Climatology of landfalling atmospheric rivers and its attribution to extreme precipitation events over Yangtze River Basin

Atmospheric rivers (ARs) have been reported to be related to Extreme Precipitation Events (EPEs). Hence, we made an assessment in the Yangtze River Basin (YRB) to understand the nexus between EPEs and ARs since the YRB has frequently encountered flooding. We threshold 6-hly fields of ERA-Interim Integrated Vapor Transport (IVT) based on the 85th percentile and a lower limit of 100 kg/m/s, and check for geometry requirements and other considerations indicative of ARs conditions. Large-scale climate modes were used to examine linkages between the frequency of ARs and the atmospheric circulation system. We recorded 75 EPEs for all 16 heavy precipitation-related flood events that occurred on days when precipitation exceeded 95% of the 3-day moving average from 1985 to 2019. Further, huge moisture transport amounts between 500 and 1000 kg/m/s were recorded some days before these identified events. Consequently, 14,347 ARs were identified, and the statistics showed that the length, width, length-width ratio, IVT, and coherent in IVT direction had medians of 3733 km, 615 km, 6.39, 350 kg/m/s, and 0.89, respectively. During most of the flood events, ARs frequencies were relatively high, with about 24% making landfall on YRB. Moreover, the deviance between the entire mean and mean composites during ARs days for the selected events in their respective study periods were in the range of 1.00-2.37 mm and 10-75 kg/m/s for precipitation and IVT, respectively, which could have resulted in the observed flood events. The positive tendencies of the NINO 3.4 and MeiV.2 indices enhanced ARs activities, thereby leading to more extreme events. The ARs distribution and associated impacts indicate a significant role of ARs in shaping the global hydrological cycle. These results could further bridge the gap to more robust hydro meteorological studies in China.