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arXiv2014

Global Warming and Caspian Sea Level Fluctuations

Coastal regions have a high social, economical and environmental importance. Due to this importance the sea level fluctuations can have many bad consequences. In this research the correlation between the increasing trend of temperature in coastal stations due to Global Warming and the Caspian Sea level has been established. The Caspian Sea level data has been received from the Jason-1 satellite. It was resulted that the monthly correlation between the temperature and sea level is high and also positive and almost the same for all the stations. But the yearly correlation was negative. It means that the sea level has decreased by the increase in temperature.

physics.ao-ph↗

arXiv2013

1D+4D-VAR data assimilation of lightning with WRFDA system using nonlinear observation operators

This paper addresses the impact of assimilating data from the Earth Networks Total Lightning Network (ENTLN) during two cases of severe weather. Data from the ENTLN serve as a substitute for those from the upcoming launch of the GOES Lightning Mapper (GLM). We use the Weather Research and Forecast (WRF) model and variational data assimilation techniques at 9 km spatial resolution. The main goal is to examine the potential impact of lightning observations from the future GLM. Previous efforts to assimilate lightning observations mainly utilized nudging approaches. We develop three more sophisticated approaches, 3D-VAR WRFDA and 1D+nD-VAR (n=3,4) WRFDA schemes that currently are being considered for operational implementation by the National Centers for Environmental Prediction (NCEP) and the Naval Research Laboratory (NRL). This research uses Convective Available Potential Energy (CAPE) as a proxy between lightning data and model variables. To test the performance of the aforementioned schemes, we assess the quality of resulting analysis and forecasts of precipitation compared to those from a control experiment and verify them against NCEP stage IV precipitation. Results demonstrate that assimilating lightning observations improves precipitation statistics during the assimilation window and for 3-7 h thereafter. The 1D+4D-VAR approach performs best, significantly improving precipitation root mean square errors by 25% and 27.5% compared to the control during the assimilation window on the two cases. This finding confirms that the variational nD-VAR (n=3,4) assimilation of lightning observations improves the accuracy of moisture analyses and forecasts. Finally, we briefly discuss limitations inherent in the current lightning assimilation schemes, their implications, and possible ways to improve them.

math.OC↗

arXiv2013

Influence of refraction on wind turbine noise

A semi-empirical method is applied to calculate the time-average sound level of wind turbine noise generation and propagation. Both are affected by wind shear refraction. Under upwind conditions the partially ensonified zone separates the fully ensonified zone (close to the turbine) and the shadow zone (far away from the turbine). Refraction is described in terms of the wind speed linear profile fitted to the power law profile. The rotating blades are treated as a two-dimensional circular source in the vertical plane. Inside the partially ensonified zone the effective A-weighted sound power decreases to zero when the receiver moves from the turbine toward the shadow zone. The presented results would be useful in practical applications to give a quick estimate of the effect of refraction on wind turbine noise.

physics.ao-ph↗

arXiv2013

Generation of concentration density maxima of small dispersive coal dust particles in horizontal iodine air filter at air-dust aerosol blow

The spatial distributions of the small dispersive coal dust particles with the nano and micro sizes in the granular filtering medium with the cylindrical coal granules in the absorber in the horizontal iodine air filter during its long term operation at the nuclear power plant are researched. It is shown that the concentration density maxima of the small dispersive coal dust particles appear in the granular filtering medium with the cylindrical coal absorbent granules in the horizontal iodine air filter at an action by the air dust aerosol blow. The comparison of the measured aerodynamic resistances of the horizontal and vertical iodine air filters is conducted. The main conclusion is that the magnitude of the aerodynamic resistance of the horizontal iodine air filters is much smaller in comparison with the magnitude of the aerodynamic resistance of the vertical iodine air filters at the same loads of the air dust aerosol volumes. It is explained that the direction of the air dust aerosol blow and the direction of the gravitation force in the horizontal iodine air filter are orthogonal, hence the effective accumulation of the small dispersive coal dust particles takes place at the bottom of absorber in the horizontal iodine air filter. It is found that the air dust aerosol stream flow in the horizontal iodine air filter is not limited by the appearing structures, made of the precipitated small dispersive coal dust particles, in distinction from the vertical iodine air filter, in the process of long term operation of the iodine air filters at the nuclear power plant.

cond-mat.other↗

arXiv2013

Distribution of small dispersive coal dust particles and absorbed radioactive chemical elements in conditions of forced acoustic resonance in iodine air filter at nuclear power plant

The physical features of distribution of the small dispersive coal dust particles and the adsorbed radioactive chemical elements and their isotopes in the absorber with the granular filtering medium with the cylindrical coal granules were researched in the case of the intensive air dust aerosol stream flow through the iodine air filter (IAF). It was shown that, at the certain aerodynamic conditions in the IAF, the generation of the acoustic oscillations is possible. It was found that the acoustic oscillations generation results in an appearance of the standing acoustic waves of the air pressure (density) in the IAF. In the case of the intensive blow of the air dust aerosol, it was demonstrated that the standing acoustic waves have some strong influences on both: 1) the dynamics of small dispersive coal dust particles movement and their accumulation in the IAF; 2) the oversaturation of the cylindrical coal granules by the adsorbed radioactive chemical elements and their isotopes in the regions, where the antinodes of the acoustic waves are positioned. Finally, we completed the comparative analysis of the theoretical calculations with the experimental results, obtained for the cases of: 1) the experimental aerodynamic modeling of physical processes of the absorbed radioactive chemical elements and their isotopes distribution in the IAF; and 2) the gamma-activation spectroscopy analysis of the absorbed radioactive chemical elements and their isotopes distribution in the IAF. We made the innovative propositions on the necessary technical modifications with the purpose to improve the IAF technical characteristics and increase its operational time at the nuclear power plant (NPP), going from the completed precise characterization of the IAF parameters at the long term operation.

physics.ao-ph↗

arXiv2013

Transformation of deep-water methane bubbles into hydrate

The paper is dedicated to the mechanics of the methane bubbles in the gas hydrate stability zone of the basin. Transformation of deep-water methane bubbles into solid hydrate was investigated in Lake Baikal in situ. Released from the bottom methane bubbles were caught by different traps with transparent walls. It was observed that when bubbles entered into internal space of the trap, the bubbles could be transformed into two different solid hydrate structures depending on ambient conditions. The first structure is hydrate granular matter consisted of solid fragments with sizes of order of 1 mm. The second structure is high porous solid foam consisted of solid bubbles with sizes of order of 5 mm. The formed granular matter did not change during trap lifting up to top border of gas hydrate stability zone, whereas free methane intensively released from solid foam sample during it lifting. It was concluded that the decrease of the depth of bubble sampling and the decrease of the bubble flux rate assist to formation of hydrate granular matter, whereas increase of the depth of bubble sampling and growth of bubble flux rate assist to conversation of bubbles into high porous solid hydrate foam.

physics.flu-dyn↗

arXiv2013

First measurement of the small-scale spatial variability of the rain drop size distribution: Results from a crucial experiment and maximum entropy modeling

The main challenges of measuring precipitation are related to the spatio-temporal variability of the drop-size distribution, to the uncertainties that condition the modeling of that distribution, and to the instrumental errors present in the in situ estimations. This PhD dissertation proposes advances in all these questions. The relevance of the spatial variability of the drop-size distribution for remote sensing measurements and hydro-meteorology field studies is asserted by analyzing the measurement of a set of disdrometers deployed on a network of 5 squared kilometers. This study comprises the spatial variability of integral rainfall parameters, the ZR relationships, and the variations within the one moment scaling method. The modeling of the drop-size distribution is analyzed by applying the MaxEnt method and comparing it with the methods of moments and the maximum likelihood. The instrumental errors are analyzed with a compressive comparison of sampling and binning uncertainties that affect actual devices. These analysis are further extended in several appendices where an error analysis is developed and new studies are proposed. The relevance of the pre-processing of disdrometric measurements is also assessed. The data-sets evaluated comprise experimental measurements of the GPM (NASA-JAXA) ground validation satellite mission and synthetic distributions generated computationally.

physics.ao-ph↗

arXiv2013

Continuous Forest Fire Propagation in a Local Small World Network Model

This paper presents the development of a new continuous forest fire model implemented as a weighted local small-world network approach. This new approach was designed to simulate fire patterns in real, heterogeneous landscapes. The wildland fire spread is simulated on a square lattice in which each cell represents an area of the land's surface. The interaction between burning and non-burning cells, in the present work induced by flame radiation, may be extended well beyond nearest neighbors. It depends on local conditions of topography and vegetation types. An approach based on a solid flame model is used to predict the radiative heat flux from the flame generated by the burning of each site towards its neighbors. The weighting procedure takes into account the self-degradation of the tree and the ignition processes of a combustible cell through time. The model is tested on a field presenting a range of slopes and with data collected from a real wildfire scenario. The critical behavior of the spreading process is investigated.

physics.ao-ph↗

arXiv2013

Using Data to Tune Nearshore Dynamics Models: A Bayesian Approach with Parametric Likelihood

We propose a modification of a maximum likelihood procedure for tuning parameter values in models, based upon the comparison of their output to field data. Our methodology, which uses polynomial approximations of the sample space to increase the computational efficiency, differs from similar Bayesian estimation frameworks in the use of an alternative likelihood distribution, is shown to better address problems in which covariance information is lacking, than its more conventional counterpart. Lack of covariance information is a frequent challenge in large-scale geophysical estimation. This is the case in the geophysical problem considered here. We use a nearshore model for long shore currents and observational data of the same to show the contrast between both maximum likelihood methodologies. Beyond a methodological comparison, this study gives estimates of parameter values for the bottom drag and surface forcing that make the particular model most consistent with data; furthermore, we also derive sensitivity estimates that provide useful insights regarding the estimation procedure as well as of the model itself.

physics.data-an↗

arXiv2013

Coupled Mesoscale-Large-Eddy Modeling of Realistic Stable Boundary Layer Turbulence

Site-specific flow and turbulence information are needed for various practical applications, ranging from aerodynamic/aeroelastic modeling for wind turbine design to optical diffraction calculations. Even though highly desirable, collecting on-site meteorological measurements can be an expensive, time-consuming, and sometimes a challenging task. In this work, we propose a coupled mesoscale-large-eddy modeling framework to synthetically generate site-specific flow and turbulence data. The workhorses behind our framework are a state-of-the-art, open-source atmospheric model called the Weather Research and Forecasting (WRF) model and a tuning-free large-eddy simulation (LES) model. Using this coupled framework, we simulate a nighttime stable boundary layer (SBL) case from the well-known CASES-99 field campaign. One of the unique aspects of this work is the usage of a diverse range of observations for characterization and validation. The coupled models reproduce certain characteristics of observed low-level jets. They also capture various scaling regimes of energy spectra, including the so-called spectral gap. However, the coupled models are unable to capture the intermittent nature of the observed surface fluxes. Lastly, we document and discuss: (i) the tremendous spatio-temporal variabilities of observed and modeled SBL flow fields, and (ii) the significant disagreements among different observational platforms. Based on these results, we strongly recommend that future SBL modeling studies consider rigorous validation exercises based on multi-sensor/multi-platform datasets. In summary, we believe that the numerical generation of realistic SBL is not an impossible task. Without any doubt, there remain several computational and fundamental challenges. The present work should be viewed as a first step to confront some of these challenges.

physics.ao-ph↗

arXiv2013

On the choice of ingredients for a theory of the Ice Ages

"With five parameters one can fit an elephant". This provocative statement expresses the fact that when a theory has several adjustable parameters, an agreement with empirical data can be of modest value. What about a theory which contains unobserved objects? This is the subject of this paper. It is motivated by a model of the Ice Ages of the Pleistocene, which postulates a hot planet in an extremely eccentric orbit. This object has many consequences. It is rather well defined by the requirements, that it must not be in conflict with laws of nature, nor with empirical data. It must have sufficient mass to produce a rapid geographic pole shift on Earth after a close flyby at the end of the Pleistocene, and also be small enough to disintegrate at this occasion and to evaporate during the Holocene. These requirements leave hardly any adaptable parameters. In this situation, the agreement with further data, in particular the reverse Dansgaard-Oeschger events of the Holocene, represents a significant support of this theory.

physics.ao-ph↗

arXiv2013

Krypton-85 in the atmosphere

Measurement results are presented on 85Kr content in the atmosphere over the European part of Russia in 1971-1995 based on the analysis of the commercial krypton, which is separated from air by industrial plants. Our results are by 15 per cent lower then 85Kr activites observed over West Europe. According our prediction by 2030 85Kr content in the atmosphere over Europe will amount to 1,5-3 Bq in m3 air. Average 85Kr release to the atmosphere from regeneration of spent nuclear fuel (SNF) is estimated, some 180 TBq per a ton SNF. It is advisable to recommence monitoring of 85Kr content within Russia.

physics.ao-ph↗

arXiv2013

Features of adsorbed radioactive chemical elements and their isotopes distribution in iodine air filters AU-1500 at nuclear power plants

The main aim of research is to investigate the physical features of spatial distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the iodine air filters of the type of AU1500 in the forced exhaust ventilation systems at the nuclear power plant. The gamma activation analysis method is applied to accurately characterize the distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the AU1500 iodine air filter after its long term operation at the nuclear power plant. The typical spectrum of the detected chemical elements and their isotopes in the AU1500 iodine air filter, which was exposed to the bremsstrahlung gamma quantum irradiation, produced by the accelerating electrons in the tantalum target, are obtained. The spatial distributions of the detected chemical element 127I and some other chemical elements and their isotopes in the layer of absorber, which was made of the cylindrical coal granules of the type of SKT3, in the AU1500 iodine air filter are also researched. The possible influences by the standing acoustic wave of air pressure in the iodine air filter on the spatial distribution of the chemical elements and their isotopes in the iodine air filter are discussed. The comprehensive analysis of obtained research results on the distribution of the adsorbed chemical elements and their isotopes in the absorber of iodine air filter is performed.

physics.ao-ph↗

arXiv2013

On the effects of size factor on albedo versus wavelength for light scattered by small particles under Mie and Rayleigh regimes

Scattering by particles significantly smaller than the wavelength is an important physical process in the rocky bodies in our solar system and beyond. A number of observations of spectral bluing (referred to in those papers as "Rayleigh scattering") on planetary surfaces have been recently reported, however, the necessary mathematical modeling of this phenomenon has not yet achieved maturity. This paper is a first step to this effect, by examining the effect of grain size and optical index on the albedo of small conservative and absorbing particles as a function of wavelength. The basic conditions necessary for spectral bluing or reddening to be observed in real-world situations are identified. We find that any sufficiently monomodal size distribution of scattering particles will cause spectral bluing in some part of the EM spectrum regardless of its optical index.

physics.optics↗

arXiv2013

Multi-horizon solar radiation forecasting for Mediterranean locations using time series models

Considering the grid manager's point of view, needs in terms of prediction of intermittent energy like the photovoltaic resource can be distinguished according to the considered horizon: following days (d+1, d+2 and d+3), next day by hourly step (h+24), next hour (h+1) and next few minutes (m+5 e.g.). Through this work, we have identified methodologies using time series models for the prediction horizon of global radiation and photovoltaic power. What we present here is a comparison of different predictors developed and tested to propose a hierarchy. For horizons d+1 and h+1, without advanced ad hoc time series pre-processing (stationarity) we find it is not easy to differentiate between autoregressive moving average (ARMA) and multilayer perceptron (MLP). However we observed that using exogenous variables improves significantly the results for MLP . We have shown that the MLP were more adapted for horizons h+24 and m+5. In summary, our results are complementary and improve the existing prediction techniques with innovative tools: stationarity, numerical weather prediction combination, MLP and ARMA hybridization, multivariate analysis, time index, etc.

physics.ao-ph↗

arXiv2013

The Earth's Equilibrium Climate Sensitivity and Thermal Inertia

The Earth's equilibrium climate sensitivity has received much attention because of its relevance and importance for global warming policymaking. This paper focuses on the Earth's \emph{thermal inertia time scale} which has received relatively little attention. The difference between the observed transient climate sensitivity and the equilibrium climate sensitivity is shown to be proportional to the thermal inertia time scale, and the numerical value of the proportionality factor is determined using recent observational data. Many useful policymaking insights can be extracted from the resulting empirical quantitative relation.

physics.ao-ph↗

arXiv2013

Contextualizing the global relevance of local land change observations

To understand global changes in the Earth system, scientists must generalize globally from observations made locally and regionally. In land change science (LCS), local field-based observations are costly and time consuming, and generally obtained by researchers working at disparate local and regional case-study sites chosen for different reasons. As a result, global synthesis efforts in LCS tend to be based on non-statistical inferences subject to geographic biases stemming from data limitations and fragmentation. Thus, a fundamental challenge is the production of generalized knowledge that links evidence of the causes and consequences of local land change to global patterns and vice versa. The GLOBE system was designed to meet this challenge. GLOBE aims to transform global change science by enabling new scientific workflows based on statistically robust, globally relevant integration of local and regional observations using an online social-computational and geovisualization system. Consistent with the goals of Digital Earth, GLOBE has the capability to assess the global relevance of local case-study findings within the context of over 50 global biophysical, land-use, climate, and socio-economic datasets. We demonstrate the implementation of one such assessment - a representativeness analysis - with a recently published meta-study of changes in swidden agriculture in tropical forests. The analysis provides a standardized indicator to judge the global representativeness of the trends reported in the meta-study, and a geovisualization is presented that highlights areas for which sampling efforts can be reduced and those in need of further study. GLOBE will enable researchers and institutions to rapidly share, compare, and synthesize local and regional studies within the global context, as well as contributing to the larger goal of creating a Digital Earth.

stat.AP↗

arXiv2013

Statistical significance of rising and oscillatory trends in global ocean and land temperature in the past 160 years

Various interpretations of the notion of a trend in the context of global warming are discussed, contrasting the difference between viewing a trend as the deterministic response to an external forcing and viewing it as a slow variation which can be separated from the background spectral continuum of long-range persistent climate noise. The emphasis in this paper is on the latter notion, and a general scheme is presented for testing a multi-parameter trend model against a null hypothesis which models the observed climate record as an autocorrelated noise. The scheme is employed to the instrumental global sea-surface temperature record and the global land-temperature record. A trend model comprising a linear plus an oscillatory trend with period of approximately 60 yr, and the statistical significance of the trends, are tested against three different null models: first-order autoregressive process, fractional Gaussian noise, and fractional Brownian motion. The linear trend is significant in all cases, but the oscillatory trend is insignificant for ocean data and barely significant for land data. By means of a Bayesian iteration, however, using the significance of the linear trend to formulate a sharper null hypothesis, the oscillatory trend in the land record appears to be statistically significant. The results suggest that the global land record may be better suited for detection of the global warming signal than the ocean record.

physics.ao-ph↗