Preconditions to GPS water vapour tomography with a resolution relevant for data assimilation in weather forecast models

GPS 水蒸气层析成像的先决条件，其分辨率与天气预报模型中的数据同化相关

• 批准号: 5426184
• 负责人: Dr. Armin Raabe
• 金额: --
• 依托单位: Institut für Meteorologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2004
• 资助国家: 德国
• 起止时间: 2003-12-31 至 2005-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5426184?language=en
• 关键词: Preconditions; GPS; water; vapour; tomography

Improved knowledge of water vapour fields are necessary for various meteorological and atmospheric research applications. Moisture distributions are used as input for atmospheric models and serve for precise numerical weather forecast. In the last decade, GPS-derived data products made many contributions to provide integrated water vapour (IWV). The knowledge of IWV characteristics is retrieved by analysing delays an the GPS signal caused by atmospheric gradients, using mapping functions and under the assumption of a known dry pressure field. The combination of several stations allow to produce two-dimensional maps of vertical IWV fields. Directly, it is possible to extract the water vapour content along single GPS rays, which state a integrated measurements. Considering a sufficient number of records in a defined area allows tomographic data assimilation. This would be a helpful tool to improve algorithms of moisture and precipitation forecast. A drawback of using only ground-based GPS receivers for water vapour reconstruction is the poor vertical resolution that can be achieved using links of small zenith angle only. In resent times, Low Earth Orbiter (LEO) satellites have been launched carrying an GPS receiver. Therefore, adding GPS-LEO links will significantly improve the vertical resolution, provided a large number of LEO satellite measurements are available. The spatial resolution that should be provided by such threedimensional fields are those used in local/regional weather forecast models. The aim of this study is to investigate the amount and constellation of GPS measurements - both groundbased and spacebased - necessary to perform tomographic reconstructions of water vapour content under the specifications requisite for use in numerical models.

提高对水汽场的了解对于各种气象和大气研究应用是必要的。湿度分布用作大气模型的输入，并用于精确的数值天气预报。在过去的十年中，GPS 衍生的数据产品为提供综合水汽 (IWV) 做出了许多贡献。 IWV 特性的知识是通过分析由大气梯度引起的 GPS 信号的延迟、使用映射函数并在已知干压力场的假设下获得的。多个站点的组合可以生成垂直 IWV 场的二维地图。可以直接沿着单条 GPS 射线提取水蒸气含量，这表明了综合测量结果。考虑到定义区域中的足够数量的记录允许断层摄影数据同化。这将是改进湿度和降水预报算法的有用工具。仅使用地面 GPS 接收器进行水汽重建的一个缺点是仅使用小天顶角链路即可实现的垂直分辨率较差。最近，携带 GPS 接收器的低地球轨道 (LEO) 卫星已发射升空。因此，如果有大量 LEO 卫星测量可用，添加 GPS-LEO 链路将显着提高垂直分辨率。这种三维场应提供的空间分辨率是在本地/区域天气预报模型中使用的空间分辨率。本研究的目的是调查 GPS 测量的数量和星座（地面和空间），以根据数值模型使用所需的规范进行水蒸气含量的层析成像重建。