简单平衡模型中锋生的能量学
Energetics of frontogenesis in simple balanced models
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中文总结 AI 辅助
研究简单平衡模型中亚中尺度锋生的能量学，通过分析经典应变诱导锋生的动能收支，探讨准地转和半地转锋生理论对相关现象的捕捉情况，发现非地转尺度传递有重要作用，未考虑的过程可能影响锋生能量学。
中文摘要 AI 辅助
亚中尺度锋被认为是将动能从地转约束的中尺度涡旋传递到小尺度并耗散的通道。实际原始方程模拟表明，亚中尺度的能量向下传递主要集中在锋面锐化上，气旋侧的辐合起主导作用。本研究探讨简单的准地转（QG）和半地转（SG）锋生理论能捕捉多少这种现象。经典应变诱导锋生的动能收支分析表明，QG和SG锋面都有向下传递。在QG锋生中，锋面变窄的急流由浮力产生驱动，应变场导致的地转向下传递起重要作用。在SG锋生中，非地转跨锋环流加速锋面锐化，非地转平流增强了锋面气旋侧的向下传递，反气旋侧非地转环流发散，动能的非地转尺度传递向上，部分抵消地转向下传递。虽然与实际原始方程模拟模式匹配，但在此考虑的绝热无摩擦理论中，非地转尺度传递虽重要但非主导，这表明这些理论中未考虑的过程可能起重要作用，如混合层湍流可能增强非地转环流及相关的尺度传递偶极子，非地转动量平流在某些情况下也可能很重要。
英文摘要
Submesoscale fronts have been proposed to act as conduits funneling kinetic energy from geostrophically constrained mesoscale eddies down to small scales, where the energy can be dissipated. Realistic primitive-equation simulations suggest that the downscale energy transfer at submesoscales is strongly concentrated in sharpening fronts, with convergence on the cyclonic side playing a dominant role. This study explores how much of this phenomenology can be captured by simple quasi-geostrophic (QG) and semi-geostrophic (SG) theories of frontogenesis. An analysis of the kinetic energy budget of classical strain-induced frontogenesis shows that there is downscale transfer in both QG and SG fronts. In QG frontogenesis, the narrowing jet along the sharpening front is powered by buoyancy production, but geostrophic downscale transfer due to the strain field plays an important role. In SG frontogenesis, where frontal sharpening is accelerated by the ageostrophic cross-frontal circulation, ageostrophic advection enhances this downscale transfer on the cyclonic side of the front, where the surface flow is convergent. On the anticyclonic side, where the ageostrophic circulation is divergent, the ageostrophic scale transfer of kinetic energy is upscale and partially offsets the geostrophic downscale transfer. While matching patterns in realistic primitive-equation simulations, the ageostrophic scale transfers remain important but not dominant in the adiabatic and frictionless theory considered here. This suggests that processes absent from these theories may play an important role. For example, mixed-layer turbulence may enhance the ageostrophic circulation and the associated dipole of scale transfers. The advection of ageostrophic momentum may also be important in some circumstances.
