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首页> 外文期刊>Journal of the Atmospheric Sciences >A local model for planetary atmospheres forced by small-scale convection
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A local model for planetary atmospheres forced by small-scale convection

机译：小尺度对流强迫的行星大气局部模型

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An equivalent-barotropic fluid on the beta plane, forced at small scales by random stirring and dissipated by linear heat and vorticity drag, is considered as a local model for flow in the weather layer of internally forced planetary atmospheres. The combined presence of beta, a finite deformation scale, and large-scale dissipation produce novel dynamics with possible relevance to the giant gas planets, which are apparently driven by small-scale convective stirring. It is shown that in order for anisotropy to form, one must have beta(epsilonlambda(5)) (-1/3) greater than or equal to 3.9, where epsilon is the (convectively driven) energy generation rate, lambda is the deformation wavenumber, and beta is the Coriolis gradient. The critical value above is not equivalent to the barotropic stability criterion, and numerical simulations demonstrate that anisotropic flow with average zonal velocities that are supercritical with respect to the latter can form. The formation of jets (a different matter) is not implied by the excess of zonal kinetic energy, and is instead sensitive to the relevant stability criterion for the flow geometry at hand. When beta is sufficiently large that anisotropy does form, the flow scale and rms zonal velocity are set by a combination of Rossby wave cascade inhibition, the total energy constraint imposed by the large-scale dissipation, and the partitioning between available potential and kinetic energies. The resulting theory demonstrates that a relatively narrow range of parameters will allow for the formation of anisotropic flow with scale larger than the deformation scale. This is consistent with observations that indicate little separation between the jet scales and deformation scales on Jupiter and Saturn.
机译：在β平面上的等效正压流体，是通过随机搅拌在小范围内强迫作用，并通过线性热和涡旋阻力消散，被认为是内部强迫行星大气天气层中流动的局部模型。 β的存在，有限的变形尺度和大规模的耗散共同产生了可能与巨型气行星有关的新颖动力学，这显然是由小型对流搅拌驱动的。结果表明，要形成各向异性，必须使beta（epsilonlambda（5））（-1/3）大于或等于3.9，其中epsilon是（对流驱动的）能量产生速率，lambda是变形波数，而β是科里奥利梯度。上面的临界值不等于正压稳定性准则，数值模拟表明，可以形成具有平均纬向速度（相对于后者为超临界）的各向异性流。射流的形成（一种不同的物质）不会被过量的区域动能所隐含，而是对当前流动几何学的相关稳定性标准敏感。当β足够大到可以形成各向异性时，流量大小和均方根速度由Rossby波级联抑制，大规模耗散施加的总能量约束以及可用势能和动能之间的分配共同设定。所得理论表明，相对狭窄的参数范围将允许形成规模大于变形尺度的各向异性流。这与在木星和土星上的射流尺度和变形尺度之间几乎没有分离的观察结果一致。

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