## 2 Study Area and Data
### Data
#### 2.2.1 Satellite Data  
The Visible and Infrared Radiometer (VIRR) aboard the Fengyun-3C (FY-3C) satellite was developed by the China Meteorological Administration (CMA) and is operated by the National Satellite Meteorological Center (NSMC) in Beijing, China. VIRR LST is one of the most commonly used TIR LST products in China, with a spatial resolution of 1 km and a temporal resolution of daily. VIRR LST is a TIR LST product retrieved using a windowing algorithm, offering high spatial resolution and accuracy, making it a reliable data source for surface temperature monitoring. Additionally, the VIRR LST will show \"NoData\" values in areas with cloud coverage, which makes it easier to identify and check for cloud-covered pixels in the experiment. Therefore, this study uses VIRR LST as the primary component for generating all-weather LST. In addition, VIRR NVI (Normalized Vegetation Index, NDVI) and MCD12Q1 land cover (LC) data are selected as auxiliary data for the all-weather surface temperature generation process. The spatial resolution of VIRR NVI is 5 km, with a temporal resolution of 10 days. To match the temporal resolution of VIRR LST, this study applies a time interpolation method based on Savitzky-Golay filtering \begin{table}
\begin{tabular}{c c c c c} \hline
**Dataset** & **Variables** & **Spatial Resolution** & \
\begin{tabular}{c} **Temporal Resolution** \\ \end{tabular} &
\begin{tabular}{c} **Source (URL)** \\ \end{tabular} \\ \hline MWRI & PMW LST & 25,000 m & 1-day & [[http://data.nsmc.org.cn/](http://data.nsmc.org.cn/)]([http://data.nsmc.org.cn/](http://data.nsmc.org.cn/)) \\ \hline VIRR & TIR LST & 1000 m & 1-day & PortalSite/Data/Satellite.aspx (accessed on 23 March 2024) \\ \hline MCD12Q1 & LC & 500 m & 365-days & [[https://code.earthegnine.google.com/](https://code.earthegnine.google.com/)]([https://code.earthegnine.google.com/](https://code.earthegnine.google.com/)) (accessed on 23 March 2024) \\ \hline STRM & DEM & 900 m & - & [[https://srtm.csi.cgiar.org/srtmdata/](https://srtm.csi.cgiar.org/srtmdata/)]([https://srtm.csi.cgiar.org/srtmdata/](https://srtm.csi.cgiar.org/srtmdata/)) (accessed on 23 March 2024) \\ \hline \end{tabular}
\end{table} 
Table 1: Basic information of the datasets used in this study. \begin{table}
\begin{tabular}{c c c c c} \hline
**Site** & **Longitude** & **Latitude** & \
\begin{tabular}{c} **Underlying Surface** \\ \end{tabular} &
\begin{tabular}{c} **Location** \\ \end{tabular} \\ \hline Arou & 100.4643 & 38.0473 & Alpine meadow & Caodaban Village, Aruo Township, \\  & & & & & Qilian County, Qinghai Province \\ Daman & 100.3722 & 38.8555 & Maize & Farmland in Daman Irrigation District, \\ Dashalong & 98.9406 & 38.8399 & Alpine meadow & Qilian County, Qinghai Province \\ Huangmo & 100.9872 & 42.1135 & Desert & Ejina Banner, Inner Mongolia \\ Huazhaizi & 100.3201 & 38.7659 & Desert & Zhangye City, Gansu Province \\ Hunhelin & 101.1335 & 41.9903 & Populus euphratica & Sidaoqiao, Dalaihubu Town, Ejina Banner, Inner Mongolia \\ Sidaoqiao & 101.1374 & 42.0012 & Tamarix & Dalaihubu, Ejina Banner, Inner Mongolia \\ Yakou & 100.2421 & 38.0142 & Alpine meadow & Qilian County, Qinghai Province \\ Zhangye & 100.4464 & 38.97514 & Wetland & Zhangye City, Gansu Province \\ \hline \end{tabular}
\end{table} 
Table 2: Validation site information. to the VIRR NVI, generating daily NDVI products. The MCD12Q1 LC used in this study is a land cover product based on the IGBP global vegetation classification scheme. It has a spatial resolution of 500 m and a temporal resolution of once per year. To generate all-weather LST based on the VIRR LST dataset, several additional variables were incorporated, including seamless spatial PMW LST, digital elevation model (DEM), longitude and latitude, and slope. The spatially seamless PMW LST dataset used in this study comes from the processed MWRI LST, which is a surface temperature product from the Microwave Radiation Imager (MWRI). MWRI LST has a spatial resolution of 25 km and a temporal resolution of one day.