Construction and Validation of a Dawn and Dusk Land Surface Temperature Using MERSI-LL FY-3E

Dawn and dusk land surface temperature (LST) is important for constructing subdaily LSTs and understanding diurnal temperature cycles. In this study, a dawn–dusk LST was developed using the medium-resolution spectral imager-low-light (MERSI-LL) instrument onboard Fengyun-3E. A temperature and emissivity separation algorithm was first implemented using the three thermal infrared bands of MERSI-LL. The retrieved LST was validated against in situ measurements at 46 sites. An RMSE of 2.07 K was obtained for vegetated surfaces, while a large negative bias (–3.63 K) and high RMSE (4.09 K) were observed at one barren site. Then, intercomparisons with LST products from two geostationary satellites indicated that the proposed LST exhibited a reasonable performance over two sample regions with varying vegetation densities. Finally, the emissivity intercomparison showed close agreement with other low Earth orbit (LEO) sensors at the sites, supporting the reasonability of the retrieved LST. This dawn–dusk time LST could potentially be combined with other LEO satellite-based LSTs to achieve gapless LST products in the future.