Equatorial Waves 1

Summary

This video explores equatorial waves, including Equatorial Rossby, mixed Rossby-gravity, and Kelvin waves, which influence tropical weather patterns. The script breaks down the physical and mathematical characteristics of these waves, highlighting their distinct pressure and wind anomalies. It emphasizes the formation of thunderstorms behind low-pressure areas and the eastward movement of Kelvin waves. The video also explains how these waves interact with atmospheric conditions and how they can be monitored in noisy satellite data, offering insight into the dynamics of tropical weather systems.

Takeaways

• 😀 Equatorial waves are atmospheric phenomena that influence weather patterns, especially thunderstorms near the equator.
• 😀 Equatorial Rossby waves have flow that is strongest at the equator and weakens as you move away from it, causing pressure anomalies that are strongest near the equator and opposite between hemispheres.
• 😀 Mixed Rossby-Gravity waves act similarly to inertia gravity waves, with large wave numbers leading to longer periods and more complex behaviors.
• 😀 Kelvin waves are a type of gravity wave that moves eastward, unlike other waves, and are characterized by high pressure anomalies at the equator and low pressure anomalies to the east.
• 😀 The wind dynamics of Kelvin waves show counterclockwise rotation in the Northern Hemisphere and clockwise in the Southern Hemisphere, which are linked to low pressure areas.
• 😀 Convergence (air coming together) occurs where thunderstorms preferentially form, typically behind areas of low pressure as equatorial waves move eastward.
• 😀 The speed of equatorial waves decreases as you move away from the equator, with wave frequencies and periods being influenced by wave numbers and buoyancy.
• 😀 In Kelvin waves, wind rotation results in convergence east of high-pressure anomalies and west of low-pressure anomalies, creating favorable conditions for thunderstorm formation.
• 😀 The interaction of winds and pressure anomalies in these waves drives atmospheric behavior such as convection and thunderstorm development.
• 😀 Identifying and monitoring equatorial waves in atmospheric data, especially noisy satellite-derived data, is a key skill for understanding their impact on weather patterns.

Q & A

What are the three main types of equatorial waves discussed in the transcript?

The three main types of equatorial waves discussed are Equatorial Rossby waves, Mixed Rossby-Gravity waves, and Kelvin waves.

How do the pressure anomalies in Equatorial Rossby waves behave?

In Equatorial Rossby waves, the pressure anomalies are strongest just off the equator, with opposite anomalies in the two hemispheres. These anomalies weaken as you move away from the equator.

What is the key characteristic of Mixed Rossby-Gravity waves?

Mixed Rossby-Gravity waves have a similar structure to Equatorial Rossby waves but feature a faster flow near the equator, which slows down as you move away. The waves are associated with westward movement and convection that forms behind low-pressure regions.

How do Kelvin waves differ from other equatorial waves in terms of movement?

Kelvin waves move eastward, unlike other equatorial waves, which typically move westward. This is due to the positive buoyancy and wave number that drive eastward flow.

What role does buoyancy play in the behavior of Kelvin waves?

Buoyancy plays a significant role in Kelvin waves by creating a positive buoyancy term, which causes the waves to move eastward. The frequency and phase speed are influenced by this positive buoyancy.

What does the equation in the transcript help to determine?

The equation helps to determine the velocity and gravity wave components of different equatorial wave types, with variations in wave number leading to different periods and behaviors in the waves.

How does the concept of convergence relate to thunderstorm formation in equatorial waves?

Convergence of air is maximized in areas west of low-pressure regions and east of high-pressure regions. This convergence helps to form thunderstorms, particularly in the regions of rising air and deep convection.

What is the significance of the 'stick in the wind' analogy used in the explanation of Kelvin waves?

The 'stick in the wind' analogy demonstrates how winds rotate around areas of high and low pressure in Kelvin waves. In the northern hemisphere, the rotation is counterclockwise, and in the southern hemisphere, it is clockwise, reflecting the respective wind and pressure patterns.

What happens to equatorial waves as they move away from the equator?

As equatorial waves move away from the equator, their intensity decays. The wind field becomes weaker, and the overall effects of the wave diminish further from the equator.

How can the understanding of equatorial waves be applied to satellite data?

The understanding of equatorial waves can be used to identify and monitor wave patterns within complex and noisy atmospheric data from satellites. This helps in tracking the movement and impact of these waves on weather systems.