Search results for "Ocean engineering"
showing 10 items of 404 documents
Traitement de données RGB et Lidar à extrêmement haute résolution: retombées de la compétition de fusion de données 2015 de l'IEEE GRSS - Partie A / …
2016
International audience; In this paper, we discuss the scientific outcomes of the 2015 data fusion contest organized by the Image Analysis and Data Fusion Technical Committee (IADF TC) of the IEEE Geoscience and Remote Sensing Society (IEEE GRSS). As for previous years, the IADF TC organized a data fusion contest aiming at fostering new ideas and solutions for multisource studies. The 2015 edition of the contest proposed a multiresolution and multisensorial challenge involving extremely high-resolution RGB images and a three-dimensional (3-D) LiDAR point cloud. The competition was framed in two parallel tracks, considering 2-D and 3-D products, respectively. In this paper, we discuss the sci…
Sentinel-3/FLEX Biophysical Product Confidence Using Sentinel-2 Land-Cover Spatial Distributions
2021
The estimation of biophysical variables from remote sensing data raises important challenges in terms of the acquisition technology and its limitations. In this way, some vegetation parameters, such as chlorophyll fluorescence, require sensors with a high spectral resolution that constrains the spatial resolution while significantly increasing the subpixel land-cover heterogeneity. Precisely, this spatial variability often makes that rather different canopy structures are aggregated together, which eventually generates important deviations in the corresponding parameter quantification. In the context of the Copernicus program (and other related Earth Explorer missions), this article propose…
The Added-Value of Remotely-Sensed Soil Moisture Data for Agricultural Drought Detection in Argentina
2021
In countries where the economy relies mostly on agricultural-livestock activities, such as Argentina, droughts cause significant economic losses. Currently, the most-used drought indices by the Argentinian National Meteorological and Hydrological Services are based on field precipitation data, such as the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI). In this article, we explored the performance of the satellite-based soil moisture agricultural drought index (SMADI) for agricultural drought detection in Argentina during 2010-2015, and compared it with the one from the standardized soil moisture anomalies (SSMA), SPI and SPEI (at on…
Sorption-Caused Attenuation and Delay of Water Vapor Signals in Eddy-Covariance Sampling Tubes and Filters
2014
AbstractAdsorption and desorption (together called sorption) processes in sampling tubes and filters of eddy-covariance stations cause attenuation and delay of water vapor signals, leading to an underestimation of water vapor fluxes by tens of percent. The aim of this work was (i) to quantify the effects on sorption in filters and tubes of humidity, flow rate, and dirtiness and (ii) to test a recently introduced sorption model that facilitates correction of fluxes. Laboratory measurements on the transport of water vapor pulses through tubes and filters were carried out, and eddy-covariance field measurements were also used.In the laboratory measurements, the effects of sorption processes we…
Comparison of Different Techniques for the Measurement of Precipitation in Tropical Montane Rain Forest Regions
2007
Abstract Characteristics of different precipitation measurements in a tropical mountain valley in southern Ecuador are compared in this study to determine potential errors. The instruments are used for different ecological purposes like erosion studies, through fall measurements, investigation of atmospheric chemistry, and modeling of area rainfall distribution. Five recording devices (two precipitation radars, an electro-optical present weather sensor, and two tipping buckets) and three totaling gauges were operated in parallel at a designated site. Data were taken between 1998 and 2003 with different temporal resolution and different operational periods. The general agreement between the …
Observation of Interference Patterns in Reconstructed Digital Holograms of Atmospheric Ice Crystals
2009
Abstract The observation of interference patterns in reconstructed digital holograms of natural ice crystals is reported. It is suggested that an investigation of the interference fringes’ origin will yield a new application of holography in atmospheric sciences by revealing information on otherwise hardly accessible properties of the crystals.
Examining the Effects of Dust Aerosols on Satellite Sea Surface Temperatures in the Mediterranean Sea Using the Medspiration Matchup Database
2011
Abstract Dust aerosol plumes from the Sahara cover the Mediterranean Sea regularly during the summer months (June–August) and occasionally during other seasons. Dust can absorb infrared longwave radiation, thus causing a drop in sea surface temperature (SST) retrievals from satellite. To quantify the magnitude of this absorption and to understand the sources of the biases that might be introduced when trying to validate SST algorithms with in situ bulk temperatures, the effects of the dust absorption are studied using the Medspiration Match-up Database. This database provides in situ and satellite SSTs derived from the Advanced Very High Resolution Radiometer (AVHRR) and the Advanced Along-…
Autonomous Measurements of Sea Surface Temperature Using In Situ Thermal Infrared Data
2004
Abstract In situ and autonomous measurements of sea surface temperature (SST) have been performed with a thermal infrared radiometer mounted on a fixed oil rig. The accuracy limit was established at ±0.3 K for these SST measurements in order to meet the requirements of the Tropical Ocean Global Atmosphere (TOGA) program for global climate research and the Soil Moisture and Ocean Salinity (SMOS) mission for salinity retrieval. With this aim, the optimal observation angle and spectral channel for SST measurements have been identified. Then, a methodology has been developed for the radiometer calibration and the emissivity correction, including the reflection of the downwelling sky radiance, w…
Multitemporal Mosaicing for Sentinel-3/FLEX Derived Level-2 Product Composites
2020
The increasing availability of remote sensing data raises important challenges in terms of operational data provision and spatial coverage for conducting global studies and analyses. In this regard, existing multitemporal mosaicing techniques are generally limited to producing spectral image composites without considering the particular features of higher-level biophysical and other derived products, such as those provided by the Sentinel-3 (S3) and Fluorescence Explorer (FLEX) tandem missions. To relieve these limitations, this article proposes a novel multitemporal mosaicing algorithm specially designed for operational S3-derived products and also studies its applicability within the FLEX…
Intercomparison of spectroradiometers for global and direct solar irradiance in the visible range.
2003
This paper presents the results of the analysis of the spectral, global, and direct solar irradiance measurements in the visible range (400–700 nm) that were made in the framework of the first Iberian UV–visible (VIS) instruments intercomparison. The instruments used in this spectral range were four spectroradiometers: three Licor 1800s equipped with different receiver optics and one Optronic 754. For the direct solar irradiance measurements the spectroradiometers were equipped with collimators with different fields of view. Parallel studies have been carried out with the data given by the spectroradiometers with their original calibration file and with the same data that is corrected, foll…