Potentials of global positioning system for meteorology in low-latitude regions

Abstract

Water vapor plays an important role in weather forecasting and climate monitoring, particularly in low-latitude regions which contain large amount and inhomogeneous water vapor. The Global Positioning System (GPS) has the ability to provide observations of water vapor continuously and more frequently for wide areas with high accuracy in all weather conditions. The GPS continuously operating reference station (CORS) data processing allows the estimation of zenith path delay (ZPD) from the GPS CORS network and will be further processed into integrated water vapor (IWV) using surface meteorological data. This research aims to study the potential of using the GPS for meteorology applications in low-latitude regions. In this study, the ZPD values from Australia and Peninsular Malaysia were derived in order to investigate the variability of water vapor in these two regions. Besides, the continuous result of the GPS-derived IWV assessment with radiosonde-derived IWV for one year data in Peninsular Malaysia are also discussed. Based on the analysis of the ZPD from the two regions, the water vapor is high and its change is rapid in Peninsular Malaysia. The quality of the ZPD obtained was compared to the International GNSS Service (IGS) troposphere products; the root mean square (RMS) errors of the GPS-derived ZPD are in the range of 4 to 12 mm. Meanwhile, the large amount of IWV and its variability in Peninsular Malaysia shows a close relationship with the monsoon seasons in this area. Four GPS stations close to radiosonde stations were assessed; the RMS errors of the GPS-derived IWV are 3.447 kg/m2, 3.786 kg/m2, 4.122 kg/m2 and 4.253kg/m2 and their linear correlation coefficients are 0.877, 0.797, 0.851 and 0.849, respectively. This strong correlation shows that there is potential to develop a real-time GPS IWV system in Peninsular Malaysia. This study also reports on an initial development of real-time GPS IWV system known as UTM GPS-MET which was designed starting from data collection, data processing and results dissemination. Several tests on this initial system found that the total time delay in UTM GPS-MET from data collection until the result dissemination is within one minute and 37 seconds, the time period which can support the real-time GPS IWV application.