Atmospheric Transport Flashcards
define buoyency
netforce exerted on an object represented by the difference between the pressure gradient force and gravitational force. determined by the vertical gradient of temperature
Pressure gradient formula
p’Vg
buoyency formula
Y_b= ( (p’-p)/p)g
pressure temperature relationship
Pressure is inversely proportional to temperature
define lapse rate
Temperature decrease with altitude: -dt/dz
if T of parcel > T of surroundings
the parcel will rise
Assuming the adiabatic rise of an air parcel from z to z+dz, what happens to that air parcel.
the parcel expands, work is done. NO heat is exchanged between parcel and its surroundings, heat lost as air parcel cools goes into expansion of parcel.
air must ____ as it sinks
heat
air must ____ as it rises
cool
what is the adiabatic lapse rate?
Γ=g/Cp = 9.8 K/km
what is the specific heat of air at constant pressure?
1.01J//kg/K
When is an atmosphere unstable?
when the atmospheric lapse rate :
-dt/dz> Γ . Atmosphere cools faster per kilometer increase in altitude than the adiabatic parcel of air that follows the Γ lapse rate. Fast Vertical Mixing. Air parcel is warmer than
surroundings, and will be
accelerated upwards by
buoyancy.
when is the atmosphere stable?
when the atmospheric lapse rate :
-dt/dz < Γ . Atmosphere cools slower per kilometer increase in altitude than the adiabatic parcel of air that follows the Γ lapse rate. This causes the parcel to sink. Mixing is supressed, Air parcel is colder than surroundings, then will sink back to its original location.
What does Fast vertical mixing do to an unstable atmosphere?
maintains the lapse rate to Γ
How does solar heating cause an unstable atmosphere?
Solar heating of the surface of the earth pushes the bottom of the environmental lapse rate to a higher temperature, making its slope -dT/dz > Γ. This creates a unstable atmosphere, the strong vertical mizing that happens as a result pushes the environmental lapse rate -dT/dz towards Γ until they are approximately equal again, creating a relaxed unstable atmosphere.
How does cloud formation cause an unstable atmosphere?
Clouds adhere by the wet adiabatic lapse rate, which is even more resistant to -dT/dz.
Γ_w = 2-7 K/km
A rising adiabatic air parcel rises by some force until it reaches air cold enough to push its relative humidity to 100%, this changes its lapse rate from dry adiabatic to wet adiabatic. Through the process of cloud formation (condensation) latent heat is released causing Γ to decrease to Γ_w.
What is The planetary boundary layer (PBL)?
it is a layer that extends from the surface to
the base of the subsidence inversion.
