Tropical Pacific moisture variability: Its detection, synoptic structure and consequences in the general circulation

Satellite data analysis tools are developed and implemented for the diagnosis of atmospheric circulation systems over the tropical Pacific Ocean. The tools include statistical multi-variate procedures, a multi-spectral radiative transfer model, and the global spectral forecast model at NMC. Data include in-situ observations; satellite observations from VAS (moisture, infrared and visible) NOAA polar orbiters (including Tiros Operational Satellite System (TOVS) multi-channel sounding data and OLR grids) and scanning multichannel microwave radiometer (SMMR); and European Centre for Medium Weather Forecasts (ECHMWF) analyses. A primary goal is a better understanding of the relation between synoptic structures of the area, particularly tropical plumes, and the general circulation, especially the Hadley circulation. A second goal is the definition of the quantitative structure and behavior of all Pacific tropical synoptic systems. Finally, strategies are examined for extracting new and additional information from existing satellite observations. Although moisture structure is emphasized, thermal patterns are also analyzed. Both horizontal and vertical structures are studied and objective quantitative results are emphasized

Simple Conceptual Models for Tropical Ocean-Atmosphere Interactions on Interannual Timescales

Die Parameter von einfachen konzeptionellen Modellen für die gekoppelte Dynamik von Ozean und Atmosphäre in den Tropen werden an Beobachtungsdaten angepasst. Es wird analysiert wie gut die Modelle, angetrieben von stochastischer Anregung, die das kurzzeitskalige "Wetter-Rauschen" darstellen soll, beobachtete statistische Eigenschaften des Systems reproduzieren. El Niño Southern Oscillation (ENSO) wird gut durch das lineare "recharge oscillator" Modell beschrieben. Im "recharge oscillator" Bild wird die Oszillation durch das Aufladen bzw. Entladen des äquatorialen Wärmeinhaltes während eines La Niña bzw. El Niño Ereignisses bedingt. Das "delayed action oscillator" Modell hingegen, bei dem die Oszillation durch die Propagationszeit äquatorialer Wellen bedingt ist, erweist sich als weniger sinnvolle Approximation. Die beobachtete Schiefe und Kurtosis der Ost-Pazifischen (Niño3) Meeresoberflächentemperatur (SST) Zeitreihe kann durch nichtlineare Kopplung der SST an Anomalien in der Tiefe der Thermokline und durch die Saisonabhängigkeit der Variabilität erklärt werden. Auch die beobachtete Dynamik im Gebiet des äquatorialen Atlantiks lässt sich gut durch das "recharge oscillator" Modell beschreiben. Ein gedämpft schwingender gekoppelter Ozean Dynamik-SST Mode existiert im borealen Frühling und Sommer, während das System in Herbst und Winter überdämpft ist. Im Indischen Ozean kann kein gekoppelter periodischer Mode gefunden werden. Stattdessen ist die SST des Indischen Ozeans gut beschrieben durch einen von ENSO angetriebenen "red-noise" Prozess. Mit Hilfe eines einfachen Modelles für die Wechselwirkung des tropischen Indischen beziehungsweise Atlantischen Ozeans mit ENSO wird gezeigt dass der Indische Ozean dämpfend auf ENSO wirkt und für eine erhöhte ENSO-Frequenz verantwortlich ist. Dennoch kann die Qualität von ENSO-Vorhersagen durch die explizite Berücksichti- gung des Indischen Ozeans kaum verbessert werden, da dieser selbst stark vom ENSO Signal dominiert ist. Die Wechselwirkungen zwischen dem Atlantik und ENSO sind allgemein schwächer als zwischen dem Indischen Ozean und ENSO. Jedoch scheint ein gewisser Einfluss des Atlantiks auf ENSO zu existieren, der die Vorhersagbarkeit von ENSO verbessern könnt

Southern African climate anomalies, summer rainfall and the Angola low

Bibliography p.217-232.Anomalous climatic conditions have contributed to poverty, wlnerability and unemployment, which are major concerns of many southern African governments. Western countries continue to give food aid during drought periods and are looking for new and effective ways of supporting national food security plans (Walker, 1989a). Food security is a very difficult problem in Africa. A number of agricultural national programs have been planned to alleviate the problem but crop yields and living standards continue to deteriorate in many African countries. Unfavorable macro-economic conditions, debt repayments, civil war, political instabilities and mismanagement of resources make the situation more complex. It may be considered that anomalous climatic events (droughts or floods) are important factors, which contribute to acute food shortage. Seasonal rainfall forecasts are an important management tool for donor countries as well as local farmers. The failure to utilize forecasts based on sound scientific knowledge would negate attempts at achieving food security (W orId Meteorological Organization, 1996). It is for this reason that rainfall is an important input parameter in attaining self-sufficiency in food. Rainfall varies in space and time over southern Africa (preston-Whyte and Tyson, 1988; Walker 1989b; Mason, 1992; Rocha, 1992; Makarau, 1995). Further investigations of year-to-year variability of southern African summer rainfall are required in order to understand mechanisms and make accurate seasonal forecasts. Therefore, research work in climate should have high priority in African countries. The need to understand and predict the interannual variations of the atmosphere and the oceans has resulted in formation of global programs like the Tropical Ocean Global Atmosphere (TOGA) and World Climate Research Program (Climate Variability and Predictability, CLIVAR, 1995 and 1998). 2 Determination of the dynamics of droughts and floods continues to be a major problem. Correct prediction of extreme events such as droughts, floods, cold and warm spells involves knowing the mechanisms as well as the local and remote forcings. Several mechanisms have been suggested but more empirical research is required to understand and predict climate variability of southern African on intra-seasonal and inter-annual time scales. This study focuses on inter-annual and intra-seasonal variability of southern African climate with the view of identifying climatic regional and local features that influence summer rainfall and its fluctuations over southern Africa as whole. In order to achieve this, determination and refining of rainfall-SST anomaly relationships is carried out. Teleconnection patterns and coherent structure of interannual variability are revealed. Atmospheric mean meteorological features over Southern Africa and adjacent oceans have direct impact on summer rainfall. Thus determination of mean features using up-graded new and longer data sets provides a basis for investigating inter-annual and intraseasonal variability. This study presents mean characteristics of peak summer (December, January and February) based on 14 years ECMWF gridded data set. This study is motivated by a desire to understand climatic controls of interannual summer rainfall variability over southern African. The intensity of summer rainfall is modulated on synoptic, intra-seasonal, interannual and decadal time scales

Quantification of Acoustic Driving Rates in Gas Turbine Combustion Chambers

[ES] Los sistemas de combustión pobre premezclada cumplen un papel fundamental para la limpia y segura generación de energía eléctrica. Estas turbinas de gas son propensas a sufrir inestabilidades termoacústicas, lo cual implica una retroalimentación del propio sistema entre las fluctuaciones de generación de calor y las oscilaciones acústicas. Una Función de Termino Fuente (FTF), que describa la respuesta linear de la llama en el sistema termoacústicó, permitiría la cuantificación de la conducción de estas inestabilidades en unos puntos predeterminados. Hasta ahora, se han obtenido experimentalmente los campos de temperatura y de calor que servirán como entrada a está FTF. Sin embargo, la dinámica no linar de la llama durante los ciclos de operación inestable limitan la capacidad de este análisis linear. Con el fin de prevenir esto, se realizarán similaciones CFD (Fluent) para obtener el campo de temperatura y calor no afectado por los ciclos de inestabilidad. En primer lugar, se determinará un modelo apropiado de llama, que sea capaz de reproducir fielmente una sitiación de swirl-stabilized flow. Posteriormente, de estos datos extraídos se usarán en un programa de método de elementos finitos (COMSOL) en los puntos de interés. Finalmente, los resultados obtenidosse compararán con los datos experimentales.[EN] Lean pre-mixed combustion systems have assigned an important role towards a clean and reliable electrical power supply. These gas turbines are suspectible to develope thermoacoustic instabilities, which implies a constructive, self-sustained feedback state between unsteady heat release rate fluctuations and acoustic oscillations. A readily available Source Term Function (STF), which describes the linear flame response of the thermoacoustic system, enables the quantification of linear driving rates at pre-defined operation points. Up to now, experimentally obtained temperature and heat release rate distributions serve as the input to this STF. However, non-linear flame dynamics occuring at the so-called limit-cycle of an unstable operation point mitigate their suitability for a linear stability analysis. To circumvent this, steady-state, reactive CFD simulutions (Fluent) yielding the thermoacoustically unaffected temperature and heat release rate distributions ought to be conducted within the frame of this thesis. Firstly, a suitable flame model needs to be identified, which handles the swirl-stabilized flow situation within the combustion chamber most appropriatly. Then, the extracted simulation data is used to determine linear driving rates within a FEM environment (COMSOL) at the operation points of interest. Finally, obtained results need to be compared to previously computed results based on the experimentally obtained distributions.García Villanueva, F. (2018). Quantification of Acoustic Driving Rates in Gas Turbine Combustion Chambers. Universitat Politècnica de València. http://hdl.handle.net/10251/142928TFG

The occurrence and origin of salinity in non-coastal groundwater in the Waikato region

Aims The aims of this project are to describe the occurrence, and determine the origin of non-coastal saline groundwater in the Waikato region. High salinity limits the use of the water for supply and agricultural use. Understanding the origin and distribution of non-coastal salinity will assist with development and management of groundwater resources in the Waikato. Method The occurrence of non-coastal groundwater salinity was investigated by examining driller’s records and regional council groundwater quality information. Selected wells were sampled for water quality analyses and temperatures were profiled where possible. Water quality analyses include halogens such as chloride, fluoride, iodide and bromide. Ratios of these ions are useful to differentiate between geothermal and seawater origins of salinity (Hem, 1992). Other ionic ratio approaches for differentiating sources and influences on salinity such as those developed by Alcala and Emilio (2008) and Sanchez-Martos et al., (2002), may also be applied. Potential sources of salinity include seawater, connate water, geothermal and anthropogenic influences. The hydrogeologic settings of saline occurrence were also investigated, to explore the potential to predict further occurrence. Results Numerous occurrences of non-coastal saline groundwater have been observed in the Waikato region. Where possible, wells with relatively high total dissolved solids (TDS) were selected for further investigation. Several groundwater samples are moderately saline and exceed the TDS drinking water aesthetic guideline of 1,000 g m-3 (Ministry of Health, 2008). Selected ion ratios (predominantly halogens) were used to assist in differentiating between influences on salinity such as seawater and geothermal. Bromide to iodide ratios, in particular, infer a greater geothermal influence on salinity, although other ratios are not definitive. The anomalously elevated salinity observed appears natural but nevertheless has constrained localised groundwater resource development for dairy factory, industrial and prison water supply use. Further work may show some relationship with geology or tectonics, which could assist prediction of inland saline groundwater occurrence

An integrated study of earth resources in the State of California using remote sensing techniques

The author has identified the following significant results. The supply, demand, and impact relationships of California's water resources as exemplified by the Feather River project and other aspects of the California Water Plan are discussed

Evaluating the impact of oceanic/atmospheric teleconnections on historical wildfires in West Virginia (1939--2006)

Oceanic/atmospheric oscillations affect climate in many ways. This study quantitatively examined climate teleconnection patterns and in turn analyzed the influence of climate on wildfire activity within West Virginia from 1939--2006. Identifying the linkages between oscillations and climate variability has the potential to greatly improve seasonal forecasting capabilities. Despite the complexity inherent in local fire regimes, regional fire activity often oscillates in phase with year-to-year climatic variability. This climate-fire connection raises the possibility that historical factors inherent in the local ecosystem are overridden by regional climatic events and trends. A robust statistical analysis that utilized correlation, regression, principle components, and Superposed Epoch Analysis was conducted to explore these relationships. Results suggest that oscillations in the North Atlantic and the Northern Pacific drive West Virginia\u27s climatic variability. This study also suggests that climate influences West Virginia\u27s wildfire activity

Applied Analysis and Synthesis of Complex Systems: Proceedings of the IIASA-Kyoto University Joint Seminar, June 28-29, 2004

This two-day seminar aimed at introducing the new development of the COE by Kyoto University to IIASA and discussing general modeling methodologies for complex systems consisting of many elements, mostly via nonlinear, large-scale interactions. We aimed at clarifying fundamental principles in complex phenomena as well as utilizing and synthesizing the knowledge derived out of them. The 21st Century COE (Center of Excellence) Program is an initiative by the Japanese Ministry of Education, Culture, Science and Technology (MEXT) to support universities establishing discipline-specific international centers for education and research, and to enhance the universities to be the world's apex of excellence with international competitiveness in the specific research areas. Our program of "Research and Education on Complex Functional Mechanical Systems" is successfully selected to be awarded the fund for carrying out new research and education as Centers of Excellence in the field of mechanical engineering in 2003 (five-year project), and is expected to lead Japanese research and education, and endeavor to be the top in the world. The program covers general backgrounds in diverse fields as well as a more in-depth grasp of specific branches such as complex system modeling and analysis of the problems including: nonlinear dynamics, micro-mesoscopic physics, turbulent transport phenomena, atmosphere-ocean systems, robots, human-system interactions, and behaviors of nano-composites and biomaterials. Fundamentals of those complex functional mechanical systems are macroscopic phenomena of complex systems consisting of microscopic elements, mostly via nonlinear, large-scale interactions, which typically present collective behavior such as self-organization, pattern formation, etc. Such phenomena can be observed or created in every aspect of modern technologies. Especially, we are focusing upon; turbulent transport phenomena in climate modeling, dynamical and chaotic behaviors in control systems and human-machine systems, and behaviors of mechanical materials with complex structures. As a partial attainment of this program, IIASA and Kyoto University have exchanged Consortia Agreement at the beginning of the program in 2003, and this seminar was held to introduce the outline of the COE program of Kyoto University to IIASA researchers and to deepen the shared understandings on novel complex system modeling and analysis, including novel climate modeling and carbonic cycle management, through joint academic activities by mechanical engineers and system engineers. In this seminar, we invited a distinguished researcher in Europe as a keynote speaker and our works attained so far in the project were be presented by the core members of the project as well as by the other contributing members who participated in the project. All IIASA research staff and participants of YSSP (Young Scientist Summer Program) were cordially invited to attend this seminar to discuss general modeling methodologies for complex systems