Influence factors and mechanisms of 2015-2016 extreme flood in Pearl River Basin based on the WSDI from GRACE

Study region: Pearl River Basin (PRB) has a tropical to subtropical climate in China. Study focus: An unprecedented extreme flood broke out in PRB during 2014-2016 super El Nin & SIM;o period. We construct the water storage deficit index (WSDI) to quantify this extreme flood event. The principal component analysis approach is used to analyze the WSDI in PRB and El Nin & SIM;oSouthern Oscillation (ENSO) and the sea surface temperature (SST) anomaly in the Tropical Indian Ocean (TIOS) to identify the influence factors. Furthermore, the underlying influence mechanisms are explored via correlation analysis. New hydrological insights for the region: The severity of the extreme flood event was 483.11 km3 with a maximum surplus of terrestrial water storage in February 2016 (76.11 km3). The extreme flood was mainly influenced by the super El Nin & SIM;o and enhanced by TIOS. The WSDI is significantly correlated with ENSO and TIOS, for the first and second principal components, the correlation coefficients are 0.90 and 0.41 for ENSO after a 3-month lag, and 0.86 and 0.66 for TIOS after a 2-month lag, respectively. The super El Nin & SIM;o favored the extreme flood event by intensifying the anticyclones over the South China Sea, the Philippine Sea, and the Bay of Bengal, further promoting the attenuation of the South China Sea Monsoon and the westward extension of West Pacific Subtropical High, inducing more moisture transport towards PRB.

Automated summary

By constructing the water storage deficit index (WSDI), the extreme flood event in the Pearl River Basin during the 2014-2016 super El Nin & SIM; o period was analyzed. The results showed that the flood was mainly influenced by the super El Nin & SIM; o and enhanced by the Tropical Indian Ocean sea surface temperature anomaly. The correlation analysis revealed the underlying influence mechanisms.