9,636 research outputs found
The Mechanical Impact of the Tibetan Plateau on the Seasonal Evolution of the South Asian Monsoon
The impact of the Tibetan Plateau on the South Asian monsoon is examined using a hierarchy of atmospheric general circulation models. During the premonsoon season and monsoon onset (April–June), when westerly winds over the Southern Tibetan Plateau are still strong, the Tibetan Plateau triggers early monsoon rainfall downstream, particularly over the Bay of Bengal and South China. The downstream moist convection is accompanied by strong monsoonal low-level winds. In experiments where the Tibetan Plateau is removed, monsoon onset occurs about a month later, but the monsoon circulation becomes progressively stronger and reaches comparable strength during the mature phase. During the mature and decaying phase of monsoon (July–September), when westerly winds over the Southern Tibetan Plateau almost disappear, monsoon circulation strength is not much affected by the presence of the Tibetan Plateau.
A dry dynamical core with east–west-oriented narrow mountains in the subtropics consistently simulates downstream convergence with background zonal westerlies over the mountain. In a moist atmosphere, the mechanically driven downstream convergence is expected to be associated with significant moisture convergence. The authors speculate that the mechanically driven downstream convergence in the presence of the Tibetan Plateau is responsible for zonally asymmetric monsoon onset, particularly over the Bay of Bengal and South China
Comments on "The Role of the Central Asian Mountains on the Midwinter Suppression of North Pacific Storminess" - Reply
We thank Chang and Lin for their thoughtful and
constructive comments on our study (Park et al. 2010).
In Park et al. (2010), we did not explicitly state that the
topography-forced stationary waves are the direct cause
for the reduced downstream transient eddy kinetic energy
(EKE). The response of stationary waves to topography
may saturate even with a relatively small mountain (Cook
and Held 1992); furthermore, their magnitudes are much
smaller than thermally forced stationary waves (Chang
2009; Held et al. 2002). Instead, we suggest that quasistationary waves generated by the central Asian mountains may strongly affect North Pacific storminess by
changing the year-to-year variability of westerly winds
over the eastern Eurasian continent. Observational analyses
indicate that the midwinter suppression of North
Pacific storminess does not occur every year. Some years
experience stronger and more meridionally confined
zonal winds over the western North Pacific, leading to
stronger midwinter suppression (Harnik and Chang
2004; Nakamura and Sampe 2002)
Magnetic states and optical properties of single-layer carbon-doped hexagonal boron nitride
We show that carbon-doped hexagonal boron nitride (h-BN) has extraordinary
properties with many possible applications. We demonstrate that the
substitution-induced impurity states, associated with carbon atoms, and their
interactions dictate the electronic structure and properties of C-doped h-BN.
Furthermore, we show that stacking of localized impurity states in small C
clusters embedded in h-BN forms a set of discrete energy levels in the wide gap
of h-BN. The electronic structures of these C clusters have a plethora of
applications in optics, magneto-optics, and opto-electronics
Suppressed Andreev Reflection at the Normal-Metal / Heavy-Fermion Superconductor CeCoIn Interface
Dynamic conductance spectra are taken from Au/CeCoIn point contacts in
the Sharvin limit along the (001) and (110) directions. Our conductance
spectra, reproducibly obtained over wide ranges of temperature, constitute the
cleanest data sets ever reported for HFSs. A signature for the emerging
heavy-fermion liquid is evidenced by the development of the asymmetry in the
background in the normal state. Below , an enhancement of the sub-gap
conductance arising from Andreev reflection is observed, with the magnitude of
13.3 % and 11.8 % for the (001) and the (110) point contacts,
respectively, an order of magnitude smaller than those observed in conventional
superconductors but consistent with those in other HFSs. Our zero-bias
conductance data for the (001) point contacts are best fit with the extended
BTK model using the d-wave order parameter. The fit to the full conductance
curve of the (001) point contact indicates the strong coupling nature
(). However, our observed suppression of both the
Andreev reflection signal and the energy gap indicates the failure of existing
models. We provide possible directions for theoretical formulations of the
electronic transport across an N/HFS interface. Several qualitative features
observed in the (110) point contacts provide the first clear spectroscopic
evidence for the symmetry.Comment: 13 pages, 7 figures, LaTeX, paper invited and submitted to SPIE
Conference on Strongly Correlated Electron Materials: Physics and
Nanoengineering, in San Diego, California, July 31 - August 4, 200
Conference Tutorials-An Opportunity For Continuing Education
The Educational Services Committee of the IEEE Communications Society has sponsored eleven tutorial short courses at its major conferences over the past six years. The experience gained in developing and presenting these tutorials is shared with others so that they may be in a better position to sponsor similar continuing education activities in the future. The conference tutorial is one example of a continuing education activity that can be sponsored by an IEEE Group or Society as a service to its members. Copyright © 1978 by The Institute of Electrical and Electronics Engineers, Inc
Glacial cycles drive variations in the production of oceanic crust
Glacial cycles redistribute water between oceans and continents causing
pressure changes in the upper mantle, with consequences for melting of Earth's
interior. Using Plio-Pleistocene sea-level variations as a forcing function,
theoretical models of mid-ocean ridge dynamics that include melt transport
predict temporal variations in crustal thickness of hundreds of meters. New
bathymetry from the Australian-Antarctic ridge shows significant spectral
energy near the Milankovitch periods of 23, 41, and 100 ky, consistent with
model predictions. These results suggest that abyssal hills, one of the most
common bathymetric features on Earth, record the magmatic response to changes
in sea level. The models and data support a link between glacial cycles at the
surface and mantle melting at depth, recorded in the bathymetric fabric of the
sea floor.Comment: 30 pages, 6 figures (including supplementary information).
Resubmitted to Science on 12 December 201
Programming DNA Tube Circumferences
Synthesizing molecular tubes with monodisperse, programmable circumferences is an important goal shared by nanotechnology, materials science, and supermolecular chemistry. We program molecular tube circumferences by specifying the complementarity relationships between modular domains in a 42-base single-stranded DNA motif. Single-step annealing results in the self-assembly of long tubes displaying monodisperse circumferences of 4, 5, 6, 7, 8, 10, or 20 DNA helices
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