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Doppler W-band polarization diversity space-borne radar simulator for wind studies
CloudSat observations are used in combination with collocated European Centre for Medium-Range
Weather Forecasts (ECMWF) reanalysis to simulate spaceborne W-band Doppler observations from slant-looking
radars. The simulator also includes cross-polarization effects
which are relevant if the Doppler velocities are derived from
polarization diversity pulse pair correlation. A specific conically scanning radar configuration (WIVERN), recently proposed to the ESA-Earth Explorer 10 call that aims to provide
global in-cloud winds for data assimilation, is analysed in
detail in this study.
One hundred granules of CloudSat data are exploited to investigate the impact on Doppler velocity estimates from three
specific effects: (1) non-uniform beam filling, (2) wind shear
and (3) crosstalk between orthogonal polarization channels
induced by hydrometeors and surface targets. Errors associated with non-uniform beam filling constitute the most important source of error and can account for almost 1 m s−1
standard deviation, but this can be reduced effectively to less
than 0.5 m s−1 by adopting corrections based on estimates
of vertical reflectivity gradients. Wind-shear-induced errors
are generally much smaller (∼ 0.2 m s−1
). A methodology
for correcting these errors has been developed based on estimates of the vertical wind shear and the reflectivity gradient. Low signal-to-noise ratios lead to higher random errors
(especially in winds) and therefore the correction (particularly the one related to the wind-shear-induced error) is less
effective at low signal-to-noise ratio. Both errors can be underestimated in our model because the CloudSat data do not
fully sample the spatial variability of the reflectivity fields,
whereas the ECMWF reanalysis may have smoother velocity fields than in reality (e.g. they underestimate vertical wind
shear).
The simulator allows for quantification of the average
number of accurate measurements that could be gathered by
the Doppler radar for each polar orbit, which is strongly impacted by the selection of the polarization diversity H − V
pulse separation, Thv. For WIVERN a selection close to 20 µs
(with a corresponding folding velocity equal to 40 m s−1
)
seems to achieve the right balance between maximizing the
number of accurate wind measurements (exceeding 10 % of
the time at any particular level in the mid-troposphere) and
minimizing aliasing effects in the presence of high winds.
The study lays the foundation for future studies towards
a thorough assessment of the performance of polar orbiting
wide-swath W-band Doppler radars on a global scale. The
next generation of scanning cloud radar systems and reanalyses with improved resolution will enable a full capture of the
spatial variability of the cloud reflectivity and the in-cloud
wind fields, thus refining the results of this study
Hybrid Pixel Detector Development for the Linear Collider Vertex Tracker
In order to fully exploit the physics potential of the future high energy
e+e- linear collider, a Vertex Tracker able to provide particle track
extrapolation with very high resolution is needed. Hybrid Si pixel sensors are
an attractive technology due to their fast read-out capabilities and radiation
hardness. A novel pixel detector layout with interleaved cells has been
developed to improve the single point resolution. Results of the
characterisation of the first processed prototypes by electrostatic
measurements and charge collection studies are discussed.Comment: 5 pages, 1 figure, to appear in the Proceedings of the 9th Int.
Workshop on Vertex Detectors, Lake Michigan MI (USA), September~200
Convex Polytopes and Quasilattices from the Symplectic Viewpoint
We construct, for each convex polytope, possibly nonrational and nonsimple, a
family of compact spaces that are stratified by quasifolds, i.e. each of these
spaces is a collection of quasifolds glued together in an suitable way. A
quasifold is a space locally modelled on modulo the action of a
discrete, possibly infinite, group. The way strata are glued to each other also
involves the action of an (infinite) discrete group. Each stratified space is
endowed with a symplectic structure and a moment mapping having the property
that its image gives the original polytope back. These spaces may be viewed as
a natural generalization of symplectic toric varieties to the nonrational
setting.Comment: LaTeX, 29 pages. Revised version: TITLE changed, reorganization of
notations and exposition, added remarks and reference
Magma and fluid migration at Yellowstone Caldera in the last three decades inferred from InSAR, leveling and gravity measurements
We studied the Yellowstone caldera geological unrest between 1977 and 2010 by investigating
temporal changes in differential Interferometric Synthetic Aperture Radar (InSAR), precise spirit leveling and
gravity measurements. The analysis of the 1992–2010 displacement time series, retrieved by applying the SBAS
InSAR technique, allowed the identification of three areas of deformation: (i) the Mallard Lake (ML) and Sour
Creek (SC) resurgent domes, (ii) a region close to the Northern Caldera Rim (NCR), and (iii) the eastern Snake
River Plain (SRP). While the eastern SRP shows a signal related to tectonic deformation, the other two regions
are influenced by the caldera unrest. We removed the tectonic signal from the InSAR displacements, and we
modeled the InSAR, leveling, and gravity measurements to retrieve the best fitting source parameters. Our
findings confirmed the existence of different distinct sources, beneath the brittle-ductile transition zone, which
have been intermittently active during the last three decades. Moreover, we interpreted our results in the light
of existing seismic tomography studies. Concerning the SC dome, we highlighted the role of hydrothermal
fluids as the driving force behind the 1977–1983 uplift; since 1983–1993 the deformation source transformed
into a deeper one with a higher magmatic component. Furthermore, our results support the magmatic nature
of the deformation source beneath ML dome for the overall investigated period. Finally, the uplift at NCR is
interpreted as magma accumulation, while its subsidence could either be the result of fluids migration outside
the caldera or the gravitational adjustment of the source from a spherical to a sill-like geometr
Multi-Higgs boson production in the Standard Model and beyond
We present a calculation of the loop-induced processes gg -> HH and gg ->
HHH, and investigate the observability of multi-Higgs boson production at the
CERN Large Hadron Collider (LHC) in the Standard Model (SM) and beyond. While
the SM cross sections are too small to allow observation at the LHC, we
demonstrate that physics beyond the SM can lead to amplified, observable cross
sections. Furthermore, the applicability of the heavy top quark approximation
in two- and three-Higgs boson production is investigated. We conclude that
multi-Higgs boson production at the SuperLHC is an interesting probe of Higgs
sectors beyond the SM and warrants further study.Comment: 17 pages, 17 figure
The Symplectic Penrose Kite
The purpose of this article is to view the Penrose kite from the perspective
of symplectic geometry.Comment: 24 pages, 7 figures, minor changes in last version, to appear in
Comm. Math. Phys
Activated Tryptophan-Kynurenine metabolic system in the human brain is associated with learned fear
Fear is widely recognized as a defensive emotion that has developed as a consequence
of its adaptive function in protecting the entire animal kingdom from danger, ensuring
the survival (Bouton, 2002; Milad and Quirk, 2002). Although fear associated with specific
stimuli is an innate emotion (e.g., a loud noise triggering fear in infants, fear of potential
predators), it can also be acquired rapidly and permanently to enable an appropriate and
adaptive response to new or unpredictable environmental situations (LeDoux, 2000; Beckers
et al., 2013)
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