# Satellite Remote Sensing of Surface Urban Heat Islands: Progress, Challenges, and Perspectives
## Summary  
This review shows an exponentially increasing trend in satellite-based SUHI publications since 2005, with large biases in the geographic areas, study time of day, study seasons, and research foci. Local-scale SUHI variations in the daytime and/or summer have received more research attention. Knowledge of SUHI variations and their relationship with air UHIs has been greatly enriched by the past SUHI studies even though some findings such as the relative significance of landscape composition, configuration, and the dominant factors for SUHI variations among cities remained highly disputed. UHI researchers currently face a series of challenges in using satellite LST data, including the differences between satellite-derived LST and air temperature, the impacts of clouds and other factors on LST data, the trade-off between spatial and temporal resolutions, the methods to quantify SUHI intensity, concurrent land cover, land use mapping, accuracy assessment, and attribution of SUHI. Worse still, the resultant uncertainties have been magnified by the wide applications of very limited datasets (e.g., using one image in a season or year) in the SUHI analyses. Given the availability of long-term archive/free data, a large number of images or time-series analyses are strongly recommended for future studies to increase the robustness of the findings. Considerable scope for improving the quality and quantity of LST data and analysis remains. We suggest that more attention be paid to the understudied regions/cities, the methods to calculate SUHI intensity, inter-annual variability and long-term trends of SUHI, scale issues of SUHI, SUHI-SubUHI relationships, and the integration of remote sensing data with field observation and numeric modeling in the future.  
The following are available online at [[http://www.mdpi.com/2072-4292/11/1/48/s1](http://www.mdpi.com/2072-4292/11/1/48/s1)]([http://www.mdpi.com/2072-4292/11/1/48/s1](http://www.mdpi.com/2072-4292/11/1/48/s1)), Table S1: List of the SUHI literature reviewed in this study, Text S1: The active journals of published SUHI literature.  
Conceptualization, D.Z. and J.X.; methodology, D.Z. and J.X.; writing--original draft preparation, D.Z., S.B., C.B., K.D., Y.Z., R.Y. and Z.Q.; writing--review and editing, J.X. and S.F.  
This research was funded by the National Natural Science Foundation of China (Grant #: 41501465, 41561038, and 41601196), the National Aeronautics and Space Administration (Grant #: NNX14 AI70G, 80 NSSC18K1434, and NNX14 AJ18G), the United States National Science Foundation (Grant #: CBET-1803920), and the Jiangsu Key Laboratory of Agricultural Meteorology Foundation (Grant #: JKLAM1804). The contribution of [PERSON] was financially supported by COKAP, which is a research project funded by DLR Projektregister and the German Federal Ministry of Transport and Digital Infrastructure (BMVI) (Grant #: 50 EW1707).  
We thank [PERSON] for her assistance with literature collection, and [PERSON] for his comments on the outline of the review article.  
The authors declare no conflict of interest.