Plume Shapes and Behavior
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Atmospheric Stability
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we're discussing atmospheric stability—does anyone know what that term refers to?
Is it about how stable the weather is—like if it will rain or not?
That's a good start! Atmospheric stability actually also describes how pollutants disperse in the air. When we have unstable conditions, pollution spreads rapidly.
How do we measure whether it's unstable or stable?
Great question! We look at what's called the environmental lapse rate compared to the adiabatic lapse rate. If the environmental rate is higher than the adiabatic rate, we have unstable conditions. Think of it as 'hot air rising.'
So, what happens to pollutants in unstable conditions?
In unstable conditions, pollutants can rise quickly and spread out, showing more variation from the height they are released from. It's crucial for air quality and pollution modeling.
To remember this, think of the acronym 'SUD' for 'Stable Unstable Dispersion.' Let's summarize: unstable conditions allow pollutants to disperse widely, while stable conditions confine them. Now, let’s dive deeper into plume shapes.
Understanding Plume Shapes
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Moving forward, let’s discuss specific types of plume shapes. The first to explore is the looping plume. Who can define it?
Isn't a looping plume what happens when there's lots of turbulence and the environmental lapse rate is high?
Exactly! With a high environmental lapse rate, the plume shows significant vertical movement. Looping occurs under very unstable conditions, where turbulence causes the plume to oscillate dramatically.
What about a coning plume?
A coning plume happens under neutral conditions where the environmental lapse rate is similar to the adiabatic rate. The plume forms a cone shape as it disperses horizontally but doesn’t rise much.
And the fanning plume?
Good point! In a fanning plume, the adiabatic lapse rate and environmental lapse rate intersect just below the source. This suppresses vertical movement but allows horizontal spread—leading to a very concentrated plume near the surface.
Let's recap: looping plumes are for unstable conditions, coning for neutral, and fanning occurs when we have inversions. Remember the mnemonic 'L-C-F' for the types of plumes—Looping, Coning, and Fanning!
Mixing Height and Its Implications
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let's focus on mixing height. Why is it significant in understanding plume dynamics?
Is it about how high pollutants can rise before they mix with the ambient air?
Yes, exactly! The mixing height is the altitude at which the environmental and adiabatic lapse rates meet. It determines the vertical limit for pollution spreading.
What happens if there's no mixing height?
No mixing height can lead to concentration issues, especially in scenarios like fumigation, where pollutants can't disperse. This situation can make ground-level pollution worse for those living nearby.
How do we measure or estimate mixing height?
Typically, measurement involves meteorological balloons that gather temperature profiles at varying altitudes. This data is crucial for air quality models.
Just remember: 'Mix High with the Right Condition' for exposure safety!
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
In this section, we explore how the stability of the atmosphere affects pollutant dispersion, outlining three primary plume shapes: looping, coning, and fanning. We make connections to environmental and adiabatic lapse rates and their implications for pollutant transport and concentration levels.
Detailed
Plume Shapes and Behavior
The section on Plume Shapes and Behavior highlights the interaction between meteorological conditions and the dispersion of pollutants emitted from various sources into the atmosphere. The behavior of these plumes is heavily influenced by atmospheric stability, governed by the adiabatic lapse rate compared to the environmental lapse rate. The section categorizes the shapes of plumes into several types based on these factors:
- Looping Plume: Occurs under super adiabatic lapse rates, resulting in a highly unstable atmosphere where the plume experiences significant vertical variations due to high wind speeds.
- Coning Plume: Characteristic of neutral conditions where the thermal effects are minimal, leading to a classic cone shape as dispersion occurs due to turbulence but not thermal buoyancy.
- Fanning Plume: Involves circumstances where the adiabatic and environmental lapse rates intersect just below the source, causing downward pressure on the plume and suppressing vertical dispersion, although horizontal dispersion continues.
Additionally, the section touches on crucial concepts like mixing height, environmental lapse rate, and their effect on pollutant behavior, such as where the plume is likely to remain concentrated and hazardous for populations.
In summary, understanding these shapes and their conditions is vital for monitoring air quality and predicting pollutant behavior in atmospheric science.
Youtube Videos
![[ADI] PLUME BEHAVIOUR (ENVIRONMENT ENGINEERING) EXPLAINED (CE)!!! In Hindi](https://img.youtube.com/vi/pUaqNCqAgFc/mqdefault.jpg)
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Plume Behavior
Chapter 1 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, we have different types of plume shapes that it can take. We will go over each one of them. The first one is called as Looping, it is a super adiabatic lapse rate, which means that environmental lapse rate is greater than adiabatic.
Detailed Explanation
In this section, we're discussing different shapes that a pollutant plume can take as it rises from a source. The first shape discussed is called 'Looping'. This occurs when the environmental lapse rate, which describes how temperature changes with height, is greater than the adiabatic lapse rate. Essentially, this situation leads to very turbulent and unstable air conditions, causing the plume to rise and fall significantly, resembling a loop.
Examples & Analogies
Imagine a hot air balloon in very windy conditions. As the balloon tries to rise, the strong winds push it up and down unpredictably, creating a thorough mix of the air around it. Similarly, when pollutants rise in unstable atmospheric conditions, they can be pushed up or down, creating a looping shape.
Coning Plume Shape
Chapter 2 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The second one is called as Coning. This is neutral, which means there are thermal forces don’t play a big part in this. The environmental lapse rate is almost the same as the adiabatic lapse rate approximately.
Detailed Explanation
The 'Coning' plume shape occurs under neutral conditions where the environmental lapse rate closely matches the adiabatic lapse rate. This means that thermal effects are not significantly impacting the plume's behavior. In this scenario, the plume expands outward in the direction of the wind, creating a conical shape. It signifies a balanced dispersion of pollutants, as the vertical movement due to buoyancy is minimal.
Examples & Analogies
Think of a fountain with water spraying directly upward and outward. The water represents pollutants spreading into the atmosphere. When the conditions are neutral, the water sprays evenly, forming a cone shape. The fountain's ability to rise and fall is restricted, similar to how pollutants disperse under neutral atmospheric conditions.
Fanning Plume Behavior
Chapter 3 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The third condition is called Fanning and now you see here that the adiabatic lapse rate and environmental lapse rate intersect but they intersect right below the source just below the source.
Detailed Explanation
Fanning occurs when the adiabatic lapse rate and environmental lapse rate intersect just below the plume's source. Here, thermal buoyancy is suppressed due to the higher temperature of the surrounding air, causing the plume to remain close to the specified mixing height without significant vertical dispersion. The pollutants spread mainly in the horizontal direction, resulting in concentrated emissions that do not rise high into the atmosphere.
Examples & Analogies
Picture a candle flame that’s being blown on by a gentle wind. The flame flickers but does not move much higher; instead, it spreads its light and heat more horizontally. This represents how pollutants behave in the fanning condition – they stay low and spread out, rather than rising significantly.
Fumigation Plume Behavior
Chapter 4 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
This particular case where we have called as Fumigation, where it is exactly the opposite. There is inversion there.
Detailed Explanation
Fumigation occurs under conditions of atmospheric inversion when a stable layer of warm air traps cooler air (and the pollutants) below it. It is hazardous because pollutants that are released below this inversion layer remain confined close to the ground, leading to higher concentrations of pollutants in the air, especially in downwind areas. This phenomenon indicates the potential for harmful exposure to emissions.
Examples & Analogies
Imagine a situation where you light a campfire in a valley on a cool evening. Initially, the smoke rises, but as the night cools, a warm layer of air forms above the valley, trapping smoke closer to the ground. The smoke then spreads horizontally across the valley, creating a concentrated cloud of smoke at ground level, just as pollutants do in fumigation situations.
Lofting Plume Behavior
Chapter 5 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The last one is called as Lofting in which there are two inversions.
Detailed Explanation
Lofting occurs when two layers of warm air create an enclosure above the pollutant source, preventing the pollutants from rising lower than this zone. The pollutants spread upwards into the warmer air, where conditions may allow for dispersion. This results in a higher and more dispersed plume, which can lead to lower ground-level concentrations of pollutants.
Examples & Analogies
Think of a balloon filled with helium trapped between two layers of plastic wrap. The balloon tries to rise but is caught between the two layers. It can still float upwards but remains confined within a certain volume, preventing it from dropping down. Similarly, lofting allows pollutants to rise but keeps them from moving downwards toward the earth's surface.
Key Concepts
-
Plume Shapes: Different forms that plumes take depending on atmospheric conditions.
-
Stability: The state of the atmosphere that dictates how pollutants will behave in terms of dispersion.
-
Mixing Height: The altitude at which the atmosphere can no longer effectively mix pollutants, affecting ground-level concentration.
Examples & Applications
Example of a looping plume occurs in cities during hot summer afternoons when thermal convection is high.
Fanning plumes can often be observed during early morning hours when surface inversions occur.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
When plumes are high and looping sway, unstable winds lead the way.
Stories
Imagine a balloon filled with hot air—when it’s released on a windy day, it swirls up and down erratically—that’s a looping plume!
Memory Tools
Remember 'L-C-F': Looping for high turbulence, Coning for neutral flow, Fanning for sinking below!
Acronyms
SUD
Stable Unstable Dispersion helps remember how pollutants behave under different stability conditions.
Flash Cards
Glossary
- Plume
The visible or measurable stream of pollutants released into the atmosphere from a source.
- Adiabatic Lapse Rate
The rate of temperature change in an air parcel as it ascends or descends without transferring heat to its environment.
- Environmental Lapse Rate
The rate at which atmospheric temperature decreases with an increase in altitude.
- Mixing Height
The altitude at which pollutants can mix with the ambient air; determined by the intersection of the adiabatic and environmental lapse rates.
- Stable Conditions
Atmospheric conditions where vertical motion is suppressed, leading to minimal dispersion.
- Unstable Conditions
Atmospheric conditions characterized by strong vertical mixing and significant dispersion of pollutants.
- Looping Plume
A plume shape characterized by significant vertical movement resulting from unstable atmospheric conditions.
- Coning Plume
A plume shape that forms when thermal effects are minimal, resulting in a cone-like dispersion pattern.
- Fanning Plume
A plume shape that occurs under certain conditions, suppressing vertical dispersion.
Reference links
Supplementary resources to enhance your learning experience.