111 research outputs found
Reflections on the Scientific Legacy of Sergej S. Zilitinkevich on PBL and Urban Parameterizations in NWP Models
The paper summarizes many of the scientific achievements of Professor Sergej S. Zilitinkevich (1936–2021). It first focuses on his basic and applied atmospheric boundary layer research contributions. It then reviews their applications within research and operational numerical weather prediction and air quality modeling, showing their contribution to solving modeling problems related to extremely-stable and -unstable boundary layers
Volatility Prediction using Financial Disclosures Sentiments with Word Embedding-based IR Models
Volatility prediction--an essential concept in financial markets--has
recently been addressed using sentiment analysis methods. We investigate the
sentiment of annual disclosures of companies in stock markets to forecast
volatility. We specifically explore the use of recent Information Retrieval
(IR) term weighting models that are effectively extended by related terms using
word embeddings. In parallel to textual information, factual market data have
been widely used as the mainstream approach to forecast market risk. We
therefore study different fusion methods to combine text and market data
resources. Our word embedding-based approach significantly outperforms
state-of-the-art methods. In addition, we investigate the characteristics of
the reports of the companies in different financial sectors
Synthetic Light Curves of Shocked Dense Circumstellar Shells
We numerically investigate light curves (LCs) of shocked circumstellar shells
which are suggested to reproduce the observed LC of superluminous SN 2006gy
analytically. In the previous analytical model, the effects of the
recombination and the bolometric correction on LCs are not taken into account.
To see the effects, we perform numerical radiation hydrodynamic calculations of
shocked shells by using STELLA, which can numerically treat multigroup
radiation transfer with realistic opacities. We show that the effects of the
recombination and the bolometric correction are significant and the analytical
model should be compare to the bolometric LC instead of a single band LC. We
find that shocked circumstellar shells have a rapid LC decline initially
because of the adiabatic expansion rather than the luminosity increase and the
shocked shells fail to explain the LC properties of SN 2006gy. However, our
synthetic LCs are qualitatively similar to those of superluminous SN 2003ma and
SN 1988Z and they may be related to shocked circumstellar shells.Comment: 7 pages, 7 figures, 1 table, accepted by Monthly Notices of the Royal
Astronomical Societ
Model Simulations of Local Meteorological Conditions in the Vicinity of a Hypothetical Nuclear Power Plant in Jordan
As a solution for the increasing energy demand in Jordan, nuclear power was recommended for the energy mix at the national level. However, investigations of the meteorological conditions and mass transfer have never been conducted and reported earlier based on typical Jordanian conditions in order to have prior knowledge in case of a future hypothetical nuclear accident in Jordan. In this study, the variabilities of horizontal and vertical wind components and surface temperature differences have been investigated near one of the originally suggested locations for the construction of a nuclear power plant facility. That proposed location is the site of the Samra Energy Power Plant (SEPP). The selected domain of the simulation model was 85×85 km2 in area (17×17 grid points and 13 vertical layers) surrounding the SEPP site. The simulations revealed that the wind direction near the surface was developed to comply with the complexity of the terrain regardless of the input values of the prevailing wind direction. The wind direction propagated along the valleys that are surrounded by the dominating mountains. The surface wind speed was proportional to the input value of the wind speed as well as to the slope of the surrounding terrain. Quantitatively, the developed surface wind speed was 0.5–2.1 m/s in January compared with 1.0–4.3 m/s in July. The vertical component of wind velocity was the lowest (nearly zero in January versus ~0.1 m/s in July) near the surface. In practice, the main outcome of this investigation can serve as a base-block for considering other possible geographical locations for the construction of a nuclear power plant in Jordan and for case studies intended to assess possible consequences in case of accidental releases and other potential accidents of possible nuclear, chemical, industrial danger.Peer reviewe
Direct variational assimilation algorithm for atmospheric chemistry data with transport and transformation model
Atmospheric chemistry dynamics is studied with convection-diffusion-reaction model. The numerical Data Assimilation algorithm presented is based on the additive-averaged splitting schemes. It carries out ''fine-grained'' variational data assimilation on the separate splitting stages with respect to spatial dimensions and processes i.e. the same measurement data is assimilated to different parts of the split model. This design has efficient implementation due to the direct data assimilation algorithms of the transport process along coordinate lines. Results of numerical experiments with chemical data assimilation algorithm of in situ concentration measurements on real data scenario have been presented. In order to construct the scenario, meteorological data has been taken from EnviroHIRLAM model output, initial conditions from MOZART model output and measurements from Airbase database. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
Cell Model of In-cloud Scavenging of Highly Soluble Gases
We investigate mass transfer during absorption of highly soluble gases such
as HNO_{3}, H_{2}O_{2} by stagnant cloud droplets in the presence of inert
admixtures. Thermophysical properties of the gases and liquids are assumed to
be constant. Diffusion interactions between droplets, caused by the overlap of
depleted of soluble gas regions around the neighboring droplets, are taken into
account in the approximation of a cellular model of a gas-droplet suspension
whereby a suspension is viewed as a periodic structure consisting of the
identical spherical cells with periodic boundary conditions at the cell
boundary. Using this model we determined temporal and spatial dependencies of
the concentration of the soluble trace gas in a gaseous phase and in a droplet
and calculated the dependence of the scavenging coefficient on time. It is
shown that scavenging of highly soluble gases by cloud droplets leads to
essential decrease of soluble trace gas concentration in the interstitial air.
We found that scavenging coefficient for gas absorption by cloud droplets
remains constant and sharply decreases only at the final stage of absorption.
In the calculations we employed gamma size distribution of cloud droplets. It
was shown that despite of the comparable values of Henry's law constants for
the hydrogen peroxide (H2O2) and the nitric acid (HNO3), the nitric acid is
scavenged more effectively by cloud than the hydrogen peroxide due to a major
affect of the dissociation reaction on HNO3 scavenging.Comment: 28 pages, including 11 Figures, 1 Tabl
- …