Monitoring diurnal dynamics of surface urban heat island for urban agglomerations using ECOSTRESS land surface temperature observations

Extreme heat exposure at the regional scale is warranted for special attention due to the changing global climate yet notable regional disparities in the effect of warming. NASA's latest ECOSTRESS mission generates LST images with a swath width of about 400 km and a 70-m resolution for varying times of day/night and provides a new opportunity for regional SUHI studies. Here we demonstrated the capability of ECOSTRESS data for studying spatiotemporal variations of LST and SUHI over an urban agglomeration that centers on a megacity, Xi'an, in Northwest China and includes cities of various sizes and geographical and economic settings. Our results revealed the unequal exposures of different-sized cities to SUHI effects in the diurnal cycle, with a maximum value of about 10 °C. Meanwhile, inter-city SUHI showed higher spatial variability in the late morning, midday, and early afternoon than in the evening, midnight, and early morning. Urban vegetation and percent imperviousness can regulate SUHI spatial variations in each city, and the impact varied across cities or at different diurnal times. The findings can have implications for assessing extreme heat exposure in regional cities, enlightening the urban SUHI mitigation strategies, and informing future regional sustainability.