Reanalysis products have played an important role in space geodetic tropospheric delay retrieval and modeling in the past two decades. As the release of the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA5), with improved temporal-spatial resolutions compared to its predecessor, ECMWF Re-Analysis Interim (ERAI), the performance of ERA5 in tropospheric delay retrieval was comprehensively investigated in this study. Hourly tropospheric delays in zenith and 5° elevation directions at 312 International GNSS Service (IGS) stations covering the year of 2018 from ERA5 and ERAI were ray-traced. Taking IGS Zenith Total Delay (ZTD) as reference, the reanalysis-derived ZTDs were evaluated in annual, seasonal and diurnal scales, and superior performances of ERA5 ZTD to ERAI ZTD in all scales were revealed, with bias, Root Mean Square (RMS) and standard deviation of 1.6, 11.0 and 10.1 mm for ERA5, and of 3.1, 13.8 and 12.6 mm for ERAI, respectively. Due to the absence of reliable Slant Path Delay (SPD) references, the SPDs as well as the mapping factors derived from ERA5 and ERAI were directly compared and converted to equivalent station height errors at these stations. Obvious differences were also found for SPDs and mapping factors, especially for the wet component, with slant wet delay and wet mapping factor difference RMSs of 51.9 mm and 146.1 × 10−3, respectively, corresponding to equivalent station height RMSs of about 10.4 mm. Tropospheric delays and models (e.g., mapping functions) derived from ERA5, with improved performance and temporal resolution (e.g., to support potential tropospheric parameter diurnal variation study), therefore can be expected for space geodetic applications.

中文翻译：

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ERA5 在全球对流层延迟反演中的改进性能

近二十年来，再分析产品在空间大地测量对流层延迟反演和建模中发挥了重要作用。随着第五代欧洲中期天气预报中心 (ECMWF) 重新分析 (ERA5) 的发布，与其前身 ECMWF 重新分析中期 (ERAI) 相比，具有改进的时空分辨率，ERA5 的性能本研究对对流层延迟反演进行了全面的研究。对 ERA5 和 ERAI 2018 年 312 个国际 GNSS 服务 (IGS) 站的天顶和 5° 仰角方向的每小时对流层延迟进行了射线追踪。以IGS Zenith Total Delay (ZTD)为参考，对再分析得到的ZTDs进行年、季、日三个尺度的评价，揭示出ERA5 ZTD在所有尺度上均优于ERAI ZTD，ERA5 的偏差、均方根 (RMS) 和标准偏差分别为 1.6、11.0 和 10.1 毫米，ERAI 的偏差为 3.1、13.8 和 12.6 毫米。由于缺乏可靠的倾斜路径延迟 (SPD) 参考，SPD 以及源自 ERA5 和 ERAI 的映射因子被直接比较并转换为这些站点的等效站点高度误差。SPD 和映射因子也有明显差异，尤其是湿分量，斜湿延迟和湿映射因子差 RMS 分别为 51.9 mm 和 146.1 × 10−3，对应的等效站高 RMS 约为 10.4 mm。来自ERA5的对流层延迟和模型（例如映射函数），具有改进的性能和时间分辨率（例如，支持潜在的对流层参数日变化研究），