401140089023454620.
國立中興大學
環境工程學系所
94
This study is to measure urban surface heat fluxes, especially emphasizing on turbulent heat flux in the atmospheric surface layer using eddy covariance system. The turbulent heat fluxes were measured at 50 m height above ground level on a tower standing on the roof of the Civil and Environmental Building (24°12'' N, 120°67''E) in National Chung-Hsing University, Taichung, Taiwan, for almost four months (2006/2/11~ 2006/6/1). It is found the surface energy budget was imbalanced, the turbulent heat flux was 28.05 % lower than the available surface heat flux during the study period. Corrections are made to reduce the energy gap, including coordinate system rotation, WPL correction, urban albedo correction, advected term correction, and long-wave radiational cooling term correction. After all the above corrections, the energy closure gap is reduced to 4.08 % using two-axis rotation correction, and to 5.68 % using three-axis rotation correction. That is, the result of the two-axis rotational correction is close to the true energy balance. The average urban albedo is determined to be 0.202 estimated within the radius of 1.4 km from the tower site. The peaks of the diurnal CO2 flux were observed at 8 AM and 6 PM, and the peaks of weekly CO2 flux were observed on Monday and Friday. In addition, flux from the east was higher than other wind direction. Therefore, it is suggested that the CO2 flux was mainly from the nearby traffic source, Kuo-Kuang Road.
Falk, Ulrike. "Turbulent Fluxes of CO2, H2O and Energy in the Atmospheric Boundary Layer above Tropical Vegetation investigated by Eddy-Covariance Measurements." Doctoral thesis, 2004. http://hdl.handle.net/11858/00-1735-0000-0006-B323-2.
Markwitz, Christian. "Micrometeorological measurements and numerical simulations of turbulence and evapotranspiration over agroforestry." Thesis, 2021. http://hdl.handle.net/21.11130/00-1735-0000-0005-159F-1.
Mauder, Matthias [Verfasser]. "Quality assurance for eddy covariance measurements of turbulent fluxes and its influence on the energy balance closure problem / presented by Matthias Mauder." 2006. http://d-nb.info/978331168/34.
Falk, Ulrike [Verfasser]. "Turbulent fluxes of CO2, H2O and energy in the atmospheric boundary layer above tropical vegetation investigated by Eddy-covariance measurements / vorgelegt von Ulrike Falk." 2005. http://d-nb.info/974159387/34.
Payette, Fanny. "Échanges d’énergie et d’eau des écosystèmes nordiques dans un contexte de changement climatique." Thèse, 2015. http://hdl.handle.net/1866/16129.
Along the southern margin of permafrost, the boreal forest is underlain by ice-rich and relatively warm permafrost which is converted into permafrost-free peatlands and lake ecosystems due to warmer temperatures and increased thaw rates. At the same time, in the continuous permafrost zone the tree-line of the boreal forest is advancing northward into what is currently Arctic tundra. Both land cover changes in the Taiga Plains ecozone are affecting the magnitude of complex feedback loops, including regional biophysical feedbacks through altered net water vapor and heat exchanges caused by changes in land surface albedo, hydrology and surface roughness. Changes affecting the ecosystems are numerous and it is currently hard to estimate the direction (positive or negative) and magnitude of the resulting biophysical feedbacks. To improve our understanding of implications arising from land cover changes, the energy and water exchanges between surface and atmosphere at three sites in the Northwest Territories, Canada are characterized: Scotty Creek (boreal forest-peatland landscape with sporadic permafrost), Havikpak Creek (boreal forest with continuous permafrost) and Trail Valley Creek (tundra with continuous permafrost). The results of this study are based on measurements of water vapor and heat fluxes obtained with the eddy covariance technique, in addition to supporting ancillary measurements (e.g., net radiation, ground heat flux). For the growing season of 2013, biotic and abiotic controls (ex. light intensity, water availability, etc.) of evapotranspiration at the three sites were identified and analyzed leading to a projected increase in water and energy limitation for Trail Valley Creek. This limitation can be explained by increased energy repartition to sensible heat than to latent heat, following alterations of the land surface as the treeline moves towards the arctic tundra landscape. The relative increase in the sensible heat flux is an indication for an amplified positive feedback of rising air temperature. A comparison of modeled planetary boundary layer heights with Environment Canada atmospheric profiles for the sites leads to the same projection of a positive air temperature feedback. As the treeline moves north, at Trail Valley Creek, an increase of its planetary boundary layer is expected and the opposite phenomenon is expected at Scotty Creek. Albedo, hydrology and surface roughness will be modified, affecting energy partitioning and atmospheric layers which in turn will influence climate. The two methods have led to the same conclusion and highlight the importance of mutual influence between climate and land surface characteristics.
Helbig, Manuel. "Thawing permafrost and land-atmosphere interactions of boreal forest-wetland landscapes in northwestern Canada." Thèse, 2017. http://hdl.handle.net/1866/19533.
Boreal forests store large amounts of organic carbon and are an important component of the regional and global climate systems. Climate and land surface are closely coupled through the land-atmosphere exchange of greenhouse gases, such as CO2 and CH4, and of energy and water vapor. In lowlands of the North American sporadic permafrost region, thaw-induced surface subsidence leads to expansion of permafrost-free wetlands at the expense of boreal forests underlain by permafrost. However, the spatial extent of these land cover changes and their implications for land-atmosphere interactions are unknown. In this study, I analyze eddy covariance flux measurements from an organic-rich boreal forest-wetland landscape in the southern Taiga Plains, NT, Canada. I combine these measurements with flux footprint modeling, satellite remote sensing data, paleoecological records, and downscaled climate projections to characterize how thaw-induced land cover change affects land-atmosphere interactions and climate. In the Taiga Plains ecozone, thaw-induced boreal forest loss currently transforms the composition and structure of the boreal zone in North America and is of equal importance for tree cover dynamics as wildfire disturbance. Forest loss modifies landatmosphere energy fluxes through changes in aerodynamic and ecophysiological land surface properties. On the one hand, increasing albedo decreases total turbulent energy fluxes (i.e., sensible (H) and latent heat (LE) flux), and on the other hand decreasing surface roughness and increasing wetness enhances LE at the expense of H. The resulting maximum summer air temperatures and humidity would be substantially colder (1-2 C) and wetter (2 mmol mol-1) in a hypothetical permafrost-free wetland landscape, as indicated by planetary boundary layer model simulations. In contrast to the regional biophysical climate cooling impact of thaw-induced land cover change, wetland expansion and related increases in landscape CH4 emissions induce a net global biogeochemical climate warming impact. At the current rate of wetland expansion in the southern Taiga Plains of 0.26 % yr-1, landscape CH4 emissions increase by 0.034 g CH4 m-2 yr-1. Typical rates of long-term net CO2 uptake in these landscapes are too small to neutralize the associated climate warming effect until the end of the 21st century. The rapidly thawing boreal forest-wetland landscape still acts as a net CO2 sink taking up 74 g CO2 m-2 yr-1. Wetland expansion does not affect landscape-level net CO2 uptake as changes in gross primary productivity (GPP) and ecosystem respiration (ER) are of similar magnitude. The negligible thaw-induced effects on net CO2 fluxes are contrasted by larger direct climate change impacts of warming air temperatures and reduced incoming shortwave radiation. For a high warming scenario (RCP8.5), increases in modeled ER outpace the increasing GPP significantly. For a moderate warming scenario (RCP4.5), ER and GPP increase are of similar magnitude. Thaw-induced land cover change in the Taiga Plains causes thus biophysical and biogeochemical climate impacts of opposite sign and at contrasting scales of impacts (regional vs. global). In an increasingly warmer climate, thawing permafrost alters how boreal landscapes interact with climate highlighting the need to incorporate thaw-induced land cover changes into global Earth system models.
Bleyl, Matthias. "Experimentelle Bestimmung der Depositionsgeschwindigkeit luftgetragener Partikel mit Hilfe der Eddy-Kovarianzmethode über einem Fichtenaltbestand im Solling." Doctoral thesis, 2001. http://hdl.handle.net/11858/00-1735-0000-0006-B25A-0.