Abstract
The study of urban climate requires frequent and accurate monitoring of land surface temperature (LST), at the local scale. Since currently, no space-borne sensor provides frequent thermal infrared imagery at high spatial resolution, the scientific community has focused on synergistic methods for retrieving LST that can be suitable for urban studies. Synergistic methods that combine the spatial structure of visible and near-infrared observations with the more frequent, but low-resolution surface temperature patterns derived by thermal infrared imagery provide excellent means for obtaining frequent LST estimates at the local scale in cities. In this study, a new approach based on spatial-spectral unmixing techniques was developed for improving the spatial resolution of thermal infrared observations and the subsequent LST estimation. The method was applied to an urban area in Crete, Greece, for the time period of one year. The results were evaluated against independent high-resolution LST datasets and found to be very promising, with RMSE less than 2 K in all cases. The developed approach has therefore a high potential to be operationally used in the near future, exploiting the Copernicus Sentinel (2 and 3) observations, to provide high spatio-temporal resolution LST estimates in cities.
Highlights
The microclimate of cities is strongly influenced by man-made structures and human activities and differs from that of the surrounding natural areas, a phenomenon widely known as the urban heat island [1]
Besides the urban heat island estimations based on urban canopy temperature differences between the urban core and the peri-urban areas, the respective land surface temperature (LST)
We present some examples of the use of the daily local-scale LST estimates for urban areas
Summary
The microclimate of cities is strongly influenced by man-made structures and human activities and differs from that of the surrounding natural areas, a phenomenon widely known as the urban heat island [1]. Differences are commonly used to both characterize the surface urban heat island and support urban energy budget studies [2], since LST is closely related to human comfort and the city energy use [3]. There have been attempts to estimate more parameters related to the microclimate of cities, like the urban energy budget fluxes, with the use of thermal remote sensing [9,10,11]. Grimmond et al [12] in a review on the understanding of urban climate, highlighted, among others, the need to explore the use of new measurement techniques, including satellite systems, for the study of urban microclimate
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