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A statistical model for sea surface diurnal warming driven by numercial weather predictions fluxes and winds
A statistical model is derived relating the diurnal variation of sea surface temperature (SST) to the net surface heat flux and surface wind speed from a numerical weather prediction (NWP) model. The model is derived using fluxes and winds from the European Centre for Medium-Range Weather Forecasting (ECMWF) NWP model and SSTs from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). In the model, diurnal warming has a linear dependence on the net surface heat flux integrated since (approximately) dawn and an inverse quadratic dependence on the maximum of the surface wind speed in the same period. The model coefficients are found by matching, for a given integrated heat flux, the frequency distributions of the maximum wind speed and the observed warming. Diurnal cooling, where it occurs, is modelled as proportional to the integrated heat flux divided by the heat capacity of the seasonal mixed layer. The model reproduces the statistics (mean, standard deviation, and 95-percentile) of the diurnal variation of SST seen by SEVIRI and reproduces the geographical pattern of mean warming seen by the Advanced Microwave Scanning Radiometer (AMSR-E). We use the functional dependencies in the statistical model to test the behaviour of two physical model of diurnal warming that display contrasting systematic errors
Rapport de la campagne PROPPAC 04 à bord du N.O. Le Suroît (30 octobre au 26 novembre 1989)
La campagne PROPPAC 4, dont l'ORSTOM était maître d'oeuvre, s'est déroulée du 30 octobre au 26 novembre 1989 entre 20°S (nord de la Nouvelle-Calédonie) et 5°S le long de 165°E. L'objectif était de décrire en deux points fixes de 8 jours la variabilité à court terme des paramètres hydrologiques et planctoniques, leur répartition le long de la colonne d'eau, la distribution des différentes classes d'organismes et de mesurer l'intensité des flux : advection et mélanges, taux de sédimentation, production primaire et secondaire. Ces informations, recueillies dans deux situations oligotrophes considérées comme typiques, doivent permettre de compléter les données rudimentaires de biologie qui sont collectées au cours des stations de courte durée des radiales bi-annuelles SURTROPAC depuis 1984 et servir à la définition de la relation production-hydrologie dans le Pacifique occidental. La première station de 8 jours, dont la position a été choisie à l'issue d'une radiale préliminaire, était située à 7-8°S et caractérisée par une pycnocline profonde (75 m) et marquée, avec un maximum de chlorophylle vers 80-100 m. La seconde, située à 16°S, correspondrait à une structure hydrologique avec un faible gradient et des sels nutritifs vers 140 m, le maximum de chlorophylle se situant à 120-140 m. (Résumé d'auteur
GOODS-: identification of the individual galaxies responsible for the 80-290m cosmic infrared background
We propose a new method of pushing to its faintest detection
limits using universal trends in the redshift evolution of the far infrared
over 24m colours in the well-sampled GOODS-North field. An extension to
other fields with less multi-wavelength information is presented. This method
is applied here to raise the contribution of individually detected
sources to the cosmic infrared background (CIRB) by a factor 5 close to its
peak at 250m and more than 3 in the 350m and 500m bands. We
produce realistic mock images of the deep PACS and SPIRE images of
the GOODS-North field from the GOODS- Key Program and use them to
quantify the confusion noise at the position of individual sources, i.e.,
estimate a "local confusion noise". Two methods are used to identify sources
with reliable photometric accuracy extracted using 24m prior positions.
The clean index (CI), previously defined but validated here with simulations,
which measures the presence of bright 24m neighbours and the photometric
accuracy index (PAI) directly extracted from the mock images. After
correction for completeness, thanks to our mock images, individually
detected sources make up as much as 54% and 60% of the CIRB in the PACS bands
down to 1.1 mJy at 100m and 2.2 mJy at 160m and 55, 33, and 13% of
the CIRB in the SPIRE bands down to 2.5, 5, and 9 mJy at 250m, 350m,
and 500m, respectively. The latter depths improve the detection limits of
by factors of 5 at 250m, and 3 at 350m and 500m as
compared to the standard confusion limit. Interestingly, the dominant
contributors to the CIRB in all bands appear to be distant siblings
of the Milky Way (0.96 for 300m) with a stellar mass
of 910M.Comment: 22 pages, 16 figures. Accepted for publication by Astronomy and
Astrophysic
Estimation of absorption line indices of early-type galaxies using colours
Context. Absorption line indices are widely used to determine the stellar
population parameters such as age and metallicity of galaxies, but it is not
easy to obtain the line indices of some distant galaxies that have colours
available. Aims. This paper investigates the correlations between absorption
line indices and colours. Methods. A few statistical fitting methods are mainly
used, via both the observational data of Sloan Digital Sky Survey and a widely
used theoretical stellar population model. Results. Some correlations between
widely used absorption line indices and ugriz colours are found from both
observational data of early-type galaxies and a theoretical simple stellar
population model. In particular, good correlations between colours and widely
used absorption line indices such as Dn(4000), HgammaA, HgammaF, HdeltaA, Mg1,
Mg2, and Mgb, are shown in this paper. Conclusions. Some important absorption
line indices of early-type galaxies can be estimated from their colours using
correlations between absorption line indices and colours. For example,
age-sensitive absorption line indices can be estimated from (u-r) or (g-r)
colours and metallicity-sensitive ones from (u - z) or (g - z). This is useful
for studying the stellar populations of distant galaxies, especially for
statistical investigations.Comment: 9 pages, 21 figures, will be shown in A&
An Empirical Process Central Limit Theorem for Multidimensional Dependent Data
Let be the empirical process associated to an
-valued stationary process . We give general conditions,
which only involve processes for a restricted class of
functions , under which weak convergence of can be
proved. This is particularly useful when dealing with data arising from
dynamical systems or functional of Markov chains. This result improves those of
[DDV09] and [DD11], where the technique was first introduced, and provides new
applications.Comment: to appear in Journal of Theoretical Probabilit
CoRoT light curves of RR Lyrae stars. CoRoT 101128793: long-term changes in the Blazhko effect and excitation of additional modes
The CoRoT (Convection, Rotation and planetary Transits) space mission
provides a valuable opportunity to monitor stars with uninterrupted time
sampling for up to 150 days at a time. The study of RR Lyrae stars, performed
in the framework of the Additional Programmes belonging to the exoplanetary
field, will particularly benefit from such dense, long-duration monitoring. The
Blazhko effect in RR Lyrae stars is a long-standing, unsolved problem of
stellar astrophysics. We used the CoRoT data of the new RR Lyrae variable CoRoT
101128793 (f0=2.119 c/d, P=0.4719296 d) to provide us with more detailed
observational facts to understand the physical process behind the phenomenon.
The CoRoT data were corrected for one jump and the long-term drift. We applied
different period-finding techniques to the corrected timeseries to investigate
amplitude and phase modulation. We detected 79 frequencies in the light curve
of CoRoT 101128793. They have been identified as the main frequency f0, and its
harmonics, two independent terms, the terms related to the Blazhko frequency,
and several combination terms. A Blazhko frequency fB=0.056 c/d and a triplet
structure around the fundamental radial mode and harmonics were detected, as
well as a long-term variability of the Blazhko modulation. Indeed, the
amplitude of the main oscillation is decreasing along the CoRoT survey. The
Blazhko modulation is one of the smallest observed in RR Lyrae stars. Moreover,
the additional modes f1=3.630 and f2=3.159 c/d are detected. Taking its ratio
with the fundamental radial mode into account, the term f1 could be the
identified as the second radial overtone. Detecting of these modes in
horizontal branch stars is a new result obtained by CoRoT.Comment: 13 pages, 2 figures, 2 long tables. Accepted for publication in A&
The genotype-phenotype relationship in multicellular pattern-generating models - the neglected role of pattern descriptors
Background: A deep understanding of what causes the phenotypic variation arising from biological patterning
processes, cannot be claimed before we are able to recreate this variation by mathematical models capable of
generating genotype-phenotype maps in a causally cohesive way. However, the concept of pattern in a
multicellular context implies that what matters is not the state of every single cell, but certain emergent qualities
of the total cell aggregate. Thus, in order to set up a genotype-phenotype map in such a spatiotemporal pattern
setting one is actually forced to establish new pattern descriptors and derive their relations to parameters of the
original model. A pattern descriptor is a variable that describes and quantifies a certain qualitative feature of the
pattern, for example the degree to which certain macroscopic structures are present. There is today no general
procedure for how to relate a set of patterns and their characteristic features to the functional relationships,
parameter values and initial values of an original pattern-generating model. Here we present a new, generic
approach for explorative analysis of complex patterning models which focuses on the essential pattern features
and their relations to the model parameters. The approach is illustrated on an existing model for Delta-Notch
lateral inhibition over a two-dimensional lattice.
Results: By combining computer simulations according to a succession of statistical experimental designs,
computer graphics, automatic image analysis, human sensory descriptive analysis and multivariate data modelling,
we derive a pattern descriptor model of those macroscopic, emergent aspects of the patterns that we consider
of interest. The pattern descriptor model relates the values of the new, dedicated pattern descriptors to the
parameter values of the original model, for example by predicting the parameter values leading to particular
patterns, and provides insights that would have been hard to obtain by traditional methods.
Conclusion: The results suggest that our approach may qualify as a general procedure for how to discover and
relate relevant features and characteristics of emergent patterns to the functional relationships, parameter values
and initial values of an underlying pattern-generating mathematical model
A Bayesian approach to wavelet-based modelling of discontinuous functions applied to inverse problems
Inverse problems are examples of regression with more unknowns than the amount of information in the data and hence constraints are imposed through prior information. The proposed method defines the underlying function as a wavelet approximation which is related to the data through a convolution. The wavelets provide a sparse and multi-resolution solution which can capture local behaviour in an adaptive way. Varied prior models are considered along with level-specific prior parameter estimation. Archaeological stratigraphy data are considered where vertical earth cores are analysed producing clear piecewise constant function estimates
The Cosmic Far-Infrared Background Buildup Since Redshift 2 at 70 and 160 microns in the COSMOS and GOODS fields
The Cosmic Far-Infrared Background (CIB) at wavelengths around 160 {\mu}m
corresponds to the peak intensity of the whole Extragalactic Background Light,
which is being measured with increasing accuracy. However, the build up of the
CIB emission as a function of redshift, is still not well known. Our goal is to
measure the CIB history at 70 {\mu}m and 160 {\mu}m at different redshifts, and
provide constraints for infrared galaxy evolution models. We use complete deep
Spitzer 24 {\mu}m catalogs down to about 80 {\mu}Jy, with spectroscopic and
photometric redshifts identifications, from the GOODS and COSMOS deep infrared
surveys covering 2 square degrees total. After cleaning the Spitzer/MIPS 70
{\mu}m and 160 {\mu}m maps from detected sources, we stacked the far-IR images
at the positions of the 24 {\mu}m sources in different redshift bins. We
measured the contribution of each stacked source to the total 70 and 160 {\mu}m
light, and compare with model predictions and recent far-IR measurements made
with Herschel/PACS on smaller fields. We have detected components of the 70 and
160 {\mu}m backgrounds in different redshift bins up to z ~ 2. The contribution
to the CIB is maximum at 0.3 <= z <= 0.9 at 160{\mu}m (and z <= 0.5 at 70
{\mu}m). A total of 81% (74%) of the 70 (160) {\mu}m background was emitted at
z < 1. We estimate that the AGN relative contribution to the far-IR CIB is less
than about 10% at z < 1.5. We provide a comprehensive view of the CIB buildup
at 24, 70, 100, 160 {\mu}m. IR galaxy models predicting a major contribution to
the CIB at z < 1 are in agreement with our measurements, while our results
discard other models that predict a peak of the background at higher redshifts.
Our results are available online http://www.ias.u-psud.fr/irgalaxies/ .Comment: Accepted in Astronomy & Astrophysic
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