Spatiotemporal characteristics of precipitation concentration over the Greater Mekong Subregion and the potential association with large-scale climate factors

The study area is the Greater Mekong Subregion (GMS), including Yunnan province of Southwest China, and Myanmar, Laos, Thailand, Cambodia, Vietnam. The spatiotemporal characteristics and potential climate drivers of precipitation concentration (PC) during 1981–2020 over the GMS are investigated in the study. PC is an important indicator that can reflect the extent of annual or seasonal precipitation in a region unevenly distributed and concentrated over time, and can also denote the period when the maximum precipitation occurs. Three PC indicators are examined including the precipitation concentration index (PCI), precipitation concentration degree (PCD), and precipitation concentration period (PCP). These three PC indicators present significantly interannual and interdecadal variations, with a distinct climatic feature of "concentrated gets more concentrated and earlier, and uniform gets more uniform and later" in the spatial distribution. These PC variations are strongly associated with changes in extreme precipitation over the GMS. More uniform precipitation distribution and earlier concentration period are associated with a significant increase in the frequency and intensity of extreme precipitation in areas of the GMS and vice versa. Further analysis indicates that the El Niño-Southern Oscillation on the interannual timescale and the Interdecadal Pacific Oscillation/Pacific Decadal Oscillation on the interdecadal timescale are the dominant climate drivers for PC variations over the GMS. • Precipitation concentration over the GMS variates on multiple timescales. • “Concentrated gets more concentrated, uniform gets more uniform” is evident. • Climate drivers are strongly associated with Precipitation concentration.