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Helicity Dynamics of Atmospheric Flow


doi: 10.1007/BF02666544

  • Helicity is an important physical variable which is similar to the energy and enstrophy in three-dimensional fluid. It can be used to describe the motion in the direction of fluid rotation and also can be regarded as a new physi-cal variable in turbulence theory. In recent years, it has been used in atmospheric dynamics. In this paper, helicity of atmospheric flow, especially helicity in the boundary layer and in the vicinity of front was discussed. These results show that helicity is usually positive in the boundary layer due to the effect of friction. The helicity of boundary layer flow is larger in anticyclone than that in cyclone, resulting from the different wind structures of boundary layers in an-ticyclone and cyclone under the geostrophic momentum approximation. It is possible that the helicity is negative at certain height in the baroclinic boundary layer. The influences of nonlinearity and baroclinity on the helicity are im-portant. The so called “Cloud Street” in the boundary layer is related to the dynamics of helicity. Helicity in the at-mosphere can be expressed as the temperature advection under some conditions, so helicity would be allowed to des-cribe the frontogenesis and development of frontal structure. The amplitude of helicity increases with time in the frontogenesis. A large gradient of helicity is generated in the region located to the northeast of the surface low and in which the front is formed. In warm frontal region, as well as behind the trough of temperature, the helicity is positive, while the helicity is negative in cold frontal sector and in the ahead ridge of temperature. The largest helicity occurs in the boundary.
  • [1] Wu Rongsheng, Fang Juan, 2001: Mechanism of Balanced Flow and Frontogenesis, ADVANCES IN ATMOSPHERIC SCIENCES, 18, 323-334.  doi: 10.1007/BF02919313
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    [3] YANG Shuai, GAO Shouting, LU Chungu, 2014: A Generalized Frontogenesis Function and Its Application, ADVANCES IN ATMOSPHERIC SCIENCES, 31, 1065-1078.  doi: 10.1007/s00376-014-3228-y
    [4] ZHOU Lingli, DU Huiliang, ZHAI Guoqing, WANG Donghai, 2013: Numerical Simulation of the Sudden Rainstorm Associated with the Remnants of Typhoon Meranti (2010), ADVANCES IN ATMOSPHERIC SCIENCES, 30, 1353-1372.  doi: 10.1007/s00376-012-2127-3
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    [6] Xu Yinlong, Qian Fenlan, Chen Zhi, Li Shiming, Zhou Mingyu, 2002: Observational Analyses of Baroclinic Boundary Layer Characteristics during One Frontal Winter Snowstorm, ADVANCES IN ATMOSPHERIC SCIENCES, 19, 153-168.  doi: 10.1007/s00376-002-0041-9
    [7] PENG Jiayi, FANG Juan, WU Rongsheng, 2004: Interaction of Mesoscale Convection and Frontogenesis, ADVANCES IN ATMOSPHERIC SCIENCES, 21, 814-823.  doi: 10.1007/BF02916377
    [8] Fang Juan, Wu Rongsheng, 1998: Frontogenesis, Evolution and the Time Scale of Front Formation, ADVANCES IN ATMOSPHERIC SCIENCES, 15, 233-246.  doi: 10.1007/s00376-998-0042-4
    [9] Fang Juan, Wu Rongsheng, 2001: Topographic Effect on Geostrophic Adjustment and Frontogenesis, ADVANCES IN ATMOSPHERIC SCIENCES, 18, 524-538.  doi: 10.1007/s00376-001-0042-0
    [10] Yang Hongwei, Wang Bin, Ji Zhongzhen, 2002: Application of the Artificial Compression Method to the Simulation of Two-Dimensional Frontogenesis, ADVANCES IN ATMOSPHERIC SCIENCES, 19, 863-869.  doi: 10.1007/s00376-002-0051-7
    [11] YANG Shuai, GAO Shouting, Chungu LU, 2015: Investigation of the Mei-yu Front Using a New Deformation Frontogenesis Function, ADVANCES IN ATMOSPHERIC SCIENCES, 32, 635-647.  doi: 10.1007/s00376-014-4147-7
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    [13] Zipeng YUAN, Xiaoyong ZHUGE, Yuan WANG, 2020: The Forced Secondary Circulation of the Mei-yu Front, ADVANCES IN ATMOSPHERIC SCIENCES, 37, 766-780.  doi: 10.1007/s00376-020-9177-8
    [14] He Jianzhong, 1993: Linear Momentum Approximation and Frontogenesis Caused by Baroclinic Ekman Momentum Flow, ADVANCES IN ATMOSPHERIC SCIENCES, 10, 103-112.  doi: 10.1007/BF02656958
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Manuscript History

Manuscript received: 10 April 1994
Manuscript revised: 10 April 1994
通讯作者: 陈斌, bchen63@163.com
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Helicity Dynamics of Atmospheric Flow

  • 1. Department of Atmospheric Sciences, Meso-scale Severe Weather Research Laboratory / SEC, Nanjing University, Nanjing 210008, P. R. China,Department of Atmospheric Sciences, Meso-scale Severe Weather Research Laboratory / SEC, Nanjing University, Nanjing 210008, P. R. China

Abstract: Helicity is an important physical variable which is similar to the energy and enstrophy in three-dimensional fluid. It can be used to describe the motion in the direction of fluid rotation and also can be regarded as a new physi-cal variable in turbulence theory. In recent years, it has been used in atmospheric dynamics. In this paper, helicity of atmospheric flow, especially helicity in the boundary layer and in the vicinity of front was discussed. These results show that helicity is usually positive in the boundary layer due to the effect of friction. The helicity of boundary layer flow is larger in anticyclone than that in cyclone, resulting from the different wind structures of boundary layers in an-ticyclone and cyclone under the geostrophic momentum approximation. It is possible that the helicity is negative at certain height in the baroclinic boundary layer. The influences of nonlinearity and baroclinity on the helicity are im-portant. The so called “Cloud Street” in the boundary layer is related to the dynamics of helicity. Helicity in the at-mosphere can be expressed as the temperature advection under some conditions, so helicity would be allowed to des-cribe the frontogenesis and development of frontal structure. The amplitude of helicity increases with time in the frontogenesis. A large gradient of helicity is generated in the region located to the northeast of the surface low and in which the front is formed. In warm frontal region, as well as behind the trough of temperature, the helicity is positive, while the helicity is negative in cold frontal sector and in the ahead ridge of temperature. The largest helicity occurs in the boundary.

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