Extreme precipitation variability across the Lancang-Mekong River Basin during 1952–2015 in relation to teleconnections and summer monsoons

The Lancang-Mekong River Basin (LMRB) is home to ~70 million people whose life and livelihood are mostly dependent upon precipitation as the primary freshwater source. Hence, identifying potential oceanic–atmospheric drivers of regional precipitation variability is becoming increasingly important for the sustainable development of the LMRB. This study first investigated spatio-temporal variability and trends in extreme precipitation characteristics (in terms of intensity, frequency, and duration) throughout the LMRB during 1952–2015, using gauge-based gridded daily precipitation time series. Then, the associations between the historical extreme precipitation characteristics and seven teleconnection and five summer monsoon indices were explored. On the basin scale, no statistically significant (p <.05) trends were detected in annual extreme precipitation intensity, frequency, and duration indices. The number of wet days (R1mm) significantly increased in both the Mekong River Basin (MRB) and the Lancang River Basin (LRB), predominantly leading to longer wet spells in these two sub-basins. Spatially, the relatively high extreme precipitation intensity and frequency indices, as well as consecutive wet days (CWD), significantly increased in the south, east, and northwest of MRB, while decreased in the west of MRB and the north of LRB. The intensity and frequency of historical extreme precipitations over the LMRB were most significantly correlated with the East Asian Summer Monsoon Index, North Atlantic Oscillation, and East Pacific/North Pacific pattern. However, the wet/dry spells showed the strongest associations with the Atlantic Multi-decadal Oscillation/the Southern Oscillation Index on the interannual/decadal time scales (3–4/8–15 years) during 1986–1999/1968–2002, respectively.