Evaluation and Analysis of the Effectiveness of the Main Mitigation Measures against Surface Urban Heat Islands in Different Local Climate Zones through Remote Sensing

The significant transformation of land use as a consequence of current population growth, together with global warming (atmospheric emissions and extreme weather events), is generating increases in ambient temperatures. This circumstance is affecting people’s quality of life, especially those considered more vulnerable or with fewer economic resources. Currently, 30% of the world’s population suffers climatic conditions of extreme heat, and forecasts indicate that in the next 20 years, this number will reach 74%. The present study analyzes the effectiveness of the main mitigation strategies for the surface urban heat island (SUHI) effect between the years 2002 and 2022 in the different local climate zones of the city of Granada (Spain). Using Landsat 5 and 8 images, the evolution experienced by the land surface temperature and the surface urban heat island was determined and connected to the following variables: normalized difference vegetation index, vegetal proportion, normalized difference building index, and albedo. Our results indicate that compact and industrial areas have higher temperatures and lower vegetation and albedo in contrast to open areas, which have lower temperatures and higher vegetation and albedo. The mitigation measures analyzed presented similar efficiencies, but a greater minimization of the SUHI was reported when vegetation was increased in open areas as opposed to in closed areas, where the increase in albedo was more effective. Our study will allow the implementation of more efficient measures based on the types of LCZs in cities

Analysis of Urban Heat Island and Heat Waves Using Sentinel‑3 Images: a Study of Andalusian Cities in Spain

Funding for open access charge: Universidad de Granada/CBUA.At present, understanding the synergies between the Surface Urban Heat Island (SUHI) phenomenon and extreme climatic events entailing high mortality, i.e., heat waves, is a great challenge that must be faced to improve the quality of life in urban zones. The implementation of new mitigation and resilience measures in cities would serve to lessen the effects of heat waves and the economic cost they entail. In this research, the Land Surface Temperature (LST) and the SUHI were determined through Sentinel-3A and 3B images of the eight capitals of Andalusia (southern Spain) during the months of July and August of years 2019 and 2020. The objective was to determine possible synergies or interaction between the LST and SUHI, as well as between SUHI and heat waves, in a region classified as highly vulnerable to the effects of climate change. For each Andalusian city, the atmospheric variables of ambient temperature, solar radiation, wind speed and direction were obtained from stations of the Spanish State Meteorological Agency (AEMET); the data were quantified and classified both in periods of normal environmental conditions and during heat waves. By means of Data Panel statistical analysis, the multivariate relationships were derived, determining which ones statistically influence the SUHI during heat wave periods. The results indicate that the LST and the mean SUHI obtained are statistically interacted and intensify under heat wave conditions. The greatest increases in daytime temperatures were seen for Sentinel-3A in cities by the coast (LST = 3.90 °C, SUHI = 1.44 °C) and for Sentinel-3B in cities located inland (LST = 2.85 °C, SUHI = 0.52 °C). The existence of statistically significant positive relationships above 99% (p < 0.000) between the SUHI and solar radiation, and between the SUHI and the direction of the wind, intensified in periods of heat wave, could be verified. An increase in the urban area affected by the SUHI under heat wave conditions is reported.Universidad de Granada/CBU

Spatio-temporal analysis of the urban green infrastructure of the city of Granada (Spain) as a heat mitigation measure using high-resolution images Sentinel 3

At present, and motivated by a substantial growth of the population, a considerable expansion of urban areas is taking place through the modification of land uses. These changes, together with global warming and extreme weather events, produce increases in the temperature of the earth’s surface and a deterioration of the environment that affects people’s quality of life. The green areas of cities are upheld as one of the best for adapting to such phenomena, since they help lower outdoor temperatures. In this research, using high-resolution Sentinel 3 satellite images and the TsHARP algorithm, the Land Surface Temperature (LST) and the Park Cool Island (PCI) were obtained at a resolution of 10 m over green areas in the city of Granada. The objective was to analyze the relationship between surface, PCI effect and cooling distance. In turn, for each of the eight green areas studied, the following variables were taken into account and included in a statistical analysis known as data panel: normalized difference vegetation index, vegetal proportion, sky view factor, landscape shape index, model digital elevation, wind and solar radiation. Our results report diurnal LST decreases of 1 K and night LST of 0.6 K in green areas as compared to urban areas. There is moreover a correlation between the size of the green areas, the decrease in temperature they generate, and distance of the minimizer effect.Universidad de Granada, CBU

Modeling the Surface Urban Heat Island (SUHI) to study of its relationship with variations in the thermal field and with the indices of land use in the metropolitan area of Granada (Spain)

Understanding just how the increase in the Earth’s Surface Temperature (LST) is related to alterations of the urban climate —Surface Urban Heat Island (SUHI) or Urban Hotspots (UHS)— and with the deterioration of cities´environmental quality has become a great challenge. Societies worldwide seek actions that might break these trends and improve the quality of life of local inhabitants. In this research, with the help of Landsat 5, 7 and 8 satellite images, the evolution of land use/cover (LULC), LST and SUHI were studied over a long period, from 1985 to 2020, in the metropolitan area of the city of Granada (Spain). The aim was to evaluate how these variables, together with the Urban Index (UI), Normalized Difference Built-up Index (NDBI), Normalized Difference Vegetation Index (NDVI) and Proportion of Vegetation (PV), have influenced the variability of the UHS and the level of thermal comfort according to the Urban Thermal Field Variance Index (UTFVI). Reported as results, corroborated by statistical analysis, are mean increases in LST (2.2◦C), SUHI (0.6◦C), UHS (20.4%), and class 6 of the UTFV (26.2%). NDBI and UI are associated with high variations in LULCs. These have suffered increases in built-up and bare soil coverage, and decreases in water bodies, vegetation and farmland coverage

Spatiotemporal analysis of the surface urban heat island (SUHI), air pollution and disease pattern: an applied study on the city of Granada (Spain)

Abstract There is worldwide concern about how climate change —which involves rising temperatures— may increase the risk of contracting and developing diseases, reducing the quality of life. This study provides new research that takes into account parameters such as land surface temperature (LST), surface urban heat island (SUHI), urban hotspot (UHS), air pollution ( SO2, NO2, CO, O3 and aerosols), the normalized difference vegetation index (NDVI), the normalized difference building index (NDBI) and the proportion of vegetation (PV) that allows evaluating environmental quality and establishes mitigation measures in future urban developments that could improve the quality of life of a given population. With the help of Sentinel 3 and 5P satellite images, we studied these variables in the context of Granada (Spain) during the year 2021 to assess how they may affect the risk of developing diseases (stomach, colorectal, lung, prostate and bladder cancer, dementia, cerebrovascular disease, liver disease and suicide). The results, corroborated by the statistical analysis using the Data Panel technique, indicate that the variables LST, SUHI and daytime UHS, NO2, SO2 and NDBI have important positive correlations above 99% (p value: 0.000) with an excess risk of developing these diseases. Hence, the importance of this study for the formulation of healthy policies in cities and future research that minimizes the excess risk of diseasesUniversidad de Granada/ CBU

Spatial and Multi-Temporal Analysis of Land Surface Temperature through Landsat 8 Images: Comparison of Algorithms in a Highly Polluted City (Granada)

Over the past decade, satellite imaging has become a habitual way to determine the land surface temperature (LST). One means entails the use of Landsat 8 images, for which mono window (MW), single channel (SC) and split window (SW) algorithms are needed. Knowing the precision and seasonal variability of the LST can improve urban climate alteration studies, which ultimately help make sustainable decisions in terms of the greater resilience of cities. In this study we determine the LST of a mid-sized city, Granada (Spain), applying six Landsat 8 algorithms that are validated using ambient temperatures. In addition to having a unique geographical location, this city has high pollution and high daily temperature variations, so that it is a very appropriate site for study. Altogether, 11 images with very low cloudiness were taken into account, distributed between November 2019 and October 2020. After data validation by means of R2 statistical analysis, the root mean square error (RMSE), mean bias error (MBE) and standard deviation (SD) were determined to obtain the coefficients of correlation. Panel data analysis is presented as a novel element with respect to the methods usually used. Results reveal that the SC algorithms prove more effective and reliable in determining the LST of the city studied here.ERDF (European Rural Development Fund)Ministry of Science and Innovation (State Research Agency) EQC2018-004702-

Impacts of the COVID-19 confinement on air quality, the Land Surface Temperature and the urban heat island in eight cities of Andalusia (Spain)

The COVID-19 outbreak and ensuing global lockdown situation have generated a very negative impact on the world economy, but they have also lent us a unique opportunity to research and better grasp the impacts of human activity on environmental pollution and urban climates. Such studies will be of vital importance for decision-making on measures needed to mitigate the effects of climate change in urban areas, in order to turn them into resilient environments. This study looks at eight cities in the region of Andalusia (southern Spain) to comprehensively assess their environmental quality with parameters (Pm-10, So(2), No-2, Co and O-3) obtained from meteorological stations. The aim was to determine how these parameters affect the Land Surface Temperature (LST) and the Surface Urban Heat Island (SUHI), on the basis of Sentinel 3 satellite thermal images. Knowing to what extent improved air quality can reduce the LST and SUHI of cities will be essential in the context of future environmental studies on which to base sustainable decisions. The geographic situation of cities in the Mediterranean Sea basin, highly vulnerable to climate change, and the high pollution rates and high daily temperature variations of these urban areas make them particularly attractive for analyses of this sort. During the confinement period, average reductions of some environmental pollutants were achieved: So(2) (-33.5%), Pm-10 (-38.3%), No-2 (-44.0%) and Co (-26.5%). However, the environmental variable O-3 underwent an average growth of 5.9%. The LST showed an average reduction of -4.6 degrees C (-19.3%), while the SUHI decreased by 1.02 degrees C (-59.8%). These values exhibit high spatio-temporal variations be-tween day and night, and between inland and coastal cities

Determination of land surface temperature using Landsat 8 images: Comparative study of algorithms on the city of Granada

[EN] The use of satellite images has become, in recent decades, one of the most common ways to determine the Land Surface Temperature (LST). One of them is through the use of Landsat 8 images that requires the use of single-channel (MC) and two-channel (BC) algorithms. In this study, the LST of a medium-sized city, Granada (Spain) has been determined over a year by using five Landsat 8 algorithms that are subsequently compared with ambient temperatures. Few studies compare the data source with the seasonal variations of the same metropolis, which together with its geographical location, high pollution and the significant thermal variations it experiences make it a suitable place for the development of this research. As a result of the statistical analysis process, the regression coefficients R2, mean square error (RMSE), mean error bias (MBE) and standard deviation (SD) were obtained. The average results obtained reveal that the LST derived from the BC algorithms (1.0 °C) are the closest to the ambient temperatures in contrast to the MC (-5.6 °C), although important variations have been verified between the different zones of the city according to its coverage and seasonal periods. Therefore, it is concluded that the BC algorithms are the most suitable for recovering the LST of the city under study.[ES] El empleo de imágenes satelitales se ha convertido, en las últimas décadas, en una de las formas más habituales para determinar la Temperatura de la Superficie Terrestre (TST). Una de ellas es mediante el empleo de imágenes Landsat 8 que requiere del uso de algoritmos del tipo monocanal (MC) y bicanal (BC). En este estudio se ha determinado la TST de una ciudad de tamaño medio, Granada (España) a lo largo de un año mediante el empleo de cinco algoritmos Landsat 8 que posteriormente se comparan con las temperaturas ambientales. Pocos estudios comparan la fuente de datos con las variaciones estacio-temporales de una misma metrópolis lo que unido a su situación geográfica, alta contaminación y las importantes variaciones térmicas que experimenta la convierten en un lugar adecuado para el desarrollo de esta investigación. Como resultado del proceso de análisis estadístico se obtuvieron los coeficientes de regresión R2, el error medio cuadrático (RMSE), sesgo medio del error (MBE) y la desviación estándar (DE). Los resultados medios obtenidos revelan que las TST derivada de los algoritmos BC (1,0 °C) son las más próximas a las temperaturas ambientales en contraposición con los MC (-5,6 °C) aunque se han verificado importantes variaciones entre las distintas zonas de la urbe según su cobertura y los periodos estacionales. Por todo ello, se concluye que los algoritmos BC son los más adecuados para recuperar la TST de la urbe objeto de estudio.Hidalgo-García, D. (2021). 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Impacts of Covid-19 on air quality, Land Surface Temperature and Urban Heat Island on Local Climatic Zones in the city of Granada (Spain)

El brote de Covid-19 y la situación de confinamiento ha generado un importante impacto negativo en la economía mundial, pero ha brindado una oportunidad única para comprender el impacto de la actividad humana en la contaminación ambiental y como esta afecta al clima urbano. Este estudio toma la ciudad de Granada (España) al objeto de realizar una evaluación de los parámetros ambientales (So2, No2, Co y O3) obtenidos mediante imágenes Séntinel 5P y como estos repercuten en la Temperatura de la Superficie Terrestre (TST) y la Isla de Calor Urbana de Superficie (ICUS) obtenidas mediante imágenes Séntinel 3. Conocer la repercusión ambiental en la TST e ICUS de las distintas Zonas Climáticas Locales (ZCL) de la urbe repercutirá en la realización de futuros estudios de resiliencia urbana. Como resultado, y durante el periodo de confinamiento, se han obtenidos las siguientes variaciones con respecto a los contaminantes ambientales: So2 (-24,0 %), No2 (-6,7 %), Co (-13,2 %) y O3 (+4,0%). La TST ha experimentado una reducción media de -8.7 ºC (-38,0 %) mientras que la ICUS se ha reducido en -1.6 ºC (-66,0 %).The COVID-19 outbreak and the lockdown situation have generated a significant negative impact on the world economy but have provided a unique opportunity to understand the impact of human activity on environmental pollution and how it affects the urban climate. This study takes the city of Granada (Spain) in order to carry out an evaluation of the environmental parameters (So2, No2, Co and O3) obtained through Sentinel 5P images and how they affect the Terrestrial Surface Temperature (TST) and the Surface Urban Heat Island (ICUS) obtained through Sentinel 3 images. Knowing the environmental impact on the TST and ICUS of the different Local Climate Zones (ZCL) of the city will have an impact on future urban resilience studies. As a result, and during the confinement period, the following variations have been obtained with respect to environmental pollutants: So2 (-24.0%), No2 (-6.7%), Co (-13.2%) and O3 (+4.0%). The TST has experienced an average reduction of -8.7 ºC (-38.0%) while the ICUS has decreased by -1.6 ºC (-66.0%).L'épidémie de COVID-19 et la situation de confinement ont généré un impact négatif important sur l'économie mondiale, mais ont fourni une occasion unique de comprendre l'impact de l'activité humaine sur la pollution de l'environnement et comment elle affecte le climat urbain. Cette étude prend la ville de Grenade (Espagne) afin de réaliser une évaluation des paramètres environnementaux (So2, No2, Co et O3) obtenus à travers les images Sentinel 5P et comment ils affectent la température de surface terrestre (TST) et la surface urbaine. Îlot de Chaleur (ICUS) obtenu grâce aux images Sentinelle 3. Connaître l'impact environnemental sur le TST et l'ICUS des différentes Zones Climatiques Locales (ZCL) de la ville aura un impact sur les futures études de résilience urbaine. En conséquence, et pendant la période de confinement, les variations suivantes ont été obtenues en ce qui concerne les polluants environnementaux : So2 (-24,0 %), No2 (-6,7 %), Co (-13,2 %) et O3 (+4,0 %). Le TST a connu une réduction moyenne de -8,7 ºC (-38,0 %) tandis que l'ICUS a diminué de -1,6 ºC (-66,0 %)

Spatial-Temporal Analysis of the Urban Heat Island Using Satellite Images: Capitals of Andalusia

La búsqueda de nuevas técnicas que permitan determinar de forma económica y precisa el fenómeno de alteración de clima urbano denominado Isla de Calor Urbana (ICU) se ha convertido en uno de los grandes retos de la sociedad. Su conocimiento sobre las urbes permitiría la implantación de medidas de mitigación y resiliencia que tiendan a minimizar sus efectos y el coste económico que conlleva. En esta investigación, se ha determinado la Temperatura de la Superficie Terrestre (TST) y la ICU mediante imágenes satelitales Séntinel 3 de las ocho capitales de Andalucía (España) durante el año 2020. Estas se ubican en una zona calificada como de alta vulnerabilidad a los efectos del cambio climático lo que unido al empleo de zonas climáticas locales (ZCL) permite que los resultados puedan ser extrapolados a otras ciudades con iguales tipologías de zonas climáticas. Los resultados obtenidos indican que durante la mañana se produce en las ciudades estudiadas una isla de enfriamiento urbano de temperatura media -0,76 ºC y durante la noche una ICU de temperatura media 1,29 ºC. Ambas presentan mayores intensidades en las ZCL compactas de media y baja densidad en contraposición con las ZCL abiertas e industriales. La variabilidad estacional de la ICU diurna se intensifica durante el verano y el invierno y la nocturna durante el invierno y el otoño. Se comprueba la existencia de relaciones diurnas negativas significativas al 99% (p<0,01) entre la ICU y la contaminación ambiental y de relaciones nocturnas, en iguales condiciones, entre la ICU y la TST, fracción vegetal (Pv) y la contaminación.The search for new techniques that make it possible to determine economically and precisely the phenomenon of urban climate alteration called Urban Heat Island (ICU) has become one of the great challenges of society. Their knowledge of cities would allow the implementation of mitigation and resilience measures that tend to minimize their effects and the economic cost that they entail. In this research, the Terrestrial Surface Temperature (TST) and the ICU have been determined through Sentinel 3 satellite images of the eight capitals of Andalusia (Spain) during the year 2020. These are located in an area classified as highly vulnerable to the effects of climate change, which, together with the use of local climate zones (ZCL), allows the results to be extrapolated to other cities with the same types of climate zones. The results obtained indicate that during the morning there is an urban cooling island with an average temperature of -0.76 ºC and during the night an ICU with an average temperature of 1.29 ºC. Both present higher intensities in compact ZCL of medium and low density in contrast to open and industrial ZCL. The seasonal variability of the diurnal ICU is intensified during the summer and winter and the nocturnal one during the winter and autumn. The existence of negative diurnal relationships significant at 99% (p <0.01) between the ICU and environmental contamination and of nocturnal relationships in the same conditions between the ICU and the TST, plant fraction (Pv) and contamination are verified