Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud-Resolving Simulations

Arunchandra S. Chandra, Paquita Zuidema, Steven Krueger, Adam Kochanski, Simon P. de Szoeke, Jianhao Zhang

Research output: Contribution to journalArticle

Abstract

The near-surface characteristics of approximately 300 convective cold pools over the equatorial Indian Ocean are studied using surface meteorological variables from two equatorial Indian Ocean sites, radar imagery, and constrained cloud-resolving simulations. The observed temperature drop at cold pool onset is typically accompanied by a drying and a decrease in moist static energy, signifying air transport from above the boundary layer through precipitation-induced downdrafts. The decrease in the surface water vapor mixing ratio is more pronounced for stronger temperature drops. Composites reveal a slight enhancement in moisture coincident with a slight enhancement in temperature prior to the cold pool frontal temperature drop. The slight enhancements occur prior to a gust of increased surface winds, suggesting that the immediate cause is wind convergence. A statistical analysis combined with a focus on selected case studies is consistent with a view that the strongest cold pools occur in intermediate column water vapor paths with drier midtropospheres. Such conditions are more likely to occur during convectively suppressed phases of the Madden-Julian Oscillation, when cold pool mesoscale organization facilitates the ability of cumulus congestus to reach the middle troposphere. Cold pools thus help explain why tropical cumulus congestus are common. Cloud-resolving simulations capture realistic rain rates and surface wind changes (and thereby surface fluxes). The evolution in the model near-surface moisture field is unrealistic, however, with an erroneous moisture enhancement inside the cold pool edge that is attributed to rain evaporation. This supports a further focus on the model representation of cold pool frontal dynamics and mixing.

Original languageEnglish (US)
JournalJournal of Geophysical Research: Atmospheres
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

cold pool
Indian Ocean
moisture
Moisture
simulation
augmentation
Steam
rain
Rain
water vapor
cumulus
Madden-Julian Oscillation
surface wind
gusts
radar imagery
Temperature
temperature
Troposphere
mixing ratios
troposphere

Keywords

  • cold pools
  • convection
  • DYNAMO
  • Indian Ocean
  • MJO

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology

Cite this

Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud-Resolving Simulations. / Chandra, Arunchandra S.; Zuidema, Paquita; Krueger, Steven; Kochanski, Adam; de Szoeke, Simon P.; Zhang, Jianhao.

In: Journal of Geophysical Research: Atmospheres, 01.01.2018.

Research output: Contribution to journalArticle

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