2,069 research outputs found
Data Associated with "The Key Role of Cloud-Climate Coupling in Extratropical Sea Surface Temperature Variability"
Boehm_and_Thompson_CloudLocking_2021_Data.zip contains 12 NetCDF files. Each data file contains output data from simulations run on the Max Planck Institute Earth System Model. Each file has the output for a single variable and three dimensions: time, latitude and longitude.Cloud radiative effects have long been known to play a key role in governing the mean
climate. In recent years, it has become clear that they also contribute to climate variability in the
tropics. Here we build on recent work and probe the role of cloud radiative effects in extratropical
sea-surface temperature (SST) variability. The impact of cloud radiative effects on climate
variability is explored in âcloud-lockingâ simulations run on an Earth System Model. The method
involves comparing the output from two climate simulations: one in which clouds are coupled to
the atmospheric circulation and another in which clouds are prescribed and thus decoupled from
the flow. The results reveal that coupling between cloud radiative effects and the atmospheric
circulation leads to widespread increases in the amplitudes of extratropical SST variability from
monthly to decadal timescales. Notably, the amplitude of monthly to decadal variability over both
the North Atlantic and North Pacific oceans is between ~25-40% larger when clouds are coupled
to the circulation. The increases are consistent with the âreddeningâ of cloud shortwave radiative
effects that arises when clouds interact with the large-scale circulation. The results suggest that a
notable fraction of observed Northern Hemisphere sea-surface temperature variability - including
that associated with North Pacific and North Atlantic decadal variability - is due to cloud-circulation
coupling
The signatures of large-scale patterns of atmospheric variability in Antarctic surface temperatures
We investigate the impact that the four principal large-scale patterns of Southern Hemisphere (SH) atmospheric circulation variability have on Antarctic surface air temperature (SAT): (1) the southern baroclinic annular mode (BAM), which is associated with variations in extratropical storm amplitude; (2) the Southern Annular Mode (SAM), associated with latitudinal shifts in the midlatitude jet; and (3) the two Pacific-South American patterns (PSA1 and PSA2), which are characterized by wave trains originating in the tropical Pacific that extend across the SH extratropics. A key aspect is the use of 35âyears of daily observations and reanalysis data, which affords a sufficiently large sample size to assess the signatures of the circulation patterns in both the mean and variability of daily mean SAT anomalies. The BAM exerts the weakest influence on Antarctic SAT, albeit it is still important over select regions. Consistent with previous studies, the SAM is shown to influence SAT across most of the continent throughout the year. The PSA1 also affects SAT across almost all of Antarctica. Regionally, both PSA patterns can exert a greater impact on SAT than the SAM but also have a significantly weaker influence during summer, reflecting the seasonality of the SH response to El NiñoâSouthern Oscillation. The SAM and PSA patterns have distinct signatures in daily SAT variance that are physically consistent with their signatures in extratropical dynamic variability. The broad-scale climate linkages identified here provide benchmarks for interpreting the Antarctic climate response to future changes in tropical sea surface temperatures, ozone recovery, and greenhouse gas increases
Controlling plastic flow in brittle structures
In most oxidation resistant materials, the predominant obstacle to dislocation motion is due to the changes in misfit energy as a dislocation moves, causing them to be brittle. However, at present, there is little understanding of how to design crystal structures to give easy plastic flow. Surprisingly, some hard materials deform readily, but only on a limited number of crystal planes, including ternary carbides and nitrides, such as Ti3SiC2, and compounds such as Nb2Co7, W2B5 and ζ-Ta4C3-x. Using ternary carbides as an example, it is shown that electronegativity differences within a crystal\u27s unit cell enable dislocation line defects to move much more easily, consistent with observations in other structures. Substantial changes appear possible, suggesting that such an approach might be used as a general way of to tailoring plasticity in crystals
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Dual Thermographic Monitoring of Ti-6Al-4V Cylinders During Direct Laser Deposition
Understanding the thermal phenomena associated with Direct Laser Deposition (DLD) is
necessary to begin manipulating fabricated part properties. In this study, a thermally monitored
Laser Engineered Net Shaping (LENS) system is used with time-invariant (uncontrolled) build
parameters to construct Ti-6Al-4V cylinders with two different build paths. Both paths utilize a
circular contour with serpentine hatch fill; however, successive layer patterns are varied and the
effects compared between 90° and 120° angular pattern shifts. During fabrication, the partâs
thermal history and melt pool temperature are recorded via an in-chamber infrared (IR) camera
and a dual-wavelength (DW) pyrometer, respectively. These tools are used for non-destructive
thermographic inspection (NTI) of the part to ensure target quality and/or microstructure. A
unique calibration method for the IR camera utilizing the DW pyrometer data is presented and a
calibration correction factor was utilized for high temperature ranges. The melt pool was found
to be 40-50% superheated reaching temperatures up to 2500 ÂșC at times. Temperature
characteristics of two different layers were compared for different hatching patters, and the
results show that for a given point in time, maximum temperatures can vary based on laser raster.
Temperature gradients varied and peaked at about 1000 ÂșC/mm along the diameter of the small
rods. This can lead to anisotropy in microstructural and mechanical properties allowing for
unique property growth per build path. Cooling rates within the melt pool appear to increase as
maximum melt pool temperature increases, for instance, from 16,000 ÂșC/s â 41,000 ÂșC/s.Mechanical Engineerin
Tracking a northern fulmar from a Scottish nesting site to the Charlie-Gibbs Fracture Zone : Evidence of linkage between coastal breeding seabirds and Mid-Atlantic Ridge feeding sites
Peer reviewedPublisher PD
On the Truncated Pareto Distribution with applications
The Pareto probability distribution is widely applied in different fields
such us finance, physics, hydrology, geology and astronomy. This note deals
with an application of the Pareto distribution to astrophysics and more
precisely to the statistical analysis of mass of stars and of diameters of
asteroids. In particular a comparison between the usual Pareto distribution and
its truncated version is presented. Finally a possible physical mechanism that
produces Pareto tails for the distribution of the masses of stars is suggested.Comment: 10 pages 6 figure
The signature of Southern Hemisphere atmospheric circulation patterns in Antarctic precipitation
We provide the first comprehensive analysis of the relationships between large-scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four modes of large-scale Southern Hemisphere climate variability: the southern baroclinic annular mode (BAM), the southern annular mode (SAM), and the two Pacific-South American (PSA) teleconnection patterns. Variations in all four modes influence the spatial patterns of precipitation over Antarctica, consistent with their signatures in high-latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled-climate models are able to reproduce all four patterns of atmospheric variability, but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone
Sensitivity of the g-mode frequencies to pulsation codes and their parameters
From the recent work of the Evolution and Seismic Tools Activity (ESTA,
Lebreton et al. 2006; Monteiro et al. 2008), whose Task 2 is devoted to compare
pulsational frequencies computed using most of the pulsational codes available
in the asteroseismic community, the dependence of the theoretical frequencies
with non-physical choices is now quite well fixed. To ensure that the accuracy
of the computed frequencies is of the same order of magnitude or better than
the observational errors, some requirements in the equilibrium models and the
numerical resolutions of the pulsational equations must be followed. In
particular, we have verified the numerical accuracy obtained with the Saclay
seismic model, which is used to study the solar g-mode region (60 to
140Hz). We have compared the results coming from the Aarhus adiabatic
pulsation code (ADIPLS), with the frequencies computed with the Granada Code
(GraCo) taking into account several possible choices. We have concluded that
the present equilibrium models and the use of the Richardson extrapolation
ensure an accuracy of the order of in the determination of the
frequencies, which is quite enough for our purposes.Comment: 10 pages, 5 figures, accepted in Solar Physic
Re-Examination of the Exacerbating Effect of Inflammasome Components during Radiation Injury
Radiation can be applied for therapeutic benefit against cancer or may result in devastating harm due to accidental or intentional release of nuclear energy. In all cases, radiation exposure causes molecular and cellular damage, resulting in the production of inflammatory factors and danger signals. Several classes of innate immune receptors sense the released damage associated molecules and activate cellular response pathways, including the induction of inflammasome signaling that impacts IL-1ÎČ/IL-18 maturation and cell death. A previous report indicated inflammasomes aggravate acute radiation syndrome. In contrast, here we find that inflammasome components do not exacerbate gamma-radiation-induced injury by examining heterozygous and gene-deletion littermate controls in addition to wild-type mice. Absence of some inflammasome genes, such as caspase-1/11 and Nlrp3, enhance susceptibility of treated mice to acute radiation injury, indicating importance of the inflammasome pathway in radioprotection. Surprisingly, we discover that the survival outcome may be sex-dependent as more inflammasome-deficient male mice are susceptible to radiation-induced injury. We discuss parameters that may influence the role of inflammasomes as radioprotective or radioexacerbating factors in recovery from radiation injury including the use of littermate controls, the sex of the animals, differences in microbiota within the colonies and other experimental conditions. Under the conditions tested, inflammasome components do not exacerbate radiation injury, but rather provide protective benefit
Search for Possible Variation of the Fine Structure Constant
Determination of the fine structure constant alpha and search for its
possible variation are considered. We focus on a role of the fine structure
constant in modern physics and discuss precision tests of quantum
electrodynamics. Different methods of a search for possible variations of
fundamental constants are compared and those related to optical measurements
are considered in detail.Comment: An invited talk at HYPER symposium (Paris, 2002
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