Cyclonic curvature is the curvature of the track where the fluid moves counterclockwise (in the Northern Hemisphere) in meteorology, and is specified as a positive value;On the contrary, the curvature when rotating clockwise is negative, which is called anticyclonic curvature.In the southern hemisphere, on the contrary, the clockwise motion is cyclonic curvature;Anticyclonic curvature moves counterclockwise.
Chinese name
Cyclonic curvature
English name
cyclonic curvature
definition
The extent to which the streamlines and trajectories of the movement of air masses on the horizontal plane bend counterclockwise (clockwise) in the northern (southern) hemisphere.
Applied discipline
Atmospheric Science (Level I Discipline), Weather Science (Level II Discipline)
Cyclonic curvature, the curvature of the track where the fluid moves counterclockwise (in the northern hemisphere) in meteorology, and is specified as a positive value;On the contrary, the curvature when rotating clockwise is negative, which is called anticyclonic curvature.In the southern hemisphere, on the contrary, the clockwise motion is cyclonic curvature;Anticyclonic curvature moves counterclockwise.[1]
Curvature in vorticity component
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The vertical component of vorticity can be expressed as:
The above formula shows that the vertical component of relative vorticity consists of two terms. The first term on the right is related to the bending shape of the streamline, which is called curvature vorticity.In the natural coordinate system, because Vh is always positive, when the streamline bends cyclonically, r>0, the curvature vorticity Vh/r>0;When the streamline curve is anticyclonic, r<0 and curvature vorticity Vh/r>0.
The second term in the above formula is related to the uneven distribution of the horizontal wind speed along the normal of the streamline, which is called shear vorticity.The shear vorticity is positive in areas where the velocity decreases along the streamline normal, such as the north side of the westerly jet axis or the south side of the easterly jet axis in the northern hemisphere;In areas where the velocity increases along the streamline normal, such as the south side of the westerly jet axis or the north side of the easterly jet axis in the northern hemisphere, the shear vorticity is negative.
For different flow patterns, sometimes the curvature vorticity term is relatively large, and sometimes the shear vorticity term is relatively large. Therefore, only the larger one can be considered without accurate analysis.For example, near the center of a cyclone or anticyclone, only the curvature vorticity term can be considered, while in the front area or jet stream area, only the shear vorticity term can be considered.[2]
give an example
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At the end of spring, as a transitional season, the southern branch of the plateau is still active.It will affect the weather to the east of the plateau of China;In its strong years, the other southern branch airflow, combined with the southern branch airflow in the westerlies, can not only strengthen the southern branch airflow on the eastern side of the plateau of China, but also make the flow field of cyclonic curvature appear in the downstream area of North China, providing a favorable environment for the development of northern cyclones.Because the southerly flow is strong and combined with the north branch westerlies, the northern cyclones are generated frequently and their paths are concentrated.In this case, most areas in northern China often have rainy weather in spring.[3]
