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 h...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 d BZ,but the absolute error increases when d BZ is >=40.This method demonstrates that it is a good reflection of the direction of the vertical velocity.展开更多
At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in ...At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in the continuity equation (CE) of moist air has not been taken into account generally. Though Hansen et al. listed source and sink terms in the CE ( Eq. T2 ), they still neglected these terms in the approximate form employed in computations ( Eq. T6 ). In the real atmosphere there exist condensation and evaporation, sometimes strong condensation. In this note the role of the WVSTs in the CE and its related equations of numerical models and their influences on forecast results are discussed.展开更多
基金National Key Basic Research Development Program"973"(2013CB430103,2009CB421503)National Natural Science Funding(41375058,41530427)State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences(2015LASW-A07)
文摘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 d BZ,but the absolute error increases when d BZ is >=40.This method demonstrates that it is a good reflection of the direction of the vertical velocity.
基金Project supported by the National Major Project of Science and Technology 75-09-01.
文摘At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in the continuity equation (CE) of moist air has not been taken into account generally. Though Hansen et al. listed source and sink terms in the CE ( Eq. T2 ), they still neglected these terms in the approximate form employed in computations ( Eq. T6 ). In the real atmosphere there exist condensation and evaporation, sometimes strong condensation. In this note the role of the WVSTs in the CE and its related equations of numerical models and their influences on forecast results are discussed.
