Spring Barrier to the MJO Eastward Propagation. Issue 13 (1st July 2020)

• Record Type: Journal Article
• Authors: Li, Kuiping; Yu, Weidong; Yang, Yang; Feng, Lin; Liu, Shouhua; Li, Lili
• Is Part Of: Geophysical research letters. Volume 47:Issue 13(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-07-01
• Subjects: MJO -- Maritime Continent -- barrier; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL087788
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The Maritime Continent (MC) often exerts barrier effect on the eastward propagation of the Madden‐Julian Oscillation (MJO), and the strongest (weakest) effect occurs in spring (winter). After passing over the MC, the MJO slightly weakens by approximately 10% in winter and it sharply decays by more than 50% in spring. The physics for this spring barrier are understood from the perspective of the frictionally coupled Kelvin‐Rossby wave theory. In spring, the abrupt reduction in the boundary layer moisture convergence that occurs at the MC causes the decoupling of the Kelvin‐Rossby wave packet associated with the MJO: Kelvin waves emit from the major convection, while Rossby wave component rapidly decays in the Indian Ocean. An intermediate atmospheric model involving both the fundamental dynamics of the frictionally coupled Kelvin‐Rossby wave theory and the mean states confirms that the spring barrier is determined primarily by the mean surface moisture, particularly by its zonal distribution. Plain Language Summary: Madden‐Julian Oscillation (MJO) has been considered as the major source of subseasonal predictability. However, one of the largest uncertainties in MJO simulations and predictions is the complexity of MJO behavior around the Maritime Continent. The MJO usually weakens as it propagates across the Maritime Continent; this phenomenon is known as the barrier effect. In this paper, a distinct seasonal difference is revealed regarding the barrier effect, wherein the strongest (weakest) effect occurs in spring (winter). The physics responsible for the strongest spring barrier are described based on both observation and model. The results indicate that the spring barrier to the MJO eastward propagation is determined primarily by the zonal distribution of the mean surface moisture. This improved understanding of the spring MJO potentially benefits studies of the climate systems, for example, the Asian monsoon and the El Niño‐Southern Oscillation. Key Points: MJO suffers from the strongest barrier effect at the Maritime Continent in spring The physics for the spring barrier lie in the decoupling of the Kelvin‐Rossby wave packet associated with the spring MJO MJO spring barrier is determined primarily by the zonal distribution of mean surface moisture