地面GPS观测探测大气可降水汽量的方法和前景

Methods and Promise on Monitoring Precipitable Water Vapor by Ground-based GPS

介绍了利用地面GPS观测探测大气可降水汽量（PWV）的基本原理和方法及其在气象学和天文定位上的应用．地面GPS测量的PWV估计的主要误差源来自天顶湿延迟的估计．为了提高天顶湿延迟的估计精度，根据大气湿分量随时间变化的特性，天顶湿延迟的估算可采用确定性参数估计和随机模型估计．采用这些方法能有效地提高GPS精密定位中高程测量的精度，且其估算的PWV的精度可达1-2mm，足以满足天气预报和气候研究的需要．简述了大气分布的非球对称性对PWV估计的影响并评述了利用地面GPS测量探测PWV的前景．

This paper provides an overview of applying ground-based GPS to monitoring the precip-liable water vapor above GPS receiver sites. The wet delay due to water vapor which is highly variable and inhomogeneous is difficult to be precisely estimated by surface meteorological data.But it can be estimated by multi-parameters estimates and stochastic processes, such as first-order Gauss-Markov process and random walk process. The derived zenith wet delay can be readily transformed into an estimation of precipitable water vapor. This transformation is well achieved by multiplying the zenith wet delay by a factor. Maily tests have proved that Ground-based GPS technique can offer not only both high accuracy and high temporal resolution of estimates of precipitable water vapor, but also potential facilities in nearly real time estimation of precipitable water vapor. With the rapid groWth of regionally and globally continuously operating ground-based GPS networks, it is good opportunity to observe distributions of precipitable water vapor with high spatial and temporal resolutions. The results have been proved to be valuable in regional or global climate analysis and short-range numerical weather predictions. In addition,GPS-derived precipitable water vapor may provide a powerful constraint for numerical weather prediction models. This is also helpful to improve the zenith wet delay estimate for relative positioning.