Comparative study of spatiotemporal variation in the urban heat island core in coastal and inland basin cities

Using satellite data, it is possible to precisely observe the micro-scale structure of the surface urban heat island (SUHI) and its change over time. A new approach for clustering complex heat islands patterns was proposed using a combination of the operational method and the Jenks natural breaks method. Through this, we defined the spatial range of heat island and the core with the higher temperature in it and also applied for Busan, a coastal city, and Daegu, an inland basin city in the Korean peninsula. SUHI existed in one of the following three types: single-core heat island with one core, multi-core heat island with two or more cores, and acentric heat island (AHI) without a core. Busan and Daegu had different spatiotemporal SUHI variations. Variation of the SUHI pattern in Busan was markedly different according to seasonal changes, and in Daegu, the difference between day and night was more pronounced than seasonal changes. In Busan, SUHIs bordered by mountains in the inner-city area tended to move closer to the sea in winter. Several SUHIs formed in the shape of basin during the daytime were merged into one large heat island in the downtown of the city at nighttime in Daegu. These spatiotemporal changes of SUHI were also consistent with the variation of near-surface temperature (NST). In addition, the study case had a high correlation with the distribution and intensity of SUHI averaged over 5 years. Although there are several cores in SUHIs did not appear in the 5-year average data, which was associated with its inter-annual variation, the distribution of SUHIs was agreed well with the 5-year average NST pattern.