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Circulation Response to Fast and Slow MJO Episodes



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  • Journal Title:
    Monthly Weather Review
  • Personal Author:
  • NOAA Program & Office:
  • Description:
    Fast and slow Madden–Julian oscillation (MJO) episodes have been identified from 850- and 200-hPa zonal wind and outgoing longwave radiation (OLR) for 32 winters (16 October–17 March) 1980/81–2011/12. For 26 fast cases the OLR took no more than 10 days to propagate from phase 3 (convection over the Indian Ocean) to phase 6 (convection over the western Pacific). For 8 slow cases the propagation took at least 20 days. Fast episode composite anomalies of 500-hPa height (Z500) show a developing Rossby wave in the mid-Pacific with downstream propagation through MJO phases 2–4. Changes in the frequency of occurrence of the NAO+ weather regime are modest. This Rossby wave is forced by anomalous cooling over the Maritime Continent during phases 2 and 3 (seen in phase-independent wave activity flux). The upper-level anticyclonic response to phase-3 heating is a secondary source of wave activity. The Z500 slow episode composite response to MJO phases 1 and 2 is an enhanced Aleutian low followed by a North American continental high. Following phase 4 the development of an NAO+ like pattern is seen over the Atlantic, transitioning to a strong NAO− pattern by phase 8. A dramatic increase in frequency of the NAO+ weather regime follows phases 4 and 5, while a strong increase in NAO− regime follows phases 6 and 7. The responses to MJO-related heating and cooling over the Indian and western Pacific Oceans in phases 1–4 provide a source for wave activity propagating to North America, augmented by storm-track anomalies.
  • Keywords:
  • Source:
    Monthly Weather Review, 145(5), 1577-1596
  • DOI:
  • Document Type:
    Journal Article
  • Funding:
    Grant no. NA14OAR4310160
  • Rights Information:
    Other
  • Compliance:
    CHORUS
  • Main Document Checksum:
    urn:sha256:036da5c451cd0e55b6f29908f134f676a33101616f93b18ce8c77c547725170d
  • Download URL:
  • File Type:
    Filetype[PDF - 5.30 MB ]
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