A NOVEL METHOD FOR CALCULATING VERTICAL VELOCITY: A RELATIONSHIP BETWEEN HORIZONTAL VORTICITY AND VERTICAL MOVEMENT

DING Zhi-ying; ZHAO Xiang-jun; GAO Song; LUO Ya-li

doi:10.16555/j.1006-8775.2016.02.011

Abstract:

The present work provides a novel method for calculating vertical velocity based on continuity equations in a pressure coordinate system. The method overcomes the disadvantage of accumulation of calculating errors of horizontal divergence in current kinematics methods during the integration for calculating vertical velocity, and consequently avoids its subsequent correction. In addition, through modifications of the continuity equations, it shows that the vorticity of the vertical shear vector (VVSV) is proportional to -ω, the vertical velocity in p coordinates. Furthermore, if the change of ω in the horizontal direction is neglected, the vorticity of the horizontal vorticity vector is proportional to -ω. When ω is under a fluctuating state in the vertical direction, the updraft occurs when the vector of horizontal vorticity rotates counterclockwise; the downdraft occurs when rotating clockwise. The validation result indicates that the present method is generally better than the vertical velocity calculated by the ω equation using the wet Q-vector divergence as a forcing term, and the vertical velocity calculated by utilizing the kinematics method is followed by the O'Brien method for correction. The plus-minus sign of the vertical velocity obtained with this method is not correlated with the intensity of dBZ, but the absolute error increases when dBZ is >=40. This method demonstrates that it is a good reflection of the direction of the vertical velocity.

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DING Zhi-ying, ZHAO Xiang-jun, GAO Song, et al. A NOVEL METHOD FOR CALCULATING VERTICAL VELOCITY: A RELATIONSHIP BETWEEN HORIZONTAL VORTICITY AND VERTICAL MOVEMENT [J]. Journal of Tropical Meteorology, 2016, 22(2): 208-219, https://doi.org/10.16555/j.1006-8775.2016.02.011

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A NOVEL METHOD FOR CALCULATING VERTICAL VELOCITY: A RELATIONSHIP BETWEEN HORIZONTAL VORTICITY AND VERTICAL MOVEMENT

Key Laboratory of Meteorological Disaster, Ministry of Education / Joint International Research Laboratory of Climate and Environment Change / Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of In

Rev Recd Date: 2015-12-22

Abstract: The present work provides a novel method for calculating vertical velocity based on continuity equations in a pressure coordinate system. The method overcomes the disadvantage of accumulation of calculating errors of horizontal divergence in current kinematics methods during the integration for calculating vertical velocity, and consequently avoids its subsequent correction. In addition, through modifications of the continuity equations, it shows that the vorticity of the vertical shear vector (VVSV) is proportional to -ω, the vertical velocity in p coordinates. Furthermore, if the change of ω in the horizontal direction is neglected, the vorticity of the horizontal vorticity vector is proportional to -ω. When ω is under a fluctuating state in the vertical direction, the updraft occurs when the vector of horizontal vorticity rotates counterclockwise; the downdraft occurs when rotating clockwise. The validation result indicates that the present method is generally better than the vertical velocity calculated by the ω equation using the wet Q-vector divergence as a forcing term, and the vertical velocity calculated by utilizing the kinematics method is followed by the O'Brien method for correction. The plus-minus sign of the vertical velocity obtained with this method is not correlated with the intensity of dBZ, but the absolute error increases when dBZ is >=40. This method demonstrates that it is a good reflection of the direction of the vertical velocity.

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A NOVEL METHOD FOR CALCULATING VERTICAL VELOCITY: A RELATIONSHIP BETWEEN HORIZONTAL VORTICITY AND VERTICAL MOVEMENT

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