10,927 research outputs found
Universality of Sea Wave Growth and Its Physical Roots
Modern day studies of wind-driven sea waves are usually focused on wind
forcing rather than on the effect of resonant nonlinear wave interactions. The
authors assume that these effects are dominating and propose a simple
relationship between instant wave steepness and time or fetch of wave
development expressed in wave periods or lengths. This law does not contain
wind speed explicitly and relies upon this asymptotic theory. The validity of
this law is illustrated by results of numerical simulations, in situ
measurements of growing wind seas and wind wave tank experiments. The impact of
the new vision of sea wave physics is discussed in the context of conventional
approaches to wave modeling and forecasting.Comment: submitted to Journal of Fluid Mechanics 24-Sep-2014, 34 pages, 10
figure
A shared frequency set between the historical mid-latitude aurora records and the global surface temperature
Herein we show that the historical records of mid-latitude auroras from 1700
to 1966 present oscillations with periods of about 9, 10-11, 20-21, 30 and 60
years. The same frequencies are found in proxy and instrumental global surface
temperature records since 1650 and 1850, respectively and in several planetary
and solar records. Thus, the aurora records reveal a physical link between
climate change and astronomical oscillations. Likely, there exists a modulation
of the cosmic ray flux reaching the Earth and/or of the electric properties of
the ionosphere. The latter, in turn, have the potentiality of modulating the
global cloud cover that ultimately drives the climate oscillations through
albedo oscillations. In particular, a quasi 60-year large cycle is quite
evident since 1650 in all climate and astronomical records herein studied,
which also include an historical record of meteorite fall in China from 619 to
1943. These findings support the thesis that climate oscillations have an
astronomical origin. We show that a harmonic constituent model based on the
major astronomical frequencies revealed in the aurora records is able to
forecast with a reasonable accuracy the decadal and multidecadal temperature
oscillations from 1950 to 2010 using the temperature data before 1950, and vice
versa. The existence of a natural 60-year modulation of the global surface
temperature induced by astronomical mechanisms, by alone, would imply that at
least 60-70% of the warming observed since 1970 has been naturally induced.
Moreover, the climate may stay approximately stable during the next decades
because the 60-year cycle has entered in its cooling phase.Comment: 18 pages, 11 figure
Proceedings of the 2011 New York Workshop on Computer, Earth and Space Science
The purpose of the New York Workshop on Computer, Earth and Space Sciences is
to bring together the New York area's finest Astronomers, Statisticians,
Computer Scientists, Space and Earth Scientists to explore potential synergies
between their respective fields. The 2011 edition (CESS2011) was a great
success, and we would like to thank all of the presenters and participants for
attending. This year was also special as it included authors from the upcoming
book titled "Advances in Machine Learning and Data Mining for Astronomy". Over
two days, the latest advanced techniques used to analyze the vast amounts of
information now available for the understanding of our universe and our planet
were presented. These proceedings attempt to provide a small window into what
the current state of research is in this vast interdisciplinary field and we'd
like to thank the speakers who spent the time to contribute to this volume.Comment: Author lists modified. 82 pages. Workshop Proceedings from CESS 2011
in New York City, Goddard Institute for Space Studie
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