Urban boundary delineation is essential for understanding spatial structure, monitoring urbanization, and guiding sustainable land management. Nighttime light (NTL) data effectively capture urban dynamics across multiple spatial scales. This study integrates NTL data with spectral indices to delineate the urban boundaries of the Barcelona Metropolitan Region (BMR) from 2006 to 2018. Through multivariate regression analysis, the normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) are identified as key indicators of urban spatial heterogeneity. These indices are combined with brightness thresholds derived from three NTL datasets, DMSP-OLS, Black Marble, and VIIRS, to delineate urban areas more accurately. Results indicate that VIIRS achieved the highest precision in identifying construction land and urbanized areas, with an overall accuracy exceeding 90% and consistency with population density and GDP distribution. A strong spatial correlation between urban distribution and the NDVI–NDBI relationship is confirmed in the BMR. The coupling of multisource remote sensing data improves the accuracy, stability, and reliability of urban boundary delineation, overcoming single-source limitations. This integrated method supports urban planning and sustainable land management through consistent, objective urban mapping and offers a practical reference for applying remote sensing technologies to monitor urbanization dynamics across broader spatial and temporal contexts.

According to NASA's temperature record, Earth in 2021 was about 1.1 degrees Celsius warmer than the late 19th century average, the start of the industrial revolution. The rate of Global Warming (GW), however, differs across different regions of the planet. The Mediterranean is one of the "hotspots" of climate change, with more prominent temperature increases throughout the 20th and 21st centuries (Giorgi 2006). Since the mid-20th century, the average temperature over the Mediterranean has been increasing above the global average. The recent temperature record reveals an annual mean temperature for the entire basin that is approximately 0.4°C above the global mean (Lange 2021). This increase is even higher on the Spanish coast, which has experienced increases of more than 2°C (Arellano 2022).The aim of this paper is to analyze the warming process in the main Spanish urban areas since unified records were kept in the early 1970s. For this purpose, the evolution experienced by temperatures between 1971 and 2022 in 21 meteorological stations representative of all the Spanish Autonomous Communities is analyzed. Barcelona, Madrid, Valencia, Zaragoza, Seville, Malaga, Bilbao, Valladolid, Ciudad Real, Badajoz, Asturias, Corunya, Ourense, Murcia, Logroño, Palma de Mallorca, Las Palmas de Gran Canaria and Santa Cruz de Tenerife, are studied.The results show that, if on a global scale temperatures have risen 0.94°C since 1971, the increase in the main cities of peninsular Spain has been 2.17°C. And 2022 will be the warmest year on record. The research carried out differentiates the evolution experienced by maximum and minimum temperatures, showing that the continental influence is mainly manifested in the increase of maximum temperatures, while in the area of Mediterranean influence, the increase of minimum temperatures is more pronounced. On the other hand, the Cantabrian and Atlantic coasts, as well as, above all, the Canary Islands, show less pronounced increases, below 2°C.The study also presents the heat and cold waves (Serra 2022) experienced by the cities studied. Diurnal heat waves (DHW) have increased from 0.6 per year per weather station in the decade 1971-1980, to 1.71 in 1981-1990, 1.81 in 1991-2000, 2.72 in 2001-2010, and 3.84 in 2011-2020. 2022, with 7.11 DHW per station, is the year with the highest number of diurnal heat waves in the entire series. Regarding nocturnal heat waves (NHW) they have increased from 0.47 per station per year in the decade 1971-1980, to 1.53 (1981-1990), 1.57 (1991-2000), 3.55 (2001-2010), and 4.63 (2011-2020). Again 2022 is the year with the highest number of NHW, with 7.61 per weather station.2022 appears, therefore, as the warmest year since records have been kept, and the one in which a greater number of NHW has been experienced.

With the rapid development of urbanization, the ecological environment is being degraded. Taking the Barcelona Metropolitan Region as an example, this paper developed an ecological environment quality-assessment system suitable for different times and regions, based on remote sensing, to evaluate the quality of the ecological environment from 2006 to 2018. We also built various ordinary least squares models to analyze multiple variables affecting the ecological environment. Finally, the characteristic triangular spatial structure was used to explain the interaction between the two key variables. The results showed that the ecological quality was unevenly distributed. The largest green space contributed the most benefits but was decreasing and becoming fragmented. NDVI (normalized difference vegetation index) was the most significant natural variable related to the distribution of green space. Precipitation was the most closely related climate factor to NDVI. There was a complex two-way interaction mechanism between the two, and its boundary value was getting higher and higher. In conclusion, the environmental quality of the BMR needs improvement. The characteristic triangle can effectively explain the interaction mechanism between precipitation and NDVI. This study deeply analyzes how various factors affect environmental quality from both the global and internal perspectives and provides a scientific basis for urban ecological management and sustainable development.

China is experiencing the largest and fastest urbanization process in the world (Kneebone E., 2013). At the same time, its current rapid urbanization process is almost simultaneously accompanied by urban sprawl. Since the 1990s, the sprawl process of Chinese cities has begun to reach a climax (Shan Baoguo, 2018). As the largest developing country in the world, China is also one of the countries most vulnerable to the coercion of climate change. This research takes the four municipalities that are China's urban development orientation as typical representatives, and uses multiple indicators to measure urban sprawl and climate change in them. Finally, models are established to explore the impact of urban sprawl on climate warming. The results showed that all four cities experienced sprawl, but to varying degrees. Shanghai is very compact. Also, the climate warming is definitely, yet urban sprawl doesn't always contribute to its deterioration. The proportion of arable land had the least impact on global warming, but it was the only factor that could improve temperatures, albeit conditionally. Fragmented built-up land heating the climate is most critical.

As a precious natural resource, forests are being destroyed. In previous studies, there is a lack of an interactive assessment of their distribution that comprehensively considers multiple external disturbances. This paper takes the Barcelona Metropolitan Region as an example. Based on remote sensing, it analyzes the development process of the forest from 2006 to 2018 through multiple landscape indicators, and OLS models were established to analyze variables that have direct and indirect effects on forest distribution. In addition, the ecological structure of the forest was analyzed based on NDVI. It was found that the forest area is the largest area but has been decreasing, becoming more complex in distribution structure. Much of the forest was converted to agricultural land and grassland. The green quality of the forests has been increasing, and the broad-leaved forest, the second largest area, contributes the most. NDVI is the most important positively correlated variable, and daytime surface temperature is an important inverse factor related to NDVI. In addition, NDBI is also a negative condition that inhibits forest development. In conclusion: The BMR forest area is decreasing and becoming more fragmented. NDVI and daytime LST are the two most significant factors. Climate warming may lead to worse forest development.

With the rapid development of urbanization, the ecological environment is being destroyed. Taking Barcelona Metropolitan Region as an example, this paper established an ecological environment quality assessment system suitable for different time and region based on remote sensing to evaluate it from 2006 to 2018. And built various OLS models to analyze multiple variables affecting the ecological environment. Finally, the characteristic triangular space structure was used to explain the interaction between the two key variables. The results showed that the ecological quality was unevenly distributed. The largest green space contributed the most ecological benefits, but its area was decreasing and its shape was more fragmented. NDVI was the most significant natural variable related to the distribution of green space. Precipitation was the most closely related climate factor to NDVI. And there was a complex two-way interaction mechanism between the two, and its boundary value was getting higher and higher. In conclusion: The environmental quality of BMR needs to be improved. There is a two-way relationship between the two key factors. The characteristic triangle can successfully explain the interaction mechanism between precipitation and NDVI.