高级检索

大气涡旋速度场和螺旋形成机理

Spiral Structures in Atmospheric Vortices: Velocity Fields and Formation Mechanisms

  • 摘要: 基于力的平衡原理,本文利用柱坐标系(r, θ, z)的Navier-Stokes方程,求出了大气中纬度气旋,台风和龙卷风,三维螺旋涡旋速度场。并由此求出三维速度均为零的奇点(临界点或平衡态),它们均是鞍焦点。中纬度气旋有两个奇点:一个在地面,另一个在对流层顶。龙卷风仅有一个奇点:在超级暴雨云底部。台风也有两个奇点,一个在地表眼壁处,另一个在地表台风眼中心。由速度场求出了水平散度D和垂直涡度ωz及涡旋形状曲面,它们均和实际观测相吻合。三种螺旋涡旋的形成机理不同,中纬度气旋是由于地表摩擦力穿过等压线所引起的水平辐合,龙卷风是由于暴雨云底强烈的水平辐合引起的涡管伸长,台风是由于海洋整体积云带的上升运动,辐散辐合随高度不变。

     

    Abstract: Based on the principle of force equilibrium, this study employed the Navier–Stokes equations in cylindrical coordinates (r, θ, z) to derive the three-dimensional spiral vortex velocity fields of mid-latitude cyclones, typhoons, and tornadoes. Singular points (critical points or equilibrium states), at which the three-dimensional velocity of these vortices becomes zero, were identified. All such points were classified as saddle-focus points. Mid-latitude cyclones exhibited two singular points: one at the surface of the Earth and the other at the top of the troposphere. Tornadoes possessed a single singular point at the base of the supercell storm cloud. Typhoons also exhibited two singular points: one at the eyewall surface and the other at the center of the eyewall on the surface. From the derived velocity fields, the horizontal divergence (D), vertical vorticity (ωz), and vortex shape surface were obtained, and these results were consistent with observational data. The findings indicated that the formation mechanisms of the three spiral vortices differ. Specifically, mid-latitude cyclones are caused by horizontal convergence associated with surface friction and cross-isobar flow, tornadoes are generated by vortex tube stretching resulting from strong horizontal convergence at the base of storm clouds, and typhoons are caused by the large-scale upward motion of the cumulus cloud belt over the ocean, with divergence and convergence remaining invariant with respect to height.

     

/

返回文章
返回