The Meandering Margin of the Meteorological Moist Tropics

Brian E. Mapes, Eui Seok Chung, Walter M. Hannah, Hirohiko Masunaga, Anthony J. Wimmers, Christopher S. Velden

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Bimodally distributed column water vapor (CWV) indicates a well-defined moist regime in the Tropics, above a margin value near 48 kg m−2 in current climate (about 80% of column saturation). Maps reveal this margin as a meandering, sinuous synoptic contour bounding broad plateaus of the moist regime. Within these plateaus, convective storms of distinctly smaller convective and mesoscales occur sporadically. Satellite data composites across the poleward most margin reveal its sharpness, despite the crude averaging: precipitation doubles within 100 km, marked by both enhancement and deepening of cloudiness. Transported patches and filaments of the moist regime cause consequential precipitation events within and beyond the Tropics. Distinguishing synoptic flows that cross the margin from flows that move the margin is made possible by a novel satellite-based Lagrangian CWV tendency estimate. Climate models do not reliably reproduce the observed bimodal distribution, so studying the moist mode's maintenance processes and the margin-zone air mass transformations, guided by the Lagrangian tendency product, might importantly constrain model moist process treatments.

Original languageEnglish (US)
Pages (from-to)1177-1184
Number of pages8
JournalGeophysical Research Letters
Issue number2
StatePublished - Jan 28 2018


  • bimodality
  • column water vapor
  • convective processes
  • precipitable water
  • regimes
  • tropical convection

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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