The Roles of Westward-Propagating Waves and the QBO in Limiting MJO Propagation

Journal Article · Thu Sep 15 00:00:00 EDT 2022 · Journal of Climate

DOI:https://doi.org/10.1175/JCLI-D-21-0691.1· OSTI ID:1885870

Huang, Kai  ^[1]; Pegion, Kathleen ^[1]

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1. a Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, Virginia

Abstract A recent study categorized the Madden–Julian oscillation (MJO) during boreal winter season into four types called stand, jump, slow, and fast MJO. This study focuses on the stand and jump MJO. Based on whether their convection penetrates the Maritime Continent (MC), stand and jump MJOs are seen as non-penetrating (NP) MJOs, while the other two are seen as eastward-penetrating (EP) MJOs. Results reveal the relative roles of the westward-propagating wave (WPW), as well as the QBO and ENSO, in limiting MJO propagation. Lack of the premoistening over the southern sea surface of the MC stops NP MJO from penetrating the MC. The active convection of the WPWs hinders the descending branch of the NP MJO circulation and therefore leads to the insufficient meridional advective moistening over the southern sea surface of the MC. The independent convection over the Pacific for jump MJOs is influenced by a combined effect of the QBO and ENSO. The tropopause instability induced by the MJO is found to significantly decouple from its convection over the Pacific in westerly QBO (QBOW) winters more than in easterly QBO (QBOE) winters. For jump MJOs, the independent convection over the central Pacific comes from local WPWs whose amplification and further development into deep convection are correlated to jump the MJOs’ decoupled tropopause instability. For stand MJOs, however, the seasonal-mean La Niña–like cool SST anomalies weaken the WPW activity over the central Pacific and confine WPWs within the western Pacific. Therefore, the decoupled tropopause instability of stand MJOs is out phase of WPWs and fails to induce an independent convection over the central Pacific.

• Research Organization: Univ. of Miami, FL (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0019433
• OSTI ID: 1885870
• Alternate ID(s): OSTI ID: 1980932
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Vol. 35 Journal Issue: 18; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Meteorology & Atmospheric Sciences
Madden-Julian oscillation
Quasibiennial oscillation
Intraseasonal variability