Hydroclimatology and Hydrometeorology of Flooding Over the Eastern Tibetan Plateau

The hydroclimatology and hydrometeorology of flooding over the Third Pole region is poorly understood, despite its societal and environmental significance. Here we examine extreme rainfall and flooding over the eastern Tibetan Plateau (TP) based on empirical analyses of long-term, in-situ rainfall and stream gaging observations as well as the ECMWF Reanalysis fields. We develop a flood catalog that consists of 168 extreme rainfall-runoff floods over the eastern TP, and characterize the synoptic conditions for flood-producing storms based on the principal component analysis. We show the transitional pattern form Asian summer monsoons to midlatitude systems as the most frequent synoptic conditions for flooding over the eastern TP. The interplay between complex terrains and moisture transport determines the contrasting flood characteristics (in terms of intensity and spatial pattern) under different synoptic environments. We carry out high-resolution Weather Research and Forecasting modeling analysis for four flood-producing storms over the eastern TP. We highlight the interaction of complex terrains and nocturnal low level jets as the key mesoscale ingredients in dictating a pronounced diurnal cycle of extreme rainfall over the southeastern portion of TP. Our results establish the link between large-scale synoptic environment, mesoscale process, and regional flood hydrology over the eastern TP, and therefore contribute to improved flood risk management practices over the Third Pole region under a changing climate.