Surface Moisture Exchange Under Vanishing Wind in Simulations of Idealized Tropical Convection

Under radiative‐convective equilibrium (RCE), surface moisture fluxes drive convection, while convection‐driven winds regulate surface fluxes. Most simulations of RCE do not resolve the boundary‐layer turbulence that drives near‐surface winds due to too coarse grid spacing and instead parameterize i...

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Bibliographic Details
Published in:Geophysical research letters 2019-11, Vol.46 (22), p.13602-13609
Main Authors: Mol, Wouter B., Heerwaarden, Chiel C., Schlemmer, Linda
Format: Article
Language:English
Subjects:
Aggregation
Computation
Computer simulation
Convection
Evaporation
Fluctuations
Fluxes
Heat exchange
Large‐eddy simulation
Moisture
Moisture flux
Radiation
Radiative‐convective equilibrium
Simulation
Spatial distribution
Surface fluxes
Surface wind
Tropical climate
Tropical convection
Turbulence
Wind
Wind speed
Winds
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Summary:Under radiative‐convective equilibrium (RCE), surface moisture fluxes drive convection, while convection‐driven winds regulate surface fluxes. Most simulations of RCE do not resolve the boundary‐layer turbulence that drives near‐surface winds due to too coarse grid spacing and instead parameterize its effects by enforcing a minimum wind speed in the computation of the ocean‐atmosphere exchange. We show from RCE simulations with fully resolved boundary‐layer turbulence that capturing wind dynamics at low speeds impacts the spatially averaged surface moisture flux, as well as its spatial distribution. A minimum wind speed constraint of only 1 m s−1 leads to ∼10% increase in spatially averaged surface flux in the evolution towards RCE and reduces the surface flux differences between windy and calm regions with more than a factor of two. Hence, the ability of simulations to let wind vanish is key in representing the wind‐induced surface heat exchange feedback and is potentially important in convective self‐aggregation. Key Points Vanishing wind plays a key role in setting the magnitude and spatial distribution of surface moisture fluxes in RCE Surface‐flux formulations imposing a minimum wind artificially enhance fluxes and suppress spatial variability Surface‐flux feedback in RCE studies could be underestimated if models impose minimum wind
ISSN:0094-8276
1944-8007
DOI:10.1029/2019GL085047