MAT, MAP, Z-Elevation

Daily air temperature, precipitation, and elevation of the rain-snow transition (Z-elevation) for each of the 60 elevation zones were used as inputs to the data-driven models. These elevation zone-average meteorological inputs, derived from gridded sources using spatial means, were provided by the CNFRC and are the same inputs used for their SNOW-17 and SAC-SMA models. The temperature data were from the Analysis of Record for Calibration (AORC, Kitzmiller et al. 2018). AORC is a gridded record of near-surface weather conditions covering the continental United States and Alaska, on a 0.008-degree grid mesh and one-hour temporal resolution. The precipitation data was derived from historical mean annual precipitation until WY 2003; after WY2003 precipitation is drawn from operational forcing, which is an internally adjusted dataset derived from National Center for Environmental Information’s Cooperative Observer Network and Natural Resources Conservation Service’s Snow Telemetry gages. The Z-elevation was from ERA5.本研究将60个海拔分区的逐日气温、降水量及雨雪过渡带海拔（Z-elevation）作为数据驱动模型的输入变量。上述通过空间平均方法从格点数据源推导得到的海拔分区平均气象输入变量，由CNFRC提供，且与该机构用于SNOW-17与SAC-SMA模型的输入变量完全一致。气温数据源自校准记录分析（Analysis of Record for Calibration, AORC，Kitzmiller等，2018）。AORC是一套覆盖美国本土及阿拉斯加州的近地表气象格点数据集，采用0.008°的格网间距与1小时的时间分辨率。2003水年（Water Year, WY）之前的降水数据取自历史多年平均年降水量；2003水年之后的降水数据则来源于业务化强迫数据集——该数据集经内部校正，由美国国家环境信息中心（National Center for Environmental Information, NCEI）的合作观测站网与美国自然资源保护服务局（Natural Resources Conservation Service, NRCS）的雪情遥测站数据推导得到。雨雪过渡带海拔数据源自欧洲中期天气预报中心第五代再分析资料（ERA5）。