The production of drops by the bursting of a bubble at an air liquid interface

The fundamental mechanism arising during the bursting of a bubble at an air-liquid interface is described. A single bubble was followed from an arbitrary depth in the liquid, up to the creation and motion of the film and jet drops. Several phenomena were involved and their relative order of magnitude was compared in order to point out the dimensionless parameters which govern each step of the motion. High-speed cinematography is employed. The characteristic bubble radius which separates the creation of jet drops from cap bursting without jet drops is expressed mathematically. The corresponding numerical value for water is 3 mm and agrees with experimental observations

Estimation des changements de la ligne de rivage de la zone côtière sablonneuse de Kénitra au Maroc

Les plages du littoral de Kénitra ont connu des modifications au cours de ces quatre dernières décennies. La mise en valeur économique de certaines plages par des aménagements touristiques et l’extraction massive de sables pour les travaux d’aménagements urbains sont à l’origine d’une déstabilisation des échanges transversaux de sédiments. Ils sont accentués par la succession de périodes de sécheresse et par la multiplication de construction de barrages sur le bassin versant du Sebou. Le préambule à une meilleure gestion de ces plages est la compréhension de leur comportement passé vis-à-vis des contraintes naturelles et anthropiques. Cette démarche s’appuie essentiellement sur les missions aériennes de 1963 et de 1993. Le Modèle Numérique de Terrain (MNT), d’une précision de ± 10 cm en altitude issu de ces missions et le suivi du positionnement du trait de côte par un système d’analyse numérique (DSAS), ont permis d’estimer les taux de changement.Mots-clés : Littoral, basin versant de Sebou, Maroc, photographies aériennes,MNT, DSAS

Long-term denudation rates from the Central Andes (Chile) estimated from a digital elevation model using the black top hat function and inverse distance weighting : implications for the neogene climate of the Atacama Desert

A methodology for determining long-term denudation rates from morphologic markers in a Digital Elevation Model (DEM) is checked by a comparative study of two drainage basins in the Precordillera of the Central Andes. In both cases the initial configuration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH) function and the Inverse Distance Weighting (IDW) interpolation. Where vertical incision and hillslope erosion are recorded, the 1DW appears to be the most adequate to reconstitute the pediment surfaces. Conversely, where only vertical incision is observed, the BTH describes more precisely the former pediment surfaces and it is easier to solve. By subtracting the DEM from the reconstructed marker we calculated an eroded volume, and estimated its uncertainty by considering Root Mean Square Error (RMSE) and DEM grid error. For the last similar to 10 Myr we obtained long-term denudation rates of 7.33 +/- 1.6 m/Myr in the San Andres drainage basin and 13.59 +/- 1.9 m/Myr in the El Salado drainage basin. These estimations are largely in agreement with other reported estimates of long-term denudation rates in the Atacama Desert. Comparison with long-term denudation rates reported in a wide range of climatic regimes suggests that our estimates cannot be explained by the current rainfall in the Precordillera. However they could be explained by a rainfall similar to that reported 40 km to the east in the Puna. This suggests that during the time span concerned the geomorphologic evolution of the study area, this evolution is dominated by an orographically controlled rainfall pattern. The preserved pediment surface and the small long term denudation rates determined in this study also indicate that the Precordillera was never reached by humid tropical air masses and precipitation as currently observed in the Altiplano during the summer months

Der Verbleib kupferbasierter Fungizide in Weinbergböden: Eine Fallstudie der stabilen Kupfer-Isotopenverhältnisse und Elektronenspinresonanz von Calco- und Vertisolen in Soave (Italien)

Kupferbasierte Fungizide sind im Weinbau weit verbreitet und im biologischen Weinbau die einzig erlaubten Pestizide zur Bekämpfung von falschem Mehltau. Durch den intensiven, dauerhaften Gebrauch von Kupfer reichert sich dieser, mit wachsenden ökotoxikologischen Konsequenzen, in Weinbergböden an. In dieser Studie untersuchen wir den Verbleib von Kupfer in einem Calcosol und einem Vertisol aus Soave (Italien). Beide Böden werden seit über 50 Jahren mit Kupfer behandelt. Wir stellen Massenbilanzen auf und nutzen die innovative Kombination aus Messung stabiler Cu-Isotopenverhältnisse und Elektronenspinresonanzspektroskopie (ESR), um Einblicke in die biogeochemischen Mechanismen der Kupferbindung zu erlangen. Die untersuchten Böden weisen hohe exogene Kupfergehalte auf, welche eine Akkumulation der heutigen maximalen Behandlungsmenge über 50 Jahre überschreiten. Dies belegt, dass einmal sehr viel größere Mengen Cu im Weinbau verwendet wurden und dass ein Großteil dieses Kupfers in den jeweiligen Böden verbleibt. In Vertisolen fallen die Cu-Konzentrationen unter dem vertischen Horizont schnell auf die geogene Hintergrundkonzentration, wobei in Calcosolen dieser Abfall progressiver erfolgt. Isotopenverhältnisse unterscheiden sich zwischen den verschieden Bodentypen (δCu-65 zwischen 0.12 und 0.37 ‰), obwohl sie die gleiche Behandlung erfahren haben. Kupferisotope in Oberböden sind schwerer als in Unterböden und Citratextraktionen zeigen, dass mobiles Kupfer isotopisch schwerer ist als der Gesamtgehalt. Die Horizonte des Calcosols sind systematisch leichter als die des Vertisols, was auf unterschiedliche biogeochemische Bindungsmechanismen von Kupfer hinweist. Dies wird durch die ESR-Spektren bestätigt. In Oberböden zeigen sie eine Kupferbindung an organisches Material, wobei es im gesamten Bodenprofil Unterschiede in der Cu-Bindung zwischen den beiden Bodentypen gibt. Wenn jedoch Horizonte des Calcosols mit Säure entkalkt werden, nähren sich deren ESR-Spektren denen der Vertisole an, wohingegen letztere nicht auf eine Säurebehandlung reagieren. Somit wird gezeigt, dass in Calcosolen Karbonate an der Bindung von Kupfer beteiligt sind wobei in Vertisolen der vertische Horizont eine wichtige Rolle spielt. Darüber hinaus wird durch die analoge Variation von ESR-Spektren und Isotopenverhältnissen wird die Anwendbarkeit von Cu-Isotopenanalysen und ESR-Spektroskopie zur Aufklärung von biogeochemischen Prozessen in Böden demonstriert

Use of reflected GNSS SNR data to retrieve either soil moisture or vegetation height from a wheat crop

This work aims to estimate soil moisture and vegetation height from Global Navigation Satellite System (GNSS) Signal to Noise Ratio (SNR) data using direct and reflected signals by the land surface surrounding a ground-based antenna. Observations are collected from a rainfed wheat field in southwestern France. Surface soil moisture is retrieved based on SNR phases estimated by the Least Square Estimation method, assuming the relative antenna height is constant. It is found that vegetation growth breaks up the constant relative antenna height assumption. A vegetation-height retrieval algorithm is proposed using the SNR-dominant period (the peak period in the average power spectrum derived from a wavelet analysis of SNR). Soil moisture and vegetation height are retrieved at different time periods (before and after vegetation's significant growth in March). The retrievals are compared with two independent reference data sets: in situ observations of soil moisture and vegetation height, and numerical simulations of soil moisture, vegetation height and above-ground dry biomass from the ISBA (interactions between soil, biosphere and atmosphere) land surface model. Results show that changes in soil moisture mainly affect the multipath phase of the SNR data (assuming the relative antenna height is constant) with little change in the dominant period of the SNR data, whereas changes in vegetation height are more likely to modulate the SNR-dominant period. Surface volumetric soil moisture can be estimated (R2  =  0.74, RMSE  =  0.009 m3 m−3) when the wheat is smaller than one wavelength (∼ 19 cm). The quality of the estimates markedly decreases when the vegetation height increases. This is because the reflected GNSS signal is less affected by the soil. When vegetation replaces soil as the dominant reflecting surface, a wavelet analysis provides an accurate estimation of the wheat crop height (R2  =  0.98, RMSE  =  6.2 cm). The latter correlates with modeled above-ground dry biomass of the wheat from stem elongation to ripening. It is found that the vegetation height retrievals are sensitive to changes in plant height of at least one wavelength. A simple smoothing of the retrieved plant height allows an excellent matching to in situ observations, and to modeled above-ground dry biomass

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Altimetry for the future: building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Software for multi-scale image analysis: The normalized optimized Anisotropic Wavelet Coefficient method

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