Non-integrability of the problem of motion around an oblate planet     

Alessandra Celletti  Piero Negrini 《Celestial Mechanics and Dynamical Astronomy》1995,61(3):253-260

We provide a result of non-analytic integrability of the so-called J ₂-problem. Precisely by using the Lerman theorem we are able to prove the existence of a region of the phase space, where the dynamical system exhibits chaotic motions.  相似文献   

Extreme climatic events in the Amazon basin   总被引：1，自引：0，他引：1  

Jose Antonio Marengo  Javier Tomasella  Wagner R. Soares  Lincoln M. Alves  Carlos A. Nobre 《Theoretical and Applied Climatology》2012,107(1-2):73-85

During 2009 the Amazon basin was hit by a heavy flooding with a magnitude and duration few times observed in several decades. Torrential rain in northern and eastern Amazonia during the austral summer of 2008–2009 swelled the Amazon River and its tributaries. By July 2009, water levels of the Rio Negro, a major Amazon tributary, reached at Manaus harbor a new record, the highest mark of the last 107?years. During the 2008–2009 hydrological year, the rainy season on northern and northwestern Amazonia started prematurely, and was followed by a longer-than-normal rainy season. An anomalously southward migration of the ITCZ during May–June 2009, due to the warmer than normal surface waters in the tropical South Atlantic, was responsible for abundant rainfall in large regions of eastern Amazonia and Northeast Brazil from May to July 2009. We also compared the flood of 2009 with other major events recorded in 1989 and 1999. The hydrological consequences of this pattern were earlier than normal floods in Amazon northern tributaries, which peak discharges at their confluences with the main stem almost coincided with the peaks of southern tributaries. Since the time displacement of the contribution to the main stem of northern and southern Amazon tributaries is fundamental for damping flood waves in the main stem, the simultaneous combinations of peak discharges of tributaries resulted in an extreme flood.  相似文献   

Downscaling of South America present climate driven by 4-member HadCM3 runs   总被引：5，自引：2，他引：3  

Sin Chan Chou  José A. Marengo  André A. Lyra  Gustavo Sueiro  José F. Pesquero  Lincoln M. Alves  Gillian Kay  Richard Betts  Diego J. Chagas  Jorge L. Gomes  Josiane F. Bustamante  Priscila Tavares 《Climate Dynamics》2012,38(3-4):635-653

The objective of this work is to evaluate climate simulations over South America using the regional Eta Model driven by four members of an ensemble of the UK Met Office Hadley Centre HadCM3 global model. The Eta Model has been modified with the purpose of performing long-term decadal integrations and has shown to reproduce “present climate”—the period 1961–1990—reasonably well when forced by HadCM3. The global model lateral conditions with a resolution of 2.5° latitude?×?3.75° longitude were provided at a frequency of 6?h. Each member of the global model ensemble has a different climate sensitivity, and the four members were selected to span the range of uncertainty encompassed by the ensemble. The Eta Model nested in the HadCM3 global model was configured with 40-km horizontal resolution and 38 layers in the vertical. No large-scale internal nudging was applied. Results are shown for austral summer and winter at present climate defined as 1961–90. The upper and low-level circulation patterns produced by the Eta-CPTEC/HadCM3 experiment set-up show good agreement with reanalysis data and the mean precipitation and temperature with CRU observation data. The spread in the downscaled mean precipitation and temperature is small when compared against model errors. On the other hand, the benefits in using an ensemble is clear in the improved representation of the seasonal cycle by the ensemble mean over any one realization. El Ni?o and La Ni?a years were identified in the HadCM3 member runs based on the NOAA Climate Prediction Center criterion of sea surface temperature anomalies in the Ni?o 3.4 area. The frequency of the El Ni?o and La Ni?a events in the studied period is underestimated by HadCM3. The precipitation and temperature anomalies typical of these events are reproduced by most of the Eta-CPTEC/HadCM3 ensemble, although small displacements of the positions of the anomalies occur. This experiment configuration is the first step on the implementation of Eta-CPTEC/HadCM3 upcoming experiments on climate change studies that are discussed in a companion paper.  相似文献   

Climatology of extratropical cyclones over the South American–southern oceans sector     

David Mendes  Enio P. Souza  José A. Marengo  Monica C. D. Mendes 《Theoretical and Applied Climatology》2010,100(3-4):239-250

A climatology of extratropical cyclones is presented. Extratropical cyclones, their main characteristics and their predominant tracks, as well as their interannual variability, affect weather in South America. For that purpose, a storm track database has been compiled by applying a cyclone tracking scheme to six-hourly sea level pressure fields, available from the National Center for Environmental Prediction–National Center for Atmospheric Research reanalyses II for the 1979–2003 period. The spatial distribution of the cyclogenesis frequency shows two main centers: one around Northern Argentina, Uruguay, and Southern Brazil in all seasons and the other near to the North Antarctic Peninsula. The lifetime of extratropical cyclones in the South American sector exhibits small seasonality, being typically of the order of 3.0 days during most of the year and slightly higher (3.5 days) in austral summer. The distance travelled by the cyclones formed in the South American sector tends to be smaller than the total paths found in other areas of the Southern Hemisphere. A k-mean clustering technique is used to summarize the analysis of the 25-year climatology of cyclone tracks. Three clusters were found: one storm-track cluster in Northeast Argentina; a second one west of the Andes Cordillera; and a third cluster located to the north of the Antarctic Peninsula (around the Weddell Sea). The influence of the Antarctic Oscillation (AAO) in the variability of extratropical cyclones is explored, and some signals of the impacts of the variability of the AAO can be observed in the position of the extratropical cyclones around 40°S, while the impacts on the intensity is detected around 55°S.  相似文献   

Assessment of regional seasonal predictability using the PRECIS regional climate modeling system over South America   总被引：1，自引：0，他引：1  

Lincoln M. Alves  José Marengo 《Theoretical and Applied Climatology》2010,100(3-4):337-350

The purpose of this study was to evaluate the accuracy and skill of the UK Met Office Hadley Center Regional Climate Model (HadRM3P) in describing the seasonal variability of the main climatological features over South America and adjacent oceans, in long-term simulations (30 years, 1961–1990). The analysis was performed using seasonal averages from observed and simulated precipitation, temperature, and lower- and upper-level circulation. Precipitation and temperature patterns as well as the main general circulation features, including details captured by the model at finer scales than those resolved by the global model, were simulated by the model. However, in the regional model, there are still systematic errors which might be related to the physics of the model (convective schemes, topography, and land-surface processes) and the lateral boundary conditions and possible biases inherited from the global model.  相似文献   

Future change of climate in South America in the late twenty-first century: intercomparison of scenarios from three regional climate models   总被引：2，自引：1，他引：1  

Jose A. Marengo  Tercio Ambrizzi  Rosmeri P. da Rocha  Lincoln M. Alves  Santiago V. Cuadra  Maria C. Valverde  Roger R. Torres  Daniel C. Santos  Simone E. T. Ferraz 《Climate Dynamics》2010,35(6):1073-1097

Regional climate change projections for the last half of the twenty-first century have been produced for South America, as part of the CREAS (Cenarios REgionalizados de Clima Futuro da America do Sul) regional project. Three regional climate models RCMs (Eta CCS, RegCM3 and HadRM3P) were nested within the HadAM3P global model. The simulations cover a 30-year period representing present climate (1961–1990) and projections for the IPCC A2 high emission scenario for 2071–2100. The focus was on the changes in the mean circulation and surface variables, in particular, surface air temperature and precipitation. There is a consistent pattern of changes in circulation, rainfall and temperatures as depicted by the three models. The HadRM3P shows intensification and a more southward position of the subtropical Pacific high, while a pattern of intensification/weakening during summer/winter is projected by the Eta CCS/RegCM3. There is a tendency for a weakening of the subtropical westerly jet from the Eta CCS and HadRM3P, consistent with other studies. There are indications that regions such of Northeast Brazil and central-eastern and southern Amazonia may experience rainfall deficiency in the future, while the Northwest coast of Peru-Ecuador and northern Argentina may experience rainfall excesses in a warmer future, and these changes may vary with the seasons. The three models show warming in the A2 scenario stronger in the tropical region, especially in the 5°N–15°S band, both in summer and especially in winter, reaching up to 6–8°C warmer than in the present. In southern South America, the warming in summer varies between 2 and 4°C and in winter between 3 and 5°C in the same region from the 3 models. These changes are consistent with changes in low level circulation from the models, and they are comparable with changes in rainfall and temperature extremes reported elsewhere. In summary, some aspects of projected future climate change are quite robust across this set of model runs for some regions, as the Northwest coast of Peru-Ecuador, northern Argentina, Eastern Amazonia and Northeast Brazil, whereas for other regions they are less robust as in Pantanal region of West Central and southeastern Brazil.  相似文献   

A global perspective on African climate   总被引：4，自引：1，他引：3  

Alessandra Giannini  Michela Biasutti  Isaac M. Held  Adam H. Sobel 《Climatic change》2008,90(4):359-383

We describe the global climate system context in which to interpret African environmental change to support planning and implementation of policymaking action at national, regional and continental scales, and to inform the debate between proponents of mitigation v. adaptation strategies in the face of climate change. We review recent advances and current challenges in African climate research and exploit our physical understanding of variability and trends to shape our outlook on future climate change. We classify the various mechanisms that have been proposed as relevant for understanding variations in African rainfall, emphasizing a “tropospheric stabilization” mechanism that is of importance on interannual time scales as well as for the future response to warming oceans. Two patterns stand out in our analysis of twentieth century rainfall variability: a drying of the monsoon regions, related to warming of the tropical oceans, and variability related to the El Niño–Southern Oscillation. The latest generation of climate models partly captures this recent continent-wide drying trend, attributing it to the combination of anthropogenic emissions of aerosols and greenhouse gases, the relative contribution of which is difficult to quantify with the existing model archive. The same climate models fail to reach a robust agreement regarding the twenty-first century outlook for African rainfall, in a future with increasing greenhouse gases and decreasing aerosol loadings. Such uncertainty underscores current limitations in our understanding of the global climate system that it is necessary to overcome if science is to support Africa in meeting its development goals.  相似文献   

Preface     

Alessandra Celletti  Elena Lega  Sylvio Ferraz-Mello 《Celestial Mechanics and Dynamical Astronomy》2008,102(1-3):1-2

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Regional climate modelling in CLARIS-LPB: a concerted approach towards twentyfirst century projections of regional temperature and precipitation over South America     

E. Sánchez  S. Solman  A. R. C. Remedio  H. Berbery  P. Samuelsson  R. P. Da Rocha  C. Mourão  L. Li  J. Marengo  M. de Castro  D. Jacob 《Climate Dynamics》2015,45(7-8):2193-2212

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Advances in pan‐European flood hazard mapping          下载免费PDF全文

Lorenzo Alfieri  Peter Salamon  Alessandra Bianchi  Jeffrey Neal  Paul Bates  Luc Feyen 《水文研究》2014,28(13):4067-4077

Flood hazard maps at trans‐national scale have potential for a large number of applications ranging from climate change studies, reinsurance products, aid to emergency operations for major flood crisis, among others. However, at continental scales, only few products are available, due to the difficulty of retrieving large consistent data sets. Moreover, these are produced at relatively coarse grid resolution, which limits their applications to qualitative assessments. At finer resolution, maps are often limited to country boundaries, due to limited data sharing at trans‐national level. The creation of a European flood hazard map would currently imply a collection of scattered regional maps, often lacking mutual consistency due to the variety of adopted approaches and quality of the underlying input data. In this work, we derive a pan‐European flood hazard map at 100 m resolution. The proposed approach is based on expanding a literature cascade model through a physically based approach. A combination of distributed hydrological and hydraulic models was set up for the European domain. Then, an observed meteorological data set is used to derive a long‐term streamflow simulation and subsequently coherent design flood hydrographs for a return period of 100 years along the pan‐European river network. Flood hydrographs are used to simulate areas at risk of flooding and output maps are merged into a pan‐European flood hazard map. The quality of this map is evaluated for selected areas in Germany and United Kingdom against national/regional hazard maps. Despite inherent limitations and model resolution issues, simulated maps are in good agreement with reference maps (hit rate between 59% and 78%, critical success index between 43% and 65%), suggesting strong potential for a number of applications at the European scale. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献