The Linear Combination of ARIMA Models in Constructing the Areal Rainfall Using Thiessen Polygon Weighted Method

The construction of areal rainfall is crucial aspects in water resource management and disaster risk mitigation. The areal rainfall can be constructed as the linear combination of the actual rainfall in each stasion in the respected area. Thus, the rainfall modeling also be crucial. This research explores the integration of ARIMA models for temporal rainfall analysis and Thiessen polygon method for spatial analysis in contruction of areal rainfall. The ARIMA was used to model monthly cumulative rainfall of eight rain gauge stations in Tasikmalaya area. The areal rainfall was subsequently constructed using the Thiessen polygon method based on actual rainfall, taking into account the spatial heterogeneity of the observation stations. It is obtained that the AR(1) is the appropriate model for the actual rainfall in each rain gauge station. Further analysis showed that a linear combination of AR(1) model from the rain gauge stations resulted in a consistent AR(1) model for areal rainfall. This research successfully provided practical and analytical evidence that a linear combinations of multiple AR(1) models result in a consistent AR(1) model.