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‣ Modelagem Numérica do Transporte e das Emissões de Gases Traços e Aerossóis de Queimadas no Cerrado e Floresta Tropical da América do Sul; Numerical Modeling of Transport and Emissions of Trace Gases and Aerosols from Fires in the Cerrado and Tropical Rainforest in South America

Freitas, Saulo Ribeiro de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/08/1999 Português
Relevância na Pesquisa
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Este trabalho trata do estudo do transporte atmosférico de emissões de queimadas na região Amazônica e Centro-Oeste do Brasil. Em consequência da queima de biomasa, gases (CO IND.2, CO, CH IND.4, etc.) e partículas são emitidas para a atmosfera, os quais podem provocar mudanças no equilíbrio climático e biogeo químico do planeta Terra, em várias escalas. O estudo é realizado por meio de simulação numérica dos movimentos da atmosfera utilizando o modelo atmosférico RAMS (Regional Atmospheric Modeling System). São utilizados os métodos Lagrangiano e Euleriano. No método Langrangiano o transporte é estudado por meio do cálculo de trajetórias cinemáticas 3d de massas de ar, utilizando o campo de vento simulado, na escala resolvida. A posição inicial das massas de ar é obtida a partir de mapas de queimadas detectadas por sensores a bordo de satélites como o AVHRR da série NOAA. Uma metodologia simples que contabiliza os efeitos de processos convectivos úmidos da escala sub-grade na velocidade vertical da parcela de ar para modelo atmosféricos de baixa resolução, é introduzida no modelo de trajetórias. No método Euleriano, é resolvida a equação de conservação de massa dos principais elementos emitidos. Para tanto é introduzido um modelo de fontes emissoras de gases/partículas associadas à queimadas em floresta tropical e cerrado da América do Sul...

‣ GPS/VRS positioning using atmospheric modeling

Marra Alves, Daniele Barroca; Galera Monico, Joao Francisco
Fonte: Springer Heidelberg Publicador: Springer Heidelberg
Tipo: Artigo de Revista Científica Formato: 253-261
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 08/06499-9; Processo FAPESP: 06/04008-2; Real-time dense GNSS (Global Navigation Satellite System) networks have recently become available in many countries. They allow centimeter-level positioning accuracy using a network-based strategy. When such networks are unavailable, alternative methods are needed to achieve accurate positioning. We present an alternative approach implemented in Brazil to realize network-based positioning and the VRS (Virtual Reference Station) concept. We do not resolve integer ambiguities between reference stations but derive the network corrections from external atmospheric models. The method was tested using the So Paulo State Network of Brazil, where the reference stations are about 200 km apart. Accuracy on the level of decimeters was achieved, which is suitable for many applications in Brazil. The description of the method, results and an analysis is presented.

‣ Mechanistic, sensitivity, and uncertainty studies of the atmospheric oxidation of dimethylsulfide

Lucas, Donald David, 1969-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 249 p.; 13305935 bytes; 13305736 bytes; application/pdf; application/pdf
Português
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The global-scale emissions and reactivity of dimethylsulfide (CH3SCH3, DMS) make it an integral component in the atmospheric sulfur cycle. DMS is rapidly oxidized in the atmosphere by a complex gas-phase mechanism involving many species and reactions. The resulting oxidized sulfur-bearing products are hygroscopic and interact with aerosols through condensation and secondary aerosol formation. Predictions of the impacts of DMS chemistry on aerosols and climate are inhibited by the poorly understood DMS oxidation mechanism. This thesis diagnoses the gas-phase connections between DMS and its oxidation products by simulating comprehensive DMS chemistry (approximately 50 reactions and 30 species) using three atmospheric models of varying size and complexity. A diurnally-varying box model of the DMS cycle in the remote marine boundary layer is used to identify important DMS-related parameters and propagate parameter uncertainties to the sulfur-containing species. This analysis shows that the concentrations of DMS and sulfur dioxide (SO2) are sensitive to relatively few parameters. Moreover, the concentrations of DMS and SO2 are found to have factor of 2 uncertainties caused primarily (more than 60% of the variance) by uncertainties in DMS emissions and heterogeneous removal...

‣ Models of interseismic deformation with an analytic framework for the inclusion of general linear viscoelastic rheologies

Hetland, Eric Andreas
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 255 p.; 47586545 bytes; 47585730 bytes; application/pdf; application/pdf
Português
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I investigate postseismic and interseismic deformation using two-dimensional models of a vertical strike-slip fault in an elastic layer over a viscoelastic region. Central to this, I derive an analytic framework to include general linear viscoelastic theologies into models of interseismic deformation. Models with multi-viscous viscoelastic rheologies predict multiple phases of postseismic and interseismic deformation. For instance, with bi-viscous Burgers rheologies there is transient deformation early in the seismic cycle, while the deformation is steady later in the cycle. Only layered models with multi-viscous rheologies predict multiphase postseismic deformation. Fault models containing a steady component of relaxation, evolve to mature states after a sufficient number of fault ruptures. The mature surface deformation is unrelated to the steady deformation at depth and depends only on the rupture history and locking depth of the fault and the theologies of the model. With periodic ruptures, the mature deformation is cycle invariant. If the recurrence time or magnitude of the ruptures then change, the interseismic velocities vary significantly from cycle to cycle as they evolve toward new cycle invariant velocities.; (cont.) The time for a model to equilibrate to an invariant state is proportional to the time scale of the steady component of viscoelastic relaxation...

‣ Kinematic models of deformation in Southern California constrained by geologic and geodetic data

Eich, Lori A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 69 p.; 15674176 bytes; 15673831 bytes; application/pdf; application/pdf
Português
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Using a standardized fault geometry based on the Community Block Model, we create two analytic block models of the southern California fault system. We constrain one model with only geodetic data. In the other, we assign a priori slip rates to the San Andreas, Garlock, Helendale, Newport-Inglewood, Owens Valley, Sierra Madre, and Chino faults to create a joint geologic and geodetic model, using the a priori slip rates to refine the results in areas with limited geodetic data. Our results for the San Andreas fault are consistent with geologic slip rates in the north and south, but across the Big Bend area we find its slip rates to be slower than geologic rates. Our geodetic model shows right lateral slip rates of 19.8 + 1.3 mm/yr in the Mojave area and 17.3 ± 1.6 mm/yr near the Imperial fault; the San Gorgonio Pass area displays a left lateral slip rate of 1.8 + 1.7 mm/yr. Our joint geologic and geodetic model results include right lateral slip rates of 18.6 + 1.2 mm/yr in the Mojave area, 22.1 ± 1.6 mm/yr near the Imperial fault, and 9.5 1.4 mm/yr in the San Gorgonio Pass area. Both models show high values (10-13 1 mm/yr) of right lateral slip to the east of the Blackwater fault along the Goldstone, Calico, and Hidalgo faults. We show that substantially different block geometries in the Mojave can produce statistically similar model results due to sparse geodetic data.; by Lori A. Eich.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Study of the Martian upper atmosphere using radio tracking data

Mazarico, Erwan Matías Alexandre, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 268 p.
Português
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Since the first in situ observations of the Martian atmosphere were made by the twin Viking landers, we have learned considerably more about its composition, dynamics and variability. Not only did the new data on global atmospheric densities generate opportunities to understand the atmospheric composition of early Mars and supply constraints at the upper limit of General Circulation Models, it is critical for the design and planning of future exploration missions. We can complement the successes of remote sensing and accelerometer investigations by using radio tracking data that have not been studied from an atmospheric science perspective, or are available for the first time. Due to the very low density of the higher layers atmosphere, the estimation of the drag acceleration using Precision Orbit Determination is a challenge. We developed new numerical models of the non-conservative forces acting on the spacecraft. In particular, the spacecraft crosssectional area is calculated using improved spacecraft macro-models which include interplate shadowing. These improvements in the force modeling enable a more robust estimation of the atmospheric density. The density structure from the middle atmosphere up to the exosphere is studied using radio tracking data from the Mars Odyssey and the Mars Reconnaissance Orbiter spacecraft. Measurements in the Martian middle atmosphere...

‣ Acoplamento do modelo hidrológico MGB ao modelo atmosférico WRF visando estimar vazão na bacia do rio Paraíba do Meio AL/PE; Engagement of the hydrological model MGB atmospheric model WRF aiming to estimate flow river basin Paraiba Meio AL/PE

Rodrigues, Mikael Timóteo
Fonte: Universidade Federal de Alagoas; BR; Processos de superfície terrestre; Programa de Pós-Graduação em Meteorologia; UFAL Publicador: Universidade Federal de Alagoas; BR; Processos de superfície terrestre; Programa de Pós-Graduação em Meteorologia; UFAL
Tipo: Dissertação Formato: application/pdf
Português
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Because of computational advances its evolution in relation to speed and memory capacity in recent years, along with adding the weather, the coupling between atmospheric and hydrological models has been the object of study in several studies in recent decades. The management of large river basins is determined by several variables, with the main system and the volume of river flows. Given volume water in a basin can be affected in different ways and many different factors, as the main factors having the variability in time and space of rainfall that produces immediate changes in the flow of a given system. As the results of large precipitation events directly affect the flow regimes, this work has as main objective the coupling of the hydrological model MGB - HPI with the WRF atmospheric model in an attempt to estimate flow in the basin of the Middle Rio Paraíba,. The rainfall data provided were simulated by WRF model and the observed rainfall and flow observed awarded by the National Water Agency - ANA, for 3 (three) station pluviometric and 4 (four) fluviometric respectively. The flow simulation was carried out hydrological rainfall-runoff model MGBIPH. Analyses were made in two steps: Kriging interpolation in KGM-normal rainfall and observed...

‣ Description of atmospheric conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)

Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, Ivone Freire da Mota e; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antici'
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
Português
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Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malargue and averaged monthly models, the utility of the GDAS data is shown. (C) 2012 Elsevier B.V. All rights reserved.; Comision Nacional de Energia Atomica; Comision Nacional de Energia Atomica; Fundacion Antorchas; Fundacion Antorchas; Gobierno De La Provincia de Mendoza; Gobierno De La Provincia de Mendoza; Municipalidad de Malargue; Municipalidad de Malargue; NDM Holdings; NDM Holdings; Valle Las Lenas; Valle Las Lenas; Australian Research Council; Australian Research Council; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Financiadora de Estudos e Projetos (FINEP); Financiadora de Estudos e Projetos (FINEP); Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ); Fundacao de Amparo a Pesquisa do Estado de Rio de Janeiro (FAPERJ); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Ministerio de Ciencia e Tecnologia (MCT)...

‣ Description of atmospheric conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)

Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antici'c, T.; Aramo,
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.125215%
Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malargue and averaged monthly models, the utility of the GDAS data is shown. (C) 2012 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

‣ Anisotropy and deformation in the Earth's mantle : seismological observations, geodynamical models, and laboratory experiments

Long, Maureen Devaney
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 316 p.
Português
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In this thesis I report the results of several studies of elastic anisotropy and deformation in the Earth's mantle, using shear wave splitting measurements, numerical models of geodynamical processes, and laboratory experiments on mantle minerals. I evaluate the performance of several methods for measuring shear wave splitting at broadband stations, and discuss how different measurements can inform our interpretation of mantle anisotropy. I describe a set of shear wave splitting measurements from both teleseismic and local earthquakes at 65 stations of the F-net array in Japan. I find considerable evidence from the measured splitting patterns for complex and heterogeneous anisotropy beneath Japan associated with the subduction of the Pacific and Philippine Sea plates beneath Eurasia. The comparison of teleseismic and local splitting at stations in southwestern Japan provides strong evidence for trench-parallel anisotropy in the mantle wedge above the subducting slab. I consider several scenarios that would produce the observed anisotropy and conclude that the most likely model for deformation beneath the Ryukyu arc is corner flow in the mantle wedge, with a region extending ~ 150 kilometers from the trench dominated by B-type olivine fabric.; (cont.) To characterize further the detailed pattern of flow and anisotropy...

‣ Single stars in the Hyades open cluster. Fiducial sequence for testing stellar and atmospheric models

Kopytova, Taisiya G.; Brandner, Wolfgang; Tognelli, Emanuele; Moroni, Pier Giorgio Prada; Da Rio, Nicola; Röser, Siegfried; Schilbach, Elena
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/08/2015 Português
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Age and mass determinations for isolated stellar objects remain model-dependent. While stellar interior and atmospheric theoretical models are rapidly evolving, we need a powerful tool to test them. Open clusters are good candidates for this role. We complement previous studies on the Hyades multiplicity by Lucky Imaging observations with the AstraLux Norte camera. This allows us to exclude possible binary and multiple systems with companions outside 2--7 AU separation and to create a "single-star sequence" for the Hyades. The sequence encompasses 250 main-sequence stars ranging from A5V to M6V. Using the "Tool for Astrophysical Data Analysis" (TA-DA), we create various theoretical isochrones applying different combinations of interior and atmospheric models. We compare the isochrones with the observed Hyades single-star sequence on J vs. J - K_s, J vs. J - H and K_s vs. H - K_s color-magnitude diagrams. As a reference we also compute absolute fluxes and magnitudes for all stars from X-ray to mid-infrared based on photometric measurements available in the literature(ROSAT X-ray, GALEX UV, APASS gri, 2MASS JHK_s, and WISE W1 to W).We find that combinations of both PISA and DARTMOUTH stellar interior models with BT-Settl 2010 atmospheric models describe the observed sequence well. The full sequence covers the mass range 0.13 to 2.3 Msun...

‣ Fundamental parameters of bright Ap stars from wide-range energy distributions and advanced atmospheric models

Shulyak, D.; Ryabchikova, T.; Kochukhov, O.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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As a well-established procedure for the vast majority of normal main-sequence stars, determination of atmospheric and stellar parameters turns to be a challenging process in case of magnetic chemically peculiar stars. Inhomogeneous distribution of chemical elements and strong magnetic fields make most of the standard photometric and spectroscopic calibrations inapplicable for this class of stars. In this work we make use of available observed energy distributions calibrated to absolute units, stellar parallaxes, high-resolution spectroscopic observations, and advanced stellar atmosphere models to derive parameters of three bright Ap stars: 33Lib, gammaEqu, and betaCrB. Model atmospheres and fluxes were computed with the LLmodels code. Synth3 and Synthmag codes were used to compute profiles of individual spectral lines involved in abundance analysis. For each of the stars, we construct a self-consistent atmospheric models assuming normal and depleted helium compositions and derive empirically stratification profiles of certain elements. The effective temperatures and surface gravities are found from the simultaneous fit to spectroscopic, photometric, and spectrophotometric observations calibrated to absolute units. We show that using advanced model atmospheres and accurate stellar parallaxes allows one to derive stellar radii with high accuracy...

‣ Strong Scaling for Numerical Weather Prediction at Petascale with the Atmospheric Model NUMA

Müller, Andreas; Kopera, Michal A.; Marras, Simone; Wilcox, Lucas C.; Isaac, Tobin; Giraldo, Francis X.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/11/2015 Português
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Numerical weather prediction (NWP) has proven to be computationally challenging due to its inherent multiscale nature. Currently, the highest resolution NWP models use a horizontal resolution of approximately 15km. At this resolution many important processes in the atmosphere are not resolved. Needless to say this introduces errors. In order to increase the resolution of NWP models highly scalable atmospheric models are needed. The Non-hydrostatic Unified Model of the Atmosphere (NUMA), developed by the authors at the Naval Postgraduate School, was designed to achieve this purpose. NUMA is used by the Naval Research Laboratory, Monterey as the engine inside its next generation weather prediction system NEPTUNE. NUMA solves the fully compressible Navier-Stokes equations by means of high-order Galerkin methods (both spectral element as well as discontinuous Galerkin methods can be used). Mesh generation is done using the p4est library. NUMA is capable of running middle and upper atmosphere simulations since it does not make use of the shallow-atmosphere approximation. This paper presents the performance analysis and optimization of the spectral element version of NUMA. The performance at different optimization stages is analyzed. By using vector intrinsics the main computations reach 1.2 PFlops on the entire machine Mira. The paper also presents scalability studies for two idealized test cases that are relevant for NWP applications. The atmospheric model NUMA delivers an excellent strong scaling efficiency of 99% on the entire supercomputer Mira using a mesh with 1.8 billion grid points. This allows us to run a global forecast of a baroclinic wave test case at 3km uniform horizontal resolution and double precision within the time frame required for operational weather prediction.; Comment: 10 pages...

‣ Hunting for brown dwarf binaries and testing atmospheric models with X-Shooter

Manjavacas, E.; Goldman, B.; Alcalá, J. M.; Zapatero-Osorio, M. R.; Béjar, V. J. S.; Homeier, D.; Bonnefoy, M.; Smart, R. L.; Henning, T.; Allard, F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/09/2015 Português
Relevância na Pesquisa
47.14304%
The determination of the brown dwarf binary fraction may contribute to the understanding of the substellar formation mechanisms. Unresolved brown dwarf binaries may be revealed through their peculiar spectra or the discrepancy between optical and near-infrared spectral type classification. We obtained medium-resolution spectra of 22 brown dwarfs with these characteristics using the X-Shooter spectrograph at the VLT. We aimed to identify brown dwarf binary candidates, and to test if the BT-Settl 2014 atmospheric models reproduce their observed spectra. To find binaries spanning the L-T boundary, we used spectral indices and compared the spectra of the selected candidates to single spectra and synthetic binary spectra. We used synthetic binary spectra with components of same spectral type to determine as well the sensitivity of the method to this class of binaries. We identified three candidates to be combination of L plus T brown dwarfs. We are not able to identify binaries with components of similar spectral type. In our sample, we measured minimum binary fraction of $9.1^{+9.9}_{-3.0}$. From the best fit of the BT-Settl models 2014 to the observed spectra, we derived the atmospheric parameters for the single objects. The BT-Settl models were able to reproduce the majority of the SEDs from our objects...

‣ Calibration of stellar and atmospheric models using the Hyades

Kopytova, Taisiya G.; Brandner, Wolfgang; Röser, Siegfried; Schilbach, Elena; Da Rio, Nicola
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/01/2014 Português
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Calibration and benchmarking of evolutionary and atmospheric models is essential for the study of low-mass stars and brown dwarfs, as for isolated objects these models are the only way to determine basic parameters like mass and age. The Hyades star cluster with an age of around 625 Myr and located at the distance of ~ 45 pc, is the most accessible cluster in the solar neighborhood. R\"oser et al. (2011) establish a list of 724 likely Hyades members. Using available literature data (HST, HIPPARCOS, WDS, Patience et al. 1998, Mermilliod et al. 2009, Morzinski 2011) and our own lucky imaging observations with AstraLux at the 2.2m telescope in Calar Alto, we establish a single-star sequence containing 255 Hyades members spanning the mass range ~ 0.2--1.5 solar masses . This sequence is used for testing and calibration of various existing stellar and atmospheric models (PADOVA, DARTMOUTH, BCAH, BT-Settl); Comment: 4 pages, 4 figures. Proceedings from "Brown dwarfs come of age" meeting in Fuerteventura 2013

‣ Downscaling near-surface atmospheric fields with multi-objective Genetic Programming

Zerenner, Tanja; Venema, Victor; Friederichs, Petra; Simmer, Clemens
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/07/2014 Português
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The coupling of models for the different components of the Soil-Vegetation-Atmosphere-System is required to investigate component interactions and feedback processes. However, the component models for atmosphere, land-surface and subsurface are usually operated at different resolutions in space and time owing to the dominant processes. The computationally often more expensive atmospheric models, for instance, are typically employed at a coarser resolution than land-surface and subsurface models. Thus up- and downscaling procedures are required at the interface between the atmospheric model and the land-surface/subsurface models. We apply multi-objective Genetic Programming (GP) to a training data set of high-resolution atmospheric model runs to learn equations or short programs that reconstruct the fine-scale fields (e.g., 400 m resolution) of the near-surface atmospheric state variables from the coarse atmospheric model output (e.g., 2.8 km resolution). Like artificial neural networks, GP can flexibly incorporate multivariate and nonlinear relations, but offers the advantage that the solutions are human readable and thus can be checked for physical consistency. Using the Strength Pareto Approach for multi-objective fitness assignment allows us to consider multiple characteristics of the fine-scale fields during the learning procedure.

‣ An atmospheric radiation model for Cerro Paranal. I. The optical spectral range

Noll, S.; Kausch, W.; Barden, M.; Jones, A. M.; Szyszka, C.; Kimeswenger, S.; Vinther, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/05/2012 Português
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The Earth's atmosphere affects ground-based astronomical observations. Scattering, absorption, and radiation processes deteriorate the signal-to-noise ratio of the data received. For scheduling astronomical observations it is, therefore, important to accurately estimate the wavelength-dependent effect of the Earth's atmosphere on the observed flux. In order to increase the accuracy of the exposure time calculator of the European Southern Observatory's (ESO) Very Large Telescope (VLT) at Cerro Paranal, an atmospheric model was developed as part of the Austrian ESO In-Kind contribution. It includes all relevant components, such as scattered moonlight, scattered starlight, zodiacal light, atmospheric thermal radiation and absorption, and non-thermal airglow emission. This paper focuses on atmospheric scattering processes that mostly affect the blue (< 0.55 mum) wavelength regime, and airglow emission lines and continuum that dominate the red (> 0.55 mum) wavelength regime. While the former is mainly investigated by means of radiative transfer models, the intensity and variability of the latter is studied with a sample of 1186 VLT FORS1 spectra. For a set of parameters such as the object altitude angle, Moon-object angular distance, ecliptic latitude...

‣ AtmoHEAD 2013 workshop / Atmospheric Monitoring for High-Energy Astroparticle Detectors

Bernlöhr, K.; Bellassai, G.; Blanch, O.; Bourgeat, M.; Bruno, P.; Buscemi, M.; Cassardo, C.; Chadwick, P. M.; Chalme-Calvet, R.; Chouza, F.; Cilmo, M.; Coco, M.; Colombi, J.; Compin, M.; Daniel, M. K.; Reyes, R. De Los; Ebr, J.; D'Elia, R.; Deil, C.; Etc
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/03/2014 Português
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A 3-day international workshop on atmospheric monitoring and calibration for high-energy astroparticle detectors, with a view towards next-generation facilities. The atmosphere is an integral component of many high-energy astroparticle detectors. Imaging atmospheric Cherenkov telescopes and cosmic-ray extensive air shower detectors are the two instruments driving the rapidly evolving fields of very-high- and ultra-high-energy astrophysics. In these instruments, the atmosphere is used as a giant calorimeter where cosmic rays and gamma rays deposit their energy and initiate EASs; it is also the medium through which the resulting Cherenkov light propagates. Uncertainties in real-time atmospheric conditions and in the fixed atmospheric models typically dominate all other systematic errors. With the improved sensitivity of upgraded IACTs such as H.E.S.S.-II and MAGIC-II and future facilities like the Cherenkov Telescope Array (CTA) and JEM-EUSO, statistical uncertainties are expected to be significantly reduced, leaving the atmosphere as the limiting factor in the determination of astroparticle spectra. Varying weather conditions necessitate the development of suitable atmospheric monitoring to be integrated in the overall instrument calibration...

‣ Emission factors for open and domestic biomass burning for use in atmospheric models

Akagi, S. K.; Yokelson, R. J.; Wiedinmyer, C.; Alvarado, M. J.; Reid, J. S.; Karl, T.; Crounse, J. D.; Wennberg, P. O.
Fonte: Copernicus Publications Publicador: Copernicus Publications
Tipo: Article; PeerReviewed Formato: application/pdf; application/zip
Publicado em //2011 Português
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Biomass burning (BB) is the second largest source of trace gases and the largest source of primary fine carbonaceous particles in the global troposphere. Many recent BB studies have provided new emission factor (EF) measurements. This is especially true for non-methane organic compounds (NMOC), which influence secondary organic aerosol (SOA) and ozone formation. New EF should improve regional to global BB emissions estimates and therefore, the input for atmospheric models. In this work we present an up-to-date, comprehensive tabulation of EF for known pyrogenic species based on measurements made in smoke that has cooled to ambient temperature, but not yet undergone significant photochemical processing. All EFs are converted to one standard form (g compound emitted per kg dry biomass burned) using the carbon mass balance method and they are categorized into 14 fuel or vegetation types. Biomass burning terminology is defined to promote consistency. We compile a large number of measurements of biomass consumption per unit area for important fire types and summarize several recent estimates of global biomass consumption by the major types of biomass burning. Post emission processes are discussed to provide a context for the emission factor concept within overall atmospheric chemistry and also highlight the potential for rapid changes relative to the scale of some models or remote sensing products. Recent work shows that individual biomass fires emit significantly more gas-phase NMOC than previously thought and that including additional NMOC can improve photochemical model performance. A detailed global estimate suggests that BB emits at least 400 Tg yr^(−1) of gas-phase NMOC...

‣ Generating a VRS Using Atmospheric Models: Concept, Implementation and Results; GERAÇÃO DE VRS A PARTIR DE MODELOS ATMOSFÉRICOS: CONCEITO, IMPLEMENTAÇÃO E RESULTADOS

Alves, Daniele Barroca Marra; Monico, João Francisco Galera; Dalbelo, Luiz Fernando Antonio
Fonte: Universidade Federal do Paraná-UFPR Publicador: Universidade Federal do Paraná-UFPR
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 25/02/2008 Português
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Nowadays, with the implantation of GNSS (Global Navigation Satellite System)reference station networks, several positioning techniques have been developedand/or improved. Using such kind of network data it is possible to model the GNSSdistance dependent errors and to compute correction terms for the network region.Several methods have been developed to formulate the corrections terms fromnetwork stations data. A method that has been received a great attention is theVirtual Reference Station (VRS). The idea is that the VRS data resemble as much aspossible a real receiver data placed in the same local. Therefore, the user has thepossibility of using the VRS as if it were a real reference station in your proximities,and to accomplish the relative positioning with a single frequency receiver. In thispaper it is described a different methodology applied to implement the VRSconcept, using atmospheric models developed by Brazilian researchers. Besides,experiments for evaluating the quality of generated VRS are presented, showing theefficiency of the proposed method.; Atualmente, com a implantação das redes de estações de referência GNSS (GlobalNavigation Satellite System), diversas técnicas de posicionamento têm sidodesenvolvidas e/ou melhoradas. Utilizando os dados dessa rede é possível modelaros erros GNSS dependentes da distância e calcular parâmetros de correção para aregião de abrangência da mesma. Diversos métodos têm sido desenvolvidos paraformular os parâmetros de correção a partir dos dados de uma rede de estações dereferência. Um método que tem se destacado é o que utiliza o conceito de VRS(Virtual Reference Station). A idéia é que os dados da VRS se assemelhem tantoquanto possível com aqueles provenientes de um receptor real colocado no mesmolocal. Assim...