192 research outputs found
SMOKE for Europe – adaptation, modification and evaluation of a comprehensive emission model for Europe
The US EPA regional emission model SMOKE was adopted and modified to create temporally and spatially distributed emission for Europe and surrounding countries based on official reports and public domain data only. The aim is to develop a flexible model capable of creating consistent high resolution emission data for long-term runs of Chemical Transport Models (CTMs). This modified version of SMOKE, called SMOKE for EUROPE (SMOKE-EU) was successfully used to create hourly gridded emissions for the timespan 1970–2010. <br><br> In this paper the SMOKE-EU model and the underlying European datasets are introduced. Emission data created by SMOKE-EU for the year 2000 are evaluated by comparison to data of three different state-of-the-art emission models. SMOKE-EU produced a range of values comparable to the other three datasets. Further, concentrations of criteria pollutants calculated by the CTM CMAQ using the four different emission datasets were compared against EMEP measurements with hourly and daily resolution. Using SMOKE-EU gave the most reliable modelling of O<sub>3</sub>, NO<sub>2</sub> and SO<sub>4</sub><sup>2&minus;</sup>. The amount of simulated concentrations within a factor of 2 (F2) of the observations for these species are: O<sub>3</sub> (F2 = 0.79, <i>N</i> = 329 197), NO<sub>2</sub> (F2 = 0.55, <i>N</i> = 11 465) and SO<sub>4</sub><sup>2&minus;</sup> (F2 = 0.62, <i>N</i> = 17 536). The lowest values were found for NH<sub>4</sub><sup>+</sup> (F2 = 0.34, <i>N</i> = 7400) and NO<sub>3</sub><sup>&minus;</sup> (F2 = 0.25, <i>N</i> = 6184). NH<sub>4</sub><sup>+</sup> concentrations were generally overestimated, leading to a fractional bias (FB) averaged over 22 measurement stations of (FB = 0.83 ± 0.41) while better agreements with observations were found for SO<sub>4</sub><sup>2&minus;</sup> (FB = 0.06 ± 0.38, 51 stations) and NO<sub>3</sub><sup>&minus;</sup> (FB = 0.13 &plusmn; 0.75, 18 stations). <br><br> CMAQ simulations using the three other emission datasets were similar to those modelled using SMOKE-EU emissions. Highest differences where found for NH<sub>4</sub><sup>+</sup> while O<sub>3</sub> concentrations were almost identical
Correcting for Distortions due to Ionization in the STAR TPC
Physics goals of the STAR Experiment at RHIC in recent (and future) years
drive the need to operate the STAR TPC at ever higher luminosities, leading to
increased ionization levels in the TPC gas. The resulting ionic space charge
introduces field distortions in the detector which impact tracking performance.
Further complications arise from ionic charge leakage into the main TPC volume
from the high gain anode region. STAR has implemented corrections for these
distortions based on measures of luminosity, which we present here.
Additionally, we highlight a novel approach to applying the corrections on an
event-by-event basis applicable in conditions of rapidly varying ionization
sources.Comment: 6 pages, 7 figures, proceedings of the Workshop on Tracking in High
Multiplicity Environments (TIME 05) in Zurich, Switzerland, submitted to
Nucl. Instr. and Meth.
Mercury distribution in the upper troposphere and lowermost stratosphere according to measurements by the IAGOS-CARIBIC observatory: 2014-2016
Mercury was measured onboard the IAGOSCARIBIC passenger aircraft from May 2005 until February 2016 during near monthly sequences of mostly four intercontinental flights from Germany to destinations in North and South America, Africa and South and East Asia. Most of these mercury data were obtained using an internal default signal integration procedure of the Tekran instrument but since April 2014 more precise and accurate data were obtained using post-flight manual integration of the instrument raw signal. In this paper we use the latter data. Increased upper tropospheric total mercury (TM) concentrations due to large scale biomass burning were observed in the upper troposphere (UT) at the equator and southern latitudes during the flights to Latin America and South Africa in boreal autumn (SON) and boreal winter (DJF). TM concentrations in the lowermost stratosphere (LMS) decrease with altitude above the thermal tropopause but the gradient is less steep than reported before. Seasonal variation of the vertical TM distribution in the UT and LMS is similar to that of other trace gases with surface sources and stratospheric sinks. Speciation experiments suggest comparable TM and gaseous elementary mercury (GEM) concentrations at and below the tropopause leaving little space for Hg2+ (TM-GEM) being the dominating component of TM here. In the stratosphere significant GEM concentrations were found to exist up to 4 km altitude above the thermal tropopause. Correlations with N2O as a reference tracer suggest stratospheric lifetimes of 72 ± 37 and 74 ± 27 years for TM and GEM, respectively, comparable to the stratospheric lifetime of COS. This coincidence, combined with pieces of evidence from us and other researchers, corroborates the hypothesis that Hg2+ formed by oxidation in the stratosphere attaches to sulfate particles formed mainly by oxidation of COS and is removed with them from the stratosphere by air mass exchange, gravitational sedimentation and cloud scavenging processes
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Thin window Si(Li) detectors for the ISEE-C Telescope
Special detectors have been developed for the NASA ISEE-C Cosmic Ray Telescope. These are Li-drifted silicon detectors 5 mm thick and 1500 mm/sup 2/ area with the criteria that thickness variations on the whole area be less than +-10 ..mu..m and that the Li-diffused contact dead-layer not exceed 15 ..mu..m. Techniques used to fabricate and test these detectors are presented
The energy dependence of flow in Ni induced collisions from 400 to 1970A MeV
We study the energy dependence of collective (hydrodynamic-like) nuclear
matter flow in 400-1970 A MeV Ni+Au and 1000-1970 A MeV Ni+Cu reactions. The
flow increases with energy, reaches a maximum, and then gradually decreases at
higher energies. A way of comparing the energy dependence of flow values for
different projectile-target mass combinations is introduced, which demonstrates
a common scaling behaviour among flow values from different systems.Comment: 12 pages, 3 figures. Submitted to Physical Review Letter
Radial Flow in Au+Au Collisions at E=0.25-1.15 A GeV
A systematic study of energy spectra for light particles emitted at
midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant
non-thermal component consistent with a collective radial flow. This component
is evaluated as a function of bombarding energy and event centrality.
Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck
(BUU) models are made for different equations of state.Comment: 10 pages of text and 4 figures (all ps files in a uuencoded package)
Seasonal ozone vertical profiles over North America using the AQMEII3 group of air quality models: model inter-comparison and stratospheric intrusions
This study evaluates simulated vertical ozone profiles produced in the
framework of the third phase of the Air Quality Model Evaluation
International Initiative (AQMEII3) against ozonesonde observations in North
America for the year 2010. Four research groups from the United States (US)
and Europe have provided modeled ozone vertical profiles to conduct this
analysis. Because some of the modeling systems differ in their meteorological
drivers, wind speed and temperature are also included in the analysis. In
addition to the seasonal ozone profile evaluation for 2010, we also analyze
chemically inert tracers designed to track the influence of lateral boundary
conditions on simulated ozone profiles within the modeling domain. Finally,
cases of stratospheric ozone intrusions during May–June 2010 are investigated
by analyzing ozonesonde measurements and the corresponding model simulations
at Intercontinental Chemical Transport Experiment Ozonesonde Network Study
(IONS) experiment sites in the western United States. The evaluation of the
seasonal ozone profiles reveals that, at a majority of the stations, ozone
mixing ratios are underestimated in the 1–6 km range. The seasonal change
noted in the errors follows the one seen in the variance of ozone mixing
ratios, with the majority of the models exhibiting less variability than the
observations. The analysis of chemically inert tracers highlights the
importance of lateral boundary conditions up to 250 hPa for the
lower-tropospheric ozone mixing ratios (0–2 km). Finally, for the stratospheric
intrusions, the models are generally able to reproduce the location and
timing of most intrusions but underestimate the magnitude of the maximum
mixing ratios in the 2–6 km range and overestimate ozone up to the first kilometer
possibly due to marine air influences that are not accurately described by
the models. The choice of meteorological driver appears to be a greater
predictor of model skill in this altitude range than the choice of air
quality model.</p
The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
The STAR Time Projection Chamber (TPC) is used to record collisions at the
Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a
suite of detectors that surrounds the interaction vertex. The TPC provides
complete coverage around the beam-line, and provides complete tracking for
charged particles within +- 1.8 units of pseudo-rapidity of the center-of-mass
frame. Charged particles with momenta greater than 100 MeV/c are recorded.
Multiplicities in excess of 3,000 tracks per event are routinely reconstructed
in the software. The TPC measures 4 m in diameter by 4.2 m long, making it the
largest TPC in the world.Comment: 28 pages, 11 figure
Statistical signatures of critical behavior in small systems
The cluster distributions of different systems are examined to search for
signatures of a continuous phase transition. In a system known to possess such
a phase transition, both sensitive and insensitive signatures are present;
while in systems known not to possess such a phase transition, only insensitive
signatures are present. It is shown that nuclear multifragmentation results in
cluster distributions belonging to the former category, suggesting that the
fragments are the result of a continuous phase transition.Comment: 31 pages, two columns with 30 figure
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