Climatology of monsoonal rainstorm events over the Lower Mekong Region: A regional analysis using a spatiotemporal Object-based rainfall method for GPM-IMERG

Abstract:

The interaction between the Indian summer monsoon (ISM) and East Asian summer monsoon (EASM) make the weather in the Lower Mekong basin region highly dynamic and there are indications of climatic change. From June to October, rainfall storm events trigger landslides and flash floods causing human loss and economic damage. Understanding the dynamics of these events is vital for flood risk management in the region. However, the regional characterization in monsoon environments is challenging due to the localised nature of the storm events. To address this challenge, we use observations from the final version of the Integrated Multi-satellite Retrievals for the Global Precipitation Mission (GPM-IMERG), to analyse the regional climatology over the Lower Mekong Basin region during the monsoon seasons 2014 to 2019. A Spatiotemporal Contiguous Object-based Rainfall Analysis method (ST-CORA) was used to identify the main storm features of the storm events. This method enables a complete description of the storm event in space and time. Storm features include storm duration, maximum extension, total volume and maximum intensity. The results allow for identifying the main population and quantifying the rainfall contribution of storms events classified into short-lived and long-lived categories. Long-lived storm events represent a minority population, however, these events contribute to more than 97% of the total rainfall in the monsoon season. Short-lived events represent more than 80% of the population in the Mekong area. These events are mainly localized over elevated areas upstream the river basin. Further analysis and development are aimed at testing of ST-CORA for near real-time operational storm event tracking over the Lower Mekong Basin region.