Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/1088
Wed, 25 May 2016 21:30:26 GMT2016-05-25T21:30:26ZContinuation of bifurcations of cycles in dissipative PDEs
http://hdl.handle.net/2117/86729
Continuation of bifurcations of cycles in dissipative PDEs
Sánchez Umbría, Juan; Net Marcé, Marta
A new efficient methodology for the continuation of the
codimension-one bifurcations of periodic orbits, including pitchfork bifurcations present in reflection--symmetric systems, has been developed. It is based on the combination of Newton-Krylov techniques applied to extended systems, and the integration of systems of
variational equations up to second order. The extended systems are adapted from those usually found in the literature for fixed points of maps. A deflation term is needed in some cases to remove the trivial +1 multiplier of the periodic orbits. It will be shown that to evaluate the action of the Jacobian it is only necessary to integrate
systems of ODEs of dimension at most four times that of the original system. This minimizes the computational cost.
Two main tools are required to implement the algorithms presented here, a generic continuation code, and a time integrator for the particular problem at hand including the required variational equations.
The thermal convection of a mixture of two fluids in a two-dimensional rectangular box is used as test problem. It is known that the onset of convection is oscillatory below a certain negative value of one of the parameters (the separation ratio), giving rise to a rich dynamics. A
non-trivial diagram of periodic orbits is first deployed, by varying the Rayleigh number. Some of the bifurcations found on the main branch of periodic orbits are followed by adding as second parameter the Prandtl number. Several codimension-two points are found, and a
double-Hopf bifurcation is studied in more detail. Finally the boundaries of a resonance region, found on a branch of invariant tori, are also continued.
Fri, 06 May 2016 18:06:19 GMThttp://hdl.handle.net/2117/867292016-05-06T18:06:19ZSánchez Umbría, JuanNet Marcé, MartaA new efficient methodology for the continuation of the
codimension-one bifurcations of periodic orbits, including pitchfork bifurcations present in reflection--symmetric systems, has been developed. It is based on the combination of Newton-Krylov techniques applied to extended systems, and the integration of systems of
variational equations up to second order. The extended systems are adapted from those usually found in the literature for fixed points of maps. A deflation term is needed in some cases to remove the trivial +1 multiplier of the periodic orbits. It will be shown that to evaluate the action of the Jacobian it is only necessary to integrate
systems of ODEs of dimension at most four times that of the original system. This minimizes the computational cost.
Two main tools are required to implement the algorithms presented here, a generic continuation code, and a time integrator for the particular problem at hand including the required variational equations.
The thermal convection of a mixture of two fluids in a two-dimensional rectangular box is used as test problem. It is known that the onset of convection is oscillatory below a certain negative value of one of the parameters (the separation ratio), giving rise to a rich dynamics. A
non-trivial diagram of periodic orbits is first deployed, by varying the Rayleigh number. Some of the bifurcations found on the main branch of periodic orbits are followed by adding as second parameter the Prandtl number. Several codimension-two points are found, and a
double-Hopf bifurcation is studied in more detail. Finally the boundaries of a resonance region, found on a branch of invariant tori, are also continued.Filtrado transversal adaptativo de varianza constante para la ecualización de canal
http://hdl.handle.net/2117/86209
Filtrado transversal adaptativo de varianza constante para la ecualización de canal
Vázquez Grau, Gregorio; Gasull Llampallas, Antoni; Sánchez Umbría, Juan; Oliveras Vergés, Albert
This paper describes the problem of lineal filtering of noisy data under a Maximum Likelihood objective. In this sense, the paper shows that a weighted square error cost function deals and it is necessary to weight the filtering error sequence by a factor that, basically, depends the probability density function of the error sequence and on its first derivate. As it is well known, this information used to be not available and other proposals must be made. For this purpose, going around this problem, the paper discusses the design of this weighting factor for including sorne kind of data-selection mechanism for the final filter weight-vector solution design. The underlying of the proposal is the development of a recursive algorithm in such a way that for any measure or observation, its associated
Tue, 26 Apr 2016 14:37:29 GMThttp://hdl.handle.net/2117/862092016-04-26T14:37:29ZVázquez Grau, GregorioGasull Llampallas, AntoniSánchez Umbría, JuanOliveras Vergés, AlbertThis paper describes the problem of lineal filtering of noisy data under a Maximum Likelihood objective. In this sense, the paper shows that a weighted square error cost function deals and it is necessary to weight the filtering error sequence by a factor that, basically, depends the probability density function of the error sequence and on its first derivate. As it is well known, this information used to be not available and other proposals must be made. For this purpose, going around this problem, the paper discusses the design of this weighting factor for including sorne kind of data-selection mechanism for the final filter weight-vector solution design. The underlying of the proposal is the development of a recursive algorithm in such a way that for any measure or observation, its associatedNumerical simulation of the genesis of superhighway convection in a slightly inclined layer of a binary liquid mixture
http://hdl.handle.net/2117/84854
Numerical simulation of the genesis of superhighway convection in a slightly inclined layer of a binary liquid mixture
Alonso Maleta, María Aránzazu; Mercader Calvo, María Isabel; Batiste Boleda, Oriol
Convection in a fluid layer is affected by its orientation with
respect to the gravitational field. In the present work, we
investigate numerically pattern selection in a vertical cylindrical
cell heated from below for positive Soret coefficient mixtures and
analyse the effect of marginal inclinations of gravity in pattern
formation.
The dynamics of mixtures with a positive value of the Soret
coefficient without inclination has essentially been studied in
laboratory experiments, and numerical simulations reduce to periodic
domains. According to these studies, close to convective onset, the
motion is dominated by the solute gradient, and a stationary square
pattern with negligible change in heat transport is reached (Soret regime).
Far from threshold, convection selects the usual roll structure observed
in pure fluid convection, where a strong change in heat transport takes
place. In the crossover region, a cross roll regime is observed and the
competition between square and roll patterns leads to oscillations.
Interestingly, positive Soret coefficient mixtures have been used in
the recent experimental work of Croccolo et al. to investigate the effect
of inclination of the layer on the long-term stability. At small Rayleigh
numbers, the mass transfer is dominated by the induced large scale shear flow,
while at larger Rayleigh numbers, it is dominated by solutal convection.
Unexpected results are reported at the transition: drifting columnar flows moving
in opposite directions along parallel lanes in a superhighway configuration have
been observed.
We will present simulations corresponding to both non-inclined and
inclined cells. In particular, we have been able to obtain numerically
superhighway convection (SHC). The numerical analysis should shed
some light on the origin of these fast drifting columnar flows
observed in experiments.
Wed, 30 Mar 2016 10:37:42 GMThttp://hdl.handle.net/2117/848542016-03-30T10:37:42ZAlonso Maleta, María AránzazuMercader Calvo, María IsabelBatiste Boleda, OriolConvection in a fluid layer is affected by its orientation with
respect to the gravitational field. In the present work, we
investigate numerically pattern selection in a vertical cylindrical
cell heated from below for positive Soret coefficient mixtures and
analyse the effect of marginal inclinations of gravity in pattern
formation.
The dynamics of mixtures with a positive value of the Soret
coefficient without inclination has essentially been studied in
laboratory experiments, and numerical simulations reduce to periodic
domains. According to these studies, close to convective onset, the
motion is dominated by the solute gradient, and a stationary square
pattern with negligible change in heat transport is reached (Soret regime).
Far from threshold, convection selects the usual roll structure observed
in pure fluid convection, where a strong change in heat transport takes
place. In the crossover region, a cross roll regime is observed and the
competition between square and roll patterns leads to oscillations.
Interestingly, positive Soret coefficient mixtures have been used in
the recent experimental work of Croccolo et al. to investigate the effect
of inclination of the layer on the long-term stability. At small Rayleigh
numbers, the mass transfer is dominated by the induced large scale shear flow,
while at larger Rayleigh numbers, it is dominated by solutal convection.
Unexpected results are reported at the transition: drifting columnar flows moving
in opposite directions along parallel lanes in a superhighway configuration have
been observed.
We will present simulations corresponding to both non-inclined and
inclined cells. In particular, we have been able to obtain numerically
superhighway convection (SHC). The numerical analysis should shed
some light on the origin of these fast drifting columnar flows
observed in experiments.Thermal convection in autogravitating spheres at low Ekman numbers
http://hdl.handle.net/2117/82106
Thermal convection in autogravitating spheres at low Ekman numbers
Net Marcé, Marta; García González, Fernando; Sánchez Umbría, Juan
Wed, 27 Jan 2016 10:52:49 GMThttp://hdl.handle.net/2117/821062016-01-27T10:52:49ZNet Marcé, MartaGarcía González, FernandoSánchez Umbría, JuanFlash heat and flash cold phenomena in the Iberian Peninsula since 1900
http://hdl.handle.net/2117/77662
Flash heat and flash cold phenomena in the Iberian Peninsula since 1900
Mazon, Jordi; Cortés, Jacob; Almarza, Victor; Pino González, David
Rapid and sudden changes in air temperature can be classified as extreme events, having a risk for human activities, human health and ecosystems.
Flash heat and flash cold events are investigated in the Iberian Peninsula during since 1900. Flash heat events
(Mazon et al., 2014; http://glossary.ametsoc.org/wiki/Flash_heat) is described as a discrete period of abnormal warming, nominally lasting more than an hour but less than a day (between heat burst and heat wave phenomena),
occurring on the meso-beta scale. In a similar way, flash cold has been defined as a rapid drop of the air temperature lasting more than an hour but less than a day.
We investigate the tendency since 1900 of these type of flash events in the Iberian Peninsula from homogeneous series of daily maximum and minimum temperature. The trend and the distribution of the intensity of these events are shown.
Additionally, we show the convenience to analyze these type of flash events for a better understanding of the atmospheric dynamics
Wed, 14 Oct 2015 07:39:30 GMThttp://hdl.handle.net/2117/776622015-10-14T07:39:30ZMazon, JordiCortés, JacobAlmarza, VictorPino González, DavidRapid and sudden changes in air temperature can be classified as extreme events, having a risk for human activities, human health and ecosystems.
Flash heat and flash cold events are investigated in the Iberian Peninsula during since 1900. Flash heat events
(Mazon et al., 2014; http://glossary.ametsoc.org/wiki/Flash_heat) is described as a discrete period of abnormal warming, nominally lasting more than an hour but less than a day (between heat burst and heat wave phenomena),
occurring on the meso-beta scale. In a similar way, flash cold has been defined as a rapid drop of the air temperature lasting more than an hour but less than a day.
We investigate the tendency since 1900 of these type of flash events in the Iberian Peninsula from homogeneous series of daily maximum and minimum temperature. The trend and the distribution of the intensity of these events are shown.
Additionally, we show the convenience to analyze these type of flash events for a better understanding of the atmospheric dynamicsTransdisciplinary and multiscale reconstruction of the major floods
http://hdl.handle.net/2117/77590
Transdisciplinary and multiscale reconstruction of the major floods
Mazon, Jordi; Romero, Laura; Pino González, David; Balasch Solanes, Josep Carles; Ruiz Bellet, Josep Lluís; Tuset Mestre, Jordi; Barriendos Valve, Mariano
Floods are the most severe natural hazard in the western Mediterranean basin. Flash floods in the northeast of the Iberian Peninsula are caused by a limited array of meteorological processes, which must be identified and classified in order to improve flash floods forecasting. In the case of small catchments (<500 km2), floods cause
most of the damages and most of the victims.
By using historical data (Barriendos et al. 2014) and, in some cases, hydraulical and hydrological reconstruction (Ruiz-Bellet et al., 2015) we select the 21 most catastrophic flash floods affecting more than one basin with similar intensity -and the rainstorms that caused them- occurred in the northeast of the Iberian Peninsula since 1871. Therefore, we classify the selected floods according to the basin, the season and the damages they produced. We show that most of then occurred during autumn (13). During winter or summer occurred 4 flash
floods in each season.
Regarding the atmospheric conditions that caused the floods, we use, depending on the period, NCEP 20th Century Reanalysis (Compo et al., 2011), surface pressure and rainfall observations to analyze the synoptic
situation and to calculate different convective indexes: the Convective Available Potential Energy (CAPE), the Lift Index (LI), the K index (KI), the Vertical, Cross and Total Totals (VT, CT, TT respectively). The analysis allow us to classify the floods, despite they might produce similar damages, in different synoptic situations and stability of the atmosphere
Tue, 13 Oct 2015 10:51:54 GMThttp://hdl.handle.net/2117/775902015-10-13T10:51:54ZMazon, JordiRomero, LauraPino González, DavidBalasch Solanes, Josep CarlesRuiz Bellet, Josep LluísTuset Mestre, JordiBarriendos Valve, MarianoFloods are the most severe natural hazard in the western Mediterranean basin. Flash floods in the northeast of the Iberian Peninsula are caused by a limited array of meteorological processes, which must be identified and classified in order to improve flash floods forecasting. In the case of small catchments (<500 km2), floods cause
most of the damages and most of the victims.
By using historical data (Barriendos et al. 2014) and, in some cases, hydraulical and hydrological reconstruction (Ruiz-Bellet et al., 2015) we select the 21 most catastrophic flash floods affecting more than one basin with similar intensity -and the rainstorms that caused them- occurred in the northeast of the Iberian Peninsula since 1871. Therefore, we classify the selected floods according to the basin, the season and the damages they produced. We show that most of then occurred during autumn (13). During winter or summer occurred 4 flash
floods in each season.
Regarding the atmospheric conditions that caused the floods, we use, depending on the period, NCEP 20th Century Reanalysis (Compo et al., 2011), surface pressure and rainfall observations to analyze the synoptic
situation and to calculate different convective indexes: the Convective Available Potential Energy (CAPE), the Lift Index (LI), the K index (KI), the Vertical, Cross and Total Totals (VT, CT, TT respectively). The analysis allow us to classify the floods, despite they might produce similar damages, in different synoptic situations and stability of the atmosphereFrontogenesis at the whole mesoscale in the West Mediterranean basin: from raincells to rainbands
http://hdl.handle.net/2117/77583
Frontogenesis at the whole mesoscale in the West Mediterranean basin: from raincells to rainbands
Mazon, Jordi; Pino González, David
The mesoscale is one of the common scales in which atmospheric phenomena occur. Its length scale ranges from few to thousands kilometers, and time lapse from few minutes to few days (Orlanski, 1975), and depths from few
hundreds of meters to one kilometer (Markowski and Richardson, 2010).
The scale in which coastal fronts occurs in the West Mediterranean basin (WMB) is investigated by using remote sensing instruments (weather radar and satellite) and mesoscale numerical simulations by using the WRF model. Two types of atmospheric dynamic forming coastal fronts in the WMB are noticed in this area Nocturnal coastal fronts develop within the meso-beta and meso-gamma scales during the night when drainage winds move offshore the inland cold air (Mazon and Pino, 2013, 2014). When this air mass interacts with the warmer and wetter
maritime air mass cloud and rain may appear having an area from 20 km to 150-200 km, and lasting from 3 to 10 hours occurs. Additionally, cold outbreaks from the gulf of Lion may form a coastal front in the meso-alpha scale, when the inland cold air reaches the Mediterranean Sea. This type of cold fronts moves offshore southward until north Africa, reaching 2000 km and lasting around 30 hours.
By using the version 3.3 of WRF mesoscale model three coastal fronts are simulated and characterized, which cover the whole mesoscale.
According the observations and the simulations, we conclude that in the WMB fronts form and develop, and consequently we can say that this region can be considered as a frontogenesis region at the whole mesoscale.
These fronts are not associated to low pressures areas
Tue, 13 Oct 2015 10:11:45 GMThttp://hdl.handle.net/2117/775832015-10-13T10:11:45ZMazon, JordiPino González, DavidThe mesoscale is one of the common scales in which atmospheric phenomena occur. Its length scale ranges from few to thousands kilometers, and time lapse from few minutes to few days (Orlanski, 1975), and depths from few
hundreds of meters to one kilometer (Markowski and Richardson, 2010).
The scale in which coastal fronts occurs in the West Mediterranean basin (WMB) is investigated by using remote sensing instruments (weather radar and satellite) and mesoscale numerical simulations by using the WRF model. Two types of atmospheric dynamic forming coastal fronts in the WMB are noticed in this area Nocturnal coastal fronts develop within the meso-beta and meso-gamma scales during the night when drainage winds move offshore the inland cold air (Mazon and Pino, 2013, 2014). When this air mass interacts with the warmer and wetter
maritime air mass cloud and rain may appear having an area from 20 km to 150-200 km, and lasting from 3 to 10 hours occurs. Additionally, cold outbreaks from the gulf of Lion may form a coastal front in the meso-alpha scale, when the inland cold air reaches the Mediterranean Sea. This type of cold fronts moves offshore southward until north Africa, reaching 2000 km and lasting around 30 hours.
By using the version 3.3 of WRF mesoscale model three coastal fronts are simulated and characterized, which cover the whole mesoscale.
According the observations and the simulations, we conclude that in the WMB fronts form and develop, and consequently we can say that this region can be considered as a frontogenesis region at the whole mesoscale.
These fronts are not associated to low pressures areasTrend of flash heat events in the Iberian Peninsula during the period 1900-2010
http://hdl.handle.net/2117/28116
Trend of flash heat events in the Iberian Peninsula during the period 1900-2010
Mazón Bueso, Jordi; Pino González, David
Sat, 30 May 2015 14:26:08 GMThttp://hdl.handle.net/2117/281162015-05-30T14:26:08ZMazón Bueso, JordiPino González, DavidStudying the Boundary Layer Late Afternoon nd Sunset Turbulence (BLLAST)
http://hdl.handle.net/2117/28114
Studying the Boundary Layer Late Afternoon nd Sunset Turbulence (BLLAST)
Pino González, David; Lothon, Marie; Angevine, Wayne M.; Bange, Jens; Beare, R.J.; Beyrich, Frank; Canut, Guylaine; Couvreux, Fleur; Delbarre, Hervé; Gibert, Fabien; Jonker, Harm J. J.; Lenschow, Donald; Lohou, Fabienne; Mahrt, Larry; Pardyjak, Eric; Sorbjan, Zibgniew; Vilà-Guerau de Arellano, Jordi
At the end of the afternoon, when the surface heat
fluxes start to sharply decrease, the CBL turns from a
convective well-mixed layer to an intermittently turbulent
residual layer overlying a stably-stratified boundary layer.
This transition raises several observational and modeling
issues. Even the definition of the boundary layer during
this period is fuzzy, since there is no consensus on what
criteria to use and no simple scaling laws to apply. Yet it
plays an important role in such diverse atmospheric phenomena
as transport and diffusion of trace constituents
or wind energy production.
This phase of the diurnal cycle remains largely unexplored,
partly due to the difficulty of measuring weak
and intermittent turbulence, anisotropy, horizontal heterogeneity,
and rapid time changes.
The Boundary Layer Late Afternoon and Sunset
Turbulence (BLLAST) project is gathering about thirty
research scientists from the European Union and the
United States to work on this issue. A field campaign
(BLLAST-FE) is planned for spring or summer 2011 in Europe.
BLLAST will utilize these observations, as well as
previous datasets, large-eddy and direct numerical simulations,
and mesoscale modeling to better understand the
processes, suggest new parameterizations, and evaluate
forecast models during this transitional period.
We will present the issues raised by the late afternoon
transition and our strategy to study it.
Sat, 30 May 2015 13:56:45 GMThttp://hdl.handle.net/2117/281142015-05-30T13:56:45ZPino González, DavidLothon, MarieAngevine, Wayne M.Bange, JensBeare, R.J.Beyrich, FrankCanut, GuylaineCouvreux, FleurDelbarre, HervéGibert, FabienJonker, Harm J. J.Lenschow, DonaldLohou, FabienneMahrt, LarryPardyjak, EricSorbjan, ZibgniewVilà-Guerau de Arellano, JordiAt the end of the afternoon, when the surface heat
fluxes start to sharply decrease, the CBL turns from a
convective well-mixed layer to an intermittently turbulent
residual layer overlying a stably-stratified boundary layer.
This transition raises several observational and modeling
issues. Even the definition of the boundary layer during
this period is fuzzy, since there is no consensus on what
criteria to use and no simple scaling laws to apply. Yet it
plays an important role in such diverse atmospheric phenomena
as transport and diffusion of trace constituents
or wind energy production.
This phase of the diurnal cycle remains largely unexplored,
partly due to the difficulty of measuring weak
and intermittent turbulence, anisotropy, horizontal heterogeneity,
and rapid time changes.
The Boundary Layer Late Afternoon and Sunset
Turbulence (BLLAST) project is gathering about thirty
research scientists from the European Union and the
United States to work on this issue. A field campaign
(BLLAST-FE) is planned for spring or summer 2011 in Europe.
BLLAST will utilize these observations, as well as
previous datasets, large-eddy and direct numerical simulations,
and mesoscale modeling to better understand the
processes, suggest new parameterizations, and evaluate
forecast models during this transitional period.
We will present the issues raised by the late afternoon
transition and our strategy to study it.Meteorological reconstruction of major floods in early instrumental period in Catalonia (NE Iberian Peninsula)
http://hdl.handle.net/2117/28109
Meteorological reconstruction of major floods in early instrumental period in Catalonia (NE Iberian Peninsula)
Mazón Bueso, Jordi; Balasch Solanes, Josep Carles; Barriendos Valve, Mariano; Ruiz Bellet, Josep Lluís; Pino González, David; Tuset Mestre, Jordi
Floods are among the most dangerous natural hazards in the Western Mediterranean area. Historically, these types of events have generated many affectations over several fields, such as agriculture or infrastructures, and
even hundreds of fatalities. The historical archive data allow for a historical (Barriendos et al. 1993) and for a hydraulical and hydrological reconstruction (Balasch et al., 2010, 2011) of floods. However, there are few studies dealing with the meteorological reconstruction of historical floods.
Within the early instrumental period (1780-1950), the 20 major floods (according to the affected area, peak and overflow magnitudes, high social damages) since 1870 affecting Catalonia (NE Iberian Peninsula) have been chosen with the aim of characterizing them under a meteorological point of view. By doing this, we improve the understanding of their atmospheric dynamics. For this purpose, the NOAA 3/6 Hourly 20thC V2 Reanalysis Data Composites database has been used to obtain the vertical profile of the air temperature from 1000 hPa to 200 hPa.
This database allows us to evaluate several parameters related to convection, such as the Convective Available Potential Energy (CAPE), the Lift Index (LI), the K index (KI), the Vertical, Cross and Total Totals (VT, CT, TT respectively), and wind shear between surface and 1, 3 and 6 km levels, among many others. Moreover, the
synoptic condition has been also reconstructed for each flood event.
As a preliminary result, the estimated convective parameters as well as the prevailing synoptic conditions that favor convective precipitation have shown a good correspondence with the geographical and hydrological reconstruction. These results will be useful for the synoptic classification of the largest floods occurred in the past, in order to improve their forecasting in the future.
Sat, 30 May 2015 11:17:40 GMThttp://hdl.handle.net/2117/281092015-05-30T11:17:40ZMazón Bueso, JordiBalasch Solanes, Josep CarlesBarriendos Valve, MarianoRuiz Bellet, Josep LluísPino González, DavidTuset Mestre, JordiFloods are among the most dangerous natural hazards in the Western Mediterranean area. Historically, these types of events have generated many affectations over several fields, such as agriculture or infrastructures, and
even hundreds of fatalities. The historical archive data allow for a historical (Barriendos et al. 1993) and for a hydraulical and hydrological reconstruction (Balasch et al., 2010, 2011) of floods. However, there are few studies dealing with the meteorological reconstruction of historical floods.
Within the early instrumental period (1780-1950), the 20 major floods (according to the affected area, peak and overflow magnitudes, high social damages) since 1870 affecting Catalonia (NE Iberian Peninsula) have been chosen with the aim of characterizing them under a meteorological point of view. By doing this, we improve the understanding of their atmospheric dynamics. For this purpose, the NOAA 3/6 Hourly 20thC V2 Reanalysis Data Composites database has been used to obtain the vertical profile of the air temperature from 1000 hPa to 200 hPa.
This database allows us to evaluate several parameters related to convection, such as the Convective Available Potential Energy (CAPE), the Lift Index (LI), the K index (KI), the Vertical, Cross and Total Totals (VT, CT, TT respectively), and wind shear between surface and 1, 3 and 6 km levels, among many others. Moreover, the
synoptic condition has been also reconstructed for each flood event.
As a preliminary result, the estimated convective parameters as well as the prevailing synoptic conditions that favor convective precipitation have shown a good correspondence with the geographical and hydrological reconstruction. These results will be useful for the synoptic classification of the largest floods occurred in the past, in order to improve their forecasting in the future.