Son Jun-Hyeok, Franzke Christian L E, Kim Han-Kyoung, Park Jae-Heung, Chu Jung-Eun
Center for Climate Physics, Institute for Basic Science (IBS), Busan, 46241, Republic of Korea.
Pusan National University, Busan, 46241, Republic of Korea.
Sci Rep. 2024 Sep 27;14(1):22236. doi: 10.1038/s41598-024-73269-z.
The Indian summer monsoon (ISM) rainfall interannual variability is known to be strongly linked to the El-Niño-Southern Oscillation (ENSO). This linear relationship is the primary factor in controlling the interannual variation in ISM precipitation. However, there are many outlier cases, and such deviations pose significant challenges in seasonal prediction over this region. Here we show that such challenges can be attributed to anomalous atmospheric pressure patterns in the Western North Pacific (WNP) region. The anticyclonic circulation anomaly over WNP region causes the easterly wind toward the Indian subcontinent, leading to positive precipitation anomalies with stronger low-level moist convergence, while the cyclonic circulation decreases ISM precipitation. The linear baroclinic model simulation results further support that the WNP circulation pattern can serve as an independent factor for forecasting precipitation over India. The WNP circulation anomaly play the crucial role generating ISM precipitation particularly for July and September. Our study suggests that the role of the WNP circulation anomaly should be carefully considered as the secondary prevailing mechanism on the subseasonal timescale during the boreal summer in addition to the ENSO signal.
印度夏季风（ISM）降水的年际变化与厄尔尼诺-南方涛动（ENSO）密切相关。这种线性关系是控制ISM降水年际变化的主要因素。然而，存在许多异常情况，这些偏差给该地区的季节预测带来了重大挑战。在此我们表明，此类挑战可归因于北太平洋西部（WNP）地区异常的大气压力模式。WNP地区的反气旋环流异常导致东风吹向印度次大陆，引发降水正异常，伴有更强的低层水汽辐合，而气旋环流则减少ISM降水。线性斜压模型模拟结果进一步支持WNP环流模式可作为预测印度降水的一个独立因素。WNP环流异常在产生ISM降水方面起着关键作用，尤其是在7月和9月。我们研究表明，除了ENSO信号外，在北半球夏季的次季节时间尺度上，WNP环流异常的作用应作为次要主导机制予以仔细考虑。
