On trade wind cumulus cold pools

Paquita Zuidema, Zhujun Li, Reginald J. Hill, Ludovic Bariteau, Bob Rilling, Chris Fairall, W. Alan Brewer, Bruce A Albrecht, Jeff Hare

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

Shallow precipitating cumuli within the easterly trades were investigated using shipboard measurements, scanning radar data, and visible satellite imagery from 2 weeks in January 2005 of the Rain in Cumulus over the Ocean (RICO) experiment. Shipboard rainfall rates of up to 2 mm h -1 were recorded almost daily, if only for 10-30 min typically, almost always from clouds within mesoscale arcs. The precipitating cumuli, capable of reaching above 4 km, cooled surface air by 1-2 K, in all cases lowered surface specific humidities by up to 1.5 g kg -1, reduced surface equivalent potential temperatures by up to 6 K, and were often associatedwith shortlived increases in wind speed. Upper-level downdrafts were inferred to explain double-lobed moisture and temperature sounding profiles, as well as multiple inversions in wind profiler data. In two cases investigated further, the precipitating convection propagated fasterwestward than themean surfacewind by about 2-3 m s -1, consistentwith a density current of depth~200 m. In their cold pool recovery zones, the surface air temperatures equilibrated with time to the sea surface temperatures, but the surface air specific humidities stayed relatively constant after initial quick recoveries. This suggested that entrainment of drier air fromabove fully compensated themoistening fromsurface latent heat fluxes. Recovery zone surfacewind speeds and latent heat fluxeswere not higher than environmental values. Nonprecipitating clouds developed after the surface buoyancy had recovered (barring encroachment of other convection). The mesoscale arcs favored atmospheres with higher water vapor paths. These observations differed from those of stratocumulus and deep tropical cumulus cold pools.

Original languageEnglish (US)
Pages (from-to)258-280
Number of pages23
JournalJournal of the Atmospheric Sciences
Volume69
Issue number1
DOIs
StatePublished - Jan 2012

Fingerprint

cold pool
trade wind
cumulus
humidity
air
convection
environmental values
stratocumulus
profiler
potential temperature
latent heat flux
density current
entrainment
satellite imagery
buoyancy
water vapor
surface temperature
sea surface temperature
air temperature
wind velocity

Keywords

  • Atmosphere-ocean interaction
  • Boundary layer
  • Cumulus clouds
  • Instrumentation/sensors
  • Mesoscale processes
  • Small scale processes

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Zuidema, P., Li, Z., Hill, R. J., Bariteau, L., Rilling, B., Fairall, C., ... Hare, J. (2012). On trade wind cumulus cold pools. Journal of the Atmospheric Sciences, 69(1), 258-280. https://doi.org/10.1175/JAS-D-11-0143.1

On trade wind cumulus cold pools. / Zuidema, Paquita; Li, Zhujun; Hill, Reginald J.; Bariteau, Ludovic; Rilling, Bob; Fairall, Chris; Brewer, W. Alan; Albrecht, Bruce A; Hare, Jeff.

In: Journal of the Atmospheric Sciences, Vol. 69, No. 1, 01.2012, p. 258-280.

Research output: Contribution to journalArticle

Zuidema, P, Li, Z, Hill, RJ, Bariteau, L, Rilling, B, Fairall, C, Brewer, WA, Albrecht, BA & Hare, J 2012, 'On trade wind cumulus cold pools', Journal of the Atmospheric Sciences, vol. 69, no. 1, pp. 258-280. https://doi.org/10.1175/JAS-D-11-0143.1
Zuidema P, Li Z, Hill RJ, Bariteau L, Rilling B, Fairall C et al. On trade wind cumulus cold pools. Journal of the Atmospheric Sciences. 2012 Jan;69(1):258-280. https://doi.org/10.1175/JAS-D-11-0143.1
Zuidema, Paquita ; Li, Zhujun ; Hill, Reginald J. ; Bariteau, Ludovic ; Rilling, Bob ; Fairall, Chris ; Brewer, W. Alan ; Albrecht, Bruce A ; Hare, Jeff. / On trade wind cumulus cold pools. In: Journal of the Atmospheric Sciences. 2012 ; Vol. 69, No. 1. pp. 258-280.
@article{44021b0adb4a43f1be53730b15ac17a2,
title = "On trade wind cumulus cold pools",
abstract = "Shallow precipitating cumuli within the easterly trades were investigated using shipboard measurements, scanning radar data, and visible satellite imagery from 2 weeks in January 2005 of the Rain in Cumulus over the Ocean (RICO) experiment. Shipboard rainfall rates of up to 2 mm h -1 were recorded almost daily, if only for 10-30 min typically, almost always from clouds within mesoscale arcs. The precipitating cumuli, capable of reaching above 4 km, cooled surface air by 1-2 K, in all cases lowered surface specific humidities by up to 1.5 g kg -1, reduced surface equivalent potential temperatures by up to 6 K, and were often associatedwith shortlived increases in wind speed. Upper-level downdrafts were inferred to explain double-lobed moisture and temperature sounding profiles, as well as multiple inversions in wind profiler data. In two cases investigated further, the precipitating convection propagated fasterwestward than themean surfacewind by about 2-3 m s -1, consistentwith a density current of depth~200 m. In their cold pool recovery zones, the surface air temperatures equilibrated with time to the sea surface temperatures, but the surface air specific humidities stayed relatively constant after initial quick recoveries. This suggested that entrainment of drier air fromabove fully compensated themoistening fromsurface latent heat fluxes. Recovery zone surfacewind speeds and latent heat fluxeswere not higher than environmental values. Nonprecipitating clouds developed after the surface buoyancy had recovered (barring encroachment of other convection). The mesoscale arcs favored atmospheres with higher water vapor paths. These observations differed from those of stratocumulus and deep tropical cumulus cold pools.",
keywords = "Atmosphere-ocean interaction, Boundary layer, Cumulus clouds, Instrumentation/sensors, Mesoscale processes, Small scale processes",
author = "Paquita Zuidema and Zhujun Li and Hill, {Reginald J.} and Ludovic Bariteau and Bob Rilling and Chris Fairall and Brewer, {W. Alan} and Albrecht, {Bruce A} and Jeff Hare",
year = "2012",
month = "1",
doi = "10.1175/JAS-D-11-0143.1",
language = "English (US)",
volume = "69",
pages = "258--280",
journal = "Journals of the Atmospheric Sciences",
issn = "0022-4928",
publisher = "American Meteorological Society",
number = "1",

}

TY - JOUR

T1 - On trade wind cumulus cold pools

AU - Zuidema, Paquita

AU - Li, Zhujun

AU - Hill, Reginald J.

AU - Bariteau, Ludovic

AU - Rilling, Bob

AU - Fairall, Chris

AU - Brewer, W. Alan

AU - Albrecht, Bruce A

AU - Hare, Jeff

PY - 2012/1

Y1 - 2012/1

N2 - Shallow precipitating cumuli within the easterly trades were investigated using shipboard measurements, scanning radar data, and visible satellite imagery from 2 weeks in January 2005 of the Rain in Cumulus over the Ocean (RICO) experiment. Shipboard rainfall rates of up to 2 mm h -1 were recorded almost daily, if only for 10-30 min typically, almost always from clouds within mesoscale arcs. The precipitating cumuli, capable of reaching above 4 km, cooled surface air by 1-2 K, in all cases lowered surface specific humidities by up to 1.5 g kg -1, reduced surface equivalent potential temperatures by up to 6 K, and were often associatedwith shortlived increases in wind speed. Upper-level downdrafts were inferred to explain double-lobed moisture and temperature sounding profiles, as well as multiple inversions in wind profiler data. In two cases investigated further, the precipitating convection propagated fasterwestward than themean surfacewind by about 2-3 m s -1, consistentwith a density current of depth~200 m. In their cold pool recovery zones, the surface air temperatures equilibrated with time to the sea surface temperatures, but the surface air specific humidities stayed relatively constant after initial quick recoveries. This suggested that entrainment of drier air fromabove fully compensated themoistening fromsurface latent heat fluxes. Recovery zone surfacewind speeds and latent heat fluxeswere not higher than environmental values. Nonprecipitating clouds developed after the surface buoyancy had recovered (barring encroachment of other convection). The mesoscale arcs favored atmospheres with higher water vapor paths. These observations differed from those of stratocumulus and deep tropical cumulus cold pools.

AB - Shallow precipitating cumuli within the easterly trades were investigated using shipboard measurements, scanning radar data, and visible satellite imagery from 2 weeks in January 2005 of the Rain in Cumulus over the Ocean (RICO) experiment. Shipboard rainfall rates of up to 2 mm h -1 were recorded almost daily, if only for 10-30 min typically, almost always from clouds within mesoscale arcs. The precipitating cumuli, capable of reaching above 4 km, cooled surface air by 1-2 K, in all cases lowered surface specific humidities by up to 1.5 g kg -1, reduced surface equivalent potential temperatures by up to 6 K, and were often associatedwith shortlived increases in wind speed. Upper-level downdrafts were inferred to explain double-lobed moisture and temperature sounding profiles, as well as multiple inversions in wind profiler data. In two cases investigated further, the precipitating convection propagated fasterwestward than themean surfacewind by about 2-3 m s -1, consistentwith a density current of depth~200 m. In their cold pool recovery zones, the surface air temperatures equilibrated with time to the sea surface temperatures, but the surface air specific humidities stayed relatively constant after initial quick recoveries. This suggested that entrainment of drier air fromabove fully compensated themoistening fromsurface latent heat fluxes. Recovery zone surfacewind speeds and latent heat fluxeswere not higher than environmental values. Nonprecipitating clouds developed after the surface buoyancy had recovered (barring encroachment of other convection). The mesoscale arcs favored atmospheres with higher water vapor paths. These observations differed from those of stratocumulus and deep tropical cumulus cold pools.

KW - Atmosphere-ocean interaction

KW - Boundary layer

KW - Cumulus clouds

KW - Instrumentation/sensors

KW - Mesoscale processes

KW - Small scale processes

UR - http://www.scopus.com/inward/record.url?scp=84862908659&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84862908659&partnerID=8YFLogxK

U2 - 10.1175/JAS-D-11-0143.1

DO - 10.1175/JAS-D-11-0143.1

M3 - Article

AN - SCOPUS:84862908659

VL - 69

SP - 258

EP - 280

JO - Journals of the Atmospheric Sciences

JF - Journals of the Atmospheric Sciences

SN - 0022-4928

IS - 1

ER -