1. Madden‐Julian Oscillation Contributes to the Skewed Intraseasonal PNA in El Niño and La Niña Winters.
- Author
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Zhou, Fang, Jian, Shenghua, Liu, Minghong, and Wang, Run
- Subjects
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ROSSBY waves , *OCEAN , *OSCILLATIONS ,EL Nino ,LA Nina - Abstract
The impact of the Madden‐Julian oscillation (MJO) on the intraseasonal PNA (ISPNA) was investigated and was found to be modulated by the El Niño‐Southern Oscillation (ENSO), which reasonably explains the skewness of the ISPNA during El Niño and La Niña winters. It was shown that the intensity and periodicity of the ISPNA was much stronger and slightly longer in La Niña winters than in the El Niño winters. The phase‐locked association between the ISPNA and MJO indicate that this skewness was controlled by the MJO. The northward Rossby wave activities derived from the tropics associated with the MJO to the subtropical Pacific sector of the ISPNA clarified that the stronger intensity of the MJO convection in the western Pacific during the La Niña winters, as well as the slower eastward propagation of the MJO, led to the asymmetric intensity and period of the ISPNA in the two ENSO phases. Plain Language Summary: While prior studies have revealed that the El Niño‐Southern Oscillation (ENSO) can impact global climate, how ENSO affects the intraseasonal variability of the Pacific‐North American pattern (ISPNA) remains unclear. It was found that the ISPNA was skewed toward a higher intensity and a longer period in the La Niña winters than in the El Niño winters after removing the interfere of winter‐mean PNA. This is quite different from the conventional understanding that the PNA is often stronger during El Niño winters than during La Niña winters because of the asymmetric heating effort of the ENSO. The phase‐locked association between the ISPNA and the Madden‐Julian Oscillation (MJO) indicate that this skewness was controlled by the MJO. The northward Rossby wave activities derived from the tropics to the subtropical Pacific sector of the ISPNA clarified the cause‐and‐effect relationship between the ISPNA and the MJO. The stronger intensity of the MJO convection in the tropical Western Pacific to oceans east of Australia during the La Niña winters, as well as the slower eastward propagation of the MJO, led to the skewness of the stronger intensity and longer period of the ISPNA in the La Niña winters than in the El Niño winters. Key Points: The intraseasonal PNA (ISPNA) was skewed toward a higher intensity and a longer period in the La Niña winters than in the El Niño wintersThe Madden‐Julian Oscillation (MJO) and the ISPNA were found to have a stable phase‐locked relationshipThe differences in the intensity and propagation of the MJO between La Niña and El Niño winters dominantly led to the skewed ISPNA [ABSTRACT FROM AUTHOR]
- Published
- 2024
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