QBO-like Oscillation in a Three-Dimensional Minimal Model Framework of the Stratosphere–Troposphere Coupled System

抄録

We present a three-dimensional minimal model that produces a self-sustained oscillation reminiscent of the quasi-biennial oscillation (QBO) in a radiative–moist convective quasi-equilibrium state. The computational domain is rectangular (640 km × 160 km) with doubly periodic boundary conditions. After initial transient time, an oscillation with a period of about 300 days emerges in the stratosphere, both in the domain-averaged zonal wind and meridional wind. A synchronization of the zonal and meridional winds is observed and is characterized as an anti-clockwise rotation of a skewed spiral feature with height in the mean horizontal wind vectors. The QBO-like wind oscillations penetrate into the troposphere. Modulation of tropospheric temperature anomalies and precipitation occurs with an irregular period of about 100 days, in which heavy precipitation is associated with positive temperature anomalies. The simulation reveals three types of precipitation patterns: isolated quasi-stationary type clusters, fast-moving back-building type and squall-line type patterns. The quasi-stationary type is newly identified in this three-dimensional model. Intermittent self-organization of convective systems into quasi-stationary type and transition back to the fast-moving back-building type or squall-line type are fundamental characteristics of self-aggregation in the three-dimensional model.