positive vorticity

positive vorticity

Vorticity caused by cyclonic turning. Vorticity is a measure of rotation in the atmosphere, or “spin,” in the air. If the spin, as viewed from above, is counterclock-wise in the Northern Hemisphere, it is called vorticity cyclonic and given a positive value (i.e., it is called positive vorticity). Positive vorticity is associated with the upward motion of air.
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Cole identified one trough, then gestured with his finger east of the trough in a counter-clockwise motion while commenting, "You have vorticity at the trough; that would be positive vorticity advection." He isolated wind speed data to determine advection: "You'd have your vorticity at the base, so it would advect with strong winds." He spent less time contemplating NVA and placed it west of the trough: "So NVA down here, in that general area."
As depicted in Figure 2(a), there exists strong negative relative vorticity in the back of the trough and positive vorticity advection in front of the trough at 700 hPa, the latter of which is in favor of the occurrence of ascending motion.
However, the negative vortices would be formed on the leeward side of the wavy flow structure (positive vorticity denotes a counterclockwise rotation and negative vorticity, a clockwise rotation).
This adds positive vorticity to the sea ice and the ocean circulation (Proshutinsky and Johnson, 1996), resulting in reduced convergence in the Beaufort Gyre.
The results show that the low-pressure system originating from the Tibetan Plateau affects the southwest vortex mainly at the middle level, causing the strength increase of the southwest vortex (SWV), and acts as a connection between the positive vorticity centers at the upper and lower layers.
Great Plains, where the vertical vorticity couplet is initially created by tilting of horizontal environmental vorticity, and then positive vorticity is rapidly intensified by the stretching of vertical vorticity within the mesocyclone (e.g., Davies-Jones et al.
Figures 3(a) and 3(b) also show the central structure, as now characterized by positive vorticity and remarkable depth (the structure has broken up in two parts).
Meanwhile, at middle levels, the mesocyclone vortex continued to separate from the updraft shear region vorticity (Figures 8(b), 8(d), and 8(f)), with a region of anticyclonic vorticity developing between the two positive vorticity regions at 0045 UTC (Figure 8(d)).
In another study, Nakamura showed that high levels of jet stream simultaneously occur with divergence and relative positive vorticity advection [20].
The influence of the eastward movement of the low-pressure plateau system on the convective clouds embedded in the SWV and the accompanied release of latent heat associated with cloud physics is important for the development and eastward shift of the SWV [22-25], which is particularly true for the development of positive vorticity in low-mid layers during the occurrence of heavy precipitation [26-28].
If varying vorticity values are obtained from different radar directions, we suggest selecting the largest positive vorticity value at a location to identify hazardous rain-cells of which the vorticity value is greater than or equal to 0.03 [s.sup.-1].
It turns out that the stretching term is directly responsible for a positive vorticity tendency that extends zonally around the cyclone center, whereas the tilting term is minor.
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