The Southern Oscillation (ENSO) is a recurrent climate pattern characterized by variations in the temperature of waters in the central and eastern tropical Pacific Ocean.
ENSO consists of two extreme phases, El Niño and La Niña, which correspond to warming and cooling anomalies on the ocean surface. Between these phases, there is a third phase known as ENSO-neutral. Depending on the location of the maximum anomalies, ENSO can be further classified into Eastern Pacific ENSO, which is associated with maximum anomalies in the eastern equatorial Pacific, and Central Pacific ENSO, which has maximum anomalies in the central equatorial Pacific. In recent decades, Central Pacific ENSO has occurred more frequently.
Meanwhile, the Northeast China cold vortex (NCCV), a crucial cyclonic circulation system in Northeast Asia, has significant effects on weather and climate anomalies in central and eastern China. The relationship between NCCV and ENSO is of great interest.
In a recent study conducted by researchers from Nanjing University of Information Science and Technology, China, it was found that late-summer NCCVs can be greatly influenced by previous-winter ENSO. El Niño (La Niña) is associated with weak (strong) NCCV intensity. The findings of this research have been published in the journal Atmospheric and Oceanic Science Letters.
A strong correlation exists between ENSO and NCCV, which is believed to be closely tied to the intensity and type of ENSO. Eastern Pacific-type El Niño tends to weaken the NCCV, while La Niña strengthens it. Additionally, the Indian Ocean basin mode, another mode of sea surface temperature anomalies, plays a crucial role in this modulation mechanism. This mode is passive in response to ENSO and can persist until late summer after the ENSO signal has decayed. The teleconnection patterns triggered by this mode create a conducive background circulation system for NCCV generation. However, the effect on NCCV generation is less apparent during Central Pacific-type El Niño and ENSO-neutral years due to the weak signal from the Indian Ocean.
“Our study has shown that late-summer NCCVs can be significantly influenced by previous-winter ENSO, particularly in terms of background circulation, which contributes to the average NCCV intensity. However, the variations in NCCV location, frequency, number of days, intensity, and pathway are all crucial factors in weather and climate anomalies. Future research should focus on the influence of external forcings on the multi-scale evolution of NCCVs and the underlying physical mechanisms,” explains Dr. Zhou, the corresponding author of the study.
More information: Shuo Han et al, Modulation of the late summer Northeast China cold vortex by previous-winter ENSO, Atmospheric and Oceanic Science Letters (2023). DOI: 10.1016/j.aosl.2023.100371
Citation: Researchers reveal how a key weather system in Northeast China is modulated by El Niño (2023, June 21) retrieved 21 June 2023 from https://phys.org/news/2023-06-reveal-key-weather-northeast-china.html
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