Influence and mechanism of solar radiation intensity on the interdecadal variability of strong Meiyu events during historical periods

Most recent studies on Meiyu over the middle and lower reaches of the Yangtze River (MLRYR) have focused on its interannual variability or the mechanism of certain abnormal events. The influence and physical mechanism of solar radiation intensity on the interdecadal frequency of strong Meiyu events over the MLRYR during historical periods were investigated using reconstructed precipitation data, reconstructed solar radiation data, and model simulation data. First, according to the solar radiation intensity, the Ming and Qing Dynasties (1470–1850) were divided into three periods of strong solar radiation and three periods of weak solar radiation. It was found that during the periods of strong solar radiation, the frequency of strong Meiyu events was significantly higher than that during the periods of weak solar radiation in the reconstructed precipitation data and model simulations. Mechanism analyses show that during the periods of strong solar radiation, the Western Pacific Subtropical High (WPSH) is stronger, and the blocking highs over the middle-high-latitudes are also stronger, which is conducive to the continuous convergence of the southward cold air and the northward warm and humid air flow at the MLRYR. Therefore, a circulation spatial pattern conducive to the occurrence of strong Meiyu events is then induced. The probability distributions of precipitation also show that, during periods of strong solar radiation, changes in circulation patterns cause the probability distribution of precipitation to shift significantly to the right, increasing the probability of strong Meiyu events occurring on the right side of the probability distribution.