Exploring diurnal cycles of surface urban heat island intensity in Boston with land surface temperature data derived from GOES-R geostationary satellites

The surface urban heat island (SUHI) is one of the most significant human-induced alterations to the Earth's surface climate and can aggravate health risks for city dwellers during heat waves. Although the SUHI effect has received growing attention, its diurnal cycles (i.e., the variations over the full 24 hours within the diel cycle) are poorly understood due to the low temporal resolution (once or twice a day) of the land surface temperature (LST) observations from the widely-used satellite sensors (e.g., Landsat Series, Terra/Aqua MODIS). Geostationary satellites provide intensive LST observations throughout the day and the night, and thereby offer unprecedented opportunities for exploring the diurnal cycles of SUHI. Here we examined how the SUHI intensity varied over the course of the diurnal cycle in the Boston Metropolitan Area using LST observations from the NOAA's latest generation of Geostationary Operational Environmental Satellites (GOES-R). GOES-R LST was strongly correlated with MODIS LST (R² = 0.98, p < 0.0001) across urban-core, suburban, and rural areas. We calculated the SUHI intensity at an hourly time step for both the urban-core and suburban areas using GOES-R LST data. The maximum SUHI intensity for the urban-core occurred near noon, and was +3.0°(12:00), +5.4° (12:00), +4.9 ° (11:00), and +3.7 ° (12:00) in winter, spring, summer, and autumn, respectively. The maximum intensity for the suburban area was about 3.0° lower in spring and summer and 2.0° lower in autumn and winter than that of the urban-core area. The minimum SUHI intensity occurred at nighttime, and ranged from -1.0° to +1.0°. The difference in the nighttime SUHI intensity between urban-core and suburban was insignificant for all seasons except the summer. The SUHI intensity showed similar diurnal variations across the seasons.We also found different relationships between SUHI intensity and potential drivers within a diurnal cycle, characterized by the strongest correlation during the middle of the day with impervious surface area and at night with tree canopy cover. Our research highlights the great potential of the new-generation geostationary satellites in revealing the detailed diurnal cycles of SUHI. Our findings have implications for informing urban planning and public health risk management.