Lectures 3 & 4 Flashcards

1
Q

What controls Qg

A

-the amount of energy required to raise the temperature object through 1°C
-thermal conductivity

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2
Q

How fast is Qg

A

Qg is a relatively slow responding flux due to conduction

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3
Q

How large is the laminar boundary layer

A

Very small - 5 to 50 mm thick around all objects

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4
Q

Breakdown of laminar boundary layer

A

speed, distance from source, and viscosity of air are reached.

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5
Q

Is low velocity more or less turbulent?

A

Less turbulent

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6
Q

Is shorter distance more or less turbulent?

A

Less turbulent

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7
Q

Is lower viscosity more or less turbulent?

A

More turbulent

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8
Q

Mechanically induced turbulence =

A

Forced convection

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9
Q

Thermically induced turbulence =

A

Free convection

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10
Q

Free convection is caused by

A

by unequal heating of the surface due to spatially varying surface conditions

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11
Q

What causes unequal heating of the surface?

A

-albedo
-wetness : is incoming radiation used for heating or evaporation?

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12
Q

Does the atmosphere get more or less dense with height?

A

Less dense due to reduced pressure

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13
Q

Adiabatic meaning

A

heat does not enter or leave system

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14
Q

Forced convection

A

air flows along the surface until it meets an obstacle

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15
Q

What is the Cook Strait an example of?

A

Forced convection

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16
Q

What is the rate of temperature change with height in dry unsaturated air?

A

9.8°C per km (DALR)

17
Q

Is the SALR or DALR higher?

A

DALR is always higher.

18
Q

What is the environmental lapse rate?

A

The measure of actual rate of temperature decrease with altitude for a given location.

19
Q

Stability

A

the relative tendency of an air parcel to move vertically

20
Q

ELR > DALR

A

Unstable, favours vertical mixing

21
Q

ELR < DALR

A

Stable, little vertical mixing

22
Q

ELR = DALR

A

Environment cools at 9.8°C per km.

23
Q

Atmospheric stability

A

The actual cooling / heating (ELR) compared to the idealised cooling / heating (DALR) determines whether the atmosphere is stable or unstable

24
Q

What controls the upper limit of turbulent activity?

A

Magnitude of surface forcing (surface roughness, surface heating)
Lost buoyancy from; mechanical mixing, condensation and latent heat release, reaching an inversion

25
What convection dominates most of the outer layer at day time?
Free convection
26
What convection dominates at night time?
Forced convection, with turbulence restricted to shallow surface layer