## Vorticity

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Vorticity implies the rotation, or angular velocity, of small (imaginary) parcels in any fluid. The air within a low-pressure system may be regarded as comprising an infinite number of small air parcels, each rotating cyclonically about an axis vertical to the earth's surface (Figure 6.8). Vorticity has three elements - magnitude (defined as twice the angular velocity, Q) (see Note 3), Figure 6.7 Cross-section of the patterns of vertical motion associated with (mass) divergence and convergence in the troposphere, illustrating mass continuity. Figure 6.8 Sketch of the relative vertical vorticity (Z) about a cyclone and an anticyclone in the northern hemisphere. The component of the earth's vorticity about its axis of rotation (or the Coriolis parameter, f) is equal to twice the angular velocity (Q) times the sine of the latitude (f). At the pole f = 2Q, diminishing to 0 at the equator. Cyclonic vorticity is in the same sense as the earth's rotation about its own axis, viewed from above, in the northern hemisphere: this cyclonic vorticity is defined as positive

Figure 6.8 Sketch of the relative vertical vorticity (Z) about a cyclone and an anticyclone in the northern hemisphere. The component of the earth's vorticity about its axis of rotation (or the Coriolis parameter, f) is equal to twice the angular velocity (Q) times the sine of the latitude (f). At the pole f = 2Q, diminishing to 0 at the equator. Cyclonic vorticity is in the same sense as the earth's rotation about its own axis, viewed from above, in the northern hemisphere: this cyclonic vorticity is defined as positive

direction (the horizontal or vertical axis about which the rotation occurs) and the sense of rotation. Rotation in the same sense as the earth's rotation - cyclonic in the northern hemisphere - is defined as positive. Cyclonic vorticity may result from cyclonic curvature of the streamlines, from cyclonic shear (stronger winds on the right side of the current, viewed downwind in the northern hemisphere), or a combination of the two (Figure 6.9). Lateral shear (see Figure 6.9B) results from changes in isobar spacing. Anticyclonic vorticity occurs with the corresponding anticyclonic situation. The component of vorticity about a vertical axis is referred to as the vertical vorticity. This is generally the most important, but near the ground surface frictional shear causes vorticity about an axis parallel to the surface and normal to the wind direction.

Vorticity is related not only to air motion around a cyclone or anticyclone (relative vorticity), but also to the location of that system on the rotating earth. The vertical component of absolute vorticity consists of the relative vorticity (Z) and the latitudinal value of the Coriolis parameter, f = 2Q sin 9 (see Chapter 6A). At the equator, the local vertical is at right-angles to the earth's axis, so f = 0, but at the North Pole cyclonic relative vorticity and the earth's rotation act in the same sense (see Figure 6.8). Figure 6.9 Streamline models illustrating in plan view the flow patterns with cyclonic and anticyclonic vorticity in the northern hemisphere. In C and D, the effects of curvature (A! and A2) and lateral shear (B: and B2) are additive, whereas in E and F they more or less cancel out. Dashed lines are schematic isopleths of wind speed.

Figure 6.9 Streamline models illustrating in plan view the flow patterns with cyclonic and anticyclonic vorticity in the northern hemisphere. In C and D, the effects of curvature (A! and A2) and lateral shear (B: and B2) are additive, whereas in E and F they more or less cancel out. Dashed lines are schematic isopleths of wind speed.

Source: After Riehl et al. (1954).

0 0 ## Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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### Responses

• Novella
What is vorticity in climatology?
2 years ago
• Biniam
What is vorticity geography#?
3 months ago
• simone
What is the importance of vorticity and divergence in weather?
1 month ago