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Title: Boundary Layer Height and Buoyancy Determine the Horizontal Scale of Convective Self-Aggregation

Journal Article · · Journal of the Atmospheric Sciences
 [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Univ. of California, Davis, CA (United States)
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Organized rainstorms and their associated overturning circulations can self-emerge over an ocean surface with uniform temperature in cloud-resolving simulations. This phenomenon is referred to as convective self-aggregation. Convective self-aggregation is argued to be an important building block for tropical weather systems and may help regulate tropical atmospheric humidity and thereby tropical climate stability. Here the author presents a boundary layer theory for the horizontal scale λ of 2D (x, z) convective self-aggregation by considering both the momentum and energy constraints for steady circulations. This theory suggests that λ scales with the product of the boundary layer height h and the square root of the amplitude of density variation between aggregated moist and dry regions in the boundary layer, and that this density variation mainly arises from the moisture variation due to the virtual effect of water vapor. Furthermore, this theory predicts the following: 1) the order of magnitude of λ is ~2000 km, 2) the aspect ratio of the boundary layer λ/h increases with surface warming, and 3) λ decreases when the virtual effect of water vapor is disabled. These predictions are confirmed using a sui te of cloud-resolving simulations spanning a wide range of climates.

Research Organization:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC); Univ. of California, Berkeley, CA (United States)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1433115
Journal Information:
Journal of the Atmospheric Sciences, Vol. 75, Issue 2; Related Information: © 2018 American Meteorological Society.; ISSN 0022-4928
Publisher:
American Meteorological SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (6)

A budget for the size of convective self‐aggregation journal February 2019
Midwinter Arctic leads form and dissipate low clouds journal January 2020
Observational Relationship Between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization journal December 2018
Self-Aggregation of Deep Convection and its Implications for Climate journal January 2019
The Multiscale Impacts of Organized Convection in Global 2-D Cloud-Resolving Models journal August 2018
Convective Heating Leads to Self‐Aggregation by Generating Available Potential Energy journal September 2019

Figures / Tables (7)

FIG. 1(p. 3)figure FIG. 1
FIG. 2(p. 5)figure FIG. 2
FIG. 3(p. 6)figure FIG. 3
FIG. 4(p. 7)figure FIG. 4
FIG. 5(p. 7)figure FIG. 5
FIG. 6(p. 8)figure FIG. 6
FIG. 7(p. 9)figure FIG. 7

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Related Subjects

54 ENVIRONMENTAL SCIENCES
Atmosphere
Buoyancy
Convection
Boundary layer
Climate change
Cloud resolving models