Does quality control matter? Surface urban heat island intensity variations estimated by satellite-derived land surface temperature products

The temporally regular and spatially comprehensive monitoring of surface urban heat islands (SUHIs) have been extremely difficult, until the advent of satellite-based land surface temperature (LST) products. However, these LST products have relatively higher errors compared to in situ measurements. This has resulted in comparatively inaccurate estimations of SUHI indicators and, consequently, may have distorted interpretations of SUHIs. Although reports have shown that LST qualities are important for SUHI interpretations, systematic investigations of the response of SUHI indicators to LST qualities across cities with dissimilar bioclimates are rare. To address this issue, we chose eighty-six major cities across mainland China and analyzed SUHI intensity (SUHII) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) LST data. The LST-based SUHII differences due to inclusion or exclusion of MODIS quality control (QC) flags (i.e., ASUHII) were evaluated. Our major findings included, but are not limited to, the following four aspects: (1) SUHIls can be significantly impacted by MODIS QC flags, and the associated QC-induced Delta SUHIIs generally accounted for 24.3% (29.9%) of the total SUHII value during the day (night); (2) the Delta SUHIIs differed between seasons, with considerable differences between transitional (spring and autumn) and extreme (summer and winter) seasons; (3) significant discrepancies also appeared among cities located in northern and southern regions, with northern cities often possessing higher annual mean Delta SUHIIs. The internal variations of Delta SUHIIs within individual cities also showed high heterogeneity, with ASUHII variations that generally exceeded 5.0 K (3.0 K) in northern (southern) cities; (4) Delta SUHIIs were negatively related to SUHIls and cloud cover percentages (mostly in transitional seasons). No significant relationship was found in the extreme seasons. Our findings highlight the need to be extremely cautious when using LST product-based SUHIIs to interpret SUHIs. (C) 2018 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.