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    Rapid and sudden advection of warm and dry air in the Mediterranean Basin  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David; Barriendos Valve, Mariano
    Natural hazards and earth system sciences
    Vol. 14, num. 2, p. 235-246
    DOI: 10.5194/nhess-14-235-2014
    Date of publication: 2014-02-14
    Journal article

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    Rapid advection of extremely warm and dry air is studied during two events in the Mediterranean Basin. On 27 August 2010 a rapid advection of extremely warm and dry air affected the northeast Iberian Peninsula during a few hours. At the Barcelona city center, the temperature reached 39.3 degrees C, which is the maximum temperature value recorded during 230 yr of daily data series. On 23 March 2008 a rapid increase of temperature and drop of relative humidity were recorded for a few hours in Heraklion (Crete). During the morning on that day, the recorded temperature reached 34 degrees C for several hours on the northern coastline of this island.; According to the World Meteorological Organization none of these events can be classified as a heat wave, which requires at least two days of abnormally high temperatures; neither are they a heat burst as defined by the American Meteorological Society, where abnormal temperatures take place during a few minutes. For this reason, we suggest naming this type of event flash heat.; By using data from automatic weather stations in the Barcelona and Heraklion area and WRF mesoscale numerical simulations, these events are analyzed. Additionally, the primary risks and possible impacts on several fields are presented.

    Rapid advection of extremely warm and dry air is studied during two events in the Mediterranean Basin. On 27 August 2010 a rapid advection of extremely warm and dry air affected the northeast Iberian Peninsula during a few hours. At the Barcelona city center, the temperature reached 39.3 ° C, which is the maximum temperature value recorded during 230 yr of daily data series. On 23 March 2008 a rapid increase of temperature and drop of relative humidity were recorded for a few hours in Heraklion (Crete). During the morning on that day, the recorded temperature reached 34 °C for several hours on the northern coastline of this island. According to the World Meteorological Organization none of these events can be classified as a heat wave, which requires at least two days of abnormally high temperatures; neither are they a heat burst as defined by the American Meteorological Society, where abnormal temperatures take place during a few minutes. For this reason, we suggest naming this type of event flash heat. By using data from automatic weather stations in the Barcelona and Heraklion area and WRF mesoscale numerical simulations, these events are analyzed. Additionally, the primary risks and possible impacts on several fields are presented.

    Postprint (author’s final draft)

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    Role of the residual layer and large-scale subsidence on the development and evolution of the convective boundary layer  Open access

     Blay Carreras, Estel; Pino Gonzalez, David; Vilà Guerau de Arellano, Jordi; van de Boer, Anneke; de Coster, Olivier; Darbieu, Clara; Hartogensis, Oskar; Lohou, Fabienne; Lothon, Marie; Pietersen, Henk
    Atmospheric chemistry and physics
    Vol. 14, p. 4515-4530
    DOI: 10.5194/acp-14-4515-2014
    Date of publication: 2014-01-01
    Journal article

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    Observations, mixed-layer theory and the Dutch Large-Eddy Simulation model (DALES) are used to analyze the dynamics of the boundary layer during an intensive operational period (1 July 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence campaign. Continuous measurements made by remote sensing and in situ instruments in combination with radio soundings, and measurements done by remotely piloted aircraft systems and two manned aircrafts probed the vertical structure and the temporal evolution of the boundary layer during the campaign. The initial vertical profiles of potential temperature, specific humidity and wind, and the temporal evolution of the surface heat and moisture fluxes prescribed in the models runs are inspired by some of these observations.; The research focuses on the role played by the residual layer during the morning transition and by the large-scale subsidence on the evolution of the boundary layer. By using DALES, we show the importance of the dynamics of the boundary layer during the previous night in the development of the boundary layer at the morning. DALES numerical experiments including the residual layer are capable of modeling the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. These simulations show a large increase of the entrainment buoyancy flux when the residual layer is incorporated into the mixed layer. We also examine how the inclusion of the residual layer above a shallow convective boundary layer modifies the turbulent kinetic energy budget.; Large-scale subsidence mainly acts when the boundary layer is fully developed, and, for the studied day, it is necessary to be considered to reproduce the afternoon observations.; Finally, we also investigate how carbon dioxide (CO2) mixing ratio stored the previous night in the residual layer plays a fundamental role in the evolution of the CO2 mixing ratio during the following day.

  • Transitional periods of the atmospheric boundary layer  Open access

     Blay Carreras, Estel
    Department of Applied Physics, Universitat Politècnica de Catalunya
    Theses

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    La capa límit atmosfèrica és la part de la troposfera influenciada per la presència de la superfície terrestre, i on es produeixen la majoria dels fenòmens meteorològics. Durant el dia, en condicions de bon temps, es forma una capa límit convectiva. En canvi, durant la nit, apareix una capa límit estable. L'evolució d'una capa límit convectiva a una capa límit estable i viceversa passa a través de dos processos de transició. A causa de la seva complexitat i la ràpida variació, hi ha una manca d'estudis sobre les transicions del dia a la nit o viceversa.Aquesta tesi vol resoldre algunes de les incerteses relacionades amb les transicions de la capa límit atmosfèrica. La tesi es basa en les observacions obtingudes durant la campanya Boundary-Layer Late Afternoon and Sunset Turbulence i simulacions numèriques desenvolupades amb dos models: un model de capa de mescla i un model de tipus large-eddy simulation.Primerament, es desenvolupa una anàlisi centrada en el paper de la capa residual durant la transició entre la nit i el dia i en el paper de la subsidència en l'evolució de la capa límit. Les simulacions que inclouen la capa residual són capaces de modelar l¿augment sobtat de l¿alçada de la capa límit durant aquesta transició i també la posterior evolució de la capa límit. Aquestes simulacions mostren un gran augment del flux que entra des de la atmosfera lliure quan la capa residual s'incorpora a la capa convectiva. També s¿analitza els efectes de considerar la capa residual en el balanç d'energia cinètica turbulenta. La subsidència actua principalment quan la capa límit està totalment desenvolupada i , pel dia seleccionat, cal tenir-la en compte per tal de reproduir les observacions durant la tarda. Finalment, també investiguem com el diòxid de carboni (CO2) emmagatzemat a la capa residual juga un paper fonamental en l'evolució del CO2 durant el dia.En segon lloc, s'analitza el fet de que durant la transició del dia a la nit hi ha una demora entre el moment en què el flux de flotació esdevé zero i el moment en què el gradient de la temperatura potencial virtual canvia de signa. Aquest fet contradiu el supòsit en què estan basats els models de simulació. Els resultats d'aquest treball confirmen i quantifiquen aquest demora. Específicament, els valors observats de la demora són aproximadament d'entre 30 i 80 min. L'existència de la demora i la seva durada es pot explicar a través del temps convectiu i de les forces associades amb el problema de Rayleigh-Bénard. La teoria proposada considera que l'últim remolí format abans de cessament del flux de superfície produeix el retard en el canvi de signe del gradient del flux de calor. Alhora aquest últim remoli es pot frenar a través de l'acció de la viscositat i la difusivitat tèrmica, i el retard està relacionat amb el temps que dura el recorregut del remolí. Les observacions indiquen que, com més important és el cisallament de vent horitzontal, el temps de retard aparentment augmenta a valors més grans que el temps convectiu.Finalment , s'estudia l'existència i característiques d'un Mínim Elevat de Temperatura (LTM) durant la transició entre el dia i la nit. L'estudi mostra que el LTM es pot detectar en condicions de calma durant aquesta transició hores abans de l'hora d¿observació descrita en els treballs anteriors. Aquestes condicions de calma es compleixen quan les forces sinòptiques són febles i el vent local canvia de direcció en una orografia relativament complexa (durant el dia prové de la vall i durant la nit de la muntanya). En aquestes condicions especials, la turbulència es converteix en un paràmetre fonamental per determinar les condicions ideals per a l'observació de LTM. A més, la correlació de la radiació d'ona llarga mesurada a 0,8 m i estimada a terra varia quan s'observa el LTM. Per tant, el LTM també està relacionada amb un canvi de les característiques radiatives de l¿atmosfera en condicions de calma.

    The atmospheric boundary layer is the part of the troposphere influenced by the presence of the surface, and where most weather phenomena occur. During the day, with fair weather conditions, a convective boundary layer exists. In contrast, during the night, a stable boundary layer appears. It is important to note that the evolution from a convective boundary layer to a stable boundary layer and vice versa happens through two transitional processes. Due to its complexity and the rapid variability, there is a lack of studies about the morning or afternoon/evening transitions. This thesis wants to solve some of the uncertainties related with the morning and afternoon/evening transition of the atmospheric boundary layer. It is based on observations from the project Boundary-Layer Late Afternoon and Sunset Turbulence (BLLAST) and numerical simulation experiments developed with mixed-layer and large-eddy simulation models. In this thesis, we develop an analysis focused on the role played by the residual layer during the morning transition and by the large-scale subsidence on the evolution of the boundary layer. DALES numerical experiments that include the residual layer are capable of modeling the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. These simulations show a large increase in the entrainment buoyancy flux when the residual layer is incorporated into the mixed layer. We also examine how the inclusion of the residual layer above a shallow convective boundary layer modifies the turbulent kinetic energy budget. Large-scale subsidence mainly acts when the boundary layer is fully developed and, for the studied day, it is necessary to consider this in order to reproduce the afternoon observations. Finally, we also investigate how CO2 stored the previous night in the residual layer plays a fundamental role in the evolution of the CO2 mixing ratio during the following day. Moreover, we hypothesize that during the evening transition a delay exists between the instant when the buoyancy flux goes to zero and the time when the local gradient of the virtual potential temperature changes sign contradict the assumption in which are base the gradient-based turbulence models. The results from this work confirm and quantify a flux-gradient delay. Specifically, the observed values of the delay are between approximately 30 and 80 min. The existence of the delay and its duration can be explained by considering the convective time and the competition of forces associated with the classical Rayleigh-Bénard problem. This combined theory predicts that the last eddy formed should produce a delay when the sensible heat flux changes sign during the evening transition. It appears that this last eddy is decelerated through the action of turbulent momentum and thermal diffusivity, and that the delay is related to the convective turnover time. Observations indicate that, as horizontal shear becomes more important, the delay time apparently increases to values greater than the convective turnover time. Finally, we study the existence and characteristics of Lifted Temperature Minimum (LTM) during the evening transition. The study shows that LTM can be detected in calm conditions already during day¿night transition, several hours earlier than the usual time of occurrence reported by previous works. These conditions are fulfilled when weak synoptic forcing exists and the local flow shifts from valley to mountain breeze in a relatively complex orography. Under these special conditions, turbulence becomes a crucial parameter to determine the ideal conditions for observing LTM. Additionally, the correlation of longwave radiation measured at 0.8 m and estimated at the ground varies when the LTM is observed. Therefore, LTM is also related to a change in the atmospheric radiative characteristics under calm conditions.

    La capa límit atmosfèrica és la part de la troposfera influenciada per la presència de la superfície terrestre, i on es produeixen la majoria dels fenòmens meteorològics. Durant el dia, en condicions de bon temps, es forma una capa límit convectiva. En canvi, durant la nit, apareix una capa límit estable. L'evolució d'una capa límit convectiva a una capa límit estable i viceversa passa a través de dos processos de transició. A causa de la seva complexitat i la ràpida variació, hi ha una manca d'estudis sobre les transicions del dia a la nit o viceversa. Aquesta tesi vol resoldre algunes de les incerteses relacionades amb les transicions de la capa límit atmosfèrica. La tesi es basa en les observacions obtingudes durant la campanya Boundary-Layer Late Afternoon and Sunset Turbulence i simulacions numèriques desenvolupades amb dos models: un model de capa de mescla i un model de tipus large-eddy simulation. Primerament, es desenvolupa una anàlisi centrada en el paper de la capa residual durant la transició entre la nit i el dia i en el paper de la subsidència en l'evolució de la capa límit. Les simulacions que inclouen la capa residual són capaces de modelar l’augment sobtat de l’alçada de la capa límit durant aquesta transició i també la posterior evolució de la capa límit. Aquestes simulacions mostren un gran augment del flux que entra des de la atmosfera lliure quan la capa residual s'incorpora a la capa convectiva. També s’analitza els efectes de considerar la capa residual en el balanç d'energia cinètica turbulenta. La subsidència actua principalment quan la capa límit està totalment desenvolupada i , pel dia seleccionat, cal tenir-la en compte per tal de reproduir les observacions durant la tarda. Finalment, també investiguem com el diòxid de carboni (CO2) emmagatzemat a la capa residual juga un paper fonamental en l'evolució del CO2 durant el dia. En segon lloc, s'analitza el fet de que durant la transició del dia a la nit hi ha una demora entre el moment en què el flux de flotació esdevé zero i el moment en què el gradient de la temperatura potencial virtual canvia de signa. Aquest fet contradiu el supòsit en què estan basats els models de simulació. Els resultats d'aquest treball confirmen i quantifiquen aquest demora. Específicament, els valors observats de la demora són aproximadament d'entre 30 i 80 min. L'existència de la demora i la seva durada es pot explicar a través del temps convectiu i de les forces associades amb el problema de Rayleigh-Bénard. La teoria proposada considera que l'últim remolí format abans de cessament del flux de superfície produeix el retard en el canvi de signe del gradient del flux de calor. Alhora aquest últim remoli es pot frenar a través de l'acció de la viscositat i la difusivitat tèrmica, i el retard està relacionat amb el temps que dura el recorregut del remolí. Les observacions indiquen que, com més important és el cisallament de vent horitzontal, el temps de retard aparentment augmenta a valors més grans que el temps convectiu. Finalment , s'estudia l'existència i característiques d'un Mínim Elevat de Temperatura (LTM) durant la transició entre el dia i la nit. L'estudi mostra que el LTM es pot detectar en condicions de calma durant aquesta transició hores abans de l'hora d’observació descrita en els treballs anteriors. Aquestes condicions de calma es compleixen quan les forces sinòptiques són febles i el vent local canvia de direcció en una orografia relativament complexa (durant el dia prové de la vall i durant la nit de la muntanya). En aquestes condicions especials, la turbulència es converteix en un paràmetre fonamental per determinar les condicions ideals per a l'observació de LTM. A més, la correlació de la radiació d'ona llarga mesurada a 0,8 m i estimada a terra varia quan s'observa el LTM. Per tant, el LTM també està relacionada amb un canvi de les característiques radiatives de l’atmosfera en condicions de calma.

  • An intercomparison of mesoscale simulations during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) experimental field campaign

     Jiménez Cortés, M. Antònia; Angevine, Wayne M.; Bazille, Eric; Couvreux, Fleur; Cuxart Rodamillans, Joan; Pino Gonzalez, David; Sastre Marugas, Mariano
    European Geosciences Union General Assembly
    Presentation's date: 2014-04-29
    Presentation of work at congresses

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  • The Boundary Layer Late Afternoon and Sunset Turbulence Project

     Lothon, Marie; Lohou, Fabienne; Darbieu, Clara; Couvreux, Fleur; Pino Gonzalez, David; Blay Carreras, Estel; Vilà Guerau de Arellano, Jordi; Pietersen, Henk; Hartogensis, Oskar; Pardyjak, Eric; Sastre Marugas, Mariano; Jiménez Cortés, M. Antònia
    European Geosciences Union General Assembly
    Presentation's date: 2014-04-28
    Presentation of work at congresses

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  • Spatial extension of the reconstruction of 1874 Santa Tecla¿s flash floods in Catalonia (NE Iberian Peninsula)

     Ruiz Bellet, Josep Lluís; Balasch Solanes, Josep Carles; Tuset Mestre, Jordi; Barriendos Valve, Mariano; Mazon Bueso, Jordi; Pino Gonzalez, David
    European Geosciences Union General Assembly
    Presentation's date: 2014-05-02
    Presentation of work at congresses

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  • Quantifying the uncertainties of advection and boundary layer dynamics on the diurnal carbon dioxide budget

     Pino Gonzalez, David; Kaikkonen, Jukka-Pekka; Vilà Guerau de Arellano, Jordi
    Journal of geophysical research
    Vol. 118, p. 1-17
    DOI: 10.1002/jgrd.50677
    Date of publication: 2013-08-22
    Journal article

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    We investigate the uncertainties in the carbon dioxide (CO2) mixing ratio and inferred surface flux associated with boundary layer processes and advection by using mixed-layer theory. By extending the previous analysis presented by Pino et al. (2012), new analytical expressions are derived to quantify the uncertainty of CO2 mixing ratio or surface flux associated to, among others, boundary layer depth, early morning CO2 mixing ratio at the mixed layer or at the free atmosphere; or CO2 advection. We identify and calculate two sorts of uncertainties associated to the CO2 mixing ratio and surface flux: instantaneous and past (due to advection). The numerical experiments are guided and constrained by meteorological and CO2 observations taken at the Cabauw 213 m tower. We select 2 days (25 September 2003 and 12 March 2004) with a well-defined convective boundary layer but different CO2 advection contributions. Our sensitivity analysis shows that uncertainty of the CO2 advection in the boundary layer due to instantaneous uncertainties represents at 1600 LT on 12 March 2004 a contribution of 2¿ppm and 0.072 mg m-2s-1 in the uncertainty of the CO2 mixing ratio and inferred surface flux, respectively. Taking into account that the monthly averaged minimum CO2 surface flux for March 2004 was -0.55 mg m-2s-1, the error on the surface flux is on the order of 10%. By including CO2 advection in the analytical expressions, we demonstrate that the uncertainty of the CO2 mixing ratio or surface flux also depends on the past uncertainties of the boundary layer depth.

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    La rubinada de Santa Tecla a Tàrrega (23 de Setembre de 1874)  Open access

     Barriendos Valve, Mariano; Tuset Mestre, Jordi; Mazon Bueso, Jordi; Pino Gonzalez, David; Ruiz Bellet, Josep Lluís; Balasch Solanes, Josep Carles
    Urtx. Revista Cultural De l'urgell
    num. 27, p. 9-25
    Date of publication: 2013-04-09
    Journal article

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    A partir de la recopilación histórica de los datos documentales disponibles y aplicando una metodología multidisci- plinar con modelos de simulación hidráulica, hidrológica y meteorológica, se han reconstruido las características prin- cipales de la devastadora crecida hidrológica (o rubinada de Santa Tecla) que padeció la ciudad de Tàrrega en la madrugada del 23 de septiembre de 1874, y se describe el contexto meteorológico que condicionó la tormenta. El caudal punta fue excepcional, causando una de las mayores mortandades de la historia de Tàrrega. Las circunstan- cias actuales no han cambiado, lo que no permite pensar que una avenida similar no pueda volver a ocurrir. The main characteristics of the Santa Tecla¿s flash flood that took place in Tàrrega the 23rd of September of 1874 are reconstructed in this paper. For this, we use historical data from available contemporary documents and apply a mul- tidisciplinary approach based on hydraulic, hydrological and meteorological simulation models. The meteorological conditions that determined the storm are also described. The peak discharge was the overriding cause of one of the major human tragedies in the history of Tàrrega. Since the circumstances have not changed, rather the opposite, such a flood is likely to occur again

    A partir de la recopilación histórica de los datos documentales disponibles y aplicando una metodología multidisci- plinar con modelos de simulación hidráulica, hidrológica y meteorológica, se han reconstruido las características prin- cipales de la devastadora crecida hidrológica (o rubinada de Santa Tecla) que padeció la ciudad de Tàrrega en la madrugada del 23 de septiembre de 1874, y se describe el contexto meteorológico que condicionó la tormenta. El caudal punta fue excepcional, causando una de las mayores mortandades de la historia de Tàrrega. Las circunstan- cias actuales no han cambiado, lo que no permite pensar que una avenida similar no pueda volver a ocurrir. The main characteristics of the Santa Tecla’s flash flood that took place in Tàrrega the 23rd of September of 1874 are reconstructed in this paper. For this, we use historical data from available contemporary documents and apply a mul- tidisciplinary approach based on hydraulic, hydrological and meteorological simulation models. The meteorological conditions that determined the storm are also described. The peak discharge was the overriding cause of one of the major human tragedies in the history of Tàrrega. Since the circumstances have not changed, rather the opposite, such a flood is likely to occur again

  • Nocturnal offshore precipitation near the Mediterranean coast of the Iberian Peninsula

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Meteorology and atmospheric physics
    Vol. 120, num. 1-2, p. 11-28
    DOI: 10.1007/s00703-012-0229-1
    Date of publication: 2013-04
    Journal article

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    While nocturnal offshore precipitation, which produces rain cells and bands, has been studied in tropical areas, few studies have analyzed the occurrence of this phenomenon at higher latitudes. Using radar reflectivity, nocturnal rainfall in the western Mediterranean area has been detected near the coast of the Iberian Peninsula and North Africa. More than 50 events have been recorded since 2009. MM5 mesoscale simulations of some of the recorded events allow us to establish that the most likely causes for these precipitation events are: (1) the interaction between cold air masses conducted by drainage and katabatic winds, and (2) a wetter and warmer synoptic wind. Two different episodes are presented: one in the northeastern Iberian Peninsula, caused by stratiform clouds, which occurred at the mouths of three rivers; the other case, produced by convective clouds, occurred at the southern Iberian Peninsula and was caused by the drainage winds flowing down from some mountain ranges located close to the coast.

    While nocturnal offshore precipitation, which produces rain cells and bands, has been studied in tropical areas, few studies have analyzed the occurrence of this phenomenon at higher latitudes. Using radar reflectivity, nocturnal rainfall in the western Mediterranean area has been detected near the coast of the Iberian Peninsula and North Africa. More than 50 events have been recorded since 2009. MM5 mesoscale simulations of some of the recorded events allow us to establish that the most likely causes for these precipitation events are: (1) the interaction between cold air masses conducted by drainage and kata- batic winds, and (2) a wetter and warmer synoptic wind. Two different episodes are presented: one in the north- eastern Iberian Peninsula, caused by stratiform clouds, which occurred at the mouths of three rivers; the other case, produced by convective clouds, occurred at the southern Iberian Peninsula and was caused by the drainage winds flowing down from some mountain ranges located close to the coast.

  • COMPRENDER Y CUANTIFICAR LA INTERACCION ENTRE LA CAPA LIMITE ATMOSFERICA Y LAS ESCALAS REGIONALES EN EL CICLO DEL CARBONO

     Mazon Bueso, Jordi; Blay Carreras, Estel; Pino Gonzalez, David
    Competitive project

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  • Flash heat simulation events in the north Mediterranean basin

     Mazon Bueso, Jordi; Pino Gonzalez, David
    European Geosciences Union General Assembly
    p. 1329
    Presentation's date: 2013-04-09
    Presentation of work at congresses

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  • The influence of the sea surface temperature on the nocturnal offshore

     Mazon Bueso, Jordi; Pino Gonzalez, David
    European Geosciences Union General Assembly
    p. 1326
    Presentation's date: 2013-04-11
    Presentation of work at congresses

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  • Clouds caused by human activities: the anthropoclouds

     Mazon Bueso, Jordi; Pino Gonzalez, David
    European Geosciences Union General Assembly
    p. 1330
    Presentation's date: 2013-04-10
    Presentation of work at congresses

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  • Multidisciplinary reconstruction of 1874 Santa Tecla flash-floods in the Ebreo river basin (NE Iberian Peninsula)

     Mazon Bueso, Jordi; Pino Gonzalez, David; Barriendos Valve, Mariano; Balasch, Josep Maria; Ruiz Bellet, Josep Lluís; Tuset Mestre, Jordi
    European Geosciences Union General Assembly
    p. 11180
    Presentation's date: 2013-04-12
    Presentation of work at congresses

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    The role of sea-land air thermal difference, shape of the coastline and sea surface temperature in the nocturnal offshore convection  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Tellus. Series A, dynamic meteorology and oceanography
    Vol. 65, num. 20027
    Date of publication: 2013-01-31
    Journal article

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    Nocturnal precipitation cells and lines occur near the coastline in the whole Mediterranean basin in all seasons. The precipitation events are mainly located in areas where coastal mountain ranges and rivers enhance convergence though the interaction of nocturnal mesoscale and local flows (land breeze, katabatic and drainages winds) with prevailing synoptic wind or with other mesoscale and local flows. The methodology used here to study this phenomenon consists of three stages. First, the Tropical Rainfall Measuring Mission (TRMM) radar satellite database is used to detect nocturnal precipitation near the coastline, from 18 to 09 UTC. An event is included in the study if the 3 hours accumulated precipitation detected by TRMM is stationary near the coast, or has moved slightly onshore or offshore, and has lasted no more than six consecutive hours. Second, the NCEP reanalysis database is used to describe the synoptic conditions and to discard precipitation associated with synoptic events (large low pressure areas, dynamic polar fronts, or troughs, for example). In the final step by using the version 3 of the Weather Research Forecast model, we simulate and analyse some of the selected events to determine the role of the land sea temperature differences, the curvature of the coastline and the sea surface temperature. The simulations confirm that the nocturnal precipitation studied in the Mediterranean basin near the coastline is formed from the interaction between relatively warm and wet sea-air with the cold air mass from drainage winds, as well as from the convergence of several drainage winds offshore. The mechanism is the same that is used to explain nocturnal precipitation in tropical areas.

  • The role of the nocturnal-coastal-front height in the occurrence of clouds and rainbands in the Mediterranean basin

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Annual Meeting European Meteorological Society organised with European Conference on Aplications of Meteorology
    p. 1
    Presentation's date: 2013-09-10
    Presentation of work at congresses

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  • Analysis of the decoupling between surface heat flux and temperature gradient during afternoon transition

     Blay Carreras, Estel; Pardyjak, Eric; Pino Gonzalez, David; Lothon, Marie; Lohou, Fabienne
    European Meteorological Society Annual Meeting & European Conference on Applied Climatology
    p. 1
    Presentation's date: 2013-09-10
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    Nocturnal offshore precipitation near the coastline in the Mediterranean basin  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Internations Meeting on Meteorology and Climatology in the Mediterranean
    Presentation's date: 2013-03-01
    Presentation of work at congresses

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    Frontogenesis in the meso-a and meso-ß scales in the Mediterranean basin: From cloud arch to cloud cells.  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    International Meeting on Meteorology and Climatology of the Mediterranean
    Presentation's date: 2013-03-01
    Presentation of work at congresses

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  • Observations and large-eddy simulations of entrainment in the sheared sahelian boundary layer

     Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Pino Gonzalez, David; Saïd, Frédérique
    Boundary-layer meteorology
    Vol. 142, num. 1, p. 79-101
    DOI: 10.1007/s10546-011-9661-x
    Date of publication: 2012-01
    Journal article

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    At the top of the planetary boundary layer, the entrainment of air, which incorporates dry and warm air from the free troposphere into the boundary layer, is a key process for exchanges with the free troposphere since it controls the growth of the boundary layer. Here, we focus on the semi-arid boundary layer where the entrainment process is analyzed using aircraft observations collected during the African Monsoon Multidisciplinary Analysis experiment and large-eddy simulations. The role of the entrainment is specifically enhanced in this region where very large gradients at the planetary boundary-layer top can be found due to the presence of the moist, cold monsoon flow on which the dry, warm Harmattan flow is superimposed. A first large-eddy simulation is designed based on aircraft observations of 5 June 2006 during the transition period between dry conditions and the activemonsoon phase. The simulation reproduces the boundary-layer development and dynamics observed on this day. From this specific case, sensitivity tests are carried out to cover a range of conditions observed during seven other flightsmade in the same transition period in order to describe the entrainment processes in detail. The combination of large-eddy simulations and observations allows us to test the parametrization of entrainment in a mixed-layer model with zero-order and first-order approximations for the entrainment zone. The latter representation of the entrainment zone gives a better fit with the conditions encountered in the Sahelian boundary layer during the transition period because large entrainment thicknesses are observed. The sensitivity study also provides an opportunity to highlight the contribution of shear stress and scalar jumps at the top of the boundary layer in the entrainment process, and to test a relevant parametrization published in the recent literature for a mixed-layer model.

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    A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios  Open access

     Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi; Peters, Wouter; Schröter, Joel; van Heerwaarden, Chiel C.; Krol, Maarten
    Atmospheric chemistry and physics
    Vol. 12, p. 2969-2985
    DOI: 10.5194/acp-12-2969-2012
    Date of publication: 2012-03-26
    Journal article

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    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  • Clouds caused by human activities

     Mazon Bueso, Jordi; Pino Gonzalez, David; Costa Vila, Marcel; Lorente, Jeroni
    Weather
    Vol. 67, num. 11, p. 302-306
    DOI: 10.1002/wea.1949
    Date of publication: 2012-11-01
    Journal article

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    Uncertainties in the CO2 budget associated to the diurnal variability of the boundary layer dynamics  Open access

     Pino Gonzalez, David; Kaikkonen, Jukka-Pekka; Vilà-Guerau de Arellano, Jordi
    American Geophysical Union Fall Meeting
    Presentation's date: 2012-12-06
    Presentation of work at congresses

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    The role of nocturnal Low-Level-Jet in nocturnal convection and rainfalls in the west Mediterranean coast: the episode of 14 December 2010 in northeast of Iberian Peninsula  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Advances in science and research (ASR)
    Vol. 8, p. 27-31
    DOI: doi:10.5194/asr-8-27-2012
    Date of publication: 2012-03-19
    Journal article

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    The night of 14 December 2010 radar images of the Spanish Weather Agency recorded a large rain band that moved o ff shore at the Northeast coast of the Iberian Peninsula. MM5 mesoscale model is used to study the atmospheric dynamics during that day. A Nocturnal Low Level Jet (NLLJ) generated by an inertial oscillation that brings cold air to the coast from inland has been simulated in the area. This cold air interacts with a warmer air mass some kilometers o ff shore. According to the MM5 mesoscale model simulation, the cold air enhances upward movements of the warm air producing condensation. Additionally, there is a return flow to the coastline at 600–900 m high. This warm air mass interacts again with the cold air moving downslope, also producing condensation inland. The simulation for the night before this episode shows large drainage winds with a NLLJ profile, but no condensation areas. The night after the 14th the simulation also shows drainage winds but without a NLLJ profile. However, an o ff shore convergence area was produced with a returned flow, but no condensation inland occurred. This fact is in agreement with radar observations which reported no precipitation for these two days. Consequently, NLLJ in combination with a synoptic wind over the sea could enhance condensation and eventually precipitation rates in the Mediterranean Iberian coast.

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    Stationary nocturnal offshore precipitatin near the coatline in the Mediterranean basin  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    EGU Plinius Conference on Mediterranean Storms
    p. 47
    Presentation's date: 2012-11-15
    Presentation of work at congresses

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    Flash heat events: the case of 27th August 2010 in northeast of Iberian  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    European Meteorological Society Annual Meeting & European Conference on Applied Climatology
    p. 210
    Presentation's date: 2012-09-13
    Presentation of work at congresses

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    The greatest recent flood in Spain: a WRF simulation of the 1962 Valles  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    EGU Plinius Conference on Mediterranean Storms
    p. 48
    Presentation's date: 2012-11-15
    Presentation of work at congresses

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    The role of large sea-land temperature, the coastline shape and the SST in  Open access

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Annual Meeting European Meteorological Society organised with European Conference on Aplications of Meteorology
    p. 209
    Presentation's date: 2012-09-10
    Presentation of work at congresses

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  • On the role of large-scale forcings on the development of the atmospheric boundary layer during the BLLAST field campaign

     Pietersen, Henk; Vilà-Guerau de Arellano, Jordi; de Coster, Olivier; van de Boer, Anneke; Hartogensis, Oskar; Pino Gonzalez, David; Gioli, Beniamino; Durand, Pierre; Lothon, Marie; Lohou, Fabienne; Reuder, Joaquim; Jonassen, Marius; Faloona, Ian
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-13
    Presentation of work at congresses

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    Boundary Layer Late Afternoon and Sunset Turbulence: the BLLAST 2011 experiment  Open access

     Pino Gonzalez, David; Lothon, Marie; Lohou, Fabienne; Pardyjak, Eric; Reuder, Joaquim; Legain, Dominique; Durand, Pierre; Couvreux, Fleur; Vilà-Guerau de Arellano, Jordi
    European Geosciences Union General Assembly
    Presentation's date: 2012-04-26
    Presentation of work at congresses

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    The Boundary Layer Late Afternoon and Sunset Turbulence 2011 field experiment (BLT)  Open access

     Lothon, Marie; Lohou, Fabienne; Durand, Pierre; Couvreux, Fleur; Hartogensis, Oskar; Legain, Dominique; Pardyjak, Eric; Pino Gonzalez, David; Reuder, Joaquim; Vilà-Guerau de Arellano, Jordi
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-13
    Presentation of work at congresses

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    Growth of the CBL over land in the middle of the day has been extensively observed and relatively successfully modeled. However the late afternoon transition (LAT), like the morning transition, is difficult to observe and model due to turbulence intermittency and anisotropy, horizontal heterogeneity, and rapid time changes. There is a striking paucity of observations of the turbulence decay within the CBL, as well as a lack of realistic modeling studies. This motivated the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) 2011 field experiment, which aimed at enhancing observations of the LAT, so as to better understand the physical processes that control it, and elucidate the role of the LAT on mesoscale and turbulence scale motions, and on species transport.

  • Evaluation of entrainment velocity from a First-order model and a Zero-order model with Large-eddy simulations and observations

     Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Pino Gonzalez, David; Saïd, Frédérique
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-09
    Presentation of work at congresses

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  • Uncertainties in the CO2 budget associated to boundary layer dynamics and CO2-advection

     Kaikkonen, Jukka-Pekka; Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-12
    Presentation of work at congresses

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  • Role of residual layer and large-scale phenomena on the evolution of the boundary layer

     Blay Carreras, Estel; Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi; van de Boer, Anneke; de Coster, Olivier; Faloona, Ian; Garrouste, Olivier; Hartogensis, Oskar; Jonassen, Marius; Legain, Dominique; Lothon, Marie; Pietersen, Henk; Román-Gascón, Carlos; Reuder, Joaquim; Saïd, Frederique; Traulle, Olivier; Yague, Carlos
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-09
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  • Understanding and representing the effect of wind shear on the turbulent transfer in the convective boundary layer

     Ronda, Reinder; Vilà-Guerau de Arellano, Jordi; Pino Gonzalez, David
    Symposium on Boundary Layers and Turbulence
    Presentation's date: 2012-07-10
    Presentation of work at congresses

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    Determination of wind speed and associated loads over the sports facility collapsed during the severe windstorm of 24 January 2009 in Sant Boi de Llobregat (Barcelona)  Open access

     Mazon Bueso, Jordi; Crespo Artiaga, Daniel; Pino Gonzalez, David
    Tethys: Journal of Mediterranean Meteorology and Climatology
    DOI: 10.3369/tethys.2011.8.07
    Date of publication: 2011-06-23
    Journal article

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    The severe windstorm of 24 January 2009, caused by an explosive cyclogenesis, affected coastal and precoastal areas of the northeast of the Iberian Peninsula, where damages were numerous and significant, both in urban areas and in forests. One of the most important effects was the collapse of a sports facility in Sant Boi de Llobregat (10 km southwest of Barcelona), killing four children. The objective of this study is to estimate the wind speed over the sports facility and calculate the suction of the wind on the roof of the building, and the consequent collapse of the walls. To get a first approximation, a simulation of the episode around the time of maximum wind gust was inspected using the mesoscale model MM5. In the second part, the damage around the collapsed facility was analyzed, with which we note the fact that a truck was dragged and knocked over by the wind. This analysis allows for the conclusion that, in conjunction with the maximum wind gust, there was a sudden and very local shift in the wind, which caused the gust to hit the building head on. Based on this observation, the wind speed on surface and at 7 m (roof of the building) was estimated, and the suction of the wind was calculated

  • The role of drainage winds in the formation of nocturnal convective systems in the western Mediterranean coast

     Mazon Bueso, Jordi; Pino Gonzalez, David
    HyMex
    Presentation's date: 2011-05-18
    Presentation of work at congresses

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  • The role of nocturnal low-level-jet in nocturnal convection and rainfalls in the Mediterranean coast: the episode of 14th December 2010 in northeast of Iberian Peninsula

     Mazon Bueso, Jordi; Pino Gonzalez, David
    European Meteorological Society Annual Meeting
    Presentation's date: 2011-09-16
    Presentation of work at congresses

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  • Rapids and sudden invasions of very hot and dry air bubbles in the east and northeast of the Iberian Peninsula: the case of 27th August 2010

     Mazon Bueso, Jordi; Barriendos Valve, Mariano; Pino Gonzalez, David; Puertas, A
    International Meeting on Meteorology and Climatology of the Mediterranean
    Presentation's date: 2011-06-08
    Presentation of work at congresses

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  • Analysis of the representativeness of backward atmospheric transport modelling at different resolutions at the Takasaki RN38 IMS station

     Arnold Arias, Delia; Pino Gonzalez, David; Vargas Drechsler, Arturo
    Comprehensive Nuclear-Test-Ban Treaty: Science & Technology
    Presentation's date: 2011-06-08
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  • Formulation of and numerical studies with the Dutch Atmospheric Large-Eddy Simulation (DALES)

     Heus, Thijs; van Heerwaarden, Chiel C.; Jonker, Harm J. J.; Siebesma, Pier; Axelsen, Simon; van den Dries, Kees; Geoffroy, Oliver; Moene, Arnold F; Pino Gonzalez, David; de Roode, Stephan; Vilà-Guerau de Arellano, Jordi
    Geoscientific model development discussions
    Vol. 3, num. 1, p. 99-180
    DOI: 10.5194/gmdd-3-99-2010
    Date of publication: 2010
    Journal article

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    Formulation of the Dutch Atmospheric Large-Eddy Simulation (DALES) and overview of its applications  Open access

     Heus, Thijs; van Heerwaarden, Chiel C.; Jonker, Harm J. J.; Siebesma, Pier; Axelsen, Simon; van den Dries, Kees; Geoffroy, Oliver; Moene, Arnold F; Pino Gonzalez, David; de Roode, Stephan; Vilà-Guerau de Arellano, Jordi
    Geoscientific model development
    Vol. 3, num. 2, p. 415-444
    DOI: 10.5194/gmd-3-415-2010
    Date of publication: 2010-09-30
    Journal article

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    The current version of the Dutch Atmospheric Large-Eddy Simulation (DALES) is presented. DALES is a large-eddy simulation code designed for studies of the physics of the atmospheric boundary layer, including convective and stable boundary layers as well as cloudy boundary layers. In addition, DALES can be used for studies of more specific cases, such as flow over sloping or heterogeneous terrain, and dispersion of inert and chemically active species. This paper contains an extensive description of the physical and numerical formulation of the code, and gives an overview of its applications and accomplishments in recent years.

  • REGIMENES DE TRANSICION Y VARIABILIDAD EN LA DINAMICA Y LA QUIMICA DE LA BAJA TROPOSFERA

     Mazon Bueso, Jordi; Blay Carreras, Estel; Pino Gonzalez, David
    Competitive project

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  • Anàlisi del temporal de vent sever del 24 de gener del 2009 al massís del Garraf

     Mazon Bueso, Jordi; Pino Gonzalez, David
    Trobada d'Estudiosos del Garraf i d'Olèrdola
    Presentation's date: 2010-11-18
    Presentation of work at congresses

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    Studying the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST)  Open access

     Lothon, Marie; Lenschow, Donald; Angevine, Wayne M.; Bange, Jens; Beare, Robert; Canut, Guylaine; Couvreux, Fleur; Delbarre, Hervé; Durand, Pierre; Gibert, Fabien; Gioli, Beniamino; Jonker, Harm J. J.; Lohou, Fabienne; Mahrt, Larry; Pardyjak, Eric; Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi
    International Symposium for the Advancement of Boundary Layer Remote Sensing
    p. 1-4
    Presentation's date: 2010-06-30
    Presentation of work at congresses

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    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 modelling 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 modelling to better understand the processes, suggest new parameterisations, 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.

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    The entrainment process between the Monsoon flow and the Saharan Air Layer in the West African Monsoon system  Open access

     Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Pino Gonzalez, David; Saïd, Frederique
    Symposium on Boundary Layers and Turbulence
    p. 1-14
    Presentation's date: 2010-08-02
    Presentation of work at congresses

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    Role of boundary layer processes on the mixed layer CO2-budget  Open access

     Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi
    Symposium on Boundary Layers and Turbulence
    p. 1-6
    Presentation's date: 2010-08-05
    Presentation of work at congresses

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    Role of boundary layer processes in understanding the CO2-budget  Open access

     Pino Gonzalez, David; Vilà-Guerau de Arellano, Jordi; Peters, Wouter
    American Geophysical Union Fall Meeting
    Presentation's date: 2010-12-16
    Presentation of work at congresses

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    Boundary layer dynamics, including surface pro- cesses determine the daily evolution of temperature and moisture in the atmospheric boundary layer (ABL, Lemone et al., 2002). Moreover, turbulent mixing drives the exchange of CO2 between the atmosphere and bio- sphere and, finally, the advection influences the distribu- tion of carbon dioxide near the surface (Yi et al., 2000; Werner et al., 2006; Eugster and Siegrist, 2000), and as a consequence Net Ecosystem-atmosphere Exchange (NEE) of carbon dioxide. NEE is continuously estimated around the world usu- ally from measurements at one height near the ground of the time evolution of the CO2 concentration and turbu- lent flux (Valentini et al., 2000; Baldocchi et al., 2001). In these observations, among other approximations, advec- tion is supposed negligible (Yi et al., 2000), and a well- mixed boundary layer is considered during the whole day. In this study the diurnal variability of the CO2 con- centration is studied by means of tower measurements, mixed-layer theory and Large-Eddy simulations done with the Dutch model DALES (Heuss et al., 2010). The work presented here is an extension of Casso-Torralba et al. (2008), where observations were presented. Particular attention is devoted to analyze the role of boundary layer processes on the CO2 evolution and to study the uncer- tainties in the calculation the Net ecosystem-atmosphere Exchange for CO2.

  • Studying the Boundary Layer Late Afternoon nd Sunset Turbulence (BLLAST)

     Pino Gonzalez, 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
    Symposium on Boundary Layers and Turbulence
    p. 1-4
    Presentation's date: 2010-08-02
    Presentation of work at congresses

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