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We identified regional differences over China of winter temperature response to large volcanic eruptions with different latitudes and seasons from 1956 to 2005, and investigated atmospheric circulations for corresponding spatial patterns of winter temperature anomalies using reanalysis data and simulations by the Community Earth System Model. Both observations and simulations show that spatial patterns of winter temperature anomalies over China are related to the latitudes and seasons of the eruptions. Tropical volcanic eruptions during summer led to winter temperature decreases of 0.4–1.6 °C in eastern China due to the increase of height gradient. Winter volcanic eruptions led to extensive warming over Tibet. Following summer volcanic eruptions at low latitude, there were warm winters in eastern China because of a weak Siberian high. An anomalous southerly wind caused slight warming over most of China following winter eruptions. With the typical "trough–ridge–trough" at high latitude of the Northern Hemisphere, the winter temperature decreased in northeastern China and increased in western China following summer eruptions at mid-latitude. However, temperature generally increased after winter eruptions. For summer eruptions at high latitude, winter temperature showed a coherent decrease over northwest and east-central China due to an intensified Siberian High and East Asian trough. The widespread warming occurred over China because of the meridional circulation between 65°N and 45°N was weaker following winter volcanic eruptions. [ABSTRACT FROM AUTHOR]

Reconstructed hydroclimatic spatial patterns from historical documents, the chronology of El Niño events since 1525, Meiyu (a unique rainy season dominated by the East Asian summer monsoon in eastern China) series since 1736, and a 1000-year control simulation using the Community Earth System Model were used to analyze the occurrence of anomalous summer precipitation patterns over eastern China with El Niño events. The results show that the frequency of the south-flood north-drought during 1525–2005 was significantly higher during El Niño episodes. Specifically, the occurrences of the triple pattern with floods in the Yangtze River Valley but droughts in its north and south (FYRDNS) as well as the dipole pattern with floods in the south but droughts in the north (FSDN) divided by the Yangtze River both increased in El Niño developing years, while the occurrence of FSDN increased in El Niño decaying years. Among 44 severe and extreme Meiyu events over the middle and lower reaches of the Yangtze River in 1736–2016, 75% of events occurred during El Niño episodes. Especially, 80% of extreme Meiyu events occurred in El Niño decaying years. The 1000-year control simulation captured well the reconstructed triple pattern of FYRDNS in developing years and the dipole pattern of FSDN in decaying years, with more noticeable precipitation anomalies for developing years of very strong and extremely strong El Niño events. These results implicated that the El Niño is likely an early signal for the occurrence of the south-flood north-drought over eastern China. [ABSTRACT FROM AUTHOR]

The hydroclimatic patterns in eastern China (EC) over the past millennium, both influenced by solar activity and Pacific decadal oscillation (PDO), are presented based on the climatic reconstructions and simulations. For strong solar activity, a consistent pattern exists where drought appears in the majority of EC initialized from the cold PDO phase, which is related to less moisture caused by the negative East Asia/Pacific-like (EAP-like) pattern and the enhanced western Pacific subtropical high (WPSH). When the initial condition with a neutral or warm PDO phase is set up, there is a tripole-like pattern from north to south, i.e., drought–flood–drought for the neutral PDO phase and flood–drought–flood for the warm PDO phase, which is related to the positive EAP-like pattern with various moisture transportation paths. For weak solar activity, there are dipole-like patterns where drought occurs in the northern part of the Yangtze River and flood appears in the southern part initialized from the cold or warm PDO phase, which is possibly related to the influence of the weakened WPSH. When the initial condition is the neutral PDO phase, there is a tripole-like pattern from north to south (flood–drought–flood) in EC affected by the weakened WPSH and the intensive India–Burma trough. Notably, the vertical velocity anomalies of airflow, representing the vertical moisture transportations, correspond well with the hydroclimatic patterns in EC whenever the various initialization strategies of PDO phases are employed. • Hydroclimatic patterns in eastern China (EC) are related to solar activity and PDO. • A consistent pattern in EC for strong solar period (SS) and cold PDO initial phase. • The tripole-like patterns for SS and the neutral or warm PDO initial phase. • A tripole-like pattern for weak solar period (WS) and neutral PDO initial phase. • The dipole-like patterns for WS and the cold or warm PDO initial phase. [ABSTRACT FROM AUTHOR]