Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Regional MJO Modulation of Northwest Pacific Tropical Cyclones Driven by Multiple Transient Controls

TitleRegional MJO Modulation of Northwest Pacific Tropical Cyclones Driven by Multiple Transient Controls
Publication TypeJournal Article
Year of Publication2020
JournalGeophysical Research Letters
Abstract / Summary

The Madden‐Julian Oscillation (MJO) is widely acknowledged for its ability to modulate Northwest Pacific tropical cyclones (TCs) but a complete understanding of the underlying mechanisms remains uncertain. Beyond established effects of the MJO's relative humidity envelope, other dynamical factors have recently been invoked via new genesis potential indices and high‐resolution modeling studies. Here we revisit the ability of the MJO to modulate West Pacific TCs through a quasi‐explicit cyclone downscaling strategy driven by composited observations, paired later with a genesis index to investigate regional drivers of modulation. We reveal two distinct spatial modes of TC modulation in which the MJO's dynamic and thermodynamic effects act in tandem to increase TCs. In the South China Sea for instance, shear reductions associated with the MJO's circulation lead to increasing potential intensity ahead of the arrival of a positive humidity anomaly, all of which combine for an extended period of cyclogenesis favorability.

URLhttp://dx.doi.org/10.1029/2020gl087148
DOI10.1029/2020gl087148
Journal: Geophysical Research Letters
Year of Publication: 2020
Publication Date: 05/2020

The Madden‐Julian Oscillation (MJO) is widely acknowledged for its ability to modulate Northwest Pacific tropical cyclones (TCs) but a complete understanding of the underlying mechanisms remains uncertain. Beyond established effects of the MJO's relative humidity envelope, other dynamical factors have recently been invoked via new genesis potential indices and high‐resolution modeling studies. Here we revisit the ability of the MJO to modulate West Pacific TCs through a quasi‐explicit cyclone downscaling strategy driven by composited observations, paired later with a genesis index to investigate regional drivers of modulation. We reveal two distinct spatial modes of TC modulation in which the MJO's dynamic and thermodynamic effects act in tandem to increase TCs. In the South China Sea for instance, shear reductions associated with the MJO's circulation lead to increasing potential intensity ahead of the arrival of a positive humidity anomaly, all of which combine for an extended period of cyclogenesis favorability.

DOI: 10.1029/2020gl087148
Citation:
Fowler, M, and M Pritchard.  2020.  "Regional MJO Modulation of Northwest Pacific Tropical Cyclones Driven by Multiple Transient Controls."  Geophysical Research Letters.  https://doi.org/10.1029/2020gl087148.