# Comparison of Methods for Reconstructing MODIS Land Surface Temperature under Cloudy Conditions
## 2 Materials and Methods
### The Satellite and Other Auxiliary Data  
The MODIS 500-m-resolution daily land surface reflectance (MOD09 GA) and 1-km-resolution land surface temperature (MOD11A1 and MYD11A1) were used for LST reconstruction calculation. The LST data from the MOD11A1 product and the MYD11A1 product were adopted, and these were acquired by the Terra and Aqua satellites, respectively. The Terra and Aqua satellites have equatorial crossing times of 10:30 a.m. and 1:30 p.m., respectively. The original MODIS data have 12 bands in total, and the LST data were calculated using the \"LST_Day_1 km\" band combined with a scale factor of 0.02. The MODIS Normalized Difference Vegetation Index (NDVI) was computed using the the reflectance of near-infrared and red bands. All MODIS data were obtained from the Application for Extracting and Exploring Analysis Ready Samples (AppEEARS) ([[https://lpdaacsvc.cr.usgs.gov/appeears/](https://lpdaacsvc.cr.usgs.gov/appeears/)]([https://lpdaacsvc.cr.usgs.gov/appeears/](https://lpdaacsvc.cr.usgs.gov/appeears/)) (accessed on 1 August 2021)).  
The advanced microwave scanning radiometer 2 (AMSR2) is a remote sensing sensor mounted on GCOM-W1, which is used to measure the weak microwave radiation on the earth's surface and in the atmosphere ([[https://gportal.jaxa.jp/gpr/search/](https://gportal.jaxa.jp/gpr/search/)]([https://gportal.jaxa.jp/gpr/search/](https://gportal.jaxa.jp/gpr/search/)) (accessed on 1 September 2021)). AMSR2 measures vertically and horizontally polarized brightness temperatures at 6.925, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz. In this study, the LST inversion scheme proposed by [PERSON] (2009), that is, that the AMSR2 brightness temperature product in the 37 GHz vertical polarization channel and the actual LST have a certain linear relationship, was used to retrieve surface temperature, will be employed in the following study [29].  
ERA5 is the fifth-generation ECMWF atmospheric reanalysis of the global climate ([[https://cds.climate.copernicus.eu/](https://cds.climate.copernicus.eu/)]([https://cds.climate.copernicus.eu/](https://cds.climate.copernicus.eu/)) (accessed on 1 August 2021)). The reanalysis combines model data with observations from across the world into a globally complete and consistent dataset. ERA5 data provide hourly estimates of atmospheric, terrestrial, and marine climate variables. The earth data are accurate to a 30 km grid, including 137 layers of atmospheric data. The skin temperature was adopted in this study.  
All of the images were geometrically rectified to the Universal Transversal Mercator projection (UTM Zone 47N) by the Pixel Information Expert (PIE) remote sensing image processing platform and resampled to a resolution of 1 km using the cubic convolution method by means of ENVI to maintain consistency with the MODIS data.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Station** & **Land Cover** & **Longitude (E)** & **Latitude (N)** & **Elevation (m)** \\ \hline Arou & Alpine meadow & 100.4643 & 38.0473 & 3033 \\ Daman & Cropland & 100.3722 & 38.8555 & 1556 \\ Dashalong & Swamp meadow & 98.9406 & 38.8399 & 3739 \\ Huazhazi & Barren land & 100.3201 & 38.7659 & 1731 \\ Hunhelin & Populus Euphratica and & 100.1335 & 41.9903 & 874 \\ Tamarix & & 100.4464 & 38.9751 & 1460 \\ Zhangye & Wetland & 100.2421 & 38.0142 & 4148 \\ Yakou & Alpine meadow & 101.1374 & 42.0012 & 873 \\ Sidaoqiao & Tamarix & 101.1374 & 42.0012 & 873 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Site location and underlying surface information of Heihe River Basin.