## 2 Data and Methods
### Models and Calibration
#### 2.2.2 WRF-Hydro  
The WRF-Hydro model used in this study was version 3.0 [38; 39], and the information about the WRF-Hydro model is available on the official website [40]. WRF-Hydro mainly includes a LSM module, a hydrologic module and a disaggregation-aggregation module. 1. Runoff generation in Noah  
The LSM coupled with WRF/WRF-Hydro are Noah in this case [38; 39]. There are four soil layers in a 2-meter soil column used in Noah, and the soil column configuration used in this study had the depth of the bottom of the layers as 0-10 cm, 10-40 cm, 40-100 cm, and 100-200 cm. The runoff generation process in Noah is divided into three parts: surface excess infiltration runoff, saturated subsurface runoff and deep underground free outflow. The process of excess infiltration runoff generation is the simple water balance (SWB), derived by [PERSON] et al. [41], which follows the assumption that when the infiltration is greater than the grid surface aquatic water capacity (precipitation reduced by the interception and evaporation), the excess part of infiltration produces surface runoff. Then, with the increase of infiltration, the subsurface water in each layer of soil column gradually accumulates. The subsurface water occurs until the existing soil water content soil moisture exceeds the total saturated soil moisture of the whole soil column. There is also a water outlet at the bottom of each grid soil column, which is used to indicate a deep free drainage process. 2. Routing in the hydrological module  
The hydrological module of WRF-Hydro compensates and strengthens the description of the lateral transport of the infiltration excess process and of the saturated subsurface process in Noah. Corresponding to runoff generation, it includes overland routing, subsurface routing, deep base flow, and a river routing. The overland routing is realized similar to [PERSON] et al. [42] by a completely unsteady, finite difference and diffusion wave method. The flow on the reverse slope and backwater effects are taken into account in the diffusion wave equation. The subsurface routing refers to the saturated flow in the soil layer, and its lateral movement is according to the method proposed by [PERSON] and [PERSON] [43], where a quasi-three-dimensional flow is computed, including the effects of topography, saturated soil depth and saturated hydraulic conductivity varying with soil depth. Channel routing, similar to overland flow, uses an explicit, one-dimensional, variable time step diffusion wave equation. When the water depth of the grid column exceeds a predefined retention depth, the stream inflow occurs and gradually flows along the channel grids. The base flow is represented by a simple, experience-based bucket model located below the soil column and is the construction of a conceptual bucket model with side openings, which is especially suitable for a long-term simulation. An exponential function is used to achieve the conceptual water depth in the bucket, and the water discharged from the soil column is mapped to the underground bucket according to a scale factor. The water in the bucket is gradually returned to the channel section directly corresponding to its downstream catchment area. The current hydrological module of WRF-Hydro does not support the coupling of river channel and base flow. 3. Configurations of WRF-Hydro and disaggregation-aggregation module  
The configurations related to the WRF-Hydro are shown in Table 3. The base flow module is closed in this study for a short simulation time and it simply collects underground runoff and reallocates