Connection between Spring Conditions and Peak Summer Monsoon Rainfall in South America: Role of Soil Moisture, Surface Temperature, and Topography in Eastern Brazil

A link between peak summer monsoon rainfall in central-east Brazil, composing part of the South American monsoon core region, and antecedent conditions in spring is disclosed. Rainfall in this region during part of spring holds a significant inverse correlation with rainfall in peak summer, especially during ENSO years. A surface–atmosphere feedback hypothesis is proposed to explain this relationship: low spring precipitation leads to low spring soil moisture and high late spring surface temperature; this induces a topographically enhanced low-level anomalous convergence and cyclonic circulation over southeast Brazil that enhances the moisture flux from northern and central South America into central-east Brazil, setting up favorable conditions for excess rainfall. Antecedent wet conditions in spring lead to opposite anomalies. The main links in this hypothesis are confirmed through correlation analysis of observed data: spring precipitation is negatively correlated to late spring surface temperature in central-east Brazil, and surface temperature in southeast Brazil is positively correlated with peak summer monsoon precipitation in central-east Brazil. The intermediary links of the surface–atmosphere feedback are tested in sensitivity experiments with the regional climate model version 3 (RegCM3). These experiments confirm that the proposed links are possible: the reduced soil moisture in central-east Brazil is shown to increase the surface temperature and produce a cyclonic anomaly over southeast Brazil, as well as increased precipitation in central-east Brazil. A crucial role of the mountains of southeast Brazil in anchoring the patterns of intraseasonal variability, and sustaining the “dipolelike” precipitation mode observed over South America, is suggested. The low predictability of monsoon rainfall anomalies in central-east Brazil during the austral summer might be partially ascribed to the fact that the models do not well reproduce the topographical features and the land–atmosphere interactions that are important for the variability in that region

VLBI como instrumento da geodésia e geofísica

Apendices: f. 192-252Orientador: José Bittencourt de AndradeDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Terra, Programa de Pós-Graduação em Ciências GeodésicasBibliografia: f. 57-58Resumo: A técnica de interferometria com bases muito longas (VLBI), aplicada a Geodésica e Geofísica, e descrita de forma abrangente. Esta técnica oferece a possibilidade da precisão de centímetros na medida de bases intercontinentais e uma re* - 4 ti solução angular de ate 10 . Assim, parâmetros dos movimentos rotacionais da Terra e efeitos geodinâmicos podem ser de: terminados com precisão sem precedentes e os modelos matemáticos que os descrevem, aperfeiçoados. Esta tese inicia-se com uma introdução aos elementos básicos de radio astronomia. A técnica de VLBI é então apresentada, através da analise da geometria de um interferômetro de VLBI, da definição das quantidades observáveis e da exposição do método e equipamentos empregados para obtê-las. Atenção especial é dedicada ao estudo dos fatores de influência sobre as observações de VLBI (geometria, equipamentos e meios de propagação do sinal), como base para o estabelecimento de modelos matemáticos. 0 estudo da influência da geometria sobre as observações inclui os efeitos relativísticos de primeira ordem e os efeitos dos movimentos rotacionais da Terra, de fenômenos geodinâmicos, da estrutura da antena e da estrutura complexa das fontes observadas. A influência dos equipamentos ê analisada considerando-se a instabi1idade dos padrões de frequência e o tempo de percurso do sinal desde a antena até o dispositivo de gravação. A ação da atmosfera,responsável principal pelo limite de precisão das medidas obtidas com VLBI, mereceu um estudo mais extenso, sendo os efeitos da atmosfera neutra e da ionosfera analisados separadamente Modelos matemáticos que expressam a dependência das observações em relação aos fatores descritos são apresentados , com a respectiva definição de sistemas de referência e quantidades de tempo utilizadas. A estimativa de parâmetros destes modelos no ajustamento de observações pelo método dos mínimos quadrados Õ revista. Problemas de singularidade que podem ocorrer neste processo, são discutidos, assim como os problemas de otimização de configurações para experiências de VLBI. Finalmente, são citadas as vantagens desta técnica e as precisões obteníveis em suas aplicações a Geodésica e Geofísica. Programas que a utilizam e desenvolvem e algumas experiências realizadas são descritos.Abstract: The Very long baseline interferometry (VLBI) technique, as applied to Geodesy and Geophysics is described in a comprising way. This technique has the potencial for centimeter accuracy level in measurement of intercontinental baselines - 4 11 and angular resolution up to 10 . Determination of Earth rc) tation parameters and geodynamic effects can be made with unprecedented accuracy and consequently their mathematical models can be improved. This thesis begins with a review of fundamentals on radio astronomy. The VLBI technique is then presented through the analysis of the geometry of a VLBI interferometer, the de finition of observables and the explanation of the method and instrumentation by wich they can be obtained, with an estimation of their precisions. Special attention is placed on study of factors with influence on VLBI observations (geometry, equipaments and si£nal propagation medium), as a background for mathematical m£dels presentation. The study of geometry influence on the observations include first order relativistic effects and the effects of Earth rotation, geodynamic phenomena, antenna stru£ ture and complex radio source structure.The influence of equi£ ments is analysed, by taking into consideration the instability of frequency standards and the travelling time of the signal from the antenna to the recording device. To atmosphere influence, the main responsable for the limit on accuracy, is dedicated a more extensive study, the effects of neutral atmosphere and of ionosphere being analysed separately. Mathematical models for the dependence among observibles and the above-mentioned factors are given, with the respective definition of reference frames and quantities of time. The estimation of model's parameters by the least squares adjustment of the observations is reviewed. Singularity problems that can arise on this process are discussed and optimal design problems for VLBI experiments are also presented. Finally,applications of VLBI to Geodesy and Geophysics are described, as well as the advantages and the obtenable a^ curacy. Some programs applying and developing this technique and some performed experiences are reported

IMPACTO DA CONCENTRAÇÃO DO DIÓXIDO DE CARBONO ATMOSFÉRICO NO GELO MARINHO ANTÁRTICO

Five numerical experiments were conducted using a coupled model of intermediate complexity, lasting for 1500 modeled years, using different CO2 concentrations (500, 600, 700 and 800 ppm). It was observed that increased atmospheric CO2 concentration leads to a warming in the Southern Hemisphere polar region with serious implications on the sea ice cover. Numerical results revealed ice thickness reduction up to 1m in Weddell and  Amuddsen Seas. In east Antarctic, from the Ross Sea to the Indian part of Antarctic Ocean, the absence of sea ice is the most prominent feature in the sensitivity experiments. The initial investigation indicates that the enhanced oceanic heat transport plays the main role in the modifications of the Southern Hemisphere sea ice under different CO2 concentration as determined by the CO2 simulations.Com base em 5 experimentos de sensibilidade numérica conduzidos com um modelo acoplado de intermediária complexidade, extendendo-se por 1500 anos do modelo, e com diferentes níveis de CO2 (500, 600, 700 e 800 ppm), demonstra-se que o aumento na concentração de CO2 leva a um aquecimento da região polar austral com sérias implicações na cobertura de gelo marinho. Os resultados numéricos mostram claramente a redução na espessura do gelo em até 1m, em particular no mar de Weddell e no mar de Amundsen. Na parte leste da Antártica, desde o mar de Ross até a zona Antártica do oceano Índico, a ausência do gelo foi a característica principal dos experimentos de sensibilidade climática. Numa análise inicial, nota-se que estas anomalias na criosfera deve-se a um substâncial aumento na quantidade de calor oceânico transportado para a região Antártica

Components of multifractality in the Central England Temperature anomaly series

We study the multifractal nature of the Central England Temperature (CET) anomaly, a time series that spans more than 200 years. The series is analyzed as a complete data set and considering a sliding window of 11 years. In both cases, we quantify the broadness of the multifractal spectrum as well as its components defined by the deviations from the Gaussian distribution and the influence of the dependence between measurements. The results show that the chief contribution to the multifractal structure comes from the dynamical dependencies, mainly the weak ones, followed by a residual contribution of the deviations from Gaussianity. However, using the sliding window, we verify that the spikes in the non-Gaussian contribution occur at very close dates associated with climate changes determined in previous works by component analysis methods. Moreover, the strong non-Gaussian contribution found in the multifractal measures from the 1960s onwards is in agreement with global results very recently proposed in the literature.Comment: 21 pages, 10 figure

The American Monsoon Systems

This paper examines similarities and differences among major features of the North and South American monsoon systems. Over both North and South America the summertime circulation shows upper-level anticyclone/low-level heat low structures. These develop at different distances from the equator. It is argued that ascent to the east where convective and subtropical convergence zones develop, and subsidence over the cool waters of the eastern Pacific where stratocumulus decks provide a radiative heat sink to the tropical atmosphere are integral and unifying aspects of both monsoon systems. The intraseasonal and interannual variability of the systems are contrasted. The reported links between anomalies in soil conditions and sea surface temperatures are marginal, and consistently long-range predictability is low. Ropelewski et al. (2004) and Grimm et al. (2004) focus on each of the American monsoon systems in companion papers

Three questions to ask before using model outputs for decision support

Decision makers must have sufficient confidence in models if they are to influence their decisions. We propose three screening questions to critically evaluate models with respect to their purpose, organization, and evidence. They enable a more transparent, robust, and secure use of model outputs

Population statistics study of radio and gamma-ray pulsars in the Galactic plane

We present results of our pulsar population synthesis of ordinary isolated and millisecond pulsars in the Galactic plane. Over the past several years, a program has been developed to simulate pulsar birth, evolution and emission using Monte Carlo techniques. We have added to the program the capability to simulate millisecond pulsars, which are old, recycled pulsars with extremely short periods. We model the spatial distribution of the simulated pulsars by assuming that they start with a random kick velocity and then evolve through the Galactic potential. We use a polar cap/slot gap model for $\gamma$-ray emission from both millisecond and ordinary pulsars. From our studies of radio pulsars that have clearly identifiable core and cone components, in which we fit the polarization sweep as well as the pulse profiles in order to constrain the viewing geometry, we develop a model describing the ratio of radio core-to-cone peak fluxes. In this model, short period pulsars are more cone-dominated than in our previous studies. We present the preliminary results of our recent study and the implications for observing these pulsars with GLAST and AGILE.Comment: 6 pages, 3 figures, 1 table, accepted in Astrophysics and Space Scienc

Light and flow regimes regulate the metabolism of rivers

Mean annual temperature and mean annual precipitation drive much of the variation in productivity across Earth's terrestrial ecosystems but do not explain variation in gross primary productivity (GPP) or ecosystem respiration (ER) in flowing waters. We document substantial variation in the magnitude and seasonality of GPP and ER across 222 US rivers. In contrast to their terrestrial counterparts, most river ecosystems respire far more carbon than they fix and have less pronounced and consistent seasonality in their metabolic rates. We find that variation in annual solar energy inputs and stability of flows are the primary drivers of GPP and ER across rivers. A classification schema based on these drivers advances river science and informs management.We thank Ted Stets, Jordan Read, Tom Battin, Sophia Bonjour, Marina Palta, and members of the Duke River Center for their help in developing these ideas. This work was supported by grants from the NSF 1442439 (to E.S.B. and J.W.H.), 1834679 (to R.O.H.), 1442451 (to R.O.H.), 2019528 (to R.O.H. and J.R.B.), 1442140 (to M.C.), 1442451 (to A.M.H.), 1442467 (to E.H.S.), 1442522 (to N.B.G.), 1624807 (to N.B.G.), and US Geological Survey funding for the working group was supported by the John Wesley Power Center for Analysis and Synthesis. Phil Savoy contributed as a postdoc- toral associate at Duke University and as a postdoctoral associate (contractor) at the US Geological Survey

Predicting how many animals will be where: how to build, calibrate and evaluate individual-based models

Individual-based models (IBMs) can simulate the actions of individual animals as they interact with one another and the landscape in which they live. When used in spatially-explicit landscapes IBMs can show how populations change over time in response to management actions. For instance, IBMs are being used to design strategies of conservation and of the exploitation of fisheries, and for assessing the effects on populations of major construction projects and of novel agricultural chemicals. In such real world contexts, it becomes especially important to build IBMs in a principled fashion, and to approach calibration and evaluation systematically. We argue that insights from physiological and behavioural ecology offer a recipe for building realistic models, and that Approximate Bayesian Computation (ABC) is a promising technique for the calibration and evaluation of IBMs. IBMs are constructed primarily from knowledge about individuals. In ecological applications the relevant knowledge is found in physiological and behavioural ecology, and we approach these from an evolutionary perspective by taking into account how physiological and behavioural processes contribute to life histories, and how those life histories evolve. Evolutionary life history theory shows that, other things being equal, organisms should grow to sexual maturity as fast as possible, and then reproduce as fast as possible, while minimising per capita death rate. Physiological and behavioural ecology are largely built on these principles together with the laws of conservation of matter and energy. To complete construction of an IBM information is also needed on the effects of competitors, conspecifics and food scarcity; the maximum rates of ingestion, growth and reproduction, and life-history parameters. Using this knowledge about physiological and behavioural processes provides a principled way to build IBMs, but model parameters vary between species and are often difficult to measure. A common solution is to manually compare model outputs with observations from real landscapes and so to obtain parameters which produce acceptable fits of model to data. However, this procedure can be convoluted and lead to over-calibrated and thus inflexible models. Many formal statistical techniques are unsuitable for use with IBMs, but we argue that ABC offers a potential way forward. It can be used to calibrate and compare complex stochastic models and to assess the uncertainty in their predictions. We describe methods used to implement ABC in an accessible way and illustrate them with examples and discussion of recent studies. Although much progress has been made, theoretical issues remain, and some of these are outlined and discussed

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured