Search results for "Monte Carlo."

A convolution of observational and model data to estimate age of air spectra in the northern hemispheric lower stratosphere

2020

Abstract. Derivation of mean age of air (AoA) and age spectra from atmospheric measurements remains a challenge and often requires data from atmospheric models. This study tries to minimize the direct influence of model data and presents an extension and application of a previously established inversion method to derive age spectra from mixing ratios of long- and short-lived trace gases. For a precise description of cross-tropopause transport processes, the inverse method is extended to incorporate air entrainment into the stratosphere across the tropical and extratropical tropopause. We first use simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) to provide a genera…

Retrieval of atmospheric CH4profiles from Fourier transform infrared data using dimension reduction and MCMC

2016

We introduce an inversion method that uses dimension reduction for the retrieval of atmospheric methane (CH4) profiles. Uncertainty analysis is performed using the Markov chain Monte Carlo (MCMC) statistical estimation. These techniques are used to retrieve CH4 profiles from the ground-based spectral measurements by the Fourier Transform Spectrometer (FTS) instrument at Sodankyla (67.4 degrees N, 26.6 degrees E), Northern Finland. The Sodankyla FTS is part of the Total Carbon Column Observing Network (TCCON), a global network that observes solar spectra in near-infrared wavelengths. The high spectral resolution of the data provides approximately 3 degrees of freedom about the vertical struc…

Depth selective Mössbauer spectroscopy: Analysis and simulation of 6.4 keV and 14.4 keV spectra obtained from rocks at Gusev Crater, Mars, and layere…

2008

[1] The miniaturized Mossbauer spectrometer (MIMOS) II Mossbauer spectrometers on the Mars Exploration Rovers (MER) simultaneously obtained 6.4 keV and 14.4 keV Mossbauer spectra from rock and soil targets. Because photons with lower energy have a shallower penetration depth, 6.4 keV spectra contain more mineralogical information about the near-surface region of a sample than do 14.4 keV spectra. The influence of surface layers of varying composition and thickness on Mossbauer spectra was investigated by Monte Carlo simulation and by measurement using a copy of the MER MIMOS II instrument and samples with one or two layers of known thicknesses. Thin sections of minerals or metallic Fe foil …

Bayesian dynamic modeling of time series of dengue disease case counts

2017

The aim of this study is to model the association between weekly time series of dengue case counts and meteorological variables, in a high-incidence city of Colombia, applying Bayesian hierarchical dynamic generalized linear models over the period January 2008 to August 2015. Additionally, we evaluate the model’s short-term performance for predicting dengue cases. The methodology shows dynamic Poisson log link models including constant or time-varying coefficients for the meteorological variables. Calendar effects were modeled using constant or first- or second-order random walk time-varying coefficients. The meteorological variables were modeled using constant coefficients and first-order …

Effects of dead time losses on terrestrial gamma ray flash measurements with the Burst and Transient Source Experiment

2010

[1] Measurements from the Burst and Transient Source Experiment (BATSE) instrument on the Compton Gamma Ray Observatory (CGRO) are the only ones where characteristics of single terrestrial gamma ray flashes (TGFs) have been obtained thus far. However, it has been reported that the measurements suffer from significant dead time losses which complicates the analysis and raises question about earlier BATSE studies. These losses are due to the high-intensity flux combined with limitations of the time resolution of the instrument. Since these losses will affect both the spectrum and the temporal distribution of the individual TGFs, results based on BATSE data need to be revisited, including our …

2017

Abstract. We present a Monte Carlo genetic algorithm (MCGA) for efficient, automated, and unbiased global optimization of model input parameters by simultaneous fitting to multiple experimental data sets. The algorithm was developed to address the inverse modelling problems associated with fitting large sets of model input parameters encountered in state-of-the-art kinetic models for heterogeneous and multiphase atmospheric chemistry. The MCGA approach utilizes a sequence of optimization methods to find and characterize the solution of an optimization problem. It addresses an issue inherent to complex models whose extensive input parameter sets may not be uniquely determined from limited in…

Pumps as turbines (PATs) in water distribution networks affected by intermittent service

2013

A hydraulic model was developed in order to evaluate the potential energy recovery from the use of centrifugal pumps as turbines (PATs) in a water distribution network characterized by the presence of private tanks. The model integrates the Global Gradient Algorithm (GGA), with a pressure-driven model that permits a more realistic representation of the influence on the network behaviour of the private tanks filling and emptying. The model was applied to a real case study: a District Metered Area in Palermo (Italy). Three different scenarios were analysed and compared with a baseline scenario (Scenario 0 – no PAT installed) to identify the system configuration with added PATs that permits th…

Ca impurity in small mixed He-4-He-3 clusters

2009

The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the He-4-He-3 interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for He-4 clusters, and to become fully solvated for He-3 clusters. We have calculated the absorption spectrum of Ca around the 4s4p <- 4s(2) transition and have found that it is bluesh…

Decomposing and Interpreting Spatial Effects in Spatio-Temporal Analysis: Evidences for Spatial Data Pooled Over Time

2017

Empirical applications using individual spatial data pooled over time usually neglect the fact that such data are not only spatially localized: they are also collected over time, i.e. temporally localized. So far, little effort has been devoted to proposing a global way for dealing with spatial data (cross-section) pooled over time, such as real estate transactions, business start-up, crime and so on. However, the spatial effect, in such a context, can be decomposed in two different components: a multidirectional spatial effect (same time period) and a unidirectional spatial effect (previous time period). Based on real estate literature, this chapter presents different spatio-temporal autor…

The Belle II Physics Book

2019

cd. autorów: L. Cao48,‡, G. Caria145,‡, G. Casarosa57,‡, C. Cecchi56,‡,D. Cˇ ervenkov10,‡,M.-C. Chang22,‡, P. Chang92,‡, R. Cheaib146,‡, V. Chekelian83,‡, Y. Chen154,‡, B. G. Cheon28,‡, K. Chilikin77,‡, K. Cho70,‡, J. Choi14,‡, S.-K. Choi27,‡, S. Choudhury35,‡, D. Cinabro170,‡, L. M. Cremaldi146,‡, D. Cuesta47,‡, S. Cunliffe16,‡, N. Dash33,‡, E. de la Cruz Burelo9,‡, E. de Lucia52,‡, G. De Nardo54,‡, †Editor. ‡Belle II Collaborator. §Theory or external contributing author. M. De Nuccio16,‡, G. De Pietro59,‡, A. De Yta Hernandez9,‡, B. Deschamps129,‡, M. Destefanis60,‡, S. Dey116,‡, F.Di Capua54,‡, S.Di Carlo75,‡, J. Dingfelder129,‡, Z. Doležal10,‡, I. Domínguez Jiménez125,‡, T.V. Dong30,26,…