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Abstract This study used radar observations and a high-resolution numerical simulation to explore the interactions between an mesoscale convective system (MCS), cold pool outflows, and atmospheric bores in a non-uniform baroclinic environment. The bores were generated by a nocturnal MCS that occurred on 2–3 June 2017 over the southern North China Plain. The goal of this investigation is to determine how the structure of bores varied within this non-uniform environment and whether and how the bores would maintain the MCS and alter its structure. To the southwest of the MCS, where there was large CAPE and a well-mixed boundary layer, discrete convection initiation occurred behind a single radar fine line (RFL) maintaining the propagation of the MCS. To the southeast of the MCS, multiple RFLs were found suggesting the generation of an undular bore in an environment containing an intense nocturnal stable boundary layer with dry upper layers and little CAPE. Hydraulic and nonlinear theory were applied to the simulation of the MCS revealing that the differences in the bore evolution depended on both the characteristics of the cold pool and the variations in the ambient environment. Thus, the characteristics of the ambient environment and the associated differences in bore structure impacted the maintenance and organization of the MCS. This study implies the importance of an accurate representation of the low-level ambient environment and the microphysics and kinematics within the MCS to accurately simulate and forecast cold pools, the generation and evolution of bores, and their impact on nocturnal MCSs. 

A connection between the quasi‐biennial oscillation (QBO), solar variability, and the short‐term convective climate oscillation, the Madden‐Julian oscillation (MJO), in boreal winter has been found in observational data, yet it is generally lacking in current global climate models (GCMs). A proposed mechanism is changes in tropical lower stratospheric upwelling rates and static stability caused by QBO and solar UV effects on extratropical wave forcing of the stratospheric residual meridional circulation (the Brewer‐Dobson circulation). The extent to which this mechanism, which operates only in boreal winter and enhances similar effects of the QBO‐induced meridional circulation, is simulated in a series of GCMs participating in the Coupled Model Intercomparison Project 6 (CMIP6) is investigated. The models are found to be often lacking complete representation of several elements of the mechanism, with particular issues being QBOs that are westerly biased and weak in the lower stratosphere, insufficient solar or QBO modulation of extratropical wave activity (the Holton‐Tan effect), too weak reductions in equatorial tropopause static stability in response to extratropical wave forcing, and MJOs that in some cases do not respond to these reductions. Through bypassing many of these deficiencies via data selection, it is demonstrated that effects on the MJO that resemble those found in observations (strengthening of the MJO following early winter sudden stratospheric warmings and during easterly QBO winters) can be simulated by a subset of the models. This supports operation of the proposed mechanism, and points to needed model improvements, although caveats exist and further work is needed.