Abstract
The Asian-Pacific Oscillation (APO) plays an important role in precipitation in Central Eastern China (CEC). This study analyzed observational and reanalysis data to investigate CEC precipitation during autumn (1960–2016) and its association with the APO. The APO index (APOI) was redefined, and an autumn CEC precipitation index (CECPI) was calculated to elucidate the relationship between the APO and CEC precipitation. Significant positive correlation (correlation coefficient: 0.60) was found between the APOI and CECPI. Further analysis revealed anomalous southerly winds at 850 hPa over CEC when the APO was strong, which corresponded to anomalous strengthened (weakened) sea level pressure and increased 500-hPa geopotential height over Asia (the Pacific), together with strong meridional shear of the East Asian jet. This configuration is conducive to transportation of warm moist air to CEC during strong APOI years (SAY), but the effect is much diminished during weak APOI years. Moreover, strengthening of both the Walker Circulation of the tropical Pacific and the anomalous upward movement (and convergence) over the Western Pacific (WP) observed during SAY is also conducive to the formation of precipitation in CEC. A possible physical explanation for the close association of the APO with tropical circulation changes is that decreased (increased) sea surface temperature in the tropical eastern Pacific (WP and extratropical Pacific) is beneficial for stimulating a strong APO teleconnection pattern, which further affects precipitation in CEC by strengthening the connection between tropical and subtropical regions.
Highlights
Introduction e Fifth AssessmentReport of the Intergovernmental Panel on Climate Change warns that increased uncertainty regarding the future supply of fresh water under the conditions of global warming could have serious socioeconomic impacts. erefore, the study of global precipitation change is a research topic recognized as becoming increasingly important
Results show that precipitation is highly correlated with the APO index (APOI) over Central Eastern China (CEC; 28°–38°N, 100°–122°E), with a correlation coefficient of ≥0.4 observed in autumn
Investigation of the relationship between the APOI and precipitation in China revealed that the Asian-Pacific Oscillation (APO) is correlated significantly and positively with CEC precipitation in autumn during 1960–2016 with a correlation coefficient of 0.60
Summary
Introduction e Fifth AssessmentReport of the Intergovernmental Panel on Climate Change warns that increased uncertainty regarding the future supply of fresh water under the conditions of global warming could have serious socioeconomic impacts. erefore, the study of global precipitation change is a research topic recognized as becoming increasingly important. With the socioeconomic boom in China during recent decades, precipitation-related disaster losses are due to abundant rainfall in summer and increasingly to anomalies of autumn precipitation. Most previous related research has focused mainly on the summertime precipitation that accompanies the East Asian Summer Monsoon [3, 4, 5], whereas the precipitation received in autumn has been somewhat overlooked. Both the Chinese government and the academic community have begun to explore the anomalies of autumn precipitation, including the variation characteristics and related atmospheric circulation mechanisms. Other studies have shown that certain oscillation patterns (e.g., the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO)) can play a crucial role in modulation of regional-scale autumn precipitation over China [11,12,13,14]
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