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A short class with Sarah and her students. The other ways are under More.
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Let's start by discussing how the temperature profile changes during the day. Can anyone tell me how the sun affects the earth's surface temperature?
The sun heats the ground, right? So, the ground should be hotter than the air.
Exactly, Student_1! This phenomenon creates a positive temperature gradient where the air near the surface is warmer than the air above. This drives vertical convection. Remember, 'warmer rises,' which can also help us remember the thermal dynamics involved!
What happens when the sun sets?
Great question, Student_2! As the sun sets, the ground begins to cool rapidly, and this affects the air above it, creating a different temperature profile. Let's explore what that looks like.
Now, as night approaches, the soil cools quickly, significantly affecting the air above it. What do you think happens to pollutants at this stage?
Doesn’t it trap them near the ground since the air is warmer?
Exactly, Student_3! This creation of a temperature inversion prevents pollutants from rising, leading to poor air quality. It's crucial to remember that during a temperature inversion, pollutants can accumulate. We can use the acronym 'INVERT' as a memory aid: 'Inversions Negatively Violate Environmental Relief of Toxins.'
So, is this why we often see fog at night in some places?
Yes, Student_4! Fog forms at night when conditions are humid, and the ground cools. Once the temperature starts rising in the morning, this fog lifts due to the warming air.
Let's now dive into the concept of the environmental lapse rate. Who remembers what influences this lapse rate?
Is it about how temperature changes with height?
That's right! The environmental lapse rate describes the rate at which temperature decreases with altitude. It varies based on the time of day and local conditions. Can anyone think of a practical implication of this?
It affects how air bubbles of pollutants move, right?
Exactly! The interaction between the environmental lapse rate and the dry adiabatic lapse rate determines the stability of the atmosphere, which is essential for pollutant transport.
Now, let’s discuss buoyancy. When talking about air parcels, what do we mean by buoyancy?
I think it's how a warmer air parcel can rise since it's lighter than surrounding air.
That's correct! So, if the environmental lapse rate is such that a parcel of air is warmer than the air above it, how does this affect the pollutant concentration?
It would mean the pollutants can rise higher, leading to lower concentrations at ground level!
Spot on, Student_4! Remember, more buoyancy means more vertical motion, while stability can trap pollutants. This disparity influences air quality significantly.
The change in temperature between the earth's surface and the atmosphere.
The rapid cooling of the earth's surface at night which affects air quality.
A condition where temperature rises with altitude affecting pollutant dispersion.
Reflect the stability of the atmosphere and its impact on pollutant transport.
The height above ground at which pollutants become effectively mixed in the atmosphere.
At night, the soil's cool and bright, Inversion traps toxins out of sight.
Imagine a cool night in the forest; the ground chills quickly, holding pollutants below, just like a blanket trapping warmth underneath, until the morning sun rises and clears the air.
Use 'HEAT' to remember: 'High air rises, Earth cools quickly, Air pockets stay trapped, Temperature inverts.'
INVERT: Inversions Negatively Violate Environmental Relief of Toxins.
Term
What is temperature inversion?
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What does environmental lapse rate indicate?
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What does buoyancy refer to in atmospheric terms?
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A phenomenon where temperature increases with height rather than decreases, leading to the trapping of pollutants.
The rate at which air temperature decreases with an increase in altitude in a given environment.
The ability of an air parcel to rise due to being warmer and lighter than the surrounding air.
The rate at which an air parcel cools as it rises in the atmosphere without exchange of heat.
The altitude at which the effects of buoyancy and turbulence allow for effective dispersion of pollutants.
This section discusses the changes in temperature profiles during nighttime and their implications for air quality and pollutant transport.
The section explores how soil and air temperature variations during the day and night affect atmospheric stability and pollutant dispersion. It details the transition from daytime heating to nighttime cooling and highlights concepts like temperature inversion and environmental lapse rates.
This section focuses on the dynamics of temperature profiles as they change from day to night, particularly how nighttime cooling affects the stability of the atmosphere and the transport of pollutants. During the day, the sun heats the ground more quickly than it heats the air above, creating a positive temperature gradient where the air closer to the surface is warmer. This gradient allows for vertical movement of air, driven by thermal forces.
As night falls, typically around 6:30 or 7 PM, radiation from the ground ceases, leading to rapid cooling of the soil. The cooler soil cools the air immediately above it, creating a scenario where the air is warmer than the ground. This temperature inversion is crucial for understanding how pollutants behave at night. It allows pollutants to remain trapped near the surface, as upward movement becomes inhibited in such stable atmospheric conditions.
By morning, as the sun rises, the cycle reverses; the ground heats up, warming the air again, which impacts fog formation and pollutant concentrations. The section concludes with a discussion on environmental and dry adiabatic lapse rates, exploring how buoyancy and stability influence pollutant transport and the concept of mixing height.