谈哲敏,伍荣生. 2000. 地形上空边界层流中低层锋面结构的理论研究Ⅱ:暖锋、均匀地转流[J]. 气象学报, 58(3):265-277, doi:10.11676/qxxb2000.028
地形上空边界层流中低层锋面结构的理论研究Ⅱ:暖锋、均匀地转流
A THEORTICAL STUDY OF LOW-LEVEL FRONTAL STRUCTURE IN THE BOUNDARY LAYER OVER OROGRAPHY, PART Ⅱ: WARM FRONT AND UNIFORM GEOSTROPHIC FLOW
投稿时间:1997-09-19  修订日期:1999-01-15
DOI:10.11676/qxxb2000.028
中文关键词:  暖锋结构  地形  边界层  动力学
英文关键词:Warm frontal structure  Orography  Boundary layer  Dynamic
基金项目:国家重点基础研究发展规划项目(G1998040907);国家自然科学基金(49735180)
作者单位
谈哲敏 南京大学大气科学系, 南京, 210093 
伍荣生 南京大学大气科学系, 南京, 210093 
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中文摘要:
      利用一个有地形、边界层摩擦作用、简化的二层浅水锋面模型,在理论上研究了地形上空边界层流动中地面暖锋的结构及环流分布特征问题。暖锋的坡度主要取决于其暖域地转流、锋面移速,它随锋面移速增大而减小,这与冷锋特征相反。地形对暖锋坡度的影响作用较小。与无地形作用时相比,静止性暖锋冷域中,位于锋面界面附近的闭合正环流系,当暖锋位于地形上游,其伸展范围增大;当暖锋位于迎风坡时,其伸展范围缩小,中心位置上抬;锋面移至背风坡时,其伸展范围重新增大。对于冷域中远离地面暖锋的另一支正环流系来说,当暖锋位于地形上游或迎风坡时,它可被地形完全阻塞于背风侧,地形高度越高,地形阻塞作用越大。在暖锋锋区附近主要存在三支垂直上升运动带:(a)由于边界层摩擦辐合作用,导致在地面暖锋后缘暖区中形成一支水平尺度较小、强度较大的垂直运动带,它随着暖锋移速增大而减弱。该垂直运动带,当暖锋位于地形迎风侧,强度增加;暖锋位于地形背风侧,其强度减弱。(b)在锋区暖域沿锋面存在均匀的上升运动,(c)在冷域远离地面暖锋处,存在一支水平范围较宽,其中心位于边界层顶部附近的垂直运动带,当暖锋位于迎风坡时,这支垂直运动带可被地形阻塞于地形背风侧。
英文摘要:
      A simplified two-layer shallow frontal model which including the effect of orography and boundary layer friction is incorporated to study theoretically the vertical structure and circulation of low-level warm front in the boundary layer flow over orography. The inclination of surface warm front (SWF) chiefly depends on the frontal moving speed and the geostrophic flow in the warm sector that is decreased with the frontal speed increasing. The feature is opposite to that of cold fronts. The effect of orography on the slope of warm front is relative smaller than that on the cold front. Comparing with the features of flat case shows that the closed circulation near the SWF in the cold sector for stationary warm front is enlarged when the SWF locates the upstream of orography and contracted on the upslope. However, it will be expanded again when the SWF moving to the leeside. The clockwise circulation away from the SWF in the cold side may be blocked in the leeside whose blocking will be increased when the orography height increasing. There are three different vertical zones in the warm front.(a) A small horizontal scale and strong vertical motion in the vicinity of SWF due to the convergence induced by boundary layer friction that decreased with the increasing of frontal moving speed. Moreover the vertical motion related to the SWF will be increased in the upside, and decreased in the leeside that is associated with the orography dynamic effect. (b) A uniform upwarding motion along the frontal interface in the warm sector that is related to the lifting effect of frontal inclination. (c) A wide vertical motion zone is away from the SWF in the cold side whose center is placed the top of boundary layer and will be blocked in the leeside when the SWF located the upslope.
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