674,117 research outputs found
Acceleration of phenological advance and warming with latitude over the past century.
In the Northern Hemisphere, springtime events are frequently reported as advancing more rapidly at higher latitudes, presumably due to an acceleration of warming with latitude. However, this assumption has not been investigated in an analytical framework that simultaneously examines acceleration of warming with latitude while accounting for variation in phenological time series characteristics that might also co-vary with latitude. We analyzed 743 phenological trend estimates spanning 86 years and 42.6 degrees of latitude in the Northern Hemisphere, as well as rates of Northern Hemisphere warming over the same period and latitudinal range. We detected significant patterns of co-variation in phenological time series characteristics that may confound estimates of the magnitude of variation in trends with latitude. Notably, shorter and more recent time series tended to produce the strongest phenological trends, and these also tended to be from higher latitude studies. However, accounting for such variation only slightly modified the relationship between rates of phenological advance and latitude, which was highly significant. Furthermore, warming has increased non-linearly with latitude over the past several decades, most strongly since 1998 and northward of 59°N latitude. The acceleration of warming with latitude has likely contributed to an acceleration of phenological advance along the same gradient
Solar cycle variation of real CME latitudes
With the assumption of radial motion and uniform longitudinal distribution of
coronal mass ejections (CMEs), we propose a method to eliminate projection
effects from the apparent observed CME latitude distribution. This method has
been applied to SOHO LASCO data from 1996 January to 2006 December. As a
result, we find that the real CME latitude distribution had the following
characteristics: (1) High-latitude CMEs ( where is
the latitude) constituted 3% of all CMEs and mainly occurred during the time
when the polar magnetic fields reversed sign. The latitudinal drift of the
high-latitude CMEs was correlated with that of the heliospheric current sheet.
(2) 4% of all CMEs occurred in the range .
These mid-latitude CMEs occurred primarily in 2000, near the middle of 2002 and
in 2005, respectively, forming a prominent three-peak structure; (3) The
highest occurrence probability of low-latitude () CMEs was
at the minimum and during the declining phase of the solar cycle. However, the
highest occurrence rate of low-latitude CMEs was at the maximum and during the
declining phase of the solar cycle. The latitudinal evolution of low-latitude
CMEs did not follow the Sp\"{o}rer sunspot law, which suggests that many CMEs
originated outside of active regions.Comment: 4 pages, 4 figures, accepted by ApJ Lette
Habitat width along a latitudinal gradient
We use the Chowdhury ecosystem model, one of the most complex agent-based
ecological models, to test the latitude-niche breadth hypothesis, with regard
to habitat width, i.e., whether tropical species generally have narrower
habitats than high latitude ones. Application of the model has given realistic
results in previous studies on latitudinal gradients in species diversity and
Rapoport's rule. Here we show that tropical species with sufficient vagility
and time to spread into adjacent habitats, tend to have wider habitats than
high latitude ones, contradicting the latitude-niche breadth hypothesis.Comment: 13 pages including all figures, draft for a biology journa
Evidence for the Galactic contribution to the IceCube astrophysical neutrino flux
We show that the Galactic latitude distribution of IceCube astrophysical
neutrino events with energies above 100~TeV is inconsistent with the isotropic
model of the astrophysical neutrino flux. Namely, the Galactic latitude
distribution of the events shows an excess at low latitudes |b|<10 degrees and
a deficit at high Galactic latitude |b|> 50 degrees. We use Monte-Carlo
simulations to show that the inconsistency of the isotropic signal model with
the data is at > 3 sigma level, after the account of trial factors related to
the choice of the low-energy threshold and Galactic latitude binning in our
analysis.Comment: 4 pages, 2 figures, accepted to Astroparticle Physic
Transitivity, Moral Latitude, and Supererogation
On what I take to be the standard account of supererogation, an act is supererogatory if and only if it is morally optional and there is more moral reason to perform it than to perform some permissible alternative. And, on this account, an agent has more moral reason to perform one act than to perform another if and only if she morally ought to prefer how things would be if she were to perform the one to how things would be if she were to perform the other. I argue that this account has two serious problems. The first, which I call the latitude problem, is that it has counterintuitive implications in cases where the duty to be exceeded is one that allows for significant latitude in how to comply with it. The second, which I call the transitivity problem, is that it runs afoul of the plausible idea that the one-reason-morally-justifies-acting-against-another relation is transitive. Whatâs more, I argue that both problems can be overcome by an alternative account, which I call the maximalist account
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Latitude and longitude vertical disparities
The literature on vertical disparity is complicated by the fact that several different definitions of the term âvertical disparityâ are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude disparities. Near the fixation point, these definitions become equivalent, but in general, they have quite different dependences on object distance and binocular eye posture, which have not previously been spelt out. We present analytical approximations for each type of vertical disparity, valid for more general conditions than previous derivations in the literature: we do not restrict ourselves to objects near the fixation point or near the plane of regard, and we allow for non-zero torsion, cyclovergence, and vertical misalignments of the eyes. We use these expressions to derive estimates of the latitude and longitude vertical disparities expected at each point in the visual field, averaged over all natural viewing. Finally, we present analytical expressions showing how binocular eye positionâgaze direction, convergence, torsion, cyclovergence, and vertical misalignmentâcan be derived from the vertical disparity field and its derivatives at the fovea
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