Land surface temperature (LST) is an essential parameter for geoscience studies, and the 1-km polar-orbiting satellite LST products are widely used due to their global coverage on a daily basis. Aimed to jointly utilize all 1-km LST products to thoroughly quantify the LST temporal tendency within one day, comprehensive evaluation of existing 1-km LST products over the same sites is meaningful. In this study, taking sparsely vegetated sites as an example, ten 1-km polar-orbiting LST products were evaluated against the in situ measurements of ten USCRN sites with high spatial representativeness (from December 2019 to November 2020 covering four seasons). The evaluated LST products included three Moderate Resolution Imaging Spectroradiometer (MODIS) LST products (i.e., MOD11, MYD11, and MYD21), two Sea and LST Radiometer (SLSTR) LST products (i.e., Sentinel-3A and Sentinel-3B), one LST product from Advanced Very High Resolution Radiometer (AVHRR) onboard Metop-B, three Visible Infrared Imaging Radiometer Suite (VIIRS) LST products (i.e., VNP21, S-NPP EDR, and NOAA-20 EDR), and one LST product from Visible and Infra-Red Radiometer (VIRR) onboard FY-3B. The results indicate that: 1) the RMSE is much higher in the daytime (2.5–4.0 K) than in the nighttime (1.7–2.5 K); 2) the daytime MBE is negative (from −0.3 to −2.8 K) and this underestimate trend is significantly slighter for nighttime MBE (from −1.7 to 0.2 K); and 3) the daytime RMSE varies from 2.7 to 4.6 K in summer, 2.7–4.5 K in spring, 2.5–3.7 K in winter, and 2.0–3.4 K in autumn. Furthermore, we found that the severe daytime RMSE is related to the thermal anisotropy amplitude, which is around 4 K in summer, 2 K in spring and autumn, and 1 K in winter. Correcting the thermal anisotropy of daytime LST is an essential step that needs to be taken seriously before conducting high-quality joint applications, such as diurnal temperature cycle (DTC) modeling.

中文翻译：

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稀疏植被区现有1km地表温度产品综合分析：基于T的评价、热各向异性及联合应用


地表温度（LST）是地球科学研究的重要参数，1公里极轨卫星地表温度产品因其日常覆盖全球而得到广泛应用。为了联合利用所有1公里LST产品来彻底量化一天内的LST时间趋势，对同一站点上现有的1公里LST产品进行综合评估是有意义的。本研究以植被稀疏站点为例，针对10个具有较高空间代表性的USCRN站点（2019年12月至2020年11月，涵盖四个季节）的原位测量，对10个1公里极轨地表温度产品进行了评估。评估的LST产品包括三款中分辨率成像光谱仪（MODIS）LST产品（即MOD11、MYD11和MYD21）、两款海洋和LST辐射计（SLSTR）LST产品（即Sentinel-3A和Sentinel-3B）、一款LST产品Metop-B 上的先进甚高分辨率辐射计 (AVHRR) 产品、三款可见红外成像辐射计套件 (VIIRS) LST 产品（即 VNP21、S-NPP EDR 和 NOAA-20 EDR）以及一款来自 Visible 和FY-3B 上装有红外辐射计 (VIRR)。结果表明：1）白天（2.5~4.0 K）的 RMSE 远高于夜间（1.7~2.5 K）； 2）白天MBE为负值（从-0.3到-2.8 K），而夜间MBE（从-1.7到0.2 K）的这种低估趋势明显更轻； 3) 白天 RMSE 变化范围为夏季 2.7 至 4.6 K，春季 2.7-4.5 K，冬季 2.5-3.7 K，秋季 2.0-3.4 K。此外，我们发现严重的白天RMSE与热各向异性幅度有关，夏季约为4 K，春秋季为2 K，冬季为1 K。 校正白天地表温度的热各向异性是进行高质量联合应用（例如昼夜温度循环（DTC）建模）之前需要认真对待的重要步骤。