Near-Real-Time GPS Sensing of Atmospheric Water Vapour
Near-Real-Time GPS Sensing of Atmospheric Water Vapour
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发表时间：
2005
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通讯作者：
Z. Bai
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作者：
Z. Bai
现代天气预报的一个重要目标是改进短期天气预报，特别是对恶劣天气和降水的预报。然而，由于缺乏对大气水蒸气的及时和准确观测，阻碍了实现这一目标的能力。由于其高度的时空变异性，大气水蒸气是地球大气中测量最差和了解最少的成分之一。全球定位系统（GPS）技术正在解决这一问题。由于大气中的温度、压力和水蒸气的变化，GPS无线电信号会变慢和弯曲。传统上，GPS信号的传播延迟被认为是一个令人讨厌的参数，它是利用GPS获得精确坐标的障碍。全球定位系统精确定位和轨道确定方面的最新发展，使得利用地面全球定位系统接收器的连续跟踪数据，能够在常规基础上高度精确地确定大气参数。本研究旨在解决澳大利亚近实时（NRT）估算大气水蒸气含量的几个关键科学挑战。本文在以下五个方面对GPS气象学领域做出了贡献：首先，研究开发了GPS地面气象学研究的技术平台，并利用澳大利亚区域GPS网络（ARGN）的观测资料进行GPS可降水量（PWV）估算。利用全球定位系统和无线电探空仪资料估计水蒸气的方法已经发展和试验。采用了基于gamit的GPS数据处理策略，并与澳大利亚高空网络（AUAN）的无线电探空水汽解决方案进行了比较分析，为进一步研究提供了有效的技术基础。其次，该研究开发了利用GPS数据和GPS站点周围收集的地面气象观测资料估算大气水蒸气的技术。理想情况下，在GPS天线附近安装一个专用气象传感器。然而，气象传感器通常不安装在大多数澳大利亚GPS站。在每个GPS站点安装新的气象传感器将需要额外的成本，大约是GPS大地测量接收器成本的三分之一或一半。我们通过实验开发和演示了插值方法，利用由气象局（BOM）运营的澳大利亚自动气象站（AWS）网络每小时收集的地面气象数据来估计大气水蒸气。第三，研究了海洋潮汐负荷及其对GPS可降水量估算值的影响。地球表面由海洋负荷引起的周期性运动是最大的周期性运动之一。然而，在澳大利亚被海水包围的地区的GPS站点上，量化它们对GPS衍生解决方案的影响的工作很少。本文介绍了ARGN网络的理论分析和实验结果，重点讨论了海洋负荷及其对GPS可降水量估算值的影响。第四项重要工作是为澳大利亚未来业务气象应用开发估算高倾斜水蒸气（SWV）值的技术，包括解决拟合后双差残差的倾斜路径延迟恢复等问题，以及克服站点多路径效应。实验结果证明了所提方法的有效性。最后，为了解决澳大利亚地区现有和未来GPS参考站的气象应用问题，近实时测量大气水汽含量，确定并讨论了实现NRT GPS水汽估算的技术问题，包括气象和气候应用的数据需求、NRT数据处理和GPS轨道质量控制程序。对NRT和后期数据处理的GPS PWV实验结果进行了比较。
An important goal in modern weather prediction is to improve short-term weather forecasts, especially of severe weather and precipitation. However, the ability to achieve this goal is hindered by the lack of timely and accurate observations of atmospheric water vapour, which is one of the most poorly measured and least understood constituents of the Earth's atmosphere due to its high temporal and spatial variability. This situation is being addressed by the Global Positioning System (GPS) technology. GPS radio signals are slowed and bent by changes in temperature, pressure and water vapour in the atmosphere. Traditionally, the GPS signal propagation delay is considered a nuisance parameter that is an impediment to obtaining precise coordinates using GPS. Recent development in GPS precise positioning and orbit determination has enabled the atmospheric parameters to be determined to a high degree of accuracy on a routine basis, using continuous tracking data from ground-based GPS receivers. The aim of this research is to address several critical scientific challenges in estimating the atmospheric water vapour content in near-real-time (NRT) in Australia. Contributions are made to the field of GPS meteorology in the following five areas: First of all, research efforts were made to develop a technical platform for the ground-based GPS meteorology studies and demonstration of GPS Precipitable Water Vapour (PWV) estimation using observations from Australian Regional GPS Networks (ARGN). Methods of estimation of water vapour from GPS and radiosonde data have been developed and tested. GAMIT-based GPS data processing strategies and compare analysis with radiosonde water vapour solutions from the Australia Upper Air Network (AUAN) were undertaken, providing an effective technical basis for further studies. Secondly, the research has developed techniques to allow estimation of atmospheric water vapour from GPS data and surface meteorological observations collected around the GPS sites. Ideally a dedicated meteorological sensor is installed adjacent to the GPS antenna. However, meteorological sensors are normally not installed at most Australian GPS stations. Installing a new meteorological sensor at each GPS station would involve additional cost at the level of one-third or half of the geodetic GPS receiver cost. We have experimentally developed and demonstrated interpolation methods for making use of hourly collected surface meteorological data from the Australian Automatic Weather Station (AWS) network operated by the Bureau of Meteorology (BOM) to estimate atmospheric water vapour. Thirdly, the research has studied ocean tidal loading and its effects on GPS derived precipitable water vapour estimates. The periodic motion of the Earth's surface due to ocean loading is one of the largest periodic motions. However, very little work has been done to quantify their effects on GPS-derived solutions at the GPS sites in the Australian region surrounded by ocean waters. The research presents the theoretical analysis and experimental results from the ARGN network, focusing on ocean loading and its effects on GPS derived precipitable water vapour estimates. The fourth important effort was the development of techniques for estimating highrate Slant Water Vapour (SWV) values for future operational meteorological applications in Australia, including addressing such issues as slant-path delay recovery from post-fit double-difference residuals, and overcoming site multipath effects. The experimental results have demonstrated the efficiency of the proposed methods. Finally, in order to address the meteorological applications with the existing and anticipated GPS reference stations in the Australian region, and measure the atmospheric water vapour content in near-real-time, the technical issues to implement NRT GPS water vapour estimation were identified and discussed, including the data requirements for meteorological and climate applications, NRT data processing and quality control procedures for GPS orbits. The experimental GPS PWV results from NRT and post data processing are compared and presented.