1,127 research outputs found
The Relative Humidity in an Isentropic AdvectionâCondensation Model: Limited Poleward Influence and Properties of Subtropical Minima
An idealized model of advection and condensation of water vapor is considered as a representation of processes influencing the humidity distribution along isentropic surfaces in the free troposphere. Results are presented for how the mean relative humidity distribution varies in response to changes in the distribution of saturation specific humidity and in the amplitude of a tropical moisture source. Changes in the tropical moisture source are found to have little effect on the relative humidity poleward of the subtropical minima, suggesting a lack of poleward influence despite much greater water vapor concentrations at lower latitudes. The subtropical minima in relative humidity are found to be located just equatorward of the inflection points of the saturation specific humidity profile along the isentropic surface. The degree of mean subsaturation is found to vary with the magnitude of the meridional gradient of saturation specific humidity when other parameters are held fixed.
The atmospheric relevance of these results is investigated by comparison with the positions of the relative humidity minima in reanalysis data and by examining poleward influence of relative humidity in simulations with an idealized general circulation model. It is suggested that the limited poleward influence of relative humidity may constrain the propagation of errors in simulated humidity fields
Extramedullary relapse of IgA-lambda myeloma after recent bortezomib therapy: a case report
Intracranial plasmacytomas are an uncommon presentation of extramedullary relapse of multiple myeloma. The optimal management of extramedullary plasmacytomas remains unclear, with initial reports of bortezomib showing promising clinical results. We describe a case of multiple extracellular, including intracranial, plasmacytoma, with no evidence of marrow involvement, in a patient with relapsed IgA multiple myeloma. To our knowledge, this is the first reported case of a patient with rapid extramedullary relapse of disease despite recent exposure to bortezomib and dexamethasone
CARMA CO(J = 2 - 1) Observations of the Circumstellar Envelope of Betelgeuse
We report radio interferometric observations of the 12C16O 1.3 mm J = 2-1
emission line in the circumstellar envelope of the M supergiant Alpha Ori and
have detected and separated both the S1 and S2 flow components for the first
time. Observations were made with the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) interferometer in the C, D, and E antenna
configurations. We obtain good u-v coverage (5-280 klambda) by combining data
from all three configurations allowing us to trace spatial scales as small as
0.9\arcsec over a 32\arcsec field of view. The high spectral and spatial
resolution C configuration line profile shows that the inner S1 flow has
slightly asymmetric outflow velocities ranging from -9.0 km s-1 to +10.6 km s-1
with respect to the stellar rest frame. We find little evidence for the outer
S2 flow in this configuration because the majority of this emission has been
spatially-filtered (resolved out) by the array. We also report a SOFIA-GREAT
CO(J= 12-11) emission line profile which we associate with this inner higher
excitation S1 flow. The outer S2 flow appears in the D and E configuration maps
and its outflow velocity is found to be in good agreement with high resolution
optical spectroscopy of K I obtained at the McDonald Observatory. We image both
S1 and S2 in the multi-configuration maps and see a gradual change in the
angular size of the emission in the high absolute velocity maps. We assign an
outer radius of 4\arcsec to S1 and propose that S2 extends beyond CARMA's field
of view (32\arcsec at 1.3 mm) out to a radius of 17\arcsec which is larger than
recent single-dish observations have indicated. When azimuthally averaged, the
intensity fall-off for both flows is found to be proportional to R^{-1}, where
R is the projected radius, indicating optically thin winds with \rho \propto
R^{-2}.Comment: 11 pages, 8 figures To be published in the Astronomical Journal
(Received 2012 February 10; accepted 2012 May 25
Moist available potential energy of the mean state of the atmosphere and the thermodynamic potential for warm conveyor belts and convection
Much of our understanding of atmospheric circulation
comes from relationships between aspects of the circulation
and the mean state of the atmosphere. In particular,
the concept of mean available potential energy (MAPE) has
been used previously to relate the strength of the extratropical
storm tracks to the zonal-mean temperature and humidity
distributions. Here, we calculate for the first time the MAPE
of the zonally varying (i.e., three-dimensional) time-mean
state of the atmosphere including the effects of latent heating.
We further calculate a local MAPE by restricting the domain
to an assumed eddy size, and we partition this local MAPE
into convective and nonconvective components. Local convective
MAPE maximizes in the subtropics and midlatitudes,
in many cases in regions of the world that are known to have
intense convection. Local nonconvective MAPE has a spatial
pattern similar to the Eady growth rate, although local
nonconvective MAPE has the advantage that it takes into account
latent heating. Furthermore, the maximum potential ascent
associated with local nonconvective MAPE is related to
the frequency of warm conveyor belts (WCBs), which are
ascending airstreams in extratropical cyclones with large impacts
on weather. This maximum potential ascent can be calculated
based only on mean temperature and humidity, and
WCBs tend to start in regions of high maximum potential ascent
on a given day. These advances in the use of MAPE are
expected to be helpful to connect changes in the mean state
of the atmosphere, such as under global warming, to changes
in important aspects of extratropical circulation
Text Line Segmentation of Historical Documents: a Survey
There is a huge amount of historical documents in libraries and in various
National Archives that have not been exploited electronically. Although
automatic reading of complete pages remains, in most cases, a long-term
objective, tasks such as word spotting, text/image alignment, authentication
and extraction of specific fields are in use today. For all these tasks, a
major step is document segmentation into text lines. Because of the low quality
and the complexity of these documents (background noise, artifacts due to
aging, interfering lines),automatic text line segmentation remains an open
research field. The objective of this paper is to present a survey of existing
methods, developed during the last decade, and dedicated to documents of
historical interest.Comment: 25 pages, submitted version, To appear in International Journal on
Document Analysis and Recognition, On line version available at
http://www.springerlink.com/content/k2813176280456k3
How closely do changes in surface and column water vapor follow Clausius-Clapeyron scaling in climate change simulations?
The factors governing the rate of change in the amount of atmospheric water vapor are analyzed in simulations of climate change. The global-mean amount of water vapor is estimated to increase at a differential rate of 7.3% K[superscript â 1] with respect to global-mean surface air temperature in the multi-model mean. Larger rates of change result if the fractional change is evaluated over a finite change in temperature (e.g., 8.2% K [superscript â 1] for a 3 K warming), and rates of change of zonal-mean column water vapor range from 6 to 12% K [superscript â 1] depending on latitude.
ClausiusâClapeyron scaling is directly evaluated using an invariant distribution of monthly-mean relative humidity, giving a rate of 7.4% K â 1 for global-mean water vapor. There are deviations from ClausiusâClapeyron scaling of zonal-mean column water vapor in the tropics and mid-latitudes, but they largely cancel in the global mean. A purely thermodynamic scaling based on a saturated troposphere gives a higher global rate of 7.9% K [superscript â 1].
Surface specific humidity increases at a rate of 5.7% K [superscript â 1], considerably lower than the rate for global-mean water vapor. Surface specific humidity closely follows ClausiusâClapeyron scaling over ocean. But there are widespread decreases in surface relative humidity over land (by more than 1% K â 1 in many regions), and it is argued that decreases of this magnitude could result from the land/ocean contrast in surface warming
Contrasting responses of mean and extreme snowfall to climate change
Snowfall is an important element of the climate system, and one that is expected to change in a warming climate. Both mean snowfall and the intensity distribution of snowfall are important, with heavy snowfall events having particularly large economic and human impacts. Simulations with climate models indicate that annual mean snowfall declines with warming in most regions but increases in regions with very low surface temperatures. The response of heavy snowfall events to a changing climate, however, is unclear. Here I show that in simulations with climate models under a scenario of high emissions of greenhouse gases, by the late twenty-first century there are smaller fractional changes in the intensities of daily snowfall extremes than in mean snowfall over many Northern Hemisphere land regions. For example, for monthly climatological temperatures just below freezing and surface elevations below 1,000 metres, the 99.99th percentile of daily snowfall decreases by 8% in the multimodel median, compared to a 65% reduction in mean snowfall. Both mean and extreme snowfall must decrease for a sufficiently large warming, but the climatological temperature above which snowfall extremes decrease with warming in the simulations is as high as â9 °C, compared to â14 °C for mean snowfall. These results are supported by a physically based theory that is consistent with the observed rainâsnow transition. According to the theory, snowfall extremes occur near an optimal temperature that is insensitive to climate warming, and this results in smaller fractional changes for higher percentiles of daily snowfall. The simulated changes in snowfall that I find would influence surface snow and its hazards; these changes also suggest that it may be difficult to detect a regional climate-change signal in snowfall extremes.National Science Foundation (U.S.) (Grant AGS-1148594)United States. National Aeronautics and Space Administration (ROSES Grant 09-IDS09-0049
Extrasolar Planet Transits Observed at Kitt Peak National Observatory
We obtained J-, H- and JH-band photometry of known extrasolar planet
transiting systems at the 2.1-m Kitt Peak National Observatory Telescope using
the FLAMINGOS infrared camera between October 2008 and October 2011. From the
derived lightcurves we have extracted the mid-transit times, transit depths and
transit durations for these events. The precise mid-transit times obtained help
improve the orbital periods and also constrain transit-time variations of the
systems. For most cases the published system parameters successfully accounted
for our observed lightcurves, but in some instances we derive improved
planetary radii and orbital periods. We complemented our 2.1-m infrared
observations using CCD z'-band and B-band photometry (plus two Hydrogen Alpha
filter observations) obtained with the Kitt Peak Visitor's Center telescope,
and with four H-band transits observed in October 2007 with the NSO's 1.6-m
McMath-Pierce Solar Telescope. The principal highlights of our results are: 1)
our ensemble of J-band planetary radii agree with optical radii, with the
best-fit relation being: (Rp/R*)J = 0.0017 + 0.979 (Rp/R*)optical, 2) We
observe star spot crossings during the transit of WASP-11/HAT-P-10, 3) we
detect star spot crossings by HAT-P-11b (Kepler-3b), thus confirming that the
magnetic evolution of the stellar active regions can be monitored even after
the Kepler mission has ended, and 4) we confirm a grazing transit for
HAT-P-27/WASP-40. In total we present 57 individual transits of 32 known
exoplanet systems.Comment: 33 pages, 6 figures, accepted in Publications of the Astronomical
Society of the Pacifi
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Travelling for Umrah:destination attributes, destination image, and post-travel intentions
This paper examines the links between cosmopolitanism, self-identity, and a desire for social interaction perceived destination image and behavioural intentions. A model tested using a sample of 538 Iranian visitors to Mecca for the purpose of Umrah. The result from the structural model suggests that destination attributes influence perceived destination image. Further, such tourists are likely to revisit or recommend Islamic destinations if their experience matches their perceived image of the destination. This implies that, while the religious characteristics of the destination remain important, destination managers cannot disregard the tangential, non-religious attributes of a destination which are crucial in order to satisfy more conventional tourist desires. As such, this study suggests that those managing religious travel destinations should endeavour to foster a welcoming image, where experience, interaction and tolerance are at the forefront of the destinationâs offering
New strategies for sustainable fisheries management: A case study of Atlantic salmon
This briefing paper considers the alarming declines in fish stocks in recent years, and how holistic, integrated approaches can help manage fish stocks within biologically sustainable limits. Using Atlantic salmon as a case study, the authors highlight the challenges facing fisheries management and conservation, and the implications for policy and management
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