Effects of Landfall Location and Approach Angle of an Idealized Tropical Cyclone over a Long Mountain Range
Effects of Landfall Location and Approach Angle of an Idealized Tropical Cyclone over a Long Mountain Range
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长山脉理想化热带气旋登陆位置和接近角的影响
DOI：
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发表时间：
2016
影响因子：
2.9
通讯作者：
Shu‐Hua Chen
中科院分区：
文献类型：
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作者：
Liping Liu;Yuh;Shu‐Hua Chen
通过一系列理想化数值实验，研究了登陆位置和接近角对热带气旋 (TC) 越过理想化的中央阿巴拉契亚山脉时的路径偏转的影响。当热带气旋登陆山脉中部时，先向上游偏转，反气旋越过山脉，然后向下游西移。 TC 运动由正涡度趋势 (VT) 引导，该趋势主要由上游和下游的水平涡度平流所主导，但还受到拉伸和剩余项的影响，这些影响主要与非绝热加热和摩擦效应有关。上下游轨道偏转机制与前期研究中的干流相似，但在山体附近却有很大不同。当热带气旋在北（南）端附近登陆时，由于尖端周围的涡度平流较强（较弱），它会经历较少（较多）的向南偏转。当热带气旋从东南方向接近山脉并在北端、中部或南端登陆时，其路径偏转与嵌入东风气流中的偏转类似，但地形阻挡较弱。这些结果与之前研究中在干流中模拟的情况类似，只是没有由于与强热带气旋对流相关的较弱的地形阻挡而导致路径不连续。当热带气旋从南方沿南北走向的山脉移动时，往往会向山体偏转，稍后再越过山体的另一侧。在这些情况下，正 VT 受到所有水平涡量平流、涡量拉伸（非绝热加热）和由于与山脉的更长更强的相互作用而产生的残余（摩擦）项的影响。湿流中的涡度伸缩主要是由非绝热加热引起的，而不是先前研究中干流中的背风坡涡度伸缩引起的。
Effects of landfall location and approach angle on track deflection associated with a tropical cyclone (TC) passing over an idealized and Central Appalachian Mountain is investigated by a series of idealized numerical experiments. When the TC landfalls on the central portion of the mountain range, it is deflected to the south upstream, passes over the mountain anticyclonically, and then moves westward downstream. The TC motion is steered by the positive vorticity tendency (VT) which is dominated by horizontal vorticity advection upstream and downstream, but with additional influence from the stretching and residual terms, which are mainly associated with diabatic heating and frictional effects. The track deflection mechanism upstream and downstream is similar to the dry flow in previous study, but is very different in the vicinity of the mountain. When the TC landfalls near the northern (southern) tip, it experiences less (more) southward deflection due to stronger (weaker) vorticity advection around the tip. When the TC approaches the mountain range from the southeast and landfalls on the northern tip, center, or southern tip, the track deflections are similar to those embedded in an easterly flow but with weaker orographic blocking. These results are similar to the cases simulated in the dry flow in previous study, except that there is no track discontinuity due to the weaker orographic blocking associated with strong TC convection. When a TC moves along the north-south mountain range from the south, it tends to deflect toward the mountain and then crosses over to the other side at later time. In these cases, the positive VT is influenced by all horizontal vorticity advection, vorticity stretching (diabatic heating) and residual (friction) terms due to longer and stronger interaction with the mountain range. The vorticity stretching is mainly caused by diabatic heating in the moist flow, instead of by lee slope vorticity stretching in the previous study for dry flow.