Time scales of shallow‐to‐deep convective transition associated with the onset of Madden‐Julian Oscillations. Issue 6 (16th March 2016)

• Record Type: Journal Article
• Authors: Xu, Weixin; Rutledge, Steven A.
• Is Part Of: Geophysical research letters. Volume 43:Issue 6(2016)
• Page Start: 2880
• Page End: 2888
• Publication Date: 2016-03-16
• Subjects: Madden‐Julian Oscillation -- shallow‐to‐deep transition -- tropical convection -- shallow convection -- deep convection -- convective moistening; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL068269
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: This study statistically investigates the timing and underlying processes of the shallow‐to‐deep convective transition (SDT) associated with Madden‐Julian Oscillations (MJO) initiation over the Indian Ocean. Results show that SDT periods have a median value of 8–10 days with a wide spectrum of 2–20 days. SDTs lasting 10–20 days occurred nearly 50% of the time, consistent with gradual tropospheric moistening and destabilization leading to MJO initiation as described by the discharge‐recharge theory. Rapid SDTs (<7 days) took place in 25% of the MJOs studied, including two MJOs observed during Dynamics of the MJO in which previous studies suggested large‐scale moistening dominates the local convective moistening during SDT. SDT length is only weakly correlated to MJO amplitude and duration defined by the Real‐Time Multivariate MJO index. SDT length is negatively correlated with the duration of the shallow convective period preceding the SDT but weakly correlated with individual parameters associated with preonset environments. Key Points: Many MJOs have gradual shallow‐to‐deep transitions consistent with convective moistening time scale Rapid transitions (one week) with convective outbreak are not rare (25% of the time) Time scale of shallow‐to‐deep transition is negatively correlated with duration of suppressed period