Which of the following is not associated with structure of a tropical cyclone?
Ekman Spirals
Understanding Tropical Cyclone Structure
Tropical cyclones are intense low-pressure weather systems that form over warm tropical or subtropical oceans. They have a distinct structure comprising several key components.
Components of a Tropical Cyclone
A typical tropical cyclone structure includes:
- Eye: The calm, clear center of the cyclone, typically 20-50 km in diameter. Air descends slowly in the eye.
- Eyewall: The most dangerous part of the cyclone, a ring of intense thunderstorms surrounding the eye. It has the strongest winds and heaviest rainfall.
- Spiral Rainbands: Bands of thunderstorms that spiral inward towards the eyewall. These can extend hundreds of kilometers from the center and bring heavy rain and gusty winds.
- Outer Region: The area outside the spiral bands, where winds gradually decrease and rainfall becomes less intense.
Some tropical cyclones, particularly strong and mature ones, can develop an 'annular' structure. An Annular Cyclone is characterized by a large, symmetric eye surrounded by a thick, uniform eyewall, with the absence of prominent spiral rainbands. While less common than cyclones with prominent spiral bands, they are still a structural characteristic observed in some cyclones.
Analyzing the Options
Let's examine each option provided in the question:
- Eye Wall: As discussed above, the eyewall is a fundamental component of a tropical cyclone's structure, containing the most violent weather.
- Spiral Bands: These are common features in tropical cyclones, comprising bands of thunderstorms spiraling towards the center, contributing to the overall structure and rainfall distribution.
- Annular Bands: This refers to the 'annular' structure sometimes observed in strong tropical cyclones, characterized by a ring-like eyewall and lack of distinct spiral bands. It relates to a specific structural type of cyclone.
- Ekman Spirals: An Ekman spiral describes the theoretical wind-driven current pattern in the ocean or wind pattern in the atmosphere where the flow direction changes with depth. It's a concept related to fluid dynamics, wind stress, and Coriolis effect, primarily used in oceanography and atmospheric boundary layer studies. While wind and ocean interaction are relevant to cyclone formation and movement, the Ekman spiral itself is a model of wind-driven flow distribution with depth or height, not a structural component of the cyclone cloud and circulation pattern as seen from above or in cross-section.
Conclusion: Identifying the Unassociated Term
Based on the analysis of tropical cyclone structure and the provided options, the Eye Wall, Spiral Bands, and Annular Bands are all associated with either typical or specific structural characteristics of a tropical cyclone. Ekman Spirals, however, describe a different physical phenomenon related to layered fluid flow under wind stress and Coriolis force, which is not considered a structural part of the visible or radar-detectable cyclone system itself.
| Term | Associated with Cyclone Structure? | Explanation |
|---|---|---|
| Eye Wall | Yes | Ring of intense thunderstorms surrounding the eye. |
| Spiral Bands | Yes | Bands of thunderstorms spiraling towards the center. |
| Annular Bands | Yes | Refers to the Annular structure (symmetric eyewall, no prominent spiral bands) seen in some cyclones. |
| Ekman Spirals | No | Describes wind/current profiles with depth/height due to wind stress and Coriolis effect. |
Therefore, Ekman Spirals are not associated with the structure of a tropical cyclone in the same way the other terms are.
Revision Table: Tropical Cyclone Structure Concepts
| Concept | Description |
|---|---|
| Eye | Calm center with descending air. |
| Eyewall | Strongest winds and rain, surrounds the eye. |
| Spiral Rainbands | Outward spiraling thunderstorm bands. |
| Annular Cyclone | A type of cyclone structure with a large, symmetric eye and thick eyewall, lacking distinct spiral bands. |
Additional Information: Ekman Transport and Spirals
The Ekman spiral concept arises from considering the forces acting on water (or air) set in motion by wind blowing over the surface. The wind stress acts on the surface layer, moving it. Due to the Coriolis effect, this layer's movement is deflected (to the right in the Northern Hemisphere, left in the Southern Hemisphere). This motion then drags the layer below it, which is also deflected, and so on. This results in a spiral pattern of current direction with increasing depth, known as the Ekman spiral. The net transport of water due to this effect, integrated over the Ekman layer depth, is called Ekman transport, which is directed 90 degrees to the right (NH) or left (SH) of the wind direction. While these dynamics are crucial for understanding ocean circulation and how sea surface temperature might influence cyclones, the Ekman spiral itself is not a part of the visible cloud or wind structure we describe when talking about the parts of a tropical cyclone.
Important Questions from Oceanography
Which one of the following is not a cold current?
Which of the following positions of Sun, Earth and Moon is/are suitable for Spring Tide?
1. SYZYGY Conjunction
2. SYZYGY Opposition
3. Quadrature
Select the correct answer using the code given below :
The maximum depth of Lithosphere is found in the
The periodic rise and fall of ocean water in response to gravitational forces is called
Consider the following statements regarding 'fronts':
1. The movement of a front causes a slow change in weather in the area over which it moves.
2. Cold fronts are associated with thunderstorms.
3. Warm front is the boundary between an advancing mass of warm air where it is overriding and rising above a mass of colder air.
Which of the statements given above is/are correct?
