An Analysis of the Effect of Topography on the Martian Hadley Cells
An Analysis of the Effect of Topography on the Martian Hadley Cells
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地形对火星哈德来环流影响的分析
DOI：
10.1175/2009jas3130.1
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发表时间：
2010
影响因子：
3.1
通讯作者：
R. J. Wilson
中科院分区：
文献类型：
--
作者：
A. Zalucha;R. A. Plumb;R. J. Wilson
之前对火星大气环流模型(MGCM)的研究表明，火星地形的南北坡度导致了哈德利环流在春分和年均值上的不对称。为了定量求解单元的分割线和极地边界的纬度，对Lindzen和Hou的Hadley单元模型进行了修改，以考虑地形。在牛顿松弛作用下，模式被热强迫作用到一个平衡的温度分布，该温度分布是根据恒定季节的日平均太阳强迫计算的。两组平衡温度被认为要么包含对流影响，要么不包含对流影响。当允许对流影响时，坡度分量的存在使分割流线上移，定性上类似于林森和侯的原始(平坦)模型中的季节变化。修正后的模型还证实了坡度的几何效应远小于坡度的热效应对高空辐射对流平衡温度的影响。结果与牛顿弛豫强迫的简单MGCM在相同的平衡温度剖面上进行了比较，除了在冬至附近的极点外，两种模型都符合。辐射-对流强迫的简单MGCM结果也显示了北夏至和北冬至的Hadley环流强度之间的不对称性。北夏至时Hadley环流强度随坡度的增大而减弱，冬至时对其强度影响不大。
Previous work with Mars general circulation models (MGCMs) has shown that the north‐south slope in Martian topography causes asymmetries in the Hadley cells at equinox and in the annual average. To quantitatively solve for the latitude of the dividing streamline and poleward boundaries of the cells, the Hadley cell model of Lindzen and Hou was modified to include topography. The model was thermally forced by Newtonian relaxation to an equilibrium temperature profile calculated with daily averaged solar forcing at constant season. Two sets of equilibrium temperatures were considered that either contained the effects of convection or did not. When convective effects were allowed, the presence of the slope component shifted the dividing streamline upslope, qualitatively similar to a change in season in Lindzen and Hou’s original (flat) model. The modified model also confirmed that the geometrical effects of the slope are much smaller than the thermal effects of the slope on the radiative‐convective equilibrium temperature aloft. The results are compared to a simple MGCM forced by Newtonian relaxation to the same equilibrium temperature profiles, and the two models agree except at the winter pole near solstice. The simple MGCM results for radiative‐ convective forcing also show an asymmetry between the strengths of the Hadley cells at the northern summer and northern winter solstices. The Hadley cell weakens with increasing slope steepness at northern summer solstice but has little effect on the strength at northern winter solstice.