Seasonal and annual variations of the GPS-based precipitable water vapor over Sumatra, Indonesia

Abstract

This study investigates the spatial distribution of seasonal and annual as well as semi-annual variations of the precipitable water vapor (PWV) over Sumatra Island, Indonesia, as revealed from a dense network of the Global Positioning System (GPS) receivers. We have analyzed the GPS-based PWV time series at 57 stations during the period of 2004 to 2020, and we revealed some features that have not yet been reported in detail by previous investigators using rainfall data. A notable feature is the presence of the seasonal PWV gradient in the northwest-southeast direction, which exist all times of the year. This gradient represents the annual migration of the Asian-Australian monsoon system, which migrates back and forth in the northwest-southeast direction. In addition, this gradient can also show the periodic changes between the wet and dry seasons over the region. The other feature is the presence of a clear demarcation line around the latitude of 2oS, separating Sumatra Island into the annual and semi-annual regimes. While the semi-annual variation tends to be concentrated in the northern side of 2oS, the annual one dominates the region in the southern side of 2oS. It is also revealed that the stations near the demarcation line are most likely to receive rainfall for most of the year.