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Title: Differences between nonprecipitating tropical and trade wind marine shallow cumuli

Journal Article · · Monthly Weather Review
 [1];  [2];  [3]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. The State Univ. of New Jersey, New Brunswick, NJ (United States)
  3. Florida International Univ., University Park, FL (United States)
+ Show Author Affiliations

Marine nonprecipitating cumulus topped boundary layers (CTBL) observed in a tropical and in a trade-wind region are contrasted based on their cloud macro-physical, dynamical, and radiative structures. Data from the Atmospheric Radiation Measurement (ARM) observational site previously operating at Manus Island and data collected during the deployment of ARM Mobile Facility at the island of Graciosa were used in this study. The tropical marine CTBL were deeper, had higher surface fluxes and boundary layer radiative cooling, but lower wind speeds compared 8 to their trade-wind counterparts. The radiative velocity scale was 50-70% of the surface convective velocity scale at both locations, highlighting the prominent role played by radiation in maintaining turbulence in marine CTBLs. Despite greater thicknesses, the chord lengths of tropical cumuli were on average lower than that of trade wind cumuli, and due to lower cloud cover, the hourly averaged (cloudy and clear) liquid water paths of tropical cumuli were lower than the trade-wind cumuli. At both locations ~70% of the cloudy profiles were updrafts, while the averaged amount of updrafts near cloud base stronger than 1 m s-1 was ~22% in tropical cumuli and ~12% in the trade-wind cumuli. The mean in-cloud radar reflectivity within updrafts and mean updraft velocity was higher in tropical cumuli than the trade-wind cumuli. Despite stronger vertical velocities and more amount of strong updrafts, due to lower cloud fraction, the updraft mass-flux was lower in tropical cumuli compared to the trade-wind cumuli. The observations suggest the tropical and trade-wind marine cumulus clouds to differ significantly in their macro-physical and dynamical structure.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States); Rutgers Univ., New Brunswick, NJ (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC02-06CH11357; SC0008584; FG02-08ER64531
OSTI ID:
1248745
Alternate ID(s):
OSTI ID: 1329838
Journal Information:
Monthly Weather Review, Vol. 144, Issue 2; ISSN 0027-0644
Publisher:
American Meteorological SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 7 works
Citation information provided by
Web of Science

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Cited By (2)

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation journal September 2017
Drizzle and Turbulence Below Closed Cellular Marine Stratocumulus Clouds journal June 2019

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Related Subjects

54 ENVIRONMENTAL SCIENCES
cumulus clouds
Atm/ocean structure/phenomena
boundary layer
physical meteorology and climatology
cloud radiative effects
clouds
Cumulus
Climate
Mass flux
Tropical
Atm/Ocean Structure/ Phenomena