Cuantificación de la variación espacio-temporal de la cobertura nival en la macrozona centro sur de Chile
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Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
En la plataforma web Google Earth Engine (GEE) se procesaron imágenes recopiladas por los sensores portados por los satelitales Landsat (5, 7, 8 y 9) y Sentinel-2 a una resolución espacial de 30 metros (homogenizado por diferencias de resolución) y una frecuencia de revisita variable de entre una a dos semanas y media, para calcular el índice espectral NDSI (Normalized Difference Snow Index) e información derivada de este, y así, caracterizar la variabilidad espaciotemporal de la cobertura nival en cuencas de cabecera de las regiones del Ñuble y Biobío desde el 01/01/2000 hasta el 31/12/2024 en dos distintas escalas espaciales. La primera escala espacial es a nivel subsubcuenca, donde solo se logró caracterizar la evolución del manto nival entre los años 2019 y 2024, debido a que previo al año 2019 no existe suficiente información (alcance de metodología), por tanto, no se logró realizar un análisis de tendencia temporal. La segunda escala espacial son segmentaciones terrenales que comparten diferentes rangos de elevación y orientación denominadas Unidades de Respuesta Nival (URN), en estas se cuantifico la diferencia de días en que se presentan los fenómenos de inicio de acumulación, inicio y fin del derretimiento de nieve entre las URN que comparten la misma discretización de altura, pero distinta orientación (norte y sur). Aquí no se encontró una diferencia significativa en cuando se presenta la fecha de inicio de acumulación de nieve entre las URN con orientaciones contrapuestas, pero si en las fechas de inicio y fin de derretimiento nival.
Este estudio contribuye a mejorar el entendimiento sobre la variabilidad espacio temporal de la cobertura de nieve integrando nuevas técnicas de análisis basadas en la computación en nube.
On the Google Earth Engine (GEE) web platform, images collected by the sensors carried by the Landsat (5, 7, 8 and 9) and Sentinel-2 satellites were processed at a spatial resolution of 30 meters (homogenized by resolution differences) and a variable revisit frequency of between one and two and a half weeks, to calculate the NDSI (Normalized Difference Snow Index) spectral index and information derived from it, and thus characterize the spatiotemporal variability of the coverage. Nival in headwaters in the Ñuble and Biobío regions from 01/01/2000 to 31/12/2024 on two different spatial scales. The first spatial scale is at the sub-basin level, where it was only possible to characterize the evolution of the nival mantle between 2019 and 2024, because prior to 2019, there is not enough information (scope of methodology), therefore, a time trend analysis was not possible. The second spatial scale are earthly segmentations that share different elevation and orientation ranges called Nival Response Units (NUR), in which the difference of days in which the phenomena of beginning of accumulation, beginning and end of snow melt between the NRU that share the same discretization of height, but different orientation (north and south) are quantified. A significant difference was not found here when the date of start of snow accumulation between the URN with conflicting orientations is presented, but on the dates of start and end of natural melting. This study helps improve understanding of the spatio-time variability of snow cover by integrating new analytics techniques based on cloud computing.
On the Google Earth Engine (GEE) web platform, images collected by the sensors carried by the Landsat (5, 7, 8 and 9) and Sentinel-2 satellites were processed at a spatial resolution of 30 meters (homogenized by resolution differences) and a variable revisit frequency of between one and two and a half weeks, to calculate the NDSI (Normalized Difference Snow Index) spectral index and information derived from it, and thus characterize the spatiotemporal variability of the coverage. Nival in headwaters in the Ñuble and Biobío regions from 01/01/2000 to 31/12/2024 on two different spatial scales. The first spatial scale is at the sub-basin level, where it was only possible to characterize the evolution of the nival mantle between 2019 and 2024, because prior to 2019, there is not enough information (scope of methodology), therefore, a time trend analysis was not possible. The second spatial scale are earthly segmentations that share different elevation and orientation ranges called Nival Response Units (NUR), in which the difference of days in which the phenomena of beginning of accumulation, beginning and end of snow melt between the NRU that share the same discretization of height, but different orientation (north and south) are quantified. A significant difference was not found here when the date of start of snow accumulation between the URN with conflicting orientations is presented, but on the dates of start and end of natural melting. This study helps improve understanding of the spatio-time variability of snow cover by integrating new analytics techniques based on cloud computing.
Description
Tesis presentada para optar al título de Ingeniero Civil Agrícola
Keywords
Nieve -- Chile-- Mediciones, Precipitación atmosférica -- Chile -- Zona Sur