[대기] [기상기후세미나] 백승윤 박사 (University of Chicago)
일시 : 2026-09-17(목) 13:30 ~ 14:30
연사 : 백승윤 박사
소속 : University of Chicago
문의 : 02-880-6723
장소 : 501동 1층 목암홀
Title: Convective Self-Aggregation Disrupts QBO-like Oscillation in Two-Dimensional Radiative-Convective Equilibrium Simulations
Abstract: Idealized radiative-convective equilibrium (RCE) simulations spontaneously generate two distinct forms of self-organization: convective self-aggregation (CSA), the clustering of convection into moist and dry regions, and a quasi-biennial-oscillation-like (QBO-like) stratospheric wind oscillation driven by resolved gravity waves. Although both phenomena emerge from the same minimal, unforced setup, whether and how they interact has received little attention. Here, we show that CSA disrupts the QBO-like oscillation using two-dimensional RCE simulations with tropospheric wind nudging. The strength of the radiative feedback driving CSA is controlled by a scaling parameter a ranging from zero to two. CSA emerges once a reaches 0.75 and intensifies as a increases. As CSA intensifies, the QBO-like oscillation weakens because the zonal-mean momentum flux carried by resolved gravity waves declines. This flux is controlled by the spectral properties of convective heating. A linear two-dimensional Boussinesq theory shows that the flux generated by a given spectral component of heating is maximized at the resonance frequency and vanishes as the frequency approaches zero. The convective heating spectrum shifts toward lower wavenumber and frequency as CSA strengthens. This shift moves the heating away from resonance and leads to the weakening of the momentum flux, which in turn disrupts the QBO-like oscillation. The additional simulations without tropospheric wind nudging show that suppressing CSA restores the QBO-like oscillation. These results identify convective organization as a mechanism that can suppress QBO-like variability, linking two forms of self-organization and offering a candidate explanation for observed QBO disruptions.
Abstract: Idealized radiative-convective equilibrium (RCE) simulations spontaneously generate two distinct forms of self-organization: convective self-aggregation (CSA), the clustering of convection into moist and dry regions, and a quasi-biennial-oscillation-like (QBO-like) stratospheric wind oscillation driven by resolved gravity waves. Although both phenomena emerge from the same minimal, unforced setup, whether and how they interact has received little attention. Here, we show that CSA disrupts the QBO-like oscillation using two-dimensional RCE simulations with tropospheric wind nudging. The strength of the radiative feedback driving CSA is controlled by a scaling parameter a ranging from zero to two. CSA emerges once a reaches 0.75 and intensifies as a increases. As CSA intensifies, the QBO-like oscillation weakens because the zonal-mean momentum flux carried by resolved gravity waves declines. This flux is controlled by the spectral properties of convective heating. A linear two-dimensional Boussinesq theory shows that the flux generated by a given spectral component of heating is maximized at the resonance frequency and vanishes as the frequency approaches zero. The convective heating spectrum shifts toward lower wavenumber and frequency as CSA strengthens. This shift moves the heating away from resonance and leads to the weakening of the momentum flux, which in turn disrupts the QBO-like oscillation. The additional simulations without tropospheric wind nudging show that suppressing CSA restores the QBO-like oscillation. These results identify convective organization as a mechanism that can suppress QBO-like variability, linking two forms of self-organization and offering a candidate explanation for observed QBO disruptions.
