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首页> 外文期刊>Journal of the Atmospheric Sciences >The influence of idealized heterogeneity on wet and dry planetary boundary layers coupled to the land surface
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The influence of idealized heterogeneity on wet and dry planetary boundary layers coupled to the land surface

机译：理想化的非均质性对耦合到陆地表面的干湿行星边界层的影响

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This manuscript describes numerical experiments investigating the influence of 2-30-km striplike heterogeneity on wet and dry convective boundary layers coupled to the land surface. The striplike heterogeneity is shown to dramatically alter the structure of the convective boundary layer by inducing significant organized circulations that modify turbulent statistics. The impact, strength, and extent of the organized motions depend critically on the scale of the heterogeneity X relative to the boundary layer height z(i). The coupling with the land surface modifies the surface fluxes and hence the circulations resulting in some differences compared to previous studies using fixed surface forcing. Because of the coupling, surface fluxes in the middle of the patches are small compared to the patch edges. At large heterogeneity scales (lambda/z(i) similar to 18) horizontal surface-flux gradients within each patch are strong enough to counter the surface-flux gradients between wet and dry patches allowing the formation of small cells within the patch coexisting with the large-scale patch-induced circulations. The strongest patch-induced motions occur in cases with 4 < lambda/z(i) < 9 because of strong horizontal pressure gradients across the wet and dry patches. Total boundary layer turbulence kinetic energy increases significantly for surface heterogeneity at scales between lambda/z(i) = 4 and 9; however, entrainment rates for all cases are largely unaffected by the striplike heterogeneity.Velocity and scalar fields respond differently to variations of heterogeneity scale. The patch-induced motions have little influence on total vertical scalar flux, but the relative contribution to the flux from organized motions compared to background turbulence varies with heterogeneity scale. Patch-induced motions are shown to dramatically impact point measurements in a free-convective boundary layer. The magnitude and sign of this impact depends on the location of the measurement within the region of heterogeneity.
机译：该手稿描述了数值实验，研究了2-30公里的条状异质性对耦合到陆地表面的干湿对流边界层的影响。通过诱导显着的有组织的循环来改变湍流的统计数据，显示出条状异质性极大地改变了对流边界层的结构。组织运动的影响，强度和程度关键取决于异质性X相对于边界层高度z（i）的大小。与以前的研究相比，与陆地表面的耦合会改变表面通量，从而改变环流，从而导致某些差异。由于耦合，与补丁边缘相比，补丁中间的表面通量较小。在较大的异质性尺度（类似于18的λ/ z（i））下，每个贴片中的水平表面通量梯度足够强，以抵消湿和干贴剂之间的表面通量梯度，从而允许在贴片中形成与细胞共存的小细胞。大规模的斑块引起的循环。在4

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