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A short class with Sarah and her students. The other ways are under More.
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Today we'll discuss atmospheric pressure. To start, atmospheric pressure is essentially the weight of air above us. How do we measure it, does anyone know?
Is it measured in millibars, like how the text says?
Exactly! At sea level, the average is about 1,013.2 millibars. And how does this pressure change with altitude?
Oh, it decreases as we go higher up.
Good! Why is this important?
Because it affects air movement?
Yes! Variations create winds. Remember: Pressure causes wind—think ‘P for Pressure, P for Movement’!
Let's explore the pressure gradient force. Can anyone explain what it is?
It determines the strength of the wind, right?
Correct! The closer the isobars, the stronger the gradient. What does that mean for wind?
That wind speeds will be higher between closely spaced isobars.
Great! So we can think of isobars as a roadmap for wind movement.
Now, let's introduce the Coriolis force. Can anyone tell me how it affects wind?
It deflects the wind to the right in the northern hemisphere and to the left in the southern hemisphere!
Exactly! So if pressure gradients are acting, how does this play out?
Winds blow parallel to isobars instead of directly from high to low.
Right! That's why we can visualize wind using the mnemonic ‘Cor-Right for North’!
Let's shift our focus to large-scale wind patterns and circulation cells. Can anyone name the three main cells?
Hadley, Ferrel, and Polar cells!
Correct! What characterizes each of these cells?
Hadley cells have ascending air near the equator, Ferrel cells come from the subtropical regions, and Polar cells are sinking cold air!
Fantastic! The mnemonic ‘HFP: Hot, Fast, Polar’ can help remember the sequence.
Lastly, let’s discuss how these concepts relate to weather systems. What happens when different air masses meet?
They create fronts!
Right! And which types of storms are associated with these systems?
Extra-tropical and tropical cyclones!
Exactly! To remember: ‘Storms by Air Masses’ or ‘SAM’.
The weight of air that influences wind movement and weather.
Determines wind speed based on distance between isobars.
Affects wind direction due to Earth's rotation.
Storm systems formed from wind patterns and air mass interactions.
Bodies of air with uniform temperature and humidity characteristics.
Pressure high, no clouds in the sky; pressure low, rain will flow.
Imagine a balloon being filled with air; the more air you add, the more pressure inside. When it pops, air rushes out - that’s wind we feel!
P-CW: Pressure causes Wind - remembering how pressure gradients lead to wind movement.
C-F-S - Coriolis, Friction, and Speed affect wind direction and velocity.
Term
What is atmospheric pressure?
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Term
What causes wind?
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Define Coriolis force.
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What are air masses?
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What is a front?
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The weight of the air above a surface, typically measured in millibars.
Lines on a map connecting points of equal atmospheric pressure.
The rate at which pressure changes in relation to distance.
The apparent deflection of moving objects due to the rotation of the Earth.
A system of winds rotating inward to an area of low atmospheric pressure.
A large body of air with uniform temperature and moisture content.
The boundary between different air masses.
The chapter discusses atmospheric pressure, its variations, and how these lead to wind patterns and the overall circulation of the atmosphere.
It details the causes of pressure differences and their effect on wind and weather systems, explaining how atmospheric circulation redistributes heat and moisture around the planet. Key concepts include the roles of pressure gradient, Coriolis force, and the formation of distinct air masses and fronts.
This section covers the general circulation of the atmosphere, elucidating the uneven distribution of temperature on Earth's surface and its profound effect on atmospheric pressure. The fundamental understanding begins with the expansion of heated air and its compression when cooled, which generates pressure differences that drive air movement or wind.
Key topics include:
Atmospheric Pressure: Atmospheric pressure is the weight of air above a unit area, measured in millibars. It decreases with altitude and is crucial for understanding wind patterns.
Pressure Variations: Variations create wind as air moves from high to low-pressure areas. It's noted that pressure gradients generate wind velocity, influenced by several forces including the Coriolis force and friction.
Global Wind Patterns: The section elaborates on the general circulation patterns, resulting from solar heating, the rotation of Earth, and geography, leading to high-pressure and low-pressure zones around the globe, especially noting the ITCZ.
Types of Circulation: It introduces the Hadley, Ferrel, and Polar cells that describe wind movement in different latitudes, emphasizing the role of Coriolis effect on wind direction.
Weather Systems: The formation of air masses and fronts leads to weather changes, with descriptions of extra-tropical and tropical cyclones as manifestations of atmospheric dynamics.
Overall, this section explains how intricate interactions within the atmosphere establish weather patterns and climatic phenomena.