Seasonal Surface Urban Heat Island Analysis

Surface Urban Heat Islands (SUHIs) show large temporal variability, which introduces considerable uncertainty into studies based on a single or a few acquisitions. Besides short-term and more random influences, they exhibit considerable systematic diurnal and seasonal variation, which has been investigated in several recent studies. Here an enhanced method for seasonal SUHI analysis based on time series analysis is presented and tested in the southwest United States using MODIS day- and nighttime land surface temperature data. Despite large scatter at the daily time scale, the method is able to identify and parameterize seasonal signals in time series. The seasonal patterns vary substantially between cities. Coastal cities show the largest nighttime SUHI intensity in spring and the lowest in late summer, while continental cities have their SUHI intensity peaks in September and October. During summer, some cities show a daytime cool island. Our study underlines the need to consider temporal patterns in SUHI assessment. The method proved useful to investigate the SUHI seasonality.