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Flattened Moisture Gradients, Trade Wind Weakening, and ITCZ Breakdown Associated with Eddy Moisture Fluxes
  • Ángel F. Adames-Corraliza,
  • Qiao-Jun Lin
Ángel F. Adames-Corraliza
University of Wisconsin System

Corresponding Author:[email protected]

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Qiao-Jun Lin
University of Wisconsin-Madison
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Abstract

A moist static energy budget (MSE)-based transformed Eulerian mean framework is applied to a two-layer model to understand how eddies impact the mean tropical circulation during boreal summer. For fixed sources and sinks of MSE, the mean overturning circulation weakens in proportion to the eddy moisture flux divided by the normalized gross moist stability (NGMS), a measure of the moist static stability. Since the NGMS exhibits values between 0.1-0.2 in the rainy areas of the tropics, the eddy moisture fluxes do not have to be large to flatten the column moisture gradient, weaken the trade winds, and cause ITCZ break down. Based on these findings, it is suggested that the recently-documented convective aggregation-disaggregation cycles are mediated by eddy activity. A comparison of days in which the mean circulation is weak versus those that are strong in ERA5 data are largely in agreement with the theory.
16 Oct 2024Submitted to ESS Open Archive
16 Oct 2024Published in ESS Open Archive