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arXiv 1906.07595astro-ph.EPnlin.CD
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在简化的全球环流模式中比较陆地大气环流体制:II。能量收支和光谱转移

Comparative terrestrial atmospheric circulation regimes in simplified global circulation models: II. energy budgets and spectral transfers

Peter Read, Fachreddin Tabataba-Vakili, Yixiong Wang, Pierre Augier, Erik Lindborg, Alexandru Valeanu, Roland Young

摘要:

利用汉堡大学便携式大学大气模式的简化大气环流模式,探讨了类地大气中可能的全球大气环流模式的能量学。通过改变行星自转速率Ω和施加的赤道到极点温差获得的一系列模拟结果进行了分析,以确定热传输和对时间平均平衡流能量预算的其他贡献。这些都显示了与Ω的明显趋势,对于一个地球大小的行星来说,最强烈的洛伦兹能量循环发生在自转速率大约是现在地球的一半的情况下。KE和APE谱,E_K(n)和E_A(n)(其中n是总球面波数),也显示出明显的趋势与Ω,与n^{-3}拟能占主导地位的频谱附近Ω* = Ω/Ω_E = 1,其中Ω_E是地球的自转速率)和更陡(\sim n^{-5})在纬向平均流中的斜率,对于逆KE级联预期的n^{-5/3}谱几乎没有证据。相反,KE和APE谱变得几乎平坦的尺度大于内部Rossby半径,L_d,并表现出近均分在高波数。在Ω* << 1时,频谱变为由KE主导,其中在大多数波数处E_K(n)\sim 2-3 E_A(n),并且在大多数频谱上斜率为\sim n^{-5/3}。谱通量的计算表明,涡度拟能和APE几乎总是级联的下尺度,无论Ω。然而,对于Ω* \lesssim 1/4,KE级联更复杂,几乎所有波数都有尺度下的传输,主要是水平发散模式。在较高的旋转速率下,KE的传递越来越多地由旋转分量所主导,当尺度大于L_d时,KE的高尺度传递(由涡动-纬向流相互作用所主导)较强,而当尺度小于L_d时,KE的低尺度传递较弱。

英文摘要:

The energetics of possible global atmospheric circulation patterns in an Earth-like atmosphere are explored using a simplified GCM based on the University of Hamburg's Portable University Model for the Atmosphere. Results from a series of simulations, obtained by varying planetary rotation rate Ω with an imposed equator-to-pole temperature difference, were analysed to determine the heat transport and other contributions to the energy budget for the time-averaged, equilibrated flow. These show clear trends with Ω, with the most intense Lorenz energy cycle for an Earth-sized planet occurring with a rotation rate around half that of the present day Earth. KE and APE spectra, E_K(n) and E_A(n) (where n is total spherical wavenumber), also show clear trends with Ω, with n^{-3} enstrophy-dominated spectra around Ω* = Ω/Ω_E = 1, where Ω_E is the rotation rate of the Earth) and steeper (\sim n^{-5}) slopes in the zonal mean flow with little evidence for the n^{-5/3} spectrum anticipated for an inverse KE cascade. Instead, both KE and APE spectra become almost flat at scales larger than the internal Rossby radius, L_d, and exhibit near-equipartition at high wavenumbers. At Ω* << 1, the spectrum becomes dominated by KE with E_K(n) \sim 2-3 E_A(n) at most wavenumbers and a slope \sim n^{-5/3} across most of the spectrum. Spectral flux calculations show that enstrophy and APE are almost always cascaded downscale, regardless of Ω. KE cascades are more complicated, however, with downscale transfers across almost all wavenumbers, dominated by horizontally divergent modes, for Ω* \lesssim 1/4. At higher rotation rates, transfers of KE become increasingly dominated by rotational components with strong upscale transfers (dominated by eddy-zonal flow interactions) for scales larger than L_d and weaker downscale transfers for scales smaller than L_d.

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