Estimates indicate that by 2050, 70% of the world's population will live in urban areas, expanding the total built-up space and density of those areas. The urban heat island (UHI) phenomenon causes increased temperatures in urban areas compared to outlying regions. It is considered one of the main anthropogenic climate modifications and is directly linked to land-use patterns. The objective of this study was to analyze the presence of the UHI effect, diurnal and nocturnal, in the dry season in 21 Brazilian metropolitan areas from 2000 to 2016. Surface temperature, mean albedo, and normalized difference vegetation index (NDVI) values generated by the MODIS sensor (Moderate-resolution Imaging Spectroradiometer) were used. The results obtained showed substantial differences between diurnal and nocturnal UHI effects. Manaus, Porto Alegre, Belém, and Recife presented the highest values of diurnal UHI, whereas Curitiba, Brasília, São Paulo, and Rio de Janeiro showed higher heat island effects at night. The results are an alert to policymakers of the need to rethink land occupation regulations and also give support to actions to mitigate the phenomenon.

据估计，到2050年，全世界70％的人口将居住在城市地区，从而扩大了这些地区的总建筑面积和密度。与外围地区相比，城市热岛（UHI）现象导致市区温度升高。它被认为是主要的人为气候变化之一，与土地利用方式直接相关。这项研究的目的是分析2000年至2016年巴西21个大都市区干旱季节UHI效应（昼夜）的存在。使用了MODIS传感器（中等分辨率成像光谱仪）。所获得的结果表明昼夜和夜间UHI效应之间存在实质性差异。马瑙斯，阿雷格里港，贝伦，累西腓（Recife）的昼夜UHI值最高，而库里蒂巴（Curitiba），巴西利亚（Brasília），圣保罗（SãoPaulo）和里约热内卢（Rio de Janeiro）在夜间表现出更高的热岛效应。结果警告政策制定者需要重新考虑土地占用规定，并为减轻这种现象的行动提供支持。