Application Study of Water Vapor obtained from GPS for Meteorology

全球定位系统(GPS)中最新的高精度地球轨道信息使从GPS测量中反演水汽成为可能。为此，在GPS气象学的基础上，开展了GPS水汽信息在气象中的应用研究。本研究是日本首次对GPS气象学进行研究。对日本地理勘探院全国台阵GPS观测资料的分析结果表明，GPS测得的可降水量与探空仪观测结果吻合较好，均方根误差为2 mm。通过对筑波地区GPS可降水量与无线电探空仪观测结果的对比分析，发现夏季可降水量与陆风和海风有显著的日变化。此外，通过基于地理调查研究所的556个GPS站点对日本岛屿上空的GPS可降水量分布进行可视化，可以清楚地检测到与横跨该岛屿的向东移动的锋面有关的可降水量分布。这表明GPS具有作为可降水量全天候传感器的能力。

Recent high precision earth orbit information in GPS (Global Positioning System) has made it possible to retrieve water vapor from GPS measurements. As a result, an application study of GPS water vapor information for meteorology has been started under GPS meteorology. The present study is the fist research on GPS meteorology in Japan.The results of analyzes of GPS data measured in nation wide array of Geographical Survey Institute reveals precipitable water obtained from GPS agree well with those from radio-sonde observatiosn with RMS difference of 2mm. A year-round comparison of GPS precipitable water with that from radio-sonde observation at Tsukuba showed a remarkable diurnal variations in precipitable water connected with land breeze and sea breeze in summer. In addition, by visalization of GPS precipitable water distributions over the Japanese Island based upon 556 GPS sites of Geographical Survey Institute, precipitable water distributions connected with a front moving eastward across the Island can be clearly detected. This indicates that GPS has an ability as an all weather sensor of precipitable water.