The combined influences of Solar Radiation and PDO on Precipitation over Eastern China during the last millennium

In this study, the influences of different PDO phases during strong and weak solar radiation periods on precipitation over eastern China during the last millennium were studied by using four solar irradiance only sensitivity experiments (SSI) and one control experiment (CTRL) from Community Earth System Model - Last Millennium Ensemble (CESM-LME) archive. Results show that there are significant positive (negative) precipitation anomalies over eastern China during the strong (weak) solar radiation periods. However, the precipitation differences between positive PDO and negative PDO phases in the SSI experiments are smaller compared with CTRL. Moreover, there is a dependency relationship between the solar radiation intensities and precipitation differences between positive PDO and negative PDO phases. The mechanism analyses show that southerly wind anomalies continuously increase with solar radiation intensities during the positive PDO phases and result in decreased precipitation anomalies, vice versa. During the positive PDO phases, the continental sea level pressure (SLP) gradient is the dominant factor of the wind anomalies over eastern China. The continental SLP gradient over the mainland of China (north-south) is strengthened with the solar radiation intensities, resulting in the decrease of precipitation over eastern China. While, during the negative PDO phases, the sea-land SLP gradient is the main factor of the wind anomalies. The sea-land SLP gradients decreas with the solar radiation intensities, so the southerly wind and the precipitation over eastern China also increase.