The paper by J. G. Charney, titled "The Dynamics of Long Waves in a Baroclinic Westerly Current," addresses the long-wave perturbations in the free atmosphere, focusing on the continuous vertical shear in the zonal current and the variations of the vertical component of the earth's angular velocity. The author aims to develop a solution that better aligns with observed atmospheric behavior. Key points include: - The perturbation equations are simplified by eliminating acoustic and shearing-gravitational oscillations, reducing the system to a more manageable form. - Exact stability criteria are derived, showing that instability increases with shear, lapse rate, and latitude, and decreases with wavelength. - Application of these criteria to seasonal averages of zonal wind suggests that the westerlies in middle latitudes are a source of constant dynamic instability. - The structure of unstable waves is similar to observed perturbations, with propagation speeds generally向东 (eastward) and approximately equal to the surface zonal current speed. Waves exhibit thermal asymmetry and a westward tilt with height. - The distribution of horizontal mass divergence is calculated, showing that a fixed level of nondivergence must be replaced by a sloping surface of nondivergence. - The Rossby formula for barotropic wave speed is generalized to a baroclinic atmosphere, showing that the formula holds if the constant value of the zonal wind is the mean zonal wind averaged from 600 mb. - The study concludes that the westerlies in middle latitudes are a constant source of dynamic instability, supported by observed storminess and wave patterns.The paper by J. G. Charney, titled "The Dynamics of Long Waves in a Baroclinic Westerly Current," addresses the long-wave perturbations in the free atmosphere, focusing on the continuous vertical shear in the zonal current and the variations of the vertical component of the earth's angular velocity. The author aims to develop a solution that better aligns with observed atmospheric behavior. Key points include: - The perturbation equations are simplified by eliminating acoustic and shearing-gravitational oscillations, reducing the system to a more manageable form. - Exact stability criteria are derived, showing that instability increases with shear, lapse rate, and latitude, and decreases with wavelength. - Application of these criteria to seasonal averages of zonal wind suggests that the westerlies in middle latitudes are a source of constant dynamic instability. - The structure of unstable waves is similar to observed perturbations, with propagation speeds generally向东 (eastward) and approximately equal to the surface zonal current speed. Waves exhibit thermal asymmetry and a westward tilt with height. - The distribution of horizontal mass divergence is calculated, showing that a fixed level of nondivergence must be replaced by a sloping surface of nondivergence. - The Rossby formula for barotropic wave speed is generalized to a baroclinic atmosphere, showing that the formula holds if the constant value of the zonal wind is the mean zonal wind averaged from 600 mb. - The study concludes that the westerlies in middle latitudes are a constant source of dynamic instability, supported by observed storminess and wave patterns.