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Now showing items 1 - 12 of 12

  • A novel technique including GPS radio occultation for detecting and monitoring volcanic clouds

    Biondi, Riccardo   Steiner, Andrea   Kirchengast, Gottfried   Hugues Brenot, Hugues   Therese Rieckh, Therese  

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  • Monte Carlo simulation for ultracold neutron experiments searching for neutron-mirror neutron oscillation

    Biondi, Riccardo  

    Neutron oscillation into mirror neutron, a sterile state exactly degenerate in mass with the neutron, could be a very rapid process, even faster than the neutron decay itself. It can be observed by comparing the neutron lose rates in an ultracold neutron trapping experiment for different experimental magnetic fields. We developed a Monte Carlo code that simulates many of the features of this kind of experiment with nonuniform magnetic fields. The aim of the simulation is to provide all necessary tools, needed for analyzing experimental results for neutron traps with different geometry and different configurations of magnetic fields. This work contains technical details on the Monte Carlo simulation used for the analysis in Ref. 46 not presented in it.
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  • Monte Carlo simulation for ultracold neutron experiments searching for neutron–mirror neutron oscillation

    Biondi, Riccardo  

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  • A Generalized Deforestation and Land-Use Change Scenario Generator for Use in Climate Modelling Studies

    Caporaso, Luca   Biondi, Riccardo   Bell, Jean Pierre  

    A new deforestation and land-use change scenario generator model (FOREST-SAGE) is presented that is designed to interface directly with dynamic vegetation models used in latest generation earth system models. The model requires a regional-scale scenario for aggregate land-use change that may be time-dependent, provided by observational studies or by regional land-use change/economic models for future projections. These land-use categories of the observations/economic model are first translated into equivalent plant function types used by the particular vegetation model, and then FOREST-SAGE disaggregates the regional-scale scenario to the local grid-scale of the earth system model using a set of risk-rules based on factors such as proximity to transport networks, distance weighted population density, forest fragmentation and presence of protected areas and logging concessions. These rules presently focus on the conversion of forest to agriculture and pasture use, but could be generalized to other land use change conversions. After introducing the model, an evaluation of its performance is shown for the land-cover changes that have occurred in the Central African Basin from 2001-2010 using retrievals from MODerate Resolution Imaging Spectroradiometer Vegetation Continuous Field data. The model is able to broadly reproduce the spatial patterns of forest cover change observed by MODIS, and the use of the local-scale risk factors enables FOREST-SAGE to improve land use change patterns considerably relative to benchmark scenarios used in the latest Coupled Model Intercomparison Project integrations. The uncertainty to the various risk factors is investigated using an ensemble of investigations, and it is shown that the model is sensitive to the population density, forest fragmentation and reforestation factors specified.
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  • Tropical cyclone cloud-top height and vertical temperature structure detection using GPS radio occultation measurements

    Biondi, Riccardo   Ho, Shu-Peng   Randel, William   Syndergaard, Stig   Neubert, Torsten  

    The accurate determination of tropical cyclone (TC) cloud-top height and its vertical thermal structure using the GPS radio occultation (RO) technique is demonstrated in this study. Cloud-top heights are determined by using the bending angle anomaly and the temperature anomaly profiles during the TC events, and the results are compared to near-coincident cloud-top heights determined by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements. Based on 34 closely located RO-CALIOP pairs during 2006 to 2009, TC cloud-top heights from RO are highly correlated with CALIOP (r=0.84), with a mean RO-CALIOP cloud-top height difference of approximately 500 m and a root-mean-square difference near 1 km. GPS RO data also allow analysis of the TC thermal structure, showing warm anomalies in the middle troposphere and cold anomalies in the upper levels, with a strong inversion near cloud top. We further investigate the thermal structure of the TCs from collocated radiosondes, and identify 246 RO-radiosonde pairs from 2001 to 2009. Radiosonde data confirm the thermal structure identified in GPS RO, with a strong inversion near the inferred cloud top. The mean difference between RO-derived inversion heights and those from radiosonde temperature profiles is approximately 500 m. Results show that, while cloud-top height detected from nadir-viewing satellites can be easily biased by a few kilometers, the biases of RO-derived cloud-top height are within similar to 500 m.
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  • Assessing the effects of air temperature and rainfall on malaria incidence:an epidemiological study across Rwanda and Uganda

    Colon-Gonzalez, Felipe J.   Tompkins, Adrian M.   Biondi, Riccardo   Bizimana, Jean Pierre   Namanya, Didacus Bambaiha  

    We investigate the short-term effects of air temperature, rainfall, and socioeconomic indicators on malaria incidence across Rwanda and Uganda from 2002 to 2011. Delayed and nonlinear effects of temperature and rainfall data are estimated using generalised additive mixed models with a distributed lag nonlinear specification. A time series cross-validation algorithm is implemented to select the best subset of socioeconomic predictors and to define the degree of smoothing of the weather variables. Our findings show that trends in malaria incidence agree well with variations in both temperature and rainfall in both countries, although factors other than climate seem to play an important role too. The estimated short-term effects of air temperature and precipitation are nonlinear, in agreement with previous research and the ecology of the disease. These effects are robust to the effects of temporal correlation. The effects of socioeconomic data are difficult to ascertain and require further evaluation with longer time series. Climate-informed models had lower error estimates compared to models with no climatic information in 77 and 60% of the districts in Rwanda and Uganda, respectively. Our results highlight the importance of using climatic information in the analysis of malaria surveillance data, and show potential for the development of climate-informed malaria early warning systems.
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  • Assessing the effects of air temperature and rainfall on malaria incidence: an epidemiological study across Rwanda and Uganda

    Colón-González, Felipe J.   Tompkins, Adrian M.   Biondi, Riccardo   Bizimana, Jean Pierre   Namanya, Didacus Bambaiha  

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  • Nonlinear dynamics of meteorological variables: multifractality and chaotic invariants in daily records from Pastaza, Ecuador RID F-5156-2011

    Millan, Humberto   Kalauzi, Aleksandar   Cukic, Milena   Biondi, Riccardo  

    Weather represents the daily state of the atmosphere. It is usually considered as a chaotic nonlinear dynamical system. The objectives of the present study were (1) to investigate multifractal meteorological trends and rhythms at the Amazonian area of Ecuador and (2) to estimate some nonlinear invariants for describing the meteorological dynamics. Six meteorological variables were considered in the study. Datasets were collected on a daily basis from January 1st 2001 to January 1st 2005 (1,460 observations). Based on a new multifractal method, we found interesting fractal rhythms and trends of antipersistence patterns (Fractal Dimension > 1.5). Nonlinear time series analyses rendered Lyapunov exponent spectra containing more than one positive Lyapunov exponent in some cases. This sort of hyperchaotic structures could explain, to some extent, larger fractal dimension values as the Kaplan-Yorke dimension was also in most cases larger than two. The maximum prediction time ranged from xi = 1.69 days (approximately 41 h) for E/P ratio to xi = 14.71 days for evaporation. Nonlinear dynamics analyses could be combined with multifractal studies for describing the time evolution of meteorological variables.
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  • Comparison of fractal dimension oscillations and trends of rainfall data from Pastaza Province, Ecuador and Veneto, Italy RID F-5156-2011

    Kalauzi, Aleksandar   Cukic, Milena   Millan, Humberto   Bonafoni, Stefania   Biondi, Riccardo  

    Since climate trends are getting considerable attention in recent years, we aimed in this study to compare trends and rhythms of complexity (fractal dimension, FD) of rainfall data series between two continents: Latin America and Europe. Two parallel nonlinear methods for calculating FD of a temporal data series, Higuchi's and consecutive differences, were combined with Fast Fourier Transform (FFT) to obtain FD oscillations of monthly accumulated rainfall. The data were collected for the last thirty years in Pastaza province, Ecuador and Veneto province, Italy. In order to calculate their FD time dependence, FD(t), moving windows of different lengths (short, 10-20 and long 21-350 samples), were applied. Both methods, each combined with FFT, detected identical (or very similar) rhythms of detrended FD(t) in the two data series, but frequencies with dominant amplitudes differed (4.4 years in Ecuador, 10.3 years in Italy). Long-term FD(t) trends were also studied using optimized long window lengths (similar to 200 samples). A linear positive trend was obtained for the Ecuadorian rainfall data over the whole recorded period. Italian fractal trend profile was, however, characterized by two periods: a constant high value for years 1974-1993, followed by a linear decrease for 1993-2005. Trend results, obtained with two different methods, were also similar. Accordance of the results, reported in the present paper by applying these two methods, validates their use as a tool in future fractal meteorological measurements. As well, these results indicate that positive ID trend obtained for Pastaza (Ecuador) and negative trend computed for Veneto (Italy) account for a local or regional phenomenon, most probably caused by extensive deforestation and land use change (Ecuador) and continental or global atmospheric pattern variability (Italy). (C) 2009 Published by Elsevier B.V.
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  • Supporting the detection and monitoring of volcanic clouds:A promising new application of Global Navigation Satellite System radio occultation

    Biondi, Riccardo   Steiner, Andrea K.   Kirchengast, Gottfried   Brenot, Hugues   Rieckh, Therese  

    The altitude of volcanic clouds and the atmospheric thermal structure after volcanic eruptions are studied using Global Navigation Satellite System (GNSS) Radio Occultation (RO) profiles co-located with independent radiometer images of ash and sulfur dioxide plumes. We use geographically co-located RO profiles to detect the top altitude of volcanic clouds and to analyze their impact in terms of temperature change signatures. We obtained about 1300 RO profiles co-located with two representative eruptions (Puyehue 2011, Nabro 2011) and found that an anomaly technique recently developed for detecting convective cloud tops and studying the vertical thermal structure of deep convective systems can also be applied to volcanic clouds. Analyzing the atmospheric thermal structure after the eruptions, we found clear cooling signatures induced by volcanic cloud tops in the upper troposphere for the Puyehue case. For the Nabro case we detected a significant warming in the stratosphere which lasted for several months, indicating that the cloud reached the stratosphere. The results are encouraging for future large-scale use of RO data for supporting the monitoring of volcanic clouds and their impacts on weather and climate. (C) 2017 COSPAR. Published by Elsevier Ltd.
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  • Supporting the detection and monitoring of volcanic clouds: a promising new application of Global Navigation Satellite System radio occultation

    Biondi, Riccardo   Steiner, Andrea K.   Kirchengast, Gottfried   Brenot, Hugues   Rieckh, Therese  

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  • Measurements of the upper troposphere and lower stratosphere during tropical cyclones using the GPS radio occultation technique RID F-5156-2011 RID F-2697-2011

    Biondi, Riccardo   Neubert, Torsten   Syndergaard, Stig   Nielsen, Johannes  

    Water vapour transport to the upper troposphere and lower stratosphere by deep convective storms affects the radiation balance of the atmosphere and has been proposed as an important component of climate change. The aim of the work presented here is to understand if the GPS radio occultation technique is useful for characterization of this process. Our assessment addresses the question if severe storms leave a significant signature in radio occultation profiles in the upper troposphere/lower stratosphere. Radio occultation data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) were analyzed, focusing on two particular tropical cyclones with completely different characteristics, the hurricane Bertha, which formed in the Atlantic Basin during July 2008 and reached a maximum intensity of Category 3, and the typhoon Hondo, which formed in the south Indian Ocean during 2008 reaching a maximum intensity of Category 4. The result is positive, suggesting that the bending angle of a GPS radio occultation signal contains interesting information on the atmosphere around the tropopause, but not any information regarding the water vapour. The maximum percentage anomaly of bending angle between 14 and 18 km of altitude during tropical cyclones is typically larger than the annual mean by 5-15% and it can reach 20% for extreme cases. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.
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