Impacts of the Pacific Decadal Oscillation and El Nino-Southern Oscillation on Regional Precipitation Concentration

Exploring the regional precipitation concentration index (PCI) provides profound insights into the distribution patterns of rainfall within a specific area. This study utilised daily precipitation data from Sichuan Province to investigate the spatiotemporal variations of PCI on annual and seasonal scales, as well as its potential relationships with the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO). A modified Mann-Kendall test was employed to identify significant trends in the PCI. Furthermore, this study examined the relationships between the daily concentration index (CID) and the monthly concentration index (CIM), along with their spatiotemporal characteristics. The remote potential relationships between PCI and ENSO/PDO were analysed using cross wavelet transform and correlation test. The results indicate that: (1) A significant positive correlation exists between CID and CIM in the central Sichuan basin (CB) region, while this correlation is not significant in other regions. (2) There is a non-significant decreasing trend in precipitation concentration across Sichuan Province, primarily observed in spring. (3) The spatial and temporal distribution of PCI in Sichuan Province becomes increasingly variable and irregular with decreasing longitude and increasing elevation. (4) The negative impact of ENSO and PDO on annual PCI and autumn PCI significantly diminish from east to west. In summer, the potential negative impact of PDO on Seasonal precipitation concentration index (SPCI) significantly decreases from north to south. This study provides key information to reveal the variations and potential influences of meteorological and hydrological processes in Sichuan Province.