Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River

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T1 - Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River

AU - du, Yiheng

AU - Berndtsson, Ronny

AU - An, Dong

AU - Zhang, Linus Tielin

AU - Yuan, Feifei

AU - Hao, Zhenchun

PY - 2019/10/1

Y1 - 2019/10/1

N2 - Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When in phase with the SOI, PDO‐induced precipitation anomalies are magnified. When out‐of‐phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.

AB - Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When in phase with the SOI, PDO‐induced precipitation anomalies are magnified. When out‐of‐phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.

KW - moisture flux

KW - SRYR

KW - PDO

KW - precipitation

KW - SOI

U2 - 10.1002/joc.6332

DO - 10.1002/joc.6332

M3 - Article

JO - International Journal of Climatology

JF - International Journal of Climatology

SN - 1097-0088

M1 - joc.6332

ER -