Análisis espacial de islas de calor en la ciudad de Bogotá: los efectos de la urbanización, un estudio desde la teledetección.
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Climate change represents one of the greatest challenges facing humanity today, demanding changes in social, economic and environmental behaviour. Cities are home to the majority of the world's population and are major centres of consumption, demanding excessive amounts of natural resources and services, making them possibly the agents that are generating the greatest pollution and environmental threat to the planet. The effects of climate change in the urban context are currently being investigated in the world, since the city is the place to which climate change and sustainable development have put the greatest challenge; opting for environmentally and socially viable growth or the modern city will be at risk for its own development. Within the context of climate change a local phenomenon of temperature variation known as heat islands arises, which seems to have an inherent behavior to the processes of urbanization in a city and together with a global climate change could put at risk the quality of life of the inhabitants of an urban center, it is known that since a couple of decades ago the terrestrial temperature has had an increase by human activities, now the phenomenon of heat islands can be generated from an urban microclimate with increases in surface temperature in relation to changes in land use and a not very timely spatial configuration of the city.
Bogotá, as one of the most populated cities in Latin America and with a particular history of urban development, is no stranger to this phenomenon. From the José Celestino Mutis Botanical Garden in Bogotá, the need arises to monitor this phenomenon and from the GRSS research seedbed, this research is formulated in which a multi-temporal analysis is carried out in the city of Bogotá of the change in land use over the last 30 years, using remote sensing tools such as supervised object-oriented classification or the calculation of spectral indices, it is possible to extract information from the surface and the variation of the soil over time. The supervised classification determines an increase of $19% in urbanization and a decrease of 57% in the city's green areas in the last 29 years, which presents a high correlation with the increase in soil temperature. Monitoring the temperature of the city from the Landsat data is an increase in soil temperature in areas with high density of urbanization, this was proven by performing an exploratory analysis, demonstrating on the one hand that the temperature of the city is not randomly distributed but presents temperature patterns known as islands of heat, on the other hand also statistically through the local Moran Bivariado index corroborates that urban soil affects the increase in surface temperature while green areas can act as a mitigating factor.
In order to quantify the effect of vegetation and urban soil, a SARAR spatial model was performed using surface temperature as the response variable and NDVI and NDBI spectral indices as independent variables, the results confirmed the theory and complement the processes developed in this research by determining that urban soil can increase soil temperature by 20º C and that vegetation could decrease it by 13º C. This is how this research confirms the presence of heat islands in the city of Bogota and quantifies the alterations that can generate urban cover in the variation of soil temperature.\
The surface temperature of 14 satellite images was calculated from the Google Earth Engine platform, with a time period from 1985 to 2018, correcting the gaps in the ETM+ images. This allowed to have a temporal series of very valuable temperature data, to which the values of average and fashion of temperature were calculated, these were correlated with the data that describe the phenomenon Niña and Niño. Using Pearson's coefficient for this correlation it was found that these data have a relation of -0.30 which means that the soil temperature has a low relation with the regional climate. This result demonstrates that in the city of Bogotá an urban micro climate is being conformed, influenced by urbanization processes that are heating the soil and forming patterns of heat islands.
This research was developed in two general phases; the first phase consisted in the extraction of soil information from satellite images, processes such as supervised classification, calculation of spectral indices and soil temperature were the data for statistical analysis, being this the second phase, which consisted in analyzing the spatial temperature clusters and those associated with the relationship of temperature with vegetation parameters and urban soil, in a confirmatory way a spatial model was calculated to quantify the effects of land use change. This research shows that from remote sensing data it is possible to monitor an urban climatic phenomenon such as heat islands that is currently a topic of great relevance for urban planning.