本篇論文主要在探討熱帶線性系統(tropical linear system) A x = b 與雙邊齊次熱帶線性系統(two-sided homogeneous tropical linear system) A x = B y 的求解方法。我們將明確的描述任何熱帶線性系統與雙邊齊次熱帶線性系統的解。 如同古典的論述, 當求解線性系統 A x = b 時, 我們首先會先找到對應的 ``齊次'' 系統 A x = 0 來求解。而對於雙邊齊次熱帶線性系統, 我們將利用勝序列的概念, 將雙邊齊次熱帶線性系統轉化為 k 組古典熱帶線性系統: 含等式系統 S: C[x^t -y^t 1]^t = 0 與不等式系統 T: D[x^t -y^t 1]^t <= 0 。除此之外, 利用相容性條件來減少 k 的數量。 過程中我們處理的 S, T 均為雙變量的系統, 係數分別為 1 與 -1, 對於 S 我們以高斯-喬登消去法(Gauss–Jordan elimination)處理。對於 T 我們將以類似高斯-喬登消去法的方式進行列運算, 因此我們定義次特殊矩陣(sub-special matrix), 而進行的過程我們稱之為次特殊化(sub–specialization)。 最後將以 MATLAB 作為工具來求解出這兩類的熱帶線性系統。 / The thesis mainly discusses the methods of finding solutions of tropical linear systems A x = b and two-sided homogeneous tropical linear systems A x = B y. We are able to give explicit descriptions of all solutions of any tropical linear systems A x = b and two-sided homogeneous tropical linear systems A x = B y. As the classical situations, when solving the linear systems of the form A x = b, we first find the solutions for the corresponding ``homogeneous'' case A x = 0. For two-sided homogeneous tropical linear systems A x = B y, we use the concept of win sequence to convert it into a finite number k of classical linear systems: either a system S: C[x^t -y^t 1]^t = 0 of equations or a system T: D[x^t -y^t 1]^t <= 0 of inequalities. Moreover, we used so called ``compatibility conditions'' to reduce the number of k. The particular feature of both S and T is that each item (equation or inequality) is bivariate. It involves exactly two variables; one variable with coefficient 1, and the other one with -1. S is solved by Gauss-Jordon elimination. We explain how to solve T by a method similar to Gauss-Jordon elimination. To achieve this, we introduce the notion of sub–special matrix. The procedure applied to T is called sub–specialization. Finally, we will use MATLAB to solve tropical linear systems of these two types.

Pourquoi la température de surface dans les Tropiques présente-t-elle un maximum autour de 30°C, quels sont les mécanismes qui contrôlent la stabilité du climat tropical, et quelles peuvent être les spécificités de l'impact d'un changement climatique dans cette région du globe? Un modèle bicolonne simple est utilisé pour confirmer la grande sensibilité du climat tropical aux changements des surfaces relatives occupées par les zones sèches et humides, en particulier dans le cadre d?un réchauffement climatique dû à une augmentation des gaz à effet de serre. L?influence des vents de surface se révèle importante. Les systèmes bicolonnes humide/sèche ont une distribution de taille bimodale dans les observations, avec un mode synoptique et un mode de grande échelle. Cette bimodalité peut être reproduite par un modèle simple, où la dynamique de surface opère la sélection d?échelle. Enfin, les limites de la modélisation idéalisée de la couche limite des alizés sont mises en évidence.

<p>This MSc thesis contributes with new information on how vulnerability to tropical cyclone (TC) induced flooding has evolved at two coastal lowland study sites in the town of Corinto in Nicaragua over a period of 50 years. The research was done through rain station data analyses, semi-structured interviews, and focus group discussions. Analyses of changing poverty, human mobility, housing conditions, and occurrence of flood-related diseases were used as additional indicators supporting the overall vulnerability assessment.</p><p>The recent increase in the North Atlantic TC activity can not be seen in the data from Corinto. The both studied neighborhoods built on dump-sites and mangrove marsh have clearly become less exposed, less sensitive, and more resilient to external stress brought by TCs. These two sites have been developing into different directions since one has reached a more prosper status whereas the other is still rather marginal. The former has been supported by the local government while the latter has been growing in a less regulated way.</p><p>This thesis suggests that there are coastal communities in developing countries, which are able to cope with and adapt to extreme climate events even though this kind of vulnerability has been predicted to increase due to global warming.</p>

Microtextures recorded on quartz sand grain surfaces provide evidence of past environment. Environmental processes, such as transport by glacial ice, create unique microtextures on sand grain surfaces that can be observed under high magnification with a scanning electron microscope. These microtextures and their proportions tend to be unique to environment type, allowing investigators to infer the environmental conditions to which sediments have been exposed, for example to distinguish sediments from fluvial versus mass-wasted environments. Microtextural evidence also allows inferences about the history of sediments of unknown origin. This thesis determines the qualitative and quantitative microtextural fingerprint of glacigenic quartz sand grains deposited by small tropical alpine glaciers in Costa Rica, and compares that fingerprint to the fingerprints of highland Dominican Republic sediments of uncertain genesis, to gauge whether those, individually or grouped, resemble the Costa Rican glacigenic samples. I selected 18 samples (9 each from Costa Rica and the Dominican Republic) and analyzed a minimum of 100 quartz sand grains per sample using a scanning electron microscope. My sample sizes were dictated by the scale of empirical 99% confidence intervals that would allow meaningful comparison of samples. Analysis using literature-recommended numbers of quartz sand grains would entail such large confidence intervals that practically any results would have been indistinguishable. I recorded the presence or absence of 25 microtextures on each grain, and calculated the percentage of each microtexture’s occurrence in the sample. The percentages constituted the sample’s microtextural fingerprint. As a whole, the Costa Rican fingerprints were very similar to each other, and so were the Dominican Republic fingerprints. Further comparison led me to conclude that the Dominican Republic samples are statistically indistinguishable from the Costa Rican glacierized samples. This thesis is part of a larger project establishing protocols for distinguishing glacigenic from non-glacigenic sediments, and testing for glacigenicity of sediments in Costa Rica, the Dominican Republic, and elsewhere. My results can be applied in other studies distinguishing tropical highland glacigenic and non-glacial samples. My contribution will hopefully contribute toward completion of the project’s goals, specifically determining the presence or absence of past glaciers in the Dominican Republic.

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.

Les termites forment un groupe animal important en milieu tropical, où leur richesse spécifique est plus élevée que dans n’importe quel autre écosystème. Ils se nourrissent de matière organique végétale à différent état de décomposition, du bois dur à la matière organique minérale du le sol. Cette diversification du régime alimentaire ne se produit que chez les Termitidae, parfois appelés « termites supérieurs », alors que les autres familles se nourrissent exclusivement de bois ou d’herbe. Les termites humivores sont extrêmement abondants en Amérique du Sud et en Afrique tropicale, mais sont relativement peu étudiés par rapport aux termites xylophages. C’est particulièrement vrai pour le groupe Anoplotermes, qui représente le groupe de termites le moins bien connu. Ce travail vise à faire la lumière sur l’écologie et la diversité de ce groupe strictement humivore, et comprend les sections suivantes : (1) Des échantillonnages standardisés dans sept sites de Guyane Française ont révèle, avec quelques exceptions, que les termites xylophages sont relativement peu spécialisés à un site. Au contraire, les espèces du groupe Anoplotermes, ainsi que les termites humivores en général, sont spécialisés à un type de forêt. Cette spécialisation contribue plus que probablement à la diversification écologique, et donc, à une augmentation de la richesse spécifique des termites humivores. (2) En utilisant les ratios d’isotopiques δ13C et δ15N, nous avons aussi trouvé qu’il existe une spécialisation des espèces le long d’un gradient d’humification chez le groupe Anoplotermes, de l’interface entre le bois pourri et le sol au sol pauvre en matière organique. Donc, au moins deux facteurs favorisent la richesse spécifique du groupe Anoplotermes dans le sol, malgré le manque d’évidence pour une séparation spatiale et temporelle entre les espèces. Cette spécialisation spécifique réduit la compétition interspécifique aux espèces se nourrissant de matière organique au même état de décomposition. (3) Ce mécanisme n’est probablement pas restreint aux espèces du groupe Anoplotermes et le ratio isotopique δ15N varie considérablement entre les termites humivores de manière générale. Les termites humivores comptent des espèces avec des régimes alimentaires différents ne partageant pas toujours les mêmes niches écologiques. Cette diversification du régime alimentaire ne c’est pas produit de manière aléatoire durant l’évolution des termites et les espèces proches tendent à se nourrir du même substrat. (4) Au niveau intraspécifique, il semble que la compétition contraigne la dynamique des colonies. En effet, chez A. banksi, nous avons trouvé que les nids matures sont surdispersés. Les nouveaux nids se trouvent principalement à une certaine distance des nids établis, plus particulièrement dans les trous laissés par les nids morts. Si ce patron est le résultat d’une sélection des sites de nidification, ou plutôt d’une exclusion compétitive reste sujet à discussion, mais met néanmoins en évidence la présence de compétition chez les termites humivores du groupe Anoplotermes. (5) Au vu de la richesse spécifique locale du groupe Anoplotermes, le nombre d’espèces décrites reste remarquablement bas. Après inspection du matériel type, seuls 30 espèces du groupe se sont avérés valides en Amérique du Sud, alors que 80% des espèces que nous avons collectées sont nouvelles pour la science. Cette disproportion entre ce qui est connu et la diversité réelle du groupe, met en évidence le besoin de réaliser des études supplémentaires pour améliorer la connaissance de ce groupe peu connu, le groupe Anoplotermes.

A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp. The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues: - the efficiency of the internal model adjustment, - the potential of the reliable background-error information, as compared to observations, - the impact of a new, space-borne line-of-sight wind measurements, and - the usefulness of multivariate relationships for data assimilation in the tropics. Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations. Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data. In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements. The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.

This MSc thesis contributes with new information on how vulnerability to tropical cyclone (TC) induced flooding has evolved at two coastal lowland study sites in the town of Corinto in Nicaragua over a period of 50 years. The research was done through rain station data analyses, semi-structured interviews, and focus group discussions. Analyses of changing poverty, human mobility, housing conditions, and occurrence of flood-related diseases were used as additional indicators supporting the overall vulnerability assessment. The recent increase in the North Atlantic TC activity can not be seen in the data from Corinto. The both studied neighborhoods built on dump-sites and mangrove marsh have clearly become less exposed, less sensitive, and more resilient to external stress brought by TCs. These two sites have been developing into different directions since one has reached a more prosper status whereas the other is still rather marginal. The former has been supported by the local government while the latter has been growing in a less regulated way. This thesis suggests that there are coastal communities in developing countries, which are able to cope with and adapt to extreme climate events even though this kind of vulnerability has been predicted to increase due to global warming.

Imperial Europes relationship with the tropical world was characterized by intrigue and fascination combined with a fear of difference. This combined intrigue and fear developed over time into a set of stereotypes and myths about the tropics, which by the 19th century had solidified into a powerful discourse historian David Arnold calls tropicality. As Europes interaction with the tropical world increased and its need for tropical resources grew, tropicality became a powerful tool for legitimizing European interference in and exploitation of the tropics. Embedded in the language of science and the promise of progress, it reaffirmed European superiority and its necessary role as the bearer of civilization for the tropical world. <p>Perhaps the most powerful characteristic of tropicality was its inherent ambivalence. The Amazon basin has been a particularly important source for the creation and maintenance of these stereotypes about the tropical world. Reinvented by Alexander von Humboldt as an exotic paradise at the beginning of the nineteenth century, the Amazon basin continued throughout the century to inspire commentary, exploration, and exploitation from abroad. As contact with the Amazon increased, ideas about the tropics began to change. What once was thought of as a pristine paradise became perceived as sinister, diseased, and savage. By the end of the nineteenth century, the tropical world, its people and nature, was considered to be an obstacle to civilization, and its very ability to become civilized began to be questioned.<p>Rubber, an increasingly important and lucrative imperial resource at the end of the nineteenth century, brought people from around the world to the Amazon basin. This resulted in the creation of a contact zone of different peoples, cultures, and idea, which was important for the moulding and maintenance of tropical stereotypes and myths. This was especially the case in the Putumayo, a border zone between modern day Colombia and Peru, where the brutal treatment of workers and the promise of civilization clashed. Through an exploration of travel diaries, newspapers, parliamentary papers, and other works about the tropics and rubber, this thesis argues that the manner in which rubber and its environment were depicted legitimized its control and exploitation from the outside. Couched in the rhetoric of civilization, tropicality helped justify the exploitation of rubber, the environment in which it grew, and the peoples that lived there.

Tropical agroforestry systems are perceived to have the capacity to be resilient to future changes in climate. This study quantifies the response of two tropical agroforestry tree seedlings; Gliricidia sepium (Jacq.) Walp and Cedrela odorata L. to increases in atmospheric concentrations of carbon dioxide (CO2) (800 ppm), temperature (+2°C daytime and +3°C nighttime) and the combined conditions. As well, this study analyzes the microbial community structure and nutrient concentration in response to elevated concentrations of CO2 on tropical silvopastoral soil, conventional pastoral soil and a regenerated forest soil. Both tree species demonstrated very individual responses to the different climate scenerios. While no significant CO2 fertilizer effect was observed in either species the combined treatment demonstrated a significant increase in seedling height for both species. The response of G. sepium to the combined treatment was similar to its response to the temperature treatment which could be a result of achieving the optimal range in temperature for growth. As well, an increase in C:N ratio from G. sepium seedling leaves under the combined treatment indicates the possibility of the nutrient concentration diminishing thereby reducing the role of this species as a provider of high nutrient biomass. The soil microbial community showed very little change in response to elevated concentrations of CO2 and differences in community structure between sites were also negligible. Soil nutrient concentration maintained the best balance over the course of both twelve week incubations for the regenerated forest site followed by the silvopastoral site and lastly the conventional pasture site. The response of soil nutrient concentration to elevated concentrations of CO2 was negligible reflecting the response of the soil microbial community.