Search results for "teledetecció"
showing 10 items of 71 documents
Assessing the relationship between microwave vegetation optical depth and gross primary production
2018
At the global scale, the uptake of atmospheric carbon dioxide by terrestrial ecosystems through photosynthesis is commonly estimated through vegetation indices or biophysical properties derived from optical remote sensing data. Microwave observations of vegetated areas are sensitive to different components of the vegetation layer than observations in the optical domain and may therefore provide complementary information on the vegetation state, which may be used in the estimation of Gross Primary Production (GPP). However, the relation between GPP and Vegetation Optical Depth (VOD), a biophysical quantity derived from microwave observations, is not yet known. This study aims to explore the …
Validation of Collection 6 MODIS land surface temperature product using in situ measurements
2019
Land surface temperature (LST) is an important physical quantity at the land-atmosphere interface. Since 2016 the Collection 6 (C6) MODIS LST product is publicly available, which includes three refinements over bare soil surfaces compared to the Collection 5 (C5) MODIS LST product. To encourage the use of the C6 MODIS LST product in a wide range of applications, it is necessary to evaluate the accuracy of the C6 MODIS LST product. In this study, we validated the C6 MODIS LST product using temperature-based method over various land cover types, including grasslands, croplands, cropland/natural vegetation mosaic, open shrublands, woody savannas, and barren/sparsely vegetated. In situ measurem…
Modeling Fire Danger in Galicia and Asturias (Spain) from MODIS images
2014
Forest fires are one of the most dangerous natural hazards, especially when they are recurrent. In areas such as Galicia (Spain), forest fires are frequent and devastating. The development of fire risk models becomes a very important prevention task for these regions. Vegetation and moisture indices can be used to monitor vegetation status; however, the different indices may perform differently depending on the vegetation species. Eight different spectral indices were selected to determine the most appropriate index in Galicia. This study was extended to the adjacent region of Asturias. Six years of MODIS (Moderate Resolution Imaging Spectroradiometer) images, together with ground fire data…
Incidence Angle Diversity on L-Band Microwave Radiometry and Its Impact on Consistent Soil Moisture Retrievals
2021
Incidence angle diversity of space-borne L-band radiometers needs to be taken into account for a consistent estimation of surface soil moisture (SM). In this study, the Land Parameter Retrieval Model (LPRM) is applied to SMOS brightness temperatures to calibrate the effective scattering albedo (w) and the soil roughness (h 1 ) parameter against ERA5-land SM. The analysis is carried out for SMOS data at three different incidence angles ( 32.5±5∘, 42.5±5∘ and 52.5±5∘ ) focusing in 2016 on the three main land cover types of the Iberian Peninsula according to the Climate Change Initiative (agricultural, forest and grassland). The parameterization shows an increasing trend of w and h 1 with rise…
Determination of the vertical distribution of aerosols in Valencia, Spain, by means of lidar measurements
2017
La Tierra atraviesa un proceso de cambio climático caracterizado por un aumento de la temperatura media del planeta. Este calentamiento es debido en gran parte al aumento de la concentración de gases de efecto invernadero derivado de las actividades humanas. No obstante, existen otros componentes atmosféricos que pueden afectar de manera significativa el balance radiativo de la Tierra. Uno de estos componentes son los aerosoles, partículas que se encuentran en suspensión en la atmósfera. Según el informe del Panel Intergubernamental sobre el Cambio Climático (IPPC) del año 2013, el efecto neto de los aerosoles sobre la temperatura media del planeta es de enfriamiento. Sin embargo, estas est…
Desarrollo de un modelo de evapotranspiración global con datos de satélite y de re-análisis
2021
La cuantificación de la evapotranspiración (ET) es fundamental para el estudio de los procesos hidrológicos, caracterización climática y agronómica, así como para la aplicación en modelos de cambio climático, y la gestión de los recursos hídricos. Cabe destacar, la importancia del conocimiento de este parámetro en el control de inundaciones y sequías, en la planificación de obras de infraestructura, entre otras. Los factores que intervienen en el proceso de ET son diversos, variables en el tiempo y en el espacio, por lo tanto, cobran relevancia los datos de satélite, debido a que con ellos se puede obtener una variación espacio-temporal de los componentes del ciclo hidrológico a diferentes …
Effect of Soil Moisture on the Angular Variation of Thermal Infrared Emissivity of Inorganic Soils
2014
Emissivity is influenced by different factors. This study deals with the effect of the soil moisture (SM) content on the zenithal (θ) variation of ratio-to-nadir emissivity (εr), for a wide variety of inorganic bare soils. To retrieve εr, a goniometer assembly was used, together with two identical CIMEL Electronique CE312-2 radiometers working at six spectral bands within 7.7-14.3 μm, performing simultaneous radiance measurements at different combinations of zenith and azimuth angles. The results showed that the effect of SM upon εr(θ) is different depending on the spectral range and textural composition of the sample. Sandy soils showed a decrease of εr(θ) from nadir up to 0.132 for θ ≥ 40…
Long-Term Hydrological Regime Monitoring of a Mediterranean Agro-Ecological Wetland Using Landsat Imagery: Correlation with the Water Renewal Rate of…
2021
The Natural Park of Albufera (Valencia, Spain) is one of the Spanish Mediterranean wetlands where rice is cultivated intensively. The hydrology of the Albufera Lake, located in the center, combines natural contributions with complex human management. The aim of our study was to develop a new methodology to accurately detect the volume of flood water in complex natural environments which experience significant seasonal changes due to climate and agriculture. The study included 132 Landsat images, covering a 15-year period. The algorithm was adjusted using the NDWI index and simultaneous measurements of water levels in the rice fields. The NDVI index was applied to monitor the cultivated area…
Retrieval and assessment of CO2 uptake by mediterranean ecosystems using remote sensing and meteorological data
2014
Reseña de tesis doctoral
Analysis of Biophysical Variables in an Onion Crop (Allium cepa L.) with Nitrogen Fertilization by Sentinel-2 Observations
2022
The production of onions bulbs (Allium cepa L.) requires a high amount of nitrogen. Ac cording to the demand of sustainable agriculture, the information-development and communication technologies allow for improving the efficiency of nitrogen fertilization. In the south of the province of Buenos Aires, Argentina, between 8000 and 10,000 hectares per year−1 are cultivated in the districts of Villarino and Patagones. This work aimed to analyze the relationship of biophysical variables: leaf area index (LAI), canopy chlorophyll content (CCC), and canopy cover factor (fCOVER), with the nitrogen fertilization of an intermediate cycle onion crop and its effects on yield. A field trial study with …