Buoyancy and Dry Adiabatic Lapse Rate
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.
Temperature Profile and Vertical Convection
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let's begin with the temperature profile as a function of height. Can anyone tell me what we might expect to see as we ascend into the atmosphere?
I think the temperature might decrease with height, right?
Exactly! Generally, the temperature decreases as you go higher in the troposphere. This is a fundamental concept to understand vertical convection, which occurs due to thermal forces.
What happens during the night? Does the temperature still decrease?
Good question! At night, the soil cools down quickly, potentially making the air just above it warmer, causing some interesting behaviors. This difference impacts air movement.
Does that mean we can see fog in the morning?
Precisely! As the ground cools overnight, humidity can lead to fog. This process ties in closely with our next topic, the environmental lapse rate.
Environmental Lapse Rate
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now let’s discuss the environmental lapse rate. It represents how temperature varies with height in the environment. Can anyone explain why this is important?
It probably helps in understanding how pollutants will behave in the atmosphere?
Exactly! Knowing how the environmental lapse rate fluctuates allows us to predict how pollutants will disperse once released. Next, let’s tie this to buoyancy.
What does buoyancy have to do with it?
Great question! Buoyant air rises if it is warmer than the air around it. This tendency is crucial in understanding how pollutants from sources, like engines, will move through our atmosphere.
Dry Adiabatic Lapse Rate
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s define what dry adiabatic lapse rate means. Can anyone summarize this concept?
It's when an air parcel rises without heat exchange, cooling at about 9.8°C per kilometer, right?
Perfect! This concept is vital in understanding how rising air changes temperature without exchanging heat with its environment.
Does that mean the initial temperature doesn't affect the rate at which it cools?
Exactly! Regardless of the starting temperature, the rate remains consistent. This is essential for predicting air parcel behavior during ascent.
Atmospheric Stability
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s explore atmospheric stability. What are the factors that determine whether an air parcel will rise or sink?
It must be about the surrounding temperatures and buoyancy forces, right?
Exactly! If an air parcel is warmer than its surroundings, it rises — and that's called instability. In contrast, if it’s cooler, it sinks, indicating a stable atmosphere.
And what about a neutral situation?
In a neutral situation, temperatures are equal, and no buoyancy difference occurs which means the wind takes control of the parcel’s movement.
So, how does this relate to pollution concentration?
Excellent connection! In stable conditions, pollutants can accumulate, while in unstable configurations, they disperse effectively.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section elaborates on the temperature profile as a function of height and how this affects vertical convection of air masses due to thermal forces. Key concepts include the environmental lapse rate, dry adiabatic lapse rate, stability conditions in the atmosphere, and their implications for pollutant dispersion.
Detailed
Buoyancy and Dry Adiabatic Lapse Rate
This section focuses on the temperature profile of the atmosphere as a function of height, shedding light on buoyancy and the dry adiabatic lapse rate's role in vertical convection and environmental conditions that influence pollutant transport.
Key Topics Covered:
- Temperature Profile: The temperature at Earth's surface is generally higher than the air above, especially during the day. This creates a positive gradient, with local variations occurring throughout the day.
- Environmental Lapse Rate: This is the observed variation in temperature with height and can vary with changes in time and season.
- Inversion and Buoyancy: Temperature inversions complicate pollutant dispersal. For instance, pollutants released from an engine tend to ascend due to buoyancy, but an inversion can trap them in lower layers.
- Dry Adiabatic Lapse Rate: This rate assumes no heat exchange with the surroundings as a parcel of air rises. It typically cools at approximately 9.8°C per kilometer of ascent.
- Atmospheric Stability: The interaction between the air parcel's temperature and environmental temperature affects whether the atmosphere is stable, unstable, or neutral, directly impacting pollutant dispersion.
Understanding these concepts is essential for predicting and analyzing pollutant transport dynamics in varying environmental conditions.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Temperature Profile and Vertical Movement
Chapter 1 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Okay, so, let’s consider two things, first thing to be considered is what is called as the temperature profile as a function of height. So, we are saying that vertical convection happens as a result of thermal forces which means there’s a temperature difference. So, what is the temperature difference that will result in vertical movement of air masses?
Detailed Explanation
This chunk introduces the concept of temperature profiles in the atmosphere. It explains that different temperatures at varying heights lead to vertical convection, where warmer, lighter air rises and cooler, denser air sinks. The focus is on understanding the relationship between temperature and height in the atmosphere, indicating that temperature differences create forces that drive air movement.
Examples & Analogies
Think of a hot air balloon. As the air inside the balloon gets heated, it becomes lighter than the cooler air outside. This light air causes the balloon to rise. Similarly, in the atmosphere, temperature differences cause air to move vertically.
Daily Temperature Changes
Chapter 2 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
During daytime the radiation heats up the soil or the land faster than it heats the air. So, the radiation directly heats the soil. And as a result, this temperature of the soil is very high.
Detailed Explanation
This chunk discusses how the sun’s radiation heats the land during the day. The land absorbs heat quicker than the air, resulting in a positive temperature gradient where the air near the surface is warmer than the air above. This creates instability in the atmosphere, encouraging vertical air movements due to buoyancy effects.
Examples & Analogies
Imagine standing on a sidewalk on a hot day—the ground feels much warmer than the air around you. This difference causes the air above to heat up and rise, similar to how warmer air rises in the atmosphere.
Cooling and Nighttime Effects
Chapter 3 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The soil then starts cooling; it cools very rapidly, given up all its heat. Then you see a certain small decrease, the air is still hot but the soil has started cooling so, you start seeing this kind of behavior.
Detailed Explanation
Here, we see the process of cooling at night. The land cools faster than the air, leading to a situation where the air remains warmer than the ground at certain heights. This creates a new layer of thermal difference, which can lead to fog formation under specific conditions, illustrating the dynamic nature of atmospheric layers.
Examples & Analogies
Think about a clear night—when the ground loses heat quickly, and you might see fog forming. This is because the cooler ground causes moisture in the air to condense, creating a layer of fog.
Environmental Lapse Rate
Chapter 4 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, this profile is called as an environmental lapse rate. It is called a lapse rate because it is a temperature profile as a function of height.
Detailed Explanation
The environmental lapse rate refers to the rate at which temperature decreases with an increase in height in the atmosphere. It varies with time and location and is measured throughout the day and across seasons, indicating characteristic temperature profiles for different environments. The concept explains how temperature stratifies in the atmosphere and its implications for air pollution and climate.
Examples & Analogies
Consider climbing a mountain; as you ascend, you often feel the temperature drop. This phenomenon illustrates the environmental lapse rate in real life—it’s the same concept applied to the atmosphere!
Buoyancy and Air Parcel Movement
Chapter 5 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now, this is what’s happening in the system. So this region is called the temperature inversion. The temperature inversion means generally in the daytime temperature is reducing as a function of height, but here temperature is increasing as height.
Detailed Explanation
This section introduces the concept of temperature inversion, where, contrary to typical conditions, temperature increases with height in certain layers of the atmosphere. This phenomenon can lead to a stable atmospheric condition inhibiting vertical air movement, which is crucial in understanding pollutant behavior in the air.
Examples & Analogies
Imagine being in a valley surrounded by hills on a calm night; the cooler air collects at lower altitudes, while warmer air rests above it, creating a blanket that traps smoke and pollution within the valley, leading to smoky conditions.
Dry Adiabatic Lapse Rate
Chapter 6 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, normally if I release a parcel here, what happens is, if its temperature is higher, it wants to go up. There are two things at play here. One is buoyancy which is making it go up, but as it goes up if there is no exchange of energy, its volume also expands like this and it cools.
Detailed Explanation
The dry adiabatic lapse rate describes the rate at which an air parcel cools as it rises without exchanging heat with its surroundings. It is defined under ideal conditions where there is no heat transfer, emphasizing conservation of energy within the moving air mass. As the parcel rises, the decrease in pressure causes it to expand and cool at a consistent rate of approximately -9.8 degrees Celsius per kilometer.
Examples & Analogies
If you have ever used a spray can, you may have noticed that as you spray, it feels colder. The spray is cooling because as the air mixes with the surrounding air, it is expanding, similar to how an air parcel expands and cools as it rises in the atmosphere!
Atmospheric Stability and Pollution
Chapter 7 of 7
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, if I move it here, what happens it goes up, but when it goes up to temperature, its temperature is lower than that of the surrounding environment. So it is buoyancy is greater so it comes back down.
Detailed Explanation
This section discusses how atmospheric stability, influenced by temperature differences, affects pollutant transport. If an air parcel is warmer than its surroundings, it will rise due to buoyancy; if it’s cooler, it will sink. Stability, neutrality, and instability are all factors that determine how pollutants can disperse in the atmosphere, with stability often leading to higher pollutant concentrations.
Examples & Analogies
A good analogy is building a stack of blocks; if one block is lighter (like warm air), it will float up, dispersing throughout the stack. Conversely, heavier blocks (cool air) fall, showing how pollutants can accumulate or spread depending on atmospheric conditions.
Key Concepts
-
Temperature Profile: Refers to how temperature changes with height, influencing air movement.
-
Environmental Lapse Rate: Describes the actual change in temperature with height in a given environment.
-
Dry Adiabatic Lapse Rate: A constant rate of cooling for a rising dry air parcel, typically 9.8°C per kilometer.
-
Atmospheric Stability: Describes whether an air parcel rises, sinks, or remains neutral based on its temperature relative to surrounding air.
Examples & Applications
During daytime, the ground heats the air above more quickly than it heats the atmosphere, creating a temperature gradient that leads to buoyancy-driven convection.
In winter, a significant temperature inversion can lead to the trapping of pollutants near the surface, causing fog or smog events.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
As you rise, feel the chill, nine point eight, the air will spill.
Stories
Imagine a balloon filled with hot air. It rises quickly but cools down as it climbs. That's how buoyancy and the dry adiabatic lapse rate work in our atmosphere.
Memory Tools
B.E.S.T: Buoyancy, Environmental lapse, Stability, Temperature inversion; Remember these for understanding air movement.
Acronyms
BALR
Buoyancy
Adiabatic
Lapse Rate; Keep these terms together for clarity!
Flash Cards
Glossary
- Buoyancy
The tendency of a fluid to rise or fall due to differences in temperature and density.
- Dry Adiabatic Lapse Rate
The rate of temperature decrease with height in an ascending dry air parcel, averaging 9.8°C per kilometer.
- Environmental Lapse Rate
The observed change in environmental temperature with height during atmospheric observation.
- Temperature Inversion
A reversal of the normal decrease of air temperature with altitude, leading to warmer air above cooler air.
- Atmospheric Stability
The tendency of an atmospheric parcel to remain in place or change altitude based on temperature differences.
Reference links
Supplementary resources to enhance your learning experience.