Journal
JOURNAL OF THE ATMOSPHERIC SCIENCES
Volume 75, Issue 12, Pages 4337-4355Publisher
AMER METEOROLOGICAL SOC
DOI: 10.1175/JAS-D-18-0152.1
Keywords
Convection; Madden-Julian oscillation; Cloud resolving models; Intraseasonal variability
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Funding
- NSF [AGS1418309, AGS1418508]
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Recent studies have suggested that the Madden-Julian oscillation is a result of an instability driven mainly by cloud-radiation feedbacks, similar in character to self-aggregation of convection in nonrotating, cloud-permitting simulations of radiative-convective equilibrium (RCE). Here we bolster that inference by simulating radiative-convective equilibrium states on a rotating sphere with constant sea surface temperature, using the cloud-permitting System for Atmospheric Modeling (SAM) with 20-km grid spacing and extending to walls at 46 degrees latitude in each hemisphere. Mechanism-denial experiments reveal that cloud-radiation interaction is the quintessential driving mechanism of the simulated MJO-like disturbances, but wind-induced surface heat exchange (WISHE) feedbacks are the primary driver of its eastward propagation. WISHE may also explain the faster Kelvin-like modes in the simulations. These conclusions are supported by a linear stability analysis of RCE states on an equatorial beta plane.
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