Exact treatment of time-dependent axisymmetric gravitation

This paper extends an earlier treatment of time-dependent gravitational fields that are axially symmetric and nonrotating. From a consideration of the canonical solution of the Einstein vacuum field equations previously obtained as an axial expansion, a new method has been found that now provides the exact solution, whenever a certain generative key function x(t, z) is known

Análisis climático de la precipitación anual e interanual en la cuenca media del río Grande de San Ramón, Costa Rica

This project investigates three sectors located in the central basin of the río Grande San Ramón in Costa Rica. In spite of their proximity to each other, these stations show considerable variation, both temporal and spatial in intra- and interannual precipitation. This variation is attributed to regional atmospheric circulation patterns in the equatorial Pacific, producing strong precipitation during some years, and declines in others. There is a greater probability of lower annual precipitation during El Niño years and higher probabilities of large totals during La Niña years. The warm phase, El Niño, of the El Niño-Southern Oscillation phenomenon (ENSO) is more pronounced in Naranjo, which is located on the lower slope of the Central Volcanic Mountain range. The influence of regional/hemispherical cannot be regarded homogeneous in mountainous areas where local conditions may prevail.Se investigan tres sectores ubicados en la Cuenca media del río Grande de San Ramón en Costa Rica que a pesar de encontrarse muy cerca unos de otros, éstos muestran variaciones espacio temporales en la precipitación anual e interanual. Dicha variación se atribuye a patrones de circulación atmosféricos que influyen anualmente, produciendo fuertes precipitaciones durante unos años, mientras que en otros, se da más bien una disminución. Pareciera que existe una mayor probabilidad que ocurran promedios bajos de precipitación anual durante los años El Niño y promedios altos durante los años La Niña. De esta forma, la fase cálida es más marcada en aquellos lugares de topografía plana, en valles, que tienen una mayor influencia marítima y de corrientes de viento, como son los casos de Palmares y San Ramón, no así el caso de Naranjo que se ubica en las faldas de la Sección de la Cordillera Volcánica Central. Por lo tanto, se manifiestan variaciones en distancias cortas, o sea no se muestra un comportamiento homogéneo aún en regiones pequeñas

ENSO related fluctiations of rainfall and their consequences for some rodent populations in North Central Chile

El Niño Southern Oscillation (ENSO) is evaluated for its effects on rainfall in semi-arid Chile. Daily precipitation records are used to identify biologically important rainfall events. Events are evaluated by crossing theory to derive estimates of the probability distributions of the number of events, dates of their annual first and last occurrence, and length of the critically important biologically wet season for three phases of ENSO. Biologically important rainfall events are most frequent during warm phases and least frequent during cold phases. Cold phases produce the earliest onset of the wet season, while neutral phases delay it. The importance of variation in rainfall and its association with rodent populations is discussed extensively

Changes in extreme rainfall events in South Africa

Extreme rainfall events can have severe impacts on society, so possible long-term changes in the intensity of extreme events are of concern. Testing for long-term changes in the intensity of extreme events is complicated by data inhomogeneities resulting from site and instrumentation changes. Using rainfall data from stations in South Africa that have not involved site relocations, but which have not been tested for inhomogeneities resulting from changes in instrumentation, a method of testing for changes in the intensity of extreme events is adopted. Significant increases in the intensity of extreme rainfall events between 1931–1960 and 1961–1990 are identified over about 70% of the country. The intensity of the 10-year high rainfall events has increased by over 10% over large areas of the country, except in parts of the north-east, north-west and in the winter rainfall region of the south-west. Percentage increases in the intensity of high rainfall events are largest for the most extreme events. While some inhomogeneities remain in the data used, the observed changes in the intensity of extreme rainfall events over South Africa are thought to be at least partly real

Variaciones en la precipitación y su posible impacto en la producción agrícola de Liberia, Costa Rica

Se investigan las variaciones en la precipitación, su relación con las fases del evento océano atmosférico El Niño Oscilación del Sur, mejor conocido como ENOS y su posible impacto en la producción agrícola en Liberia, Costa Rica. Se calculan el número de días lluviosos y la distribución de las precipitaciones que se espera que ocurra en cada ciclo de cultivo. Se hacen estimaciones durante un año determinado de la cantidad de lluvia, las fechas de siembra y la duración que podría tomar determinado cultivo en su crecimiento estacional. Igualmente, se puede determinar la cantidad de agua que necesita un cultivo para crecer normalmente. Se determinó que los agricultores podrían experimentar una mayor cantidad de precipitación durante la fase Fría que durante la fase Cálida. Durante esta última, los veranillos se alargan, teniendo el agricultor una mayor dificultad para disponer de agua para sus cultivos.Variations in precipitation, its relationship with the phases of the event atmospheric Ocean El Niño Southern Oscillation, better known as ENSO and its possible impact on the agricultural production in Liberia, Costa Rica is researched. The number of rainy days and the distribution of precipitation that is expected to occur in each crop cycle are calculated. Estimates are made for a given year in the amount of rain, sowing dates and duration which could take certain farming in their seasonal growth. Similarly, to determine the amount of water that need a crop to grow normally. Farmers could experience a greater amount of precipitation during the cold phase than during the warm phase. During the last one the rain become longer, taking the farmer more difficult to provide water for their crops.UCR::Sedes Regionales::Sede de Occident

Beyond precipitation: physiographic gradients dictate the relative importance of environmental drivers on savanna vegetation

Background: Understanding the drivers of large-scale vegetation change is critical to managing landscapes and key to predicting how projected climate and land use changes will affect regional vegetation patterns. This study aimed to improve our understanding of the role, magnitude and spatial distribution of the key environmental factors driving vegetation change in southern African savanna, and how they vary across physiographic gradients. Methodology/Principal Findings: We applied Dynamic Factor Analysis (DFA), a multivariate times series dimension reduction technique to ten years of monthly remote sensing data (MODIS-derived normalized difference vegetation index, NDVI) and a suite of environmental covariates: precipitation, mean and maximum temperature, soil moisture, relative humidity, fire and potential evapotranspiration. Monthly NDVI was described by cyclic seasonal variation with distinct spatiotemporal patterns in different physiographic regions. Results support existing work emphasizing the importance of precipitation, soil moisture and fire on NDVI, but also reveal overlooked effects of temperature and evapotranspiration, particularly in regions with higher mean annual precipitation. Critically, spatial distributions of the weights of environmental covariates point to a transition in the importance of precipitation and soil moisture (strongest in grass-dominated regions with precipitation,750 mm) to fire, potential evapotranspiration, and temperature (strongest in tree-dominated regions with precipitation.950 mm). Conclusions/Significance: We quantified the combined spatiotemporal effects of an available suite of environmental drivers on NDVI across a large and diverse savanna region. The analysis supports known drivers of savanna vegetation but also uncovers important roles of temperature and evapotranspiration. Results highlight the utility of applying the DFA approach to remote sensing products for regional analyses of landscape change in the context of global environmental change. With the dramatic increase in global change research, this methodology augurs well for further development and application of spatially explicit time series modeling to studies at the intersection of ecology and remote sensing.This study was funded by National Aeronautics and Space Administration Land-Cover/Land-Use Change Program (NASA LCLUC) Project # NNX09AI25G, titled ‘‘The Role of Socioeconomic Institutions in Mitigating Impacts of Climate Variability and Climate Change in Southern Africa’’, and National Science Foundation Integrative Graduate Education and Research Traineeship (NSF-IGERT) 0504422 Adaptive Management of Water, Wetlands and Watershed

Identifying beliefs underlying pre-drivers’ intentions to take risks: an application of the theory of planned behaviour

Novice motorists are at high crash risk during the first few months of driving. Risky behaviours such as speeding and driving while distracted are well-documented contributors to crash risk during this period. To reduce this public health burden, effective road safety interventions need to target the pre-driving period. We use the Theory of Planned Behaviour (TPB) to identify the pre-driver beliefs underlying intentions to drive over the speed limit (N = 77), and while over the legal alcohol limit (N = 72), talking on a hand-held mobile phone (N = 77) and feeling very tired (N = 68). The TPB explained between 41% and 69% of the variance in intentions to perform these behaviours. Attitudes were strong predictors of intentions for all behaviours. Subjective norms and perceived behavioural control were significant, though weaker, independent predictors of speeding and mobile phone use. Behavioural beliefs underlying these attitudes could be separated into those reflecting perceived disadvantages (e.g., speeding increases my risk of crash) and advantages (e.g., speeding gives me a thrill). Interventions that can make these beliefs safer in pre-drivers may reduce crash risk once independent driving has begun

Exact treatment of time-dependent axisymmetric gravitation

This paper extends an earlier treatment of time-dependent gravitational fields that are axially symmetric and nonrotating. From a consideration of the canonical solution of the Einstein vacuum field equations previously obtained as an axial expansion, a new method has been found that now provides the exact solution, whenever a certain generative key function x(t, z) is known