Daily asian-pacific oscillation and associated rainfall anomalies in Central-Northern China and precursory atmospheric signals

Utilizing the Asian-Pacific oscillation (APO) index on a daily scale to gain a comprehensive understanding of summer daily rainfall variations and their underlying physical mechanisms is helpful to improve the accuracy of daily rainfall pattern predictions in central-northern China. To address this, we utilized observational 24-h accumulated rainfall data from China and the reanalysis products from the European Center for Medium-Range Weather Forecast (ECMWF) and investigated the relationship between daily APO, atmospheric circulation, and rainfall in central-northern China on the daily timescale. It delves into the evolution of the daily APO index (DAI) and its connection to atmospheric circulation and rainfall. Corresponding to instances of daily extremely high and low APO, there is a notable intensification in the sea-land thermal contrast and the associated southerly winds, which leads to abundant water vapor and widespread rainfall anomalies in central-northern China. The daily APO signal emerges as an indicator of rainfall events in this region, detectable up to seven days in advance. These findings are in favor of understanding the mechanism for East Asian monsoon and associated rainfall in central-northern China on the daily timescale. • Investigate the relationship between daily Asian-Pacific Oscillation (APO), atmospheric circulation, as well as rainfall on the daily timescale in central-northern China. • Explore the evolution of the daily APO index and its correlation with atmospheric circulation and rainfall. • Propose the daily APO signal serves as a potential indicator for rainfall events. • Demonstrate that the daily APO signal can be detected up to seven days in advance.