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

Boundary Layer Height and Buoyancy Determine the Horizontal Scale of Convective Self-Aggregation AbstractOrganized 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. 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 suite of cloud-resolving simulations spanning a wide range of climates. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

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

Journal of the Atmospheric Sciences , Volume 75 (2): 10 – Feb 18, 2018

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References (38)

Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0469
DOI
10.1175/JAS-D-17-0150.1
Publisher site
See Article on Publisher Site

Abstract

AbstractOrganized 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. 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 suite of cloud-resolving simulations spanning a wide range of climates.

Journal

Journal of the Atmospheric SciencesAmerican Meteorological Society

Published: Feb 18, 2018

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