image: Conceptual diagram of the influence of horizontal vortex tubes on tornado genesis and development during the intensification stage: (a) the effect of horizontal vortex tubes on tornado rotation; (b) the effect of horizontal vortex tubes on tornado vertical motion.
Credit: Yuchen Liu
Tornadoes on the outer edges of a typhoon’s spiral rain bands are a severe convective weather phenomenon that occurs on the periphery of tropical cyclone systems. Compared to the core region near the typhoon’s center, the atmospheric instability and vertical wind shear conditions in these outer areas often combine in more subtle and easily overlooked ways, making their occurrence and development more sudden and localized. This poses greater challenges for forecasting and early warning.
However, due to the complex structure of typhoon systems themselves, the variability of environmental conditions, and the extreme scarcity of direct observational data on tornadoes in their outer regions, understanding their formation mechanisms, activity patterns, and future trends in the context of climate change remains a challenging and contentious area of research.
Building on this, Prof. Lingkun Ran from the Institute of Atmospheric Physics of the Chinese Academy of Sciences led a team in using the WRF (Weather Research and Forecasting) model to conduct a large-eddy simulation of a tornado that occurred in the Foshan area on 4 October 2015. By applying a rederived equation for vertical pressure gradient force, they analyzed the influence of horizontal vortex tubes on the tornado. The results showed that horizontal vortex tubes play a significant role in the development of tornadoes. The research findings were recently published in Atmospheric and Oceanic Science Letters.
“Tornado processes within the spiral rain bands on the periphery of typhoons are extremely complex, and traditional numerical models often have significant limitations in capturing and simulating the tornado vortices within them,” explained Prof. Lingkun Ran, the corresponding author of the study. “We attempted to use large-eddy simulations, combined with radar observation data, to simulate the fine dynamic structure of tornado occurrence. The rederived equation for vertical pressure gradient force helps us understand how horizontal vortex tubes influence the genesis and development of tornadoes.”
In the future, the team plans to conduct targeted simulations and predictions for more tornadoes, with the ultimate goal of providing higher-quality tornado forecasts for the South China region.
Journal
Atmospheric and Oceanic Science Letters