Surface-based microwave humidity retrievals over the equatorial Indian Ocean: Applications and challenges

Jianhao Zhang, Paquita Zuidema, David D. Turner, Maria P. Cadeddu

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

The interactions between equatorial convection and humidity as a function of height, at a range of time scales, remain an important research frontier. The ability of surface-based microwave radiometry to contribute to such research is assessed using retrievals of the vertical structure of atmospheric humidity above the equatorial Indian Ocean, developed as part of the Dynamics of Madden-Julian Oscillation field campaign. The optimally estimated humidity retrievals are based on radiances at five frequencies spanning 20-30 GHz and are constrained by radiometer-derived water vapor paths that compare well to radiosonde values except in highly convective conditions. The moisture retrievals possess a robust 2 degrees of freedom, allowing the atmosphere to be treated as two independent layers. A mean bias of 1 g kg-1 contains a vertical structure that is removed in the assessments. The retrieved moisture profiles are able to capture humidity variability within two layer averages at intraseasonal, synoptic, and daily time scales. The retrieved humidity profiles at hourly scales are qualitatively correct under synoptically suppressed conditions but with an exaggerated vertical bimodality. The retrievals do not match radiosonde profiles within most of the day prior to/after convection. This analysis serves to better delineate applications for radiometers. Radiometers can usefully augment more expensive radiosonde networks for longer-term monitoring given careful cross-instrument calibration. At shorter time scales, a synergism with additional instruments can likely increase the realism of the retrievals.

Original languageEnglish (US)
Pages (from-to)1765-1782
Number of pages18
JournalJournal of Applied Meteorology and Climatology
Volume57
Issue number8
DOIs
StatePublished - Aug 1 2018

Keywords

  • Bayesian methods
  • Intraseasonal variability
  • Microwave observations
  • Remote sensing
  • Soundings
  • Water vapor

ASJC Scopus subject areas

  • Atmospheric Science

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