Deep convection and column water vapor over tropical land versus tropical ocean: A comparison between the amazon and the tropical Western Pacific

Kathleen A. Schiro, J. David Neelin, David K. Adams, Benjamin R. Lintner

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

The relationships between the onset of tropical deep convection, column water vapor (CWV), and other measures of conditional instability are analyzed with 2 yr of data from the DOE Atmospheric Radiation Measurement (ARM) Mobile Facility in Manacapuru, Brazil, as part of the Green Ocean Amazon (GOAmazon) campaign, and with 3.5 yr of CWV derived from global positioning system meteorology at a nearby site in Manaus, Brazil. Important features seen previously in observations over tropical oceans-precipitation conditionally averaged by CWV exhibiting a sharp pickup at high CWV, and the overall shape of the CWV distribution for both precipitating and nonprecipitating points-are also found for this tropical continental region. The relationship between rainfall and CWV reflects the impact of lower-free-tropospheric moisture variability on convection. Specifically, CWV over land, as over ocean, is a proxy for the effect of free-tropospheric moisture on conditional instability as indicated by entraining plume calculations from GOAmazon data. Given sufficient mixing in the lower troposphere, higher CWV generally results in greater plume buoyancies through a deep convective layer. Although sensitivity of buoyancy to other controls in the Amazon is suggested, such as boundary layer and microphysical processes, the CWV dependence is consistent with the observed precipitation onset. Overall, leading aspects of the relationship between CWV and the transition to deep convection in the Amazon have close parallels over tropical oceans. The relationship is robust to averaging on time and space scales appropriate for convective physics but is strongly smoothed for averages greater than 3 h or 2.5°.

Original languageEnglish (US)
Pages (from-to)4043-4063
Number of pages21
JournalJournal of the Atmospheric Sciences
Volume73
Issue number10
DOIs
StatePublished - 2016

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Keywords

  • Amazon region
  • Atm/ocean structure/ phenomena
  • Circulation/ dynamics
  • Convection
  • Geographic location/entity
  • Physical meteorology and climatology
  • Precipitation
  • Tropics
  • Water vapor

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