Yuhan Liu

and 6 more

This study introduces a tornado perturbation model utilizing the cyclostrophic wind model, implemented through a shallow-water equation framework. We conducted numerical simulations to examine development of perturbations within a static atmosphere background. Four numerical experiments were conducted: a single cyclonic wind perturbation (EXP1), a single low-geopotential height perturbation (EXP2), a cyclonic wind perturbation with a 0 Coriolis parameter (EXP3), and a single anticyclonic wind perturbation (EXP4). The outputs of these experiments were analyzed using comparative methods. In a static atmosphere setting, EXP1 generated a tornado-like pressure structure under a small-scale cyclonic wind perturbation. The centrifugal force in the central area exceeded the pressure gradient force, causing air particles to flow outward, leading to a pressure drop and strong pressure gradient. EXP2 induced a purely radial wind field; upon initiation, the central area exhibited convergence, and the geopotential height increased rapidly, indicating that a small-scale depression is insufficient to generate a tornado’s vortex flow field. EXP3’s results, with a 0 Coriolis parameter, are marginally different from EXP1, suggesting the Coriolis force’s negligible impact on small-scale movements. EXP4 demonstrates that a small-scale anticyclonic wind field perturbation can also trigger tornado-like phenomena akin to EXP1. The results indicate that a robust cyclonic and an anticyclonic wind field can potentially generate a pair of cyclonic and anticyclonic tornadoes, when the horizontal vortex tubes in an atmosphere with strong vertical wind shear tilt, forming a pair of positive and negative vorticities. These tornadoes are similar but have different rotation directions.