A well-documented supercell thunderstorm occurred in Del City, Oklahoma, on 20 May 1977 is successfully simulated by a three-dimensional, nonhydrostatic storm-scale numerical model ARPS. With the numerical simulated d...A well-documented supercell thunderstorm occurred in Del City, Oklahoma, on 20 May 1977 is successfully simulated by a three-dimensional, nonhydrostatic storm-scale numerical model ARPS. With the numerical simulated data of the storm, the structure and evolution of the helicity, superhelicity and their dynamical influences on the development of the storm are investigated. The initial helical structure of environmental flow is favorable to the development of storm. In the developing stage of storm, low helicity is beneficial to the nonlinear energy cascade. However, the high helicity is of help to maintain the energy of convection cell at the mature stage of storm, and lead to a long life cycle of convective cell. Rotating thunderstorm has a tendency of adjusting to the Beltrami flow structure and tends to a higher helicity of flow. The negative superhelicity could lead to an increase of helicity. Superhelicity is negative in the initial developing process of storm however the superhelicity is positive in the mature stage of storm. Therefore, the superhelicity can be used as an indicator of the mature degree of convective storm.展开更多
基金National Natural Science Foundation of China under the Grant !No.49605064, 49735180 State Key Basic Research Program: Resear
文摘A well-documented supercell thunderstorm occurred in Del City, Oklahoma, on 20 May 1977 is successfully simulated by a three-dimensional, nonhydrostatic storm-scale numerical model ARPS. With the numerical simulated data of the storm, the structure and evolution of the helicity, superhelicity and their dynamical influences on the development of the storm are investigated. The initial helical structure of environmental flow is favorable to the development of storm. In the developing stage of storm, low helicity is beneficial to the nonlinear energy cascade. However, the high helicity is of help to maintain the energy of convection cell at the mature stage of storm, and lead to a long life cycle of convective cell. Rotating thunderstorm has a tendency of adjusting to the Beltrami flow structure and tends to a higher helicity of flow. The negative superhelicity could lead to an increase of helicity. Superhelicity is negative in the initial developing process of storm however the superhelicity is positive in the mature stage of storm. Therefore, the superhelicity can be used as an indicator of the mature degree of convective storm.
