The diurnal cycle of land surface temperature (LST) is an important element of the climate system. Geostationary satellites can provide the diurnal cycle of LST with low spatial resolution and incomplete global coverage, which limits its applications in some studies. In this study, we propose a method to estimate the diurnal cycle of LST at high temporal and spatial resolution from clear-sky MODIS data. This method was evaluated using the MSG-SEVIRI-derived LSTs. The results indicate that this

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... ethod fits the diurnal cycle of LST well, with root mean square error (RMSE) values less than 1 K for most pixels. Because MODIS provides at most four observations per day at a given location, this method was further evaluated using only four MSG-SEVIRI-derived LSTs corresponding to the MODIS overpass times ( 10:30, 13:30, 22:30, and 01:30 local solar time). The results show that the RMSE values using only four MSG-SEVIRI-derived LSTs are approximately two OPEN ACCESS Remote Sens. 2014, 6 3248 times larger than those using all LSTs. The spatial distribution of the modeled LSTs at the MODIS pixel scale is presented from 07:00 to 05:00 local solar time of the next day with an increment of 2 hours. The diurnal cycle of the modeled LSTs describes the temporal evolution of the LSTs at the MODIS pixel scale. Keywords: land surface temperature (LST); diurnal temperature cycle (DTC); MODIS; MSG-SEVIRI Introduction Land surface temperature (LST) and its diurnal variation are crucial for the physical processes of land surface energy and water balance at regional and global scales [1] [2] [3] [4] [5] [6] . The diurnal cycle of LST is closely related to solar insolation, the state of the atmosphere, and surface characteristics, e.g., soil type, soil moisture, and vegetation cover [7] . Satellite remote sensing provides the unique way to measure the diurnal cycle of LST over extended regions [8] [9] [10] . The diurnal cycle of LST has been used for a wide variety of applications. For example, the diurnal cycle of LST was used to analyze the urban thermal environment [11] [12] [13] [14] . In addition, the diurnal cycle of LST was used to normalize the satellite-derived LSTs at different times to the same time [15, 16] . Jin and Treadon [17] used the diurnal cycle of LST to correct the orbit drift effects on the National Oceanic and Atmospheric Administration (NOAA) Advanced Very-High-Resolution Radiometer (AVHRR) LST measurements. Schroedter-Homscheidt et al. [18] retrieved total water vapor column from Meteosat Second Generation -Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI) data with the aid of the diurnal cycle of LST. Geostationary satellites with high temporal resolution have become increasingly attractive for their ability to fully characterize the diurnal cycle of LST. However, the diurnal cycle of LST with low spatial resolution (e.g., 3 km at nadir for MSG-SEVIRI) and incomplete global coverage limits its applications in some studies, e.g., urban heat island [14] . Compared with geostationary satellite data, polar-orbiting satellite data (e.g., MODIS and NOAA-AVHRR) have high spatial resolution of approximately 1 km at nadir. Therefore, various methods have been developed to estimate the diurnal cycle of LST at high temporal and spatial resolution from polar-orbiting satellite measurements. Jin and Dickinson [19] estimated the diurnal cycle of LST by interpolating NOAA-AVHRR twice-per-day measurements into the typical patterns of the diurnal cycle of LST, which were derived from climate models. Sun and Pinker [20] performed work similar to that of Jin and Dickinson [19] , but the typical patterns of the diurnal cycle of LST were derived from Geostationary Operational Environmental Satellite (GOES) measurements. Inamdar et al. [21] developed an algorithm to disaggregate the diurnal cycle of LST at the GOES pixel scale to that at the MODIS pixel scale. Zhou et al. [14] used a diurnal temperature cycle generic algorithm to estimate the diurnal cycle of LST at the MODIS pixel scale with the aid of the diurnal cycle of the FY-2C-derived LST. The methods described above can be used to estimate the diurnal cycle of LST at high temporal and spatial resolution from polar-orbiting satellite measurements. Nevertheless, these methods require the typical patterns of the diurnal cycle of LST, which are derived from climate models or geostationary