Dissertations / Theses on the topic 'Wind speed at the sea surface'
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1
Avenas, Arthur. "Tropical cyclone dynamics revealed by satellite ocean surface wind speeds observations : the key contribution of the near-core surface wind structure." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2024. http://www.theses.fr/2024IMTA0397.
Abstract:
Malgré les avancées dans la prédiction de la trajectoire des cyclones tropicaux et des vitesses de vent dans la région externe, la représentation numérique des vents les plus forts associés aux événements les plus intenses demeure une question ouverte, principalement en raison de la faible taille du cœur du cyclone et de la difficulté à comprendre et résoudre les échanges turbulents entre l’océan et l’atmosphère. Les limitations observationnelles ont longtemps entravé des mesures précises de la surface océanique près de la région centrale dans des conditions de vent extrême, tandis que les satellites géostationnaires aident à caractériser les motifs nuageux mais ne donnent pas d’information directe sur l’interface air-mer. Récemment, le radar à ouverture de synthèse (SAR) a émergé comme une technologie satellitaire prometteuse capable de produire des mesures bidimensionnelles haute résolution des vitesses du vent à la surface de l’océan, grâce à de nouveaux modes d’acquisition et à des développements algorithmiques. Compte tenu de ces nouvelles opportunités d’observation, nous explorons la contribution des caractéristiques structurelles près du cœur, exclusivement discernables à travers des instruments haute résolution, à la dynamique des cyclones. En utilisant un cadre théorique simple et examinant sa cohérence avec les mesures SAR, nous démontrons que les vents en surface près du cœur contrôlent l’évolution de la structure du vent du cyclone. Le cadre développé permet d’illustrer comment les futures mesures des caractéristiques de la couche limite océan-atmosphère pourraient bénéficier du suivi à court et à long terme des cyclones tropicauxDespite advances in predicting the tropical cyclones (TCs) trajectory and outer-core wind speeds, the numerical representation of the strongest winds associated with the most intense events is still an open issue, essentially because of the small radial extent of the TC core and the difficulty in understanding and resolving turbulent air-sea exchanges. Observational limitations have for a long time hindered accurate measurements of the ocean surface near the core region in extreme wind conditions, while geostationary satellites help characterizing the cloud patterns but lack direct information on the air-sea interface. Recently, synthetic aperture radar (SAR) has emerged as a promising satellite technology capable of producing high-resolution two dimensional measurements of the ocean surface wind speeds, thanks to new acquisition modes and algorithmic developments. Given these new observational opportunities, we investigate the contribution of near-core structural features, exclusively discernible through high-resolution instruments, to the TC dynamics. Using a simple theoretical framework and examining its consistency with SAR measurements, we demonstrate that the near-core surface winds modulate the evolution of the TC wind structure. The developed framework allows to illustrate how future measurements of ocean-atmosphere boundary layer characteristics could benefit the short- and long-term monitoring of TCs
2
Komarov, Alexander. "New methods for detecting dynamic and thermodynamic characteristics of sea ice from radar remote sensing." Institute of Electrical and Electronics Engineers, 2014. http://hdl.handle.net/1993/30225.
Abstract:
This dissertation presents new methods for detecting dynamic and thermodynamic characteristics of Arctic sea ice using radar remote sensing.
A new technique for sea ice motion detection from sequential satellite synthetic aperture radar (SAR) images was developed and thoroughly validated. The accuracy of the system is 0.43 km obtained from a comparison between SAR-derived ice motion vectors and in-situ sea ice beacon trajectories. For the first time, we evaluated ice motion tracking results derived from co-polarization (HH) and cross-polarization (HV) channels of RADARSAT-2 ScanSAR imagery and formulated a condition where the HV channel is more reliable than the HH channel for ice motion tracking. Sea ice motion is substantially controlled by surface winds. Two new models for ocean surface wind speed retrieval from C-band SAR data have been developed and validated based on a large body of statistics on buoy observations collocated and coincided with RADARSAT-1 and -2 ScanSAR images. The proposed models without wind direction input demonstrated a better accuracy than conventionally used algorithms. As a combination of the developed methods we designed a wind speed-ice motion product which can be a useful tool for studying sea ice dynamics processes in the marginal ice zone.
To effectively asses the thermodynamic properties of sea ice advanced tools for modeling electromagnetic (EM) wave scattering from rough natural surfaces are required. In this dissertation we present a new analytical formulation for EM wave scattering from rough boundaries interfacing inhomogeneous media based on the first-order approximation of the small perturbation method. Available solutions in the literature represent special cases of our general solution. The developed scattering theory was applied to experimental data collected at three stations (with different snow thicknesses) in the Beaufort Sea from the research icebreaker Amundsen during the Circumpolar Flaw Lead system study. Good agreement between the model and experimental data were observed for all three case studies. Both model and experimental radar backscatter coefficients were considerably higher for thin snow cover (4 cm) compared to the thick snow cover case (16 cm). Our findings suggest that, winter snow thickness retrieval may be possible from radar observations under particular scattering conditions.
3
Zambra, Matteo. "Méthodes IA multimodales dans des contextes d’observation océanographique et de surveillance maritime multi-capteurs hétérogènes." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2024. http://www.theses.fr/2024IMTA0391.
Abstract:
Cette thèse vise à étudier l’utilisation simultanée d’ensembles de données océaniques hétérogènes afin d’améliorer les performances des modèles prédictifs utilisés dans les domaines scientifiques et opérationnels pour la simulation et l’analyse de l’océan et du milieu marin. Deux études de cas distinctes ont été explorées au cours des travaux de thèse. La première étude se concentre sur l’estimation locale de la vitesse du vent à la surface de la mer à partir de mesures du paysage sonore sous-marin et de produits de modèles atmosphériques. La deuxième étude considère l’extension spatiale du problème et l’utilisation d’observations à différentes échelles et résolutions spatiales, depuis les pseudo-observations simulant des images satellites jusqu’aux séries temporelles mesurées par des infrastructures in-situ. Le thème récurrent de ces recherches est la multi-modalité des données introduites dans le modèle. En d’autres termes, dans quelle mesure et comment le modèle prédictif peut bénéficier de l’utilisation de canaux d’information spatio-temporels hétérogènes. L’outil méthodologique privilégié est un système de simulation basé sur l’assimilation variationnelle des données et les concepts d’apprentissage profondThe aim of this thesis is to study the simultaneous use of heterogeneous ocean datasets to improve the performance of predictive models used in scientific and operational fields for the simulation and analysis of the ocean and marine environment. Two distinct case studies were explored in the course of the thesis work. The first study focuses on the local estimation of wind speed at the sea surface from underwater soundscape measurements and atmospheric model products. The second study considers the spatial extension of the problem and the use of observations at different scales and spatial resolutions, from pseudo-observations simulating satellite images to time series measured by in-situ infrastructures. The recurring theme of these investigations is the multi-modality of the data fed into the model. That is, to what extent and how the predictive model can benefit from the use of spatio-temporally heterogeneous information channels. The preferred methodological tool is a simulation system based on variational data assimilation and deep learning concepts
4
Song, Qingtao. "Surface wind response to oceanic fronts /." View online ; access limited to URI, 2006. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3225330.
5
Sun, Yiping. "Sea state monitoring by radar altimeter from a microsatellite." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844478/.
Abstract:
This thesis constitutes a general survey and a study of significant extensions to the usual conventional satellite radar altimetry. Historically radar altimeter has been configured to the measurement of mean sea level. It is well known that other statistics such as Significant Wave Height (SWH) and wind speed are in principle recoverable from the radar echo and these are currently of great interest. It has been the aim in this thesis to optimize such measurements, for a general meteorological application, with less interest shown in absolute measurement of sea level. Current technology makes possible a total Earth survey using a constellation of small satellites, covering the entire Earth sea surface with short revisit time. Such solutions necessitate less cost, lower power, and less precise attitude control than the scientific satellites used hitherto. The purpose of this thesis is to present a novel two mode radar altimeter for sea state monitoring. SWH is still measured by conventional high-resolution mode, which is not sensitive to off-nadir pointing. An additional novel low-resolution mode is proposed for wind speed measurement. By using this mode, wind speed measurement is much more robust to pointing error than by using conventional high-resolution mode. An improved wind speed measurement can be achieved by using a cost effective small satellite. Some considerable time was also spent on incorporating SAR (Synthetic Aperture Radar) into altimetry techniques to improve the signal to noise ratio. For sea state monitoring the improvements are relatively disappointing, although greater improvement are expected for ice sheet monitoring.
6
Park, Jeonghwan. "Investigations of GNSS-R for Ocean Wind, Sea Surface Height, and Land Surface Remote Sensing." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095954817037.
7
Masson, Diane. "Spectral evolution of wind generated surface gravity waves in a dispersed ice field." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/29020.
Abstract:
The Marginal Ice Zone includes wide areas covered by dispersed ice floes in which wave conditions are significantly affected by the ice. When the wind blows from the solid ice pack, towards the open sea, growing waves are scattered by the floes, their spectral characteristics being modified. To further understand this problem, a model for the evolution of wind waves in a sparse field of ice floes was developed. The sea state is described by a two-dimensional discrete spectrum. Time-limited wave growth is obtained by numerical integration of the energy balance equation using the exact nonlinear transfer integral. Wave scattering by a single floe is represented in terms of far-field expressions of the diffracted and forced potentials obtained numerically by the Green's function method. The combined effect of a homogeneous field of floes on the wave spectrum is expressed in terms of the Foldy-Twersky integral equations under the assumption of single scattering. The results show a strong dependence of the spectrum amplitude and directional properties on the ratio of the ice floe diameter to the wavelength. For a certain range of this parameter, the ice cover appears to be very effective in dispersing the energy; the wave spectrum rapidly tends to isotropy, limiting its growth both for the energy content and the peak frequency. It is therefore unlikely that an offshore wind blowing over the Marginal Ice Zone would generate a significant wave field.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
8
Alamaro, Moshe 1948. "Wind wave tank for experimental investigation of momentum and enthalpy transfer from the ocean surface at high wind speed." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/51587.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.Includes bibliographical references (leaves 77-79).
Thermodynamic analysis and numerical modeling of hurricane intensity has shown that its is controlled by the enthalpy transfer from the ocean surface and by drag. Direct measurements of drag, evaporation, and sensible heat transfer are not easily performed on the high seas. Therefore, a wind wave tank has been constructed in which a few aspects of a tropical storm are simulated. The air velocity inside the annular tank is comparable to that of hurricane. However, the three dimensionality of the tank obscures the quantitative comparison between experiments and actual conditions over the surface of the ocean at high wind speeds. The design of the wind wave tank and the initial experiments create a foundation for future and more comprehensive experimental programs. This thesis focuses mainly on the design and engineering of the tank, and on the fluid mechanics of the rotational flow in the tank. It also provides preliminary experimental data on the drag at high wind speeds obtained by using spindown experiments.
by Moshe Alamaro.
S.M.
9
Shinozuka, Yohei. "Sea-Salt Optical Properties Over the Remote Oceans: Their Vertical Profiles and Variations with Wind Speed." Thesis, University of Hawaii at Manoa, 2002. http://hdl.handle.net/10125/6961.
Abstract:
The size distribution and scattering coefficient of the marine aerosol was measured over the Southern Ocean during the First Aerosol Characterization Experiment (ACE 1) and over the tropical Pacific Ocean during the Second Pacific Exploratory Mission in the Tropics (PEMT-B). Thermal analysis of particles at near ambient temperature (40 °C), 150 °C, and 300 °C enabled us to estimate size distributions of the volatile (mostly sulfate and organic) and refractory (mostly sea-salt) modes as well as their contributions to optical depth and cloud condensation nuclei. When averaged spatially and temporally, sea-salt concentrations show dependence upon wind speed over the Southern Ocean up to an altitude of 1200 m. Their median contribution to column optical depth is 0.057, 0.033, and 0.021 at wind speed >10 m/s, 5 -10 m/s, and ≤ 5 m/s, respectively, and the median over all wind speed categories is 0.041. However, on a case-by-case basis, the physical and optical properties show a large variance due to other meteorological conditions. The scales of this variability are also discussed along with examples of processes that contribute to them such as cloud processing and vertical wind speed gradient.ix, 95 leaves
10
Mouton, Dawid Petrus. "Satellite derived sea surface temperature and wind field variability in the Benguela upwelling region." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/6494.
Abstract:
Bibliography : leaves 81-85.Although upwelling was found to be more or less perennial along most of the coast south of 16 °S, seasonal variations were observed for both the SST and the upwelling favorable wind conditions. Inter-annual variability is common, and with these datasets it was possible to highlight periods of anomalous conditions. Results indicated that both the seasonal and inter-annual variability between the northern and southern parts of the Benguela system is quite different, with stronger seasonality observed in the southern Benguela.
11
Neeve, Michael Robert. "Easterly waves in the tropical Pacific." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362223.
12
EL-Nimri, Salem. "AN IMPROVED MICROWAVE RADIATIVE TRANSFER MODEL FOR OCEAN EMISSIVITY AT HURRICANE FORCE SURFACE WIND SPEED." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2523.
Abstract:
An electromagnetic model for predicting the microwave blackbody emission from the ocean surface under the forcing of strong surface winds in hurricanes is being developed. This ocean emissivity model will be incorporated into a larger radiative transfer model used to infer ocean surface wind speed and rain rate in hurricanes from remotely sensed radiometric brightness temperature. The model development is based on measurements obtained with the Stepped Frequency Microwave Radiometer (SFMR), which routinely flys on the National Oceanic and Atmospheric Administration's hurricane hunter aircraft. This thesis presents the methods used in the wind speed model development and validation results for wind speeds up to 70 m/sec. The ocean emissivity model relates changes in measured C-band radiometric brightness temperatures to physical changes in the ocean surface. These surface modifications are the result of the drag of surface winds that roughen the sea surface, produce waves, and create white caps and foam from the breaking waves. SFMR brightness temperature measurements from hurricane flights and independent measurements of surface wind speed are used to define empirical relationships between microwave brightness temperature and surface wind speed. The wind speed model employs statistical regression techniques to develop a physics-based ocean emissivity model dependent on geophysical parameters, such as wind speed and sea surface temperature, and observational parameters, such as electromagnetic frequency, electromagnetic polarization, and incidence angle.M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
13
Ronglei, Hu, Yang Dongkai, Zhang Qishan, and Zhang Yiqiang. "DESIGN AND REALIZATION OF DELAY MAPPING RECEIVER BASED ON GPS FOR SEA SURFACE WIND MEASUREMENT." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/605046.
Abstract:
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, NevadaThe Delay Mapping Receiver (DMR) is used for receiving and processing the reflected GPS signal to get the information of sea surface wind by recording and matching the data with the theoretical model. The hardware architecture and software design are described in detail in this paper. The test results at near sea of Tianjin of China are provided, which prove that the design of DMR is successful and the collected data are useful for the sea surface wind measurement.
14
Seymour, Sian. "Impact of Wind Driven Variability on Sea Surface Temperature and Ocean Colour in False Bay." Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31235.
Abstract:
False Bay is the largest true bay in South Africa and is an important area for conservation, the local fishing industry and marine based recreational activities. A large amount of studies, both recent and historical, have been carried out on the biology of the bay, but studies on the physics of the bay are very few in comparison. In this study high resolution satellite imagery is used to investigate wind variability and its impact on sea surface temperature (SST) and chlorophyll concentration (Chl-a) variability within False Bay and the Cape Peninsula region. High resolution (1 km) coastal winds derived from the Sentinel-1 satellite Synthetic Aperture Radar (SAR) show that winds are strongly influenced by topography under the predominantly south-easterly wind regime. The Hottentots Holland mountain range and Cape Peninsula mountain range create wind shadows as well as areas of increased wind speed within False Bay and west of the Cape Peninsula. Our observations also show that global atmospheric models, such as ECMWF, are not able to capture the spatial variability in the wind fields driven by the orography. Analyses of the SST and ocean colour imagery show that wind shadows are generally associated with warmer surface waters and higher Chl-a. In contrast, regions of enhanced wind speeds show colder surface waters and decreased chlorophyll concentration. Our results suggest that spatial variation in the horizontal wind fields have direct and significant impact on the water properties within False Bay. This study highlights the need for high resolution wind observations and simulations to force regional oceanic models of False Bay and the Cape Peninsula region.
15
Zamo, Michaël. "Statistical Post-processing of Deterministic and Ensemble Wind Speed Forecasts on a Grid." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLA029/document.
Abstract:
Les erreurs des modèles de prévision numérique du temps (PNT) peuvent être réduites par des méthodes de post-traitement (dites d'adaptation statistique ou AS) construisant une relation statistique entre les observations et les prévisions. L'objectif de cette thèse est de construire des AS de prévisions de vent pour la France sur la grille de plusieurs modèles de PNT, pour les applications opérationnelles de Météo-France en traitant deux problèmes principaux. Construire des AS sur la grille de modèles de PNT, soit plusieurs milliers de points de grille sur la France, demande de développer des méthodes rapides pour un traitement en conditions opérationnelles. Deuxièmement, les modifications fréquentes des modèles de PNT nécessitent de mettre à jour les AS, mais l'apprentissage des AS requiert un modèle de PNT inchangé sur plusieurs années, ce qui n'est pas possible dans la majorité des cas.Une nouvelle analyse du vent moyen à 10 m a été construite sur la grille du modèle local de haute résolution (2,5 km) de Météo-France, AROME. Cette analyse se compose de deux termes: une spline fonction de la prévision la plus récente d'AROME plus une correction par une spline fonction des coordonnées du point considéré. La nouvelle analyse obtient de meilleurs scores que l'analyse existante, et présente des structures spatio-temporelles réalistes. Cette nouvelle analyse, disponible au pas horaire sur 4 ans, sert ensuite d'observation en points de grille pour construire des AS.Des AS de vent sur la France ont été construites pour ARPEGE, le modèle global de Météo-France. Un banc d'essai comparatif désigne les forêts aléatoires comme meilleure méthode. Cette AS requiert un long temps de chargement en mémoire de l'information nécessaire pour effectuer une prévision. Ce temps de chargement est divisé par 10 en entraînant les AS sur des points de grille contigü et en les élaguant au maximum. Cette optimisation ne déteriore pas les performances de prévision. Cette approche d'AS par blocs est en cours de mise en opérationnel.Une étude préalable de l'estimation du « continuous ranked probability score » (CRPS) conduit à des recommandations pour son estimation et généralise des résultats théoriques existants. Ensuite, 6 AS de 4 modèles d'ensemble de PNT de la base TIGGE sont combinées avec les modèles bruts selon plusieurs méthodes statistiques. La meilleure combinaison s'appuie sur la théorie de la prévision avec avis d'experts, qui assure de bonnes performances par rapport à une prévision de référence. Elle ajuste rapidement les poids de la combinaison, un avantage lors du changement de performance des prévisions combinées. Cette étude a soulevé des contradictions entre deux critères de choix de la meilleure méthode de combinaison : la minimisation du CRPS et la platitude des histogrammes de rang selon les tests de Jolliffe-Primo. Il est proposé de choisir un modèle en imposant d'abord la platitude des histogrammes des rangsErrors of numerical weather prediction (NWP) models can be reduced thanks to post-processing methods (model output statistics, MOS) that build a statistical relationship between the observations and associated forecasts. The objective of the present thesis is to build MOS for windspeed forecasts over France on the grid of several NWP models, to be applied on operations at Météo-France, while addressing the two main issues. First, building MOS on the grid of some NWP model, with thousands of grid points over France, requires to develop methods fast enough for operational delays. Second, requent updates of NWP models require updating MOS, but training MOS requires an NWP model unchanged for years, which is usually not possible.A new windspeed analysis for the 10 m windspeed has been built over the grid of Météo-France's local area, high resolution (2,5km) NWP model, AROME. The new analysis is the sum of two terms: a spline with AROME most recent forecast as input plus a correction with a spline with the location coordinates as input. The new analysis outperforms the existing analysis, while displaying realistic spatio-temporal patterns. This new analysis, now available at an hourly rate over 4, is used as a gridded observation to build MOS in the remaining of this thesis.MOS for windspeed over France have been built for ARPEGE, Météo-France's global NWP model. A test-bed designs random forests as the most efficient MOS. The loading times is reduced by a factor 10 by training random forests over block of nearby grid points and pruning them as much as possible. This time optimisation goes without reducing the forecast performances. This block MOS approach is currently being made operational.A preliminary study about the estimation of the continuous ranked probability score (CRPS) leads to recommendations to efficiently estimate it and to generalizations of existing theoretical results. Then 4 ensemble NWP models from the TIGGE database are post-processed with 6 methods and combined with the corresponding raw ensembles thanks to several statistical methods. The best combination method is based on the theory of prediction with expert advice, which ensures good forecast performances relatively to some reference forecast. This method quickly adapts its combination weighs, which constitutes an asset in case of performances changes of the combined forecasts. This part of the work highlighted contradictions between two criteria to select the best combination methods: the minimization of the CRPS and the flatness of the rank histogram according to the Jolliffe-Primo tests. It is proposed to choose a model by first imposing the flatness of the rank histogram
16
Da, Silva Meyre Pereira. "On the role of wind driven ocean dynamics in tropical Atlantic variability." Texas A&M University, 2003. http://hdl.handle.net/1969.1/3867.
Abstract:
The response of the tropical Atlantic Ocean to wind stress forcing on
seasonal and interannual time scales is examined using an ocean data
assimilation product from the Geophysical Fluid Dynamics Laboratory (GFDL),
and an ocean general circulation model which incorporates a three dimensional
flux correction technique to correct biases of the mean state of the ocean.
On a seasonal time scale, we investigated the impact of the annual
migration of the ITCZ on the exchange pathways of the northern tropical Atlantic.
The results indicate that seasonal variation of the zonal slope of the thermal
ridge along the boundary between the north equatorial countercurrent and north
equatorial current in response to changes in the ITCZ controls, to a large extent,
the amount of water participating in the equatorial circulation. These changes
can be explained in terms of a simple dynamical model where local Ekman
pumping dominates thermocline variation in the western part of the basin, and
Rossby wave adjustment comes into play in the eastern basin.
On an interannual time scale, we examined the upper heat budget of the
equatorial Atlantic in order to identify the key mechanisms by which wind-driven
ocean dynamics control SST variability during the onset and peak phases of the
Atlantic zonal mode. It is found that, in contrast with Pacific ENSO, both
Bjerknes and Ekman feedbacks act together to force the zonal mode, although
their relative importance and dominance depend on season and location.
17
Khattak, Sharafatullah. "Identification of sunglint areas in polar orbiting satellites imagery and determination of near-surface wind speed from sunglint radiance." Thesis, University of Dundee, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340906.
18
Lamont, Tarron. "Comparative analysis of the seasonal sea surface temperature & wind stress in the four major eastern boundary current systems." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6486.
Abstract:
Includes bibliographical references.The coastal upwelling regions along northwest Africa (the Canary system), southwest Africa (the Benguela system), North America (the California system), and South America (the Peru-Chile system) were studied and compared on a seasonal timescale. A 17 -year NOAA Pathfinder Sea Surface Temperature (SST) dataset with a spatial resolution of 9km was used to describe the large-scale temporal and spatial variability of upwelling within the four regions. An upwelling index (OSST) was derived in order to add to the patterns of upwelling variability described from the sea surface temperature. The upwelling index was also used to describe the similarities and differences between the four upwelling regions. A 10-year ERS wind stress dataset with a spatial resolution of 10 x 10 was used to derive the offshore Ekman Transport in each of the regions. The offshore Ekman Transport was used to supplement the description of SST's in each system. Principal Component Analysis was used to investigate the variance structure of the anomalies of the sea surface temperature in each of the four regions. The results of the principal component analysis are interpreted in terms of the underlying physical dynamics.
19
Hesser, William A. "Global evaluation of special sensor microwave/imager ocean surface wind speed retrieval algorithms for the period September 1991 - April 1992." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA303138.
20
Fang, Chin-Lung. "Predictability of Japan/East Sea (JES) system to uncertain initial/lateral boundary conditions and surface winds." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FFang.pdf.
Abstract:
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 2003.Thesis advisor(s): Peter C. Chu, Steve Haeger. Includes bibliographical references (p. 73-77). Also available online.
21
Galea, Anthony. "Large-Eddy Simulation for wind and tidally driven sea circulation in coastal semi-closed areas." Doctoral thesis, Università degli studi di Trieste, 2014. http://hdl.handle.net/10077/10160.
Abstract:
2012/2013A novel high-resolution, eddy-resolving numerical model (LES-COAST) is used to investigate currents, mixing and water renewal in Barcelona harbour and Taranto bay. These environmental sites are of particular importance due to the interplay between touristic and commercial activities, requiring detailed and high-definition studies of water quality within the harbour. We use Large Eddy Simulation (LES) which directly resolves the anisotropic and energetic large scales of motion and parametrizes the small, dissipative, ones. Small-scale turbulence is modelled by the Anisotropic Smagorinsky Model (ASM) which is employed in presence of large cell anisotropy. The complexity of the harbour is modelled using a combination of curvilinear, structured, non-staggered grid and the Immersed Boundary Method (IBM). Both computation grids and harbour structures are purposely constructed for these applications by appropriate programs. Boundary conditions for wind forcing at the free surface and currents at the inlets of the port are obtained from in-situ measurements (for the case of Barcelona harbour) or by nesting this numerical model into a coastal model (Taranto bay). In this dissertation thesis an important modification to LES-COAST is implemented and is proposed as a prototype scheme, namely the possibility to consider the effect of surface waves in coastal semi-closed areas. Particularly, a linear formulation of the free surface boundary condition is considered, which would be able to reproduce the presence of seiches and tides on the dynamics of the area under investigation. The methodology is validated against analytical solution for a stationary oscillating surface wave in a simple computational grid.In both harbours considered, first- and second-order statistics, such as the mean velocity field, turbulent kinetic energy, and horizontal and vertical eddy viscosities are calculated and their spatial distribution is assessed. Water residence time is also considered for the two coastal semi-closed areas examined. Finally, the LES solution is validated against available field data.The study shows the presence of sub-surface elongated rolling structures (with a time scale of a few hours), contributing to the vertical water mixing. The time-averaged velocity field reveals intense upwelling and downwelling zones along the walls of the harbours. The analysis of second-order statistics in these harbours shows strong inhomogeneity of turbulent kinetic energy and horizontal and vertical eddy viscosities in the horizontal plane, with larger values in the regions characterized by stronger currents. The water renewal within the port is quantified for particular sub-domain regions, showing that the complexity of the harbour is such that certain inner basins of Barcelona harbour have a water renewal of over five days, including its yacht marina area, and over seven days for Taranto bay. For the Barcelona simulation, the LES solution compares favourably with available current-meter data; it is also compared with a RANS solution obtained in literature for the same site under the same forcing conditions, the comparison demonstrating a large sensitivity of properties to model resolution and frictional parametrization.
XXVI Ciclo
1986
22
Du, Preez Chrisna Barbara. "A mesoscale investigation of the sea breeze in the Stellenbosch winegrowing district." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-02092007-093317.
23
Barrowes, Benjamin E. "YSCAT Backscatter Distributions." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/67.
Abstract:
YSCAT is a unique ultrawideband microwave scatterometer developed to investigate the sea surface under a variety of environmental and radar parameters. The YSCAT94 experiment consisted of a six month deployment on the WAVES research tower operated by the Canada Center for inland Waters (CCIW). Over 3500 hours of data were collected at 2Γ 3.05Γ 5.3Γ 10.02Γ and 14 GHz and at a variety of wind speeds, relative azimuth angles, and incidence angle.
A low wind speed "rolloff" of the normalized radar cross section (σ°) in YSCAT94 data is found and quantified. The rolloff wind speedΓ γΓ is estimated through regression estimation analysis using an Epanechnikov kernel. For YSCAT94 data, the rolloff is most noticeable at mid-range incidence angles with γ values ranging from 3 to 6 m/s.
In order to characterized YSCAT94 backscatter distributions, a second order polynomial in log space is developed as a model for the probability of the radar cross sectionΓρ(σ°). Following Gotwols and ThompsonΓρ(σ°) is found to adhere to a log-normal distribution for horizontal polarization and a generalized log-normal distribution for vertical polarization. If ρ(α|σ°) is assumed to be Rayleigh distributed, the instantaneous amplitude distribution ρ(α) is found to be the integral of a Rayleigh/generalized log-normal distribution.
A robust algorithm is developed to fit this probability density function to YSCAT94 backscatter distributions. The mean and variance of the generalized log-normal distribution are derived to facilitate this algorithm. Over 2700 distinct data cases sorted according to five different frequencies, horizontal and vertical polarizations, upwind and downwind, eight different incidence angles Γ1-10 m/s wind speeds, and 0.1-0.38 mean wave slope are considered. Definite trends are recognizable in the fitted parameters a1Γ a2Γ and C of the Rayleigh/generalized log-normal distribution when sorted according to wind speed and mean wave slope.
At mid-range incidence angles, the Rayleigh/generalized log-normal distribution is found to adequately characterize both low and high amplitude portions of YSCAT94 backscatter distributions. However, at higher incidence angels (50°and 60°) the more general Weibull/generalized log-normal distributions is found to better characterized the low amplitude portion of the backscatter distributions.
24
Maliniemi, V. (Ville). "Observations of solar wind related climate effects in the Northern Hemisphere winter." Doctoral thesis, University of Oulu, 2016. http://urn.fi/urn:isbn:9789526213545.
Abstract:
Abstract
This thesis studies the long-term relation between the solar wind driven energetic particle forcing into the atmosphere and the tropospheric circulation in the Northern Hemisphere winter. The work covers the period of more than one hundred years since the turn of the 20th century to present. The thesis makes a statistical analysis of satellite measurements of precipitating energetic electrons, sunspot number data and geomagnetic activity, and compares them with temperature and pressure measurements made at the Earth's surface.
Recent results, both observational and from chemistry climate models, have indicated significant effects in the Earth's middle atmosphere due to the energetic electrons precipitating from the magnetosphere. These effects include the formation of reactive hydrogen and nitrogen oxides in the high latitude mesosphere and the depletion of ozone caused by them. Ozone is a radiatively active and important gas, which affects the thermal structure and dynamics of the middle atmosphere. Accordingly, the depletion of ozone can intensify the large scale stratospheric circulation pattern called the polar vortex. Winter weather conditions on the surface have been shown to be dependent on the polar vortex strength.
This thesis shows that there is a significant relation between the average fluxes of medium energy (ten to hundred keVs) precipitating electrons and surface temperatures in parts of the Northern Hemisphere in winter time. Temperatures are positively correlated with electron fluxes in North Eurasia and negatively correlated in Greenland during the period 1980-2010 which is covered by direct satellite observations of precipitating particles. This difference is especially notable when major sudden stratospheric warmings and the quasi-biennial oscillation (QBO), which both are known to affect the polar vortex strength, are taken into account. When extended to the late 19th century, the analysis shows that a similar temperature pattern is predominated during the declining phase of the sunspot cycle. The high speed solar wind streams and energetic particle precipitation typically maximize also at the declining phase of the solar cycle. This specific temperature pattern is related to the variability of the northern annular mode (NAM), which is the most significant circulation pattern in the Northern Hemisphere winter. Before the space era, geomagnetic activity measured by ground observations can be used as a proxy for energetic particle precipitation. Earlier studies have found a significant positive correlation between geomagnetic activity and NAM since the 1960s. We find that, when the QBO measured at 30 hPa height is in the easterly phase, a positive correlation is extended to the beginning of 1900s. We also show that high geomagnetic activity causes a stronger effect in the Northern Hemisphere winter than high sunspot activity, especially in the Atlantic and Eurasia.
A comprehensive knowledge of the Earth's climate system and all its drivers is crucial for the future projection of climate. Solar variability effects have been estimated to produce only a small factor to the global climate change. However, there is increasing evidence, including the results presented in this thesis, that the different forms of solar variability can have a substantial effect to regional and seasonal climate variability. With this new evidence, the solar wind related particle effects in the atmosphere are now gaining increasing attention. These effects will soon be included in the next coupled model inter comparison project (CMIP6) as an additional solar related climate effect. This emphasizes the relevance of this thesis.
25
Anders, Ivonne [Verfasser], and Hans Von [Akademischer Betreuer] Storch. "Regional climate modelling : the Eastern European ”summer drying” problem and the representation of coastal surface wind speed in a multi model ensemble / Ivonne Anders. Betreuer: Hans von Storch." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1081768142/34.
26
Anders, Ivonne Verfasser], and Hans von [Akademischer Betreuer] [Storch. "Regional climate modelling : the Eastern European ”summer drying” problem and the representation of coastal surface wind speed in a multi model ensemble / Ivonne Anders. Betreuer: Hans von Storch." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://nbn-resolving.de/urn:nbn:de:gbv:18-77016.
27
Hung, Meng-Pai. "THE EVALUATION OF THE EAST GREENLAND SEA ODDEN ICE FEATURE USING THE COMMUNITY CLIMATE SYSTEM MODEL3.0 (CCSM3.0)." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250265410.
28
Samad-Suhaeb, Mujahid. "Aerodynamics of battle damaged finite aspect ratio wings." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/10736.
Abstract:
When an aircraft is aerodynamically or structurally damaged in battle, it may not able to complete the mission and the damage may cause its loss. The subject of aircraft battle survivability is one of critical concern to many disciplines, whether military or civil. This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and experimental investigations into the effects of simulated battle damage on the low-speed aerodynamics of a fmite aspect ratio wing. Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations, Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions, and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The prediction of Cp's achieved good agreement upstream and near the damage hole, but showed poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at upstream and higher at downstream. The results showed relatively good agreement for the case of transitional and strong jet incidences but slightly poor for weak jet incidences. From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main characteristics of the weak-jet were illustrated clearly. The increments were relatively small. Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing tests and for all damage locations, there was always a flow structure asymmetry. This was believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet' that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional results but at the weak-jet incidence of 4°. For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the damage effects at low incidence, and over-predicting at high incidences. This suggested therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.
29
Sasaki, Dalton Kei. "Mudanças dos Modos de Variabilidade do Atlântico Tropical no Século XX." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/21/21135/tde-10032015-151036/.
Abstract:
Resultados da reanálise SODA v2.2.6 (Carton, Giese, 2008) e da Renálise do Século 20 v2 (Compo, et al., 2011) foram analisados para verificar alterações dos modos de variabilidade da TSM (o modo do Gradiente Meridional de Temperatura (GMT) e o Modo Zonal) no Atlântico Tropical (de 1929 a 2008) através de funções empíricas ortogonais (EOF) e funções empíricas ortogonais associadas (jEOF). A evolução do padrão espacial do modo do GMT se inicia com a configuração de dipolo de temperatura, com eixo central em ≈ 5ºN evoluindo para o GMT com variabilidade concentrada no Atlântico Tropical Norte. O Modo Zonal apresenta inicialmente variabilidade associada à região equatorial (entre 5ºS e 5ºN) e à costa sudoeste africana, que evolui para um gradiente meridional de TSM, centrado em ≈ 5ºN. Sua variabilidade concentra-se exclusivamente no Atlântico Tropical Sul. A variabilidade equatorial se degenera ao longo do período, devido ao aumento, gerado pelo vento, da profundidade das isopicnais na termoclina. No equador o acoplamento entre o oceano e a atmosfera ocorre nos períodos de T = 30 meses e T ≈ 34 meses, com o vento antecedendo a temperatura em 1 e 2 meses, respectivamente. O Modo Zonal apresenta acoplamento com o vento durante a segunda metade das análises. O período associado é de T ≈ 34 meses, com o vento antecedendo a temperatura em cerca de 1 mês. O modo do GMT está associado aos ventos no Atlântico Tropical Norte e Atlântico Tropical Sul. Os períodos de acoplamento são de T = 96 e T = 60 meses, com o vento antecedendo a TSM em 3 e ≈ 2 meses respectivamente.The results of SODA v2.2.6 reanalysis (Carton, Giese, 2008) and 20th Century Reanalysis v2 Project (Compo, et al., 2011) were analyzed in order to verify changes of the SST modes (the Meridional Temperature Gradient mode (GMT) and the Zonal Mode) in the Tropical Atlantic (1929 to 2008) using Empirical Orthogonal Functions (EOF) and joint Empirical Orthogonal Functions (jEOF). The spatial distribution of GMT starts initially as a temperature dipole centred at ≈ 5ºN. It evolves into a meridional gradient with variability concentrated at the Tropical North Atlantic. The zonal mode variability is initially associated with the equatorial region (between 5ºS and 5ºN) and with the northwestern african coast. It evolves into a merdional gradient with central axis located at 5ºN. Its variability is concentrated exclusively in the Tropical South Atlantic. The equatorial variability degenerates throughout the period, due to the inhibition of the isopicnal uplift by the wind. At the equator, the coupling occurs in periods of T = 30 months and T ≈ 34 months, with the wind preceding the TSM by 1 and 2 months, respectively. The zonal mode presents coupling with the wind only during the second half of the analysis. The periods are of T = 34 months, with wind preciding TSM by about 1 month. GMT mode is associated to the winds of both Tropical North Atlantic and Tropical South Atlantic. Coupling periods are of T = 96 and T = 60 months, with the wind preceding TSM in 3 and ≈ 2 months respectively.
30
Astudillo, Orlando. "Rôle des interactions océan-atmosphère-continent sur la dynamique de la couche limite marine dans la région d'upwelling du Chili central." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30360.
Abstract:
Les systèmes de courant de bords est (EBUS) sont les régions océaniques des latitudes tropicales à moyennes le long des côtes ouest des continents. Ils abritent des écosystèmes marins très productifs en raison de la circulation atmosphérique de surface dirigée vers l'équateur qui font remonter des eaux profondes froides (upwelling) enrichies en éléments nutritifs à l'origine de la vie marine le longde la côte. Si les processus océaniques fondamentaux de l'upwelling côtier sont bien connus (transport et pompage d'Ekman), la modélisation océanique des EBUS reste problématique en raison des difficultés pour prendre en compte de manière réaliste des phénomènes à fine échelle spatiale dans la zone de transition entre le littoral et l'océan du large. Dans cette thèse, nous nous sommes concentrés sur le système d'upwelling dit de Humboldt (côtes du Pérou et du Chili) et sur l'influence des caractéristiques méso-échelles des vents près de la côte, en particulier la décroissance vers la cotes du vent (appelé "drop-off") qui détermine l'importance relative des processus d'Ekman, et donc, la structure spatiale de la zone d'upwelling. Une approche combinée basée sur l'analyse de données satellitaires et sur la modélisation régionale, océanique et atmosphérique, est utilisée pour étudier la sensibilité de la circulation océanique le long de la côte Chili central aux caractéristiques du drop-off. Dans un premier temps, la circulation atmosphérique de surface moyenne à saisonnière le long du littoral du Pérou et du Chili est documentée pour la première fois à partir des données altimétriques de quatre missions satellites (ENVISAT, JASON1, JASON2 et SARAL). L'analyse révèle l'existence d'une réduction marquée de la vitesse du vent le long de la côte, bien que le taux de réduction varie en fonction de la latitude. Malgré la répétitivité relativement faible des satellites, nous montrons que les données altimétriques permettent néanmoins d'échantillonner le cycle saisonnier du drop-off. L'estimation de l'upwelling côtier à partir de ces données suggère que le pompage d'Ekman tend en moyenne à dominer par rapport au transport d'Ekman le long de la côte péruvienne, alors que le long de la côte chilienne, le transport d'Ekman est le processus dominant. Dans un second temps, un modèle atmosphérique régional (WRF) à différentes résolutions horizontales (36 km, 12 km et 4 km) dans une configuration imbriquée zoomée sur la région centrale du Chili a été développé afin de produire des champs atmosphériques présentant des caractéristiques différentes du drop-off. Les solutions du modèle atmosphérique sont d'abord évaluées par rapport aux observations, indiquant un plus grand réalisme près de la côte que les réanalyses atmosphériques. Le rotationnel du vent cyclonique simulé le long de la côte associé au drop-off présente des échelles transversales comprises entre 8 et 45 km avec une variabilité latitudinale significative, en accord avec les vents altimétriques. Lorsque la résolution du modèle est augmentée, le drop-off est généralement d'autant plus confiné à la côte et le modèle indique une saisonnalité marquée avec un maximum d'intensité au printemps-automne. La contribution relative de la divergence côtière et du pompage d'Ekman présente une modulation latitudinale liée aux détails de l'orographie et de la ligne de côteEastern Boundary Upwelling Systems (EBUS) are the tropical to mid-latitudes oceanic regions along the west coast of the continents. They host very productive marine ecosystems owing to the mean equatorward low-level atmospheric circulation that uplifts cool subsurface nutrient-enriched waters that trigger marine life along the coast. While the fundamental oceanic processes behind such process are well known (i.e. Ekman transport and pumping), the oceanic modeling of the EBUS has remained problematic owing to difficulties in accounting realistically for phenomena at fine spatial scales in the transition zone between the littoral and the off-shore ocean. In this thesis we have focused on the Peru-Chile Upwelling System (so-called Humboldt system) and on the influence of the cross-shore mesoscale features of the winds near the coast, particularly the shoreward wind drop-off, which determinate the relative importance of the Ekman processes, and thus, the spatial and temporal structure of the upwelling. A combined approach based on satellite data analysis and regional modeling, both oceanic and atmospheric, is used to investigate the sensitivity of the oceanic circulation along the coast of central Chile to the characteristics of the wind drop-off. As a first step, the mean to seasonal near-shore surface atmospheric circulation along the coast of Peru and Chile is documented for the first time based on the altimeter data from four satellite missions (ENVISAT, JASON1, JASON2 and SARAL). The analysis reveals the existence of a marked shoreward reduction in the wind speed all along the coast, although the reduction rate is latitudinally dependent. Despite the relatively weak repetitivity of the satellites, it is shown that the altimetric data are able to sample the seasonal cycle of the wind drop-off at some locations. The estimate of coastal upwelling from these data suggests that Ekman pumping tends on average to dominate with respect to Ekman transport over the Peruvian coast, whereas over the central-Chilean coast, the Ekman transport is the dominant process. In a second step, a regional atmospheric model (WRF) at different horizontal resolutions (36km, 12km and 4km) in a nested configuration zoomed over the central-Chile region was developed in order to produce atmospheric fields with different characteristics of the wind-stress curl (drop-off) along the coast. The atmospheric model solutions are first evaluated against the satellite observations, showing a much larger realism than atmospheric Reanalyses near the coast. In particular, the simulated cyclonic wind curl along the coast related to the wind drop-off exhibit length scales between 8 and 45 km with a significant latitudinal variability, which is in agreement with the altimetric winds. The higher model resolution, the more confined to the coast the wind drop-off, with the latter evidencing a marked seasonality with a maximum intensity in spring-fall and minimum in winter. The relative contribution of the coastal divergence and Ekman pumping exhibits a latitudinal modulation linked to details in the orography and coastlines
31
Villafañe, Roca Laura. "Experimental Aerothermal Performance of Turbofan Bypass Flow Heat Exchangers." Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/34774.
Abstract:
The path to future aero-engines with more efficient engine architectures requires advanced
thermal management technologies to handle the demand of refrigeration and lubrication. Oil
systems, holding a double function as lubricant and coolant circuits, require supplemental
cooling sources to the conventional fuel based cooling systems as the current oil thermal
capacity becomes saturated with future engine developments. The present research focuses on
air/oil coolers, which geometrical characteristics and location are designed to minimize
aerodynamic effects while maximizing the thermal exchange. The heat exchangers composed
of parallel fins are integrated at the inner wall of the secondary duct of a turbofan. The
analysis of the interaction between the three-dimensional high velocity bypass flow and the
heat exchangers is essential to evaluate and optimize the aero-thermodynamic performances,
and to provide data for engine modeling. The objectives of this research are the development
of engine testing methods alternative to flight testing, and the characterization of the
aerothermal behavior of different finned heat exchanger configurations.
A new blow-down wind tunnel test facility was specifically designed to replicate the engine
bypass flow in the region of the splitter. The annular sector type test section consists on a
complex 3D geometry, as a result of three dimensional numerical flow simulations. The flow
evolves over the splitter duplicated at real scale, guided by helicoidally shaped lateral walls.
The development of measurement techniques for the present application involved the design
of instrumentation, testing procedures and data reduction methods. Detailed studies were
focused on multi-hole and fine wire thermocouple probes.
Two types of test campaigns were performed dedicated to: flow measurements along the test
section for different test configurations, i.e. in the absence of heat exchangers and in the
presence of different heat exchanger geometries, and heat transfer measurements on the heat
exchanger. As a result contours of flow velocity, angular distributions, total and static
pressures, temperatures and turbulence intensities, at different bypass duct axial positions, as
well as wall pressures along the test section, were obtained. The analysis of the flow
development along the test section allowed the understanding of the different flow behaviors
for each test configuration. Comparison of flow variables at each measurement plane
permitted quantifying and contrasting the different flow disturbances. Detailed analyses of the
flow downstream of the heat exchangers were assessed to characterize the flow in the fins¿
wake region. The aerodynamic performance of each heat exchanger configuration was
evaluated in terms of non dimensional pressure losses. Fins convective heat transfer
characteristics were derived from the infrared fin surface temperature measurements through a
new methodology based on inverse heat transfer methods coupled with conductive heat flux
models. The experimental characterization permitted to evaluate the cooling capacity of the
investigated type of heat exchangers for the design operational conditions. Finally, the
thermal efficiency of the heat exchanger at different points of the flight envelope during a
typical commercial mission was estimated by extrapolating the convective properties of the
flow to flight conditions.Villafañe Roca, L. (2013). Experimental Aerothermal Performance of Turbofan Bypass Flow Heat Exchangers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34774
TESIS
32
Xia, Yuan. "Sea-surface temperature and sea-surface wind-speed retrievals from spaceborne radiometer measurements." 2001. https://scholarworks.umass.edu/dissertations/AAI3012195.
Abstract:
This dissertation presents the development of a prelaunch sea-surface temperature (SST) retrieval algorithm for the Advanced Microwave Scanning Radiometer (AMSR), and validation of the GSW and GSWP wind-speed algorithms for the Special Sensor Microwave Imager/Sounder (SSMIS). Prelaunch SST retrieval algorithm work includes the selection of buoys, the simulation of the AMSR measured brightness temperatures, the D-Matrix approach to the prelaunch SST algorithm, and the validation of D-matrix approach with SSM/I, TMI, AVHRR measurements. The validation of the wind speed algorithms (GSW and GSWP) for SSMIS includes building matchup sets and residual analysis. In addition, a nonlinear wind-speed algorithm based on Artificial Neural Network (ANN) improves wind-speed retrieval at normal wind speeds, as well as in high winds. The effect of wind direction on the wind-speed retrieval is also studied.
33
Ko, Chih Shing, and 柯志軒. "Effects of wave height,wind speed on sea-surface wind stress." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/38993908586679021907.
Abstract:
碩士國立中山大學
海洋資源學系
82
A stable research platform,located at a coastal site off Taichung Harbor with an average water depth of about 8m,has been instrumented with a sonic anemometer with three-component wind speed, and air temperature sensors,and with three wind monitors at three different heights above the sea surface. A telemetry system has been used to transmit data to an inland receiving station.The wind turbulence data for the period between April 30 and November 19,1993 from this platform have been analyzed by the eddy correlation method to obtain wind stress and heat fluxes at various wind speeds. Data from near south-bound direction with longer fetch were used separately by the present study because it is unobstructed from the land and marine structures.Our results indicate that the wind stress is proportional to the square of wind speed.At lower winds,the drag coefficient,Cd,decteases with increaseing wind speed.At higher winds,it seems that Cd increases or remains unchanged with the wind speed.Cd was found to be generally larger for growing waves(smaller Co/u*)than for steady or decaying waves( larger Co/u*).The value of Cd with longer fetch from near north direction is generally higher than that with shorter fetch from near west direction.On the other hand,heat fluxes increase with the increasing wind speed and wave height.
34
Compton, Andrea Jean. "The correlation of sea surface temperatures, sea level pressure and vertical wind shear with ten tropical cyclones between 1981-2010." Thesis, 2013. http://hdl.handle.net/1805/3669.
35
Li, Hsien-Ming, and 李先明. "Seasonal and Interannual Variability of Satellite-derived Sea Surface Temperature and Sea Surface Wind in the Yellow Sea." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/96665837872071639510.
Abstract:
碩士國立臺灣海洋大學
海洋科學系
93
The purpose of this thesis is using satellite-derived sea surface temperature (SST) and sea surface wind data to investigate their variations in the Yellow Sea during the period from 1996 to 2003. The variation of the SST in the Yellow Sea is mainly seasonal. It is much lower and spatially non-homogeneous in winter than that in summer. A significant SST feature in winter is the Yellow Sea warm current, which is from the southwest side of Che-Ju Island. In summer, SST is warm except a cold water band distributed on the western Yellow Sea near the Korea Peninsula. The sea surface wind variation in the Yellow Sea is also seasonal. It is northerly in winter and southerly in summer. Wind speed in winter is higher than that in summer. In interannual scale, the highest SST anomaly temperature happened in June 1997, it seems to happen later than the onset of the El Niño. The wind speed shows lower value in 1997 and 1998 winter than the other years. The first SST empirical orthogonal function (EOF) mode, accounting for 98.2％ of total variance, indicates again that low SST in winter and high SST in summer. The first spatial-demeaned EOF of SST, accounting for 78.3％ in total variance, reveals mainly the sea surface circulation in winter. The first temporal-demeaned EOF of SST, containing 95.2％ of total variance, shows clear SST variations in summer and winter, especially at coastal and deep water. Complex EOF mode 1 of SST reveals the SST patterns in the Yellow Sea mainly from southeast to northwest in summer. The first SST anomaly EOF, containing 43.7％ of total variance, reveals a positive temperature anomaly during the 1997-1998 El Niño period. The wind speed and its anomaly EOFs show the variation of the monsoon patterns, which maybe affected by the influence of external factors (such as El Niño or atmospheric circulation). From the wind stress curl computation, it is suggested that the wind-induced anticyclonic sea surface circulation seems to be the reason to push the warm current into the Yellow Sea from south during the strong northerly monsoon season.
36
Huang, Shen-Cheng, and 黃舜成. "Determining sea surface wind from satellite microwave radiometric measurements." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/73671883564683839979.
37
Chen, Ya-Wen, and 陳雅雯. "Satellite observations of the sea surface wind and temperature in the East China Sea." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75401767154404773761.
Abstract:
碩士國立臺灣海洋大學
海洋科學系
92
Abstract In this study, the ERS-2 and QuikSCAT scatterometer and NOAA/AVHRR data from 1997 to 2001 are used to discuss the seasonal and inter-annual variations of the sea surface wind and sea surface temperature (SST) fields in the East China Sea (ECS). It is found that the sea surface wind and SST in the East China Sea are mainly annual. There is always a stronger northeastly in winter and weaker southly in summer. The results of the anomalous wind analysis indicate that the wind was behind the Southern Oscillation Index (SOI) about 4 months. Meanwhile, there is a weaker wind in 1997 fall/winter and 1998 spring. The SST in the ECS is colder in winter and warmer in summer and its spatial distribution is highly related to the bottom topography, especially in winter. The El Niño event in 1997 seems to cause a positive SST anomaly during December 1997 to November 1998. Keywords: East China Sea, satellite sea surface wind, satellite sea surface temperature, El Niño event.
38
Yang, Hong-Yuan, and 楊弘源. "Satellite observations of chlorophyll-a concentration and sea surface wind in the South China Sea." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/49267887105157509242.
Abstract:
碩士國立臺灣海洋大學
海洋科學系
93
The purpose of this thesis is using Orbview-2/Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and European Remote Sensing Satellite (ERS) -1/2 and Quick Scatterometer (QuikSCAT)/SeaWinds satellite data to discuss the chlorophyll-a (Chl-a) concentration and sea surface wind fields in the South China Sea (SCS). Chl-a in the SCS is nearly annual. Mode 1 results of the Chl-a empirical orthogonal function (EOF) analysis indicate that the higher Chl-a is mainly along the coastal areas, while the much lower Chl-a is in the offshore areas. EOF mode 2 results show a summer-winter oscillation of the Chl-a distribution in the SCS. The Chl-a anomaly data can be used to see its interannual variation. Through the comparison between EOF mode 2 results of the Chl-a anomaly and Niño 3.4 index, we find that Chl-a in the SCS is highly related to the ENSO events. The wind speed in the SCS is also annual. There is a northeasterly monsoon in winter, and a southwesterly monsoon in summer. Wind speed EOF mode 1 results indicate that the northeasterly monsoon is much stronger than southwesterly monsoon. The EOF mode 2 results of the sea surface wind indicate that the zonal area near 15。N can be a boundary to separate the wind pattern into two parts during fall, the wind in the north part is northeasterly and southwesterly in the south. Comparing Chl-a EOF mode 2 and wind speed EOF mode 1 results, we can find that Chl-a in the SCS is mainly influenced by the monsoon wind. Wind-induced coastal upwelling makes the Chl-a increase along the western SCS in summer and the eastern SCS in winter.
39
Anderson, SallyRose. "Wind River Range Snowpack Reconstruction Using Dendochronology and Sea Surface Temperatures." 2010. http://trace.tennessee.edu/utk_gradthes/771.
Abstract:
Multiple reconstructions of April 1st snow water equivalent (SWE) are generated for the Wind River Range (WRR), located in west-central Wyoming, to determine the most accurate predictors. Predictors included climate signal data (Southern Oscillation Index), traditional predictors (tree-ring chronologies), and non-spatially biased Pacific Ocean sea surface temperatures (SSTs). Incorporation of Pacific Ocean SSTs as a whole provides a more comprehensive representation of oceanic-atmospheric variability. Rotated principal component analysis (PCA) was used to regionalize April 1st snowpack data (1961 – 1999) from snow telemetry stations (SNOTEL stations). Tree-ring chronologies that were stable across the period of overlapping records (1961 – 1999) and that were positively correlated with regional snowpack at 99% confidence levels or higher were retained. Singular value decomposition (SVD) was performed on Pacific Ocean SSTs and regional snowpack data to identify coupled regions of climate (SSTs) and hydrology (SWE). Stepwise regressions were performed across the calibration period to identify the best predictor combinations. When data from the instrumental based SST regions identified by SVD were included in the pool of predictors, an increase in reconstruction skill was observed. Further regressions were performed using tree based and coral based SST data. Reconstruction equations were obtained from these regressions and regional April 1st snowpack was reconstructed for the WRR for all three types of SST data. A higher degree of snowpack variance is explained by reconstructions utilizing tree based, coral based, and instrumental based data for the Pacific Ocean SST region identified by SVD than is possible utilizing only tree-ring and SOI data, indicating that non-spatially biased SSTs are excellent predictors for snowpack reconstruction in the WRR.
40
Chen-YuChen and 陳振宇. "Effects of Wind Speed and Temperatures on the Radar Sea Return at X-band." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52112847718926680609.
Abstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
101
Since Mattie and Harris (1978) used different frequency bands of radar for observing the waves, the X-Band microwave radar has been applied for observing the sea waves. In recent years, the X-band microwave radar applications are becoming more common on the ocean observing. We can analyze the characteristics of the sea waves indirectly by the radar sea return signals. Sea and Meteorology parameters such as air temperature, water temperature, wind speed, etc. affect the sea surface roughness and the X-Band microwave radar observations. This study explores the X-band microwave radar sea return with weather stations and buoys data collected at Xingda Harbour sea area. The data analysis is divided into two parts: The first part compares the relationship between wind speed and radar sea return in the same air temperature. The other part compares the relationship between radar sea return and the difference between air and sea temperatures in the same wind speed. In addition, there are unusual radar sea return signals on the radar image nearby the place of the wastewater emissions. And the study explores the X-band microwave radar sea return with water temperature, the difference between air and sea temperatures, and the surface tension by using measured water temperature, the surface tension of CRC Handbook of Chemistry and Physics and the air temperature of weather stations.
41
Yu, Yunyue. "Sea surface temperature, geostrophic current and surface heat advection in the western tropical Pacific." 1996. http://catalog.hathitrust.org/api/volumes/oclc/37356621.html.
42
"Impact of Grid Resolution on Atmospheric Model Simulation of Offshore Surface Wind Speed." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15026.
Abstract:
abstract: This study considered the impact of grid resolution on wind velocity simulated by the Weather Research and Forecasting (WRF) model. The period simulated spanned November 2009 through January 2010, for which, multi-resolution nested domains were examined. Basic analysis was performed utilizing the data assimilation tools of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) to determine the ideal location to examine during the simulation was the Pacific Northwest portion of the United States, specifically the border between California and Oregon. The simulated mutli-resolution nested domains in this region indicated an increase in apparent wind speed as the resolution for the domain was increased. These findings were confirmed by statistical analysis which identified a positive bias for wind speed with respect to increased resolution as well as a correlation coefficient indicating the existence of a positive change in wind speed with increased resolution. An analysis of temperature change was performed in order to test the validity of the findings of the WRF simulation model. The statistical analysis performed on temperature change throughout the increased grid resolution did not indicate any change in temperature. In fact the correlation coefficient values between the domains were found in the 0.90 range, indicating the non-sensitivity of temperature across the increased resolutions. These results validate the findings of the WRF simulation: increased wind velocity can be observed at higher grid resolution. The study then considered the difference between wind velocity observed over the entire domains and the wind velocity observed solely over offshore locations. Wind velocity was observed to be significantly higher (an increase of 68.4%) in the offshore locations. The findings of this study suggest simulation tools should be utilized to examine domains at a higher resolution in order to identify potential locations for wind farms. The results go further to suggest the ideal location for these potential wind farms will be at offshore locations.Dissertation/Thesis
M.S. Mechanical Engineering 2012
43
Lai, You-Cheng, and 賴佑晟. "Investigation of the Sea Surface Wind and Flux for the Development of Tropical Cyclone." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/jhkw3r.
Abstract:
碩士國立中央大學
大氣科學學系
105
The genesis and intensification of tropical cyclone(TC) are usually occurring in the ocean where is lacking those traditional observations like surface in-situ data or radiosounde for upper atmosphere. Therefore, satellite data plays a critical role in the purpose of simulation and/or forecast of TC in these stages, and the further investigation of the evolution and intensity intensification. According to the earlier studies, part of the energy for TC intensification is associated with the planetary boundary processes, which might be through the air-sea interaction like latent heat flux and sensible heat flux. Furthermore, sea surface wind could be an important role between sea and air when gradient is presented. Therefore, sea surface wind data from the Advanced Scatterometer (ASCAT) which is aboard on ESA Metop-A satellite are used to address this issue in this study through the data assimilation technique and the use of regional Weather Research and Forecasting (WRF) model. The main focus is placed on the investigation of the impacts from sea surface wind, sensible heat flux, and latent heat flux for the TC forecast. The discussion on the relative importance of those above fluxes during the TC intensification stage. This study is divided into two parts: data assimilation experiment and sensitivity experiment. Typhoon Nuri (2008) in the northwestern Pacific Ocean is chosen to elaborate those fluxes and roles as described. In first part of experiment, the best forecast skill is from the use of ASCAT and traditional observation data sets, by examination of the TC’s intensity and track forecasts. This is due to the ASCAT data can improve the structure of surface wind in the initial time. In second part, the sensitivity experiment, we find the higher sea surface temperature might increase the temperature gradient between the sea and the air. It leads an increased air-sea flux and a stronger TC in the later forecast hours. It is also found that the sea surface wind plays an important role in the sea-air flux, that is, if there is a large temperature or humidity gradient between sea and air, the energy conversion efficiency will be poor due to the weak sea surface wind speed. Thus, TC obtains less energy from the ocean and the intensity will not be intensified. Cross-analysis of the above simulations, we conclude that the larger fluxes in the early stage of the Typhoon Nuri, the more energy can be obtained from the ocean and the intensity will become stronger.
44
Lai, Fei, and 賴飛. "A Study on Wind-Induced Sea Surface Roughness in the Eest of Hengchun Peninsula." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8aqwhw.
Abstract:
碩士國立臺灣海洋大學
海洋環境資訊系
105
Is this study, the relationship between wind-induced sea surface roughness (SSR) and sea surface temperature (SST) in the west of Hengchun Peninsula is investigated using satellite Synthetic Aperture Radar (SAR) and thermal infrared data. The normalized radar cross section (NRCS) derived from SAR data can represent the wind speed, because wind speed is related to SSR. After comparing with these two data, a negative linear relationship is found between NRCS and SST. Higher NRCS, that is, higher SSR has lower SST. The gradient of the linear relationship is then compared with the difference between air temperature and SST. The result shows a very good correlation at the condition of SST is higher than air temperature. This indicates that the higher temperature difference between air and sea can increase the release of heat from the ocean to the atmosphere.
45
Sušelj, Kay [Verfasser]. "Modelling of the near-surface wind speed : boundary layer and climate aspects / von Kay Sušelj." 2009. http://d-nb.info/996766146/34.
46
Mahajan, Salil. "Free and forced tropical variability: role of the wind-evaporation-sea surface temperature (WES) feedback." Thesis, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3107.
Abstract:
The Wind-Evaporation-Sea Surface Temperature (WES) feedback is believedto play an important role in the tropics, where climate variability is governed byatmosphere-ocean coupled interactions. This dissertation reports on studies to distinctlyisolate the WES feedback mechanism over tropical oceans using a modiedversion of an NCAR-Community Climate Model (CCM3) thermodynamically coupledto a slab ocean model, where the WES feedback is deliberately suppressed inthe bulk aerodynamic formulation for surface heat uxes. A comparison of coupledintegrations using the modified WES-off CCM3 to those carried out using the standardCCM3 conclusively identifies the role of the WES feedback in enhancing theinter-annual variability over deep tropical oceans and the westward propagation ofthe equatorial annual cycle. An important role for near surface humidity in tropicalclimate variability in enhancing inter-annual variability and in sustaining the equatorialannual cycle is also suggested. Statistical analyses over the tropical Atlanticreveal that the free coupled meridional mode of the Atlantic Ocean is amplified in thepresence of the WES feedback. Similar analyses of coupled model integrations, whenforced with an articial El Ni~no Southern Oscillation (ENSO)-like SST cycle in tropicalPacific, reveal that only in the presence of the WES feedback is the meridionalmode the preferred mode of response of the Atlantic to ENSO forcings. It is also foundthat WES feedback reinforces the tendency of the ITCZ to stay north of the equator over the Atlantic during El-Nino events. Comparative studies between Last GlacialMaximum (LGM) equivalent imposed northern hemispheric sea-ice experiments withthe WES-off model and the standard model indicate a dominant role for the WESfeedback in the southward shift of the ITCZ as indicated by paleo-climate records.However, it is found not to be the sole thermodynamic mechanism responsible for thepropagation of high latitude cold SST anomalies to the tropics, suggesting significantroles for other mechanisms in the tropical response to high latitude changes.
47
Hsieh, Yu-Chi, and 謝玉琪. "Satellite Observation of Sea Surface Temperature, Chlorophyll-a Concentration and Wind of the Luzon Strait." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/22295153248369165711.
Abstract:
碩士國立臺灣海洋大學
海洋環境資訊學系
95
Abstract The purpose of this thesis is to discuss the variation of the Aqua satellite Moderate-resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) and chlorophyll-a (Chl-a) data in the Luzon Strait during the period between 2002 and 2006 and the related Quick Scatterometer (QuikSCAT) satellite SeaWinds data from 1999 to 2006. From SST satellite images, it is found that the Kuroshio intrusion into the Luzon Strait is much clearer in winter than in summer. Meanwhile, the stronger sea surface wind can push the Kuroshio more westerward during wintertime. From Chl-a satellite images, the intrusion of the low Chl-a Kuroshio is much more obvious than that in SST images, it always displays as a clockwise loop to intrude the Luzon Strait. Comparing SST with Chl-a data, we can see a negative correlation between them in the study area, especially in the west of the Kuroshio. In interannual scale, the summer 2004 and summer 2006 are the coldest and warmest summer, respectively. Besides, the wind speed shows a clear decreasing trend during 1999~2002 no matter in summer or winter.
48
Chen, Chien-Ming, and 陳建銘. "Wind and Diurnal Effect on the Accuracy of Sea Surface Temperature Measurements from Geostationary Satellite." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/28692945954743841040.
49
LEE, WEN HORNG, and 李文鴻. "Estimation of wind stress and heat flux over the sea surface by the inertial-dissiption method." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/57902233521198500058.
Abstract:
碩士國立中山大學
海洋資源學系
83
Measurements of instantaneous wind speed and air temperature at nearly 10m above the mean sea surface as well as the sea- surface temperature were made during three cruises of R/V Ocean Researcher Ⅲ over southern Taiwna Strait. Inertial- dissipation method was used to estimate the wind stree and sensible heat flux. From spectra of wind speed and temperature it is clearly shown that the inertial subrange typically exists in high frequency band (0.5Hz-10Hz) and the -5/3 power law applies in this region. The downwind spectral value φu was found to be 3/4 times φv, the cross wind spectral value,i.e. the conditon of isotropy was satisfied. The wind spectral increases with the third power of the wind speed, and spectral value of temperature correlates well with U10n(Ts-θa), where U10n is the wind speed at 10m height under neutral condition, Ts and θa are the sea-surface and air potential temperatures respectively. Effects of atmospheric stability on momentum fluxes are especially significant under conditions of low wind and large air-sea temperature difference. Our results indicate that wind stress increase with the 7/3 power of wind speed. Neutral drag coefficent CD10n increses with increasing wind speed. Sensible heat flux has a linear relationship with U10(Ts- θa). Heat flux coefficent CT10n remains constant with varying atmospheric stability parameters under unstable stratifictions. These results are consistent wind previous studies. Finally, a time-series comparison was also made between wind stress derived from dissipation and bulk methods. Our results show that dissipation estimates of the wind stress agree well with those from bulk method and the differences are generally less than 20 percents.
50
Cheng, Wan-Chen, and 鄭婉貞. "Impacts of two-type El Niño/La Niña on Sea Surface Wind over the Tropical Pacific." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77nsg2.
Abstract:
碩士國立臺灣海洋大學
海洋環境資訊學系
101
In this study, different index values are used to select months of El Niño, El Niño Modoki, La Niña and La Niña Modoki, respectively. This case selection method (also called Niño Matrix Method) is applied to NCEP/NCAR reanalysis data to investigate the impacts of two-type El Niño/La Niña on sea surface wind over the tropical Pacific druing years of 1950~2011. The results show that the impacts of both types of El Niño/La Niña on sea surface wind over the tropical Pacific are different. Westerly anomalies of wind speed appear in the equatorial Pacific during both types of El Niño, while the values of El Niño Modoki are stronger than those of El Niño. The location with maximum value of westerly anomalies of El Niño Modoki is far west of that of El Niño. In the western Pacific near land, easterly anomalies of El Niño Modoki are also larger than those of El Niño. As for La Niña, easterly anomalies of wind speed appeare in the equatorial Pacific during both types of La Niña. The values of La Niña Modoki are stronger than those of La Niña. The range of easterly anomalies of La Niña Modoki is smaller than that of La Niña. During the period of La Niña Modoki, westerly anomalies also appear in the eastern Pacific.