Atmospheric Thermal Structure Flashcards
What layer of the atmosphere contains 80% of the total mass of the atmosphere and almost the whole quantity of water vapor?
Troposphere
What determines how a pollutant can disperse through the atmosphere?
Rate of change of temperature with altitude.
What are the physical properties of the atmosphere (state variables)?
Pressure, Density, and temperature.
How is the atmosphere divided into layers?
By the vertical distribution of temperature.
T/F: In the troposphere, temperature decreases with height?
True
Lapse Rate
Γ = -dT/dz
What are the features of the boundary layer?
- Surface Layer
- Convective mixed layer
- Temperature Inversion Layer
- Residual Layer
What does the boundary layer depend on?
Ground temperature
How is a surface inversion created during the night?
The ground cools radiatively, causing air temperatures to increase with increasing height from the ground.
T/F: Pollutants are more likely to be trapped in the surface layer at day?
False, because the surface inversion causes pollutants to stay trapped.
Ideal gas law specifically for dry air?
p = ρd Rd T
- ρ is rho, density
Rd = R*/ Md, gas constant
T = temperature
Ideal gas law for moist air?
p = ρv Rd Tv
- ρ is rho, density
Rv = R*/Mw
Tv = virtual temperature
What is virtual temperature tv?
The temperature a
hypothetical sample of dry air would need to have in order to have the same density as the sample of moist air at the same pressure.
What is the virtual temperature formula?
Tv = [1 + 0.61*rv ] * T
Hydrostatic Equations
F pressure = F gravity
−δp = gρδz
At the limit of δz -> 0
∂p/ ∂z = -g*ρ
Hydrostatic balance with ideal gas law:
∂p/ ∂z = - p*g/ Rd * Tv
1st law of thermodynamics
With Specific heat capacity
dq = cvdT +pdα
dq = cpdT − αdp
cp = cv + R
Where is cv = 717 JK-1kg-1 and cp = 717 J K-1kg*-1 are the
specific heat at constant volume and pressure respectively.
Isobaric
Constant pressure
dp = 0
δq = cp*dT
Isothermal
Constant temperature
dT = 0
du = 0 since dT = 0
-> δq = δw
All heat goes into work.
Isochoric
Constant volume
dV = 0
δw = 0 since dV = 0 (and dα = 0)
δq = du = cv*dT
No work, all heat into T changes.
Adiabatic
No heat exchanged,
δq = 0, du = - δw since δq = 0
How does temperature change with height for a rising thermal?
Temperature is the highest when nearer to the ground
Dry adiabatic lapse rate
-dT/dz = cp/g = Γd
What are the conditions for saturated adiabatic (moist adiabatic)?
All condensed water remains in rising air parcel.
No precipitation
Adiabatic - no heat exchanged with environment
Saturated Adiabatic lapse rate
Γs - not a constant like dry adiabatic lapse rate
Γs - depends on net amount of condensation
-dT/dz = Γs = Γd [1 + (Lv+Ws/RdT)/ 1+ (Lv^2ws/RvcpT^2)]
Answer in bracket is always smaller than 1, so Γs < Γd
Saturated Adiabatic lapse rate
Γs - not a constant like dry adiabatic lapse rate
Γs - depends on net amount of condensation
-dT/dz = Γs = Γd [1 + (Lv+Ws/RdT)/ 1+ (Lv^2ws/RvcpT^2)]
Answer in bracket is always smaller than 1, so Γs < Γd
T/F: Saturated lapse rate - Γs- decreases with increasing moisture content (and thus temperature)
True
Potential Temperature
θ - as
the temperature a parcel would have if it
adiabatically moved from existing pressure to a
standard pressure, defined as p0 ≡ 1000 hPa.
What process is potential temperature?
A conserved adiabatic processes
What are the four concepts of stability?
Stable
Neutral
Unstable
Conditionally unstable
Stable
Returns to its original position after displacement
Neutral
Remains in new position after being displaced
Unstable
Moves further away from its original position
after being displaced
Conditionally unstable
Becomes unstable for a large enough vertical displacement
- This is the most common instability in the atmosphere
Buoyancy
Ftot = (ρ env + ρ parc)* V*g
If density of air parcel (ρparc) is
greater than the density of
environmental air (ρenv) that it
displaces, then the air parcel will
experience a . . .
downward directed total (buoyancy + gravity) force (Ftot):
ρ parc > ρ env
If density of air parcel (ρparc) is less
than density of the environmental
air (ρenv) that it displaces, then air
parcel will experience an . . .
upward directed total (buoyancy + gravity) force (Ftot)
ρ parc < ρ env
Buoyancy force in terms of T
Parcel’s density immediately adjusts to environment (like a balloon!)
- Differences in density are due to differences in T
(Ftot = (ρ env + ρ parc)* V*g) + (ρ = p/ Rd Tv)
atot = (Tparc - Tenv / Tparc ) *g
Buoyant
T of parcel > T of environment
Sink
T of parcel < T of environment
Stays put
T of parcel = T of environment
What are the three possibilities for saturated air?
Stable
Neutral
Unstable
Characteristics of stable saturated air
Γenv < Γd –> dθ/ dz > 0
-Parcel becomes
colder than nearby
environment
-Downward buoyancy force
- Parcel will return to original location
Characteristics of neutral saturated air
Γenv = Γd –> dθ/ dz = 0
-Parcel T becomes equal to
environment
-No buoyancy force
- Parcel will remain at new location
Characteristics of unstable saturated air
Γenv > Γd –> dθ/ dz < 0
-Parcel becomes
warmer than environment
-Upward buoyancy force
- Parcel will move further away from original location
Unsaturated air is unstable if θ decreases with z!
What are the 5 possibilities for moist air (either saturated or unsaturated)?
Absolutely unstable
Dry neutral
Conditionally unstable
Moist neutral
Absolutely stable
Absolutely unstable
Γenv > Γd > Γs
Unsaturated parcel becomes warmer than nearby environment
Saturated parcel becomes warmer than nearby environment
Dry neutral
Γenv = Γd > Γs
Unsaturated parcel becomes equivalent to the nearby environment
Saturated parcel becomes warmer than nearby environment
Conditionally unstable
Γd > Γenv > Γs
Unsaturated parcel becomes colder than nearby environment
Saturated parcel becomes warmer than nearby environment
*The vertical temperature profile at many locations in our atmosphere is conditionally
unstable!
Moist neutral
Γd > Γenv = Γs
Unsaturated parcel becomes colder than nearby environment
Saturated parcel becomes equivalent to the nearby environment
Absolutely stable
Γd > Γs > Γenv
Unsaturated parcel becomes colder than nearby environment
Saturated parcel becomes colder than nearby environment
At stable atmosphere, what is the application of the source?
fanning
At unstable atmosphere, what is the application of the source?
Looping
At neutrally stable, what is the application of the source?
Coning
At smokestack above the inversion layer, what is the application of the source?
Lofting
At smokestack under the inversion layer, what is the application of the source?
Funmigation
