The Amplitude Asymmetry between Synoptic Cyclones and Anticyclones: Implications for Filtering Methods in Feature Tracking

2009 ◽  
Vol 137 (11) ◽  
pp. 3874-3887 ◽  
Author(s):  
Aaron Donohoe ◽  
David S. Battisti
Keyword(s):  
Feature Tracking ◽  
Mean Field ◽  
Spatial Filter ◽  
Large Contribution ◽  
Small Magnitude ◽  
Sea Level Pressure ◽  
Temporal Filter ◽  
Mean Fields ◽  
Comparable Magnitude ◽  
Unfiltered Data

Abstract The “background” state is commonly removed from synoptic fields by use of either a spatial or temporal filter prior to the application of feature tracking. Commonly used spatial and temporal filters applied to sea level pressure data admit substantially different information to be included in the synoptic fields. The spatial filter retains a time-mean field that has comparable magnitude to a typical synoptic perturbation. In contrast, the temporal filter removes the entire time-mean field. The inclusion of the time-mean spatially filtered field biases the feature tracking statistics toward large cyclone (anticyclone) magnitudes in the regions of climatological lows (highs). The resulting cyclone/anticyclone magnitude asymmetries in each region are found to be inconsistent with the unfiltered data fields and merely result from the spurious inclusion of the time-mean fields in the spatially filtered data. The temporally filtered fields do not suffer from the same problem and produce modest cyclone/anticyclone magnitude asymmetries that are consistent with the unfiltered data. This analysis suggests that the weather forecaster’s assertion that cyclones have larger amplitudes than anticyclones is due to a composite of a small magnitude asymmetry in the synoptic waves and a large contribution from inhomogeneity in the background (stationary) field.

scholarly journals Reflections on the origin of the EMC effect

2018 ◽  
Vol 27 (12) ◽  
pp. 1840001 ◽  
Author(s):  
Anthony W. Thomas
Keyword(s):  
Short Range ◽  
Mean Field ◽  
Atomic Nuclei ◽  
Lorentz Scalar ◽  
Valence Structure ◽  
Mean Fields ◽  
European Muon Collaboration ◽  
The Mean ◽  
Emc Effect ◽  
Short Range Correlations

In the 35 years since the European Muon Collaboration announced the astonishing result that the valence structure of a nucleus was very different from that of a free nucleon, many explanations have been suggested. The first of the two most promising explanations is based upon the different effects of the strong Lorentz scalar and vector mean fields known to exist in a nucleus on the internal structure of the nucleon-like clusters which occupy shell model states. The second links the effect to the modification of the structure of nucleons involved in short-range correlations, which are far off their mass shell. We explore some of the methods which have been proposed to give complementary information on this puzzle, especially the spin-dependent EMC effect and the isovector EMC effect, both proposed by Cloët, Bentz and Thomas. It is shown that the predictions for the spin-dependent EMC effect, in particular, differ substantially within the mean-field and short-range correlation approaches. Hence, the measurement of the spin-dependent EMC effect at Jefferson Lab should give us a deeper understanding of the origin of the EMC effect and, indeed, of the structure of atomic nuclei.

DYNAMICAL SYMMETRY OF A DIMER CLIFFORD MEAN-FIELD EXTENDED FALICOV-KIMBALL MODEL

1992 ◽  
Vol 06 (25) ◽  
pp. 1583-1592 ◽  
Author(s):  
ANDREA DANANI ◽  
MARIO RASETTI
Keyword(s):  
Mean Field ◽  
Dynamical Symmetry ◽  
Linearization Technique ◽  
Mean Fields

In this letter, resorting to the Fermi-linearization technique, implemented for a two-site (dimer) cluster, we study the structure of dynamical symmetry which the use of Grassmann-Clifford mean-fields leads to, in the case of an extended Falicov-Kimball model. The resulting scheme to diagonalize the Hamiltonian is also discussed.

scholarly journals Improved pion mean fields and masses of singly heavy baryons

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
June-Young Kim ◽  
Hyun-Chul Kim
Keyword(s):  
Heavy Quark ◽  
Mass Spectra ◽  
Valence Quark ◽  
Mean Field ◽  
Heavy Baryon ◽  
The Other ◽  
Field Approach ◽  
Heavy Baryons ◽  
Mean Fields ◽  
Color Source

Abstract A singly heavy baryon can be viewed as $N_c-1$ ($N_c$ being the number of colors) light valence quarks bound by the pion mean fields that are created by the presence of the $N_c-1$ valence quarks self-consistently, while the heavy quark inside a singly heavy baryon is regarded as a static color source. We investigate how the pion mean fields are created by the presence of $N_c$, $N_c-1$, and $N_c-2$ light valence quarks, which correspond to the systems of light baryons, singly heavy baryons, and doubly heavy baryons. As the number of colors decreases from $N_c$ to $N_c-1$, the pion mean fields undergo changes. As a result, the valence quark contributions to the moments of inertia of the soliton become larger than for $N_c$ valence quarks, whereas the sea quark contributions decrease systematically. On the other hand, the presence of the $N_c-2$ valence quarks is not enough to produce the strong pion mean fields, which leads to the classical soliton not being formed. This indicates that the pion mean-field approach is not suitable to describe doubly heavy baryons. We show that the mass spectra of the singly heavy baryons are better described by the improved pion mean fields, compared with the previous work in which the pion mean fields are assumed to be intact with $N_c$ varied.

scholarly journals Momentum dependent mean-fields of hyperons & antihyperons

2021 ◽  
Vol 252 ◽  
pp. 05006
Author(s):  
Arsenia Chorozidou ◽  
Theodoros Gaitanos
Keyword(s):  
Experimental Studies ◽  
Mean Field ◽  
Nuclear Astrophysics ◽  
Effective Field ◽  
Momentum Dependence ◽  
Chiral Effective Field Theory ◽  
Relativistic Mean Field ◽  
Optical Potentials ◽  
Nuclear Systems ◽  
Mean Fields

The in-medium properties of hyperons and antihyperons are studied with the Non-Linear Derivative (NLD) model and focus is made on the momentum dependence of strangeness optical potentials. The NLD model is based on the Relativistic Mean Field (RMF) approximation to Relativistic Hadrodynamics (RHD) approach of nuclear systems, but it incorporates an explicit momentum dependence of mean-fields. The extension of the NLD model to the baryon and antibaryon octet is based on SU(6) and G-parity arguments. It is demonstrated that with a proper choice of momentum cut-offs, the Λ and Σ optical potentials are consistent with recent studies of the chiral effective field theory(χ -EFT) and optical potentials are consistent with Lattice-QCD calculations, over a wide momentum region. We also present NLD predictions for the in-medium momentum dependence of ∧¯, ∑¯ and Ξ¯ hyperons. This work is important for future experimental studies, like CBM, PANDA at FAIR and is relevant to nuclear astrophysics as well.

scholarly journals A unified quark-nuclear matter equation of state from the cluster virial expansion within the generalized Beth–Uhlenbeck approach

2021 ◽  
Vol 57 (1) ◽  
Author(s):  
Niels-Uwe Friedrich Bastian ◽  
David Bernhard Blaschke
Keyword(s):  
Phase Diagram ◽  
Phase Shift ◽  
Mean Field ◽  
Bound State ◽  
Strongly Correlated ◽  
Continuum Threshold ◽  
First Order Phase Transition ◽  
Mean Fields ◽  
First Order Phase ◽  
Transition Behaviour

AbstractWe consider a cluster expansion for strongly correlated quark matter where the clusters are baryons with spectral properties that are described within the generalized Beth–Uhlenbeck approach by a medium dependent phase shift. We employ a simple ansatz for the phase shift which describes an on-shell bound state with an effective mass and models the continuum by an anti-bound state located at the mass of the three-quark continuum threshold, so that the Levinson theorem is fulfilled by construction. The quark and baryon interactions are accounted for by the coupling to scalar and vector meson mean fields modelled by density functionals. At increasing density and temperature, due to the different medium-dependence of quark and baryon masses, the Mott dissociation of baryons occurs and its contributions to the thermodynamics vanish. It is demonstrated on this simple example that this unified approach to quark-hadron matter is capable of describing crossover as well as first order phase transition behaviour in the phase diagram with a critical endpoint. Changing the meson mean field, the case of a “crossover all over” in the phase diagram is also obtained.

scholarly journals Patterns of Land Surface Errors and Biases in the Global Forecast System

2011 ◽  
Vol 139 (5) ◽  
pp. 1569-1582 ◽  
Author(s):  
David Werth ◽  
Alfred Garrett
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
Air Temperature ◽  
Large Contribution ◽  
Global Forecast System ◽  
Forecast System ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Dewpoint Temperature ◽  
Mean Square Errors

One year’s worth of Global Forecast System (GFS) predictions of surface meteorological variables (wind speed, air temperature, dewpoint temperature, sea level pressure) are validated for land-based stations over the entire planet for forecasts extending from 0 h into the future (an analysis) to 7 days. Approximately 12 000 surface stations worldwide were included in this analysis. Root-mean-square errors (RMSEs) increased as the forecast period increased from 0 to 36 h, but the initial RMSEs were almost as large as the 36-h forecast RMSEs for all variables. Typical RMSEs were 3°C for air temperature, 2–3 mb for sea level pressure, 3.5°C for dewpoint temperature, and 2.5 m s−1 for wind speed. An analysis of the biases at each station shows that the biggest errors are associated with mountain ranges and other areas of steep topography, with land–sea contrasts also playing a role. When the error is decomposed into the bias, variance, and correlation terms, the large initial RMSEs for the 0-h forecasts are seen to be due to a large forecast bias (which persisted into the longer forecasts) with errors in forecast correlation also making a large contribution. A validation of two subdomains showed results similar to the global validation, but the dependence of the biases on the forecast time was clearer. Finally, the RMSE values climb as forecasts go out when validated out to a period of 7 days as the correlation error term grows.

Nice things about mean fields: Mean field potentials for the classroom

2000 ◽  
Vol 68 (9) ◽  
pp. 848-853 ◽  
Author(s):  
Leo Cheng ◽  
Elisheva Goldstein ◽  
P. B. Siegel
Keyword(s):  
Mean Field ◽  
Field Potentials ◽  
Mean Fields
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