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Meteorology > The Atmosphere > Flashcards

The Atmosphere Flashcards

1
Q

Describe vertical variation of atmosphere, regarding temperature with height

A

Each bit has a temperature lapse rate.

Troposphere - decreases with height
Stratosphere - Same temp till 20km then increases
Mesosphere - Gets very cold - till -90 degC
Thermosphere - goes to 700 degC

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2
Q

List different layers

A

Troposphere
Stratosphere
Mesosphere
Thermosphere

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3
Q

Describe troposphere

A

As height increases, temperature decreases
Lapse rate is -1.98 degC per 1000ft, or 0.65 degC per 100m
Goes up to 36090ft, or 11km.
Here according to ISA, temp should be -56.5degC
75% of atmosphere mass is in troposphere

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4
Q

Describe proportions of most important gases in troposphere

A

78% Nitrogen
21% Oxygen
1% Other

4% by vol is water vapour

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5
Q

Describe variation of flight level (altitude) and temperature of tropopause from poles to equator

A

Poles - 6-8km, minus 40-50 degC
45 degrees round - 11km high. -56.5 degC
EQ - 16-18km, minus 75degC

Difference in height is due to ground temperature

Hot ground - big tropopause, so more 2deg/1000ft lapse, so colder at tropopause

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6
Q

Describe breaks in tropopause

A

The breaks are at 30deg lat and 60 degrees lat
Or, there are 3 in the north and 2 in the south

At these points, we see the Jetstreams

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7
Q

Variation of tropopause with seasons and atmospheric pressure?

A

In summer, tropopause expands as warmer
In winter, it gets smaller.

Not sure about the pressure bit

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8
Q

Describe the stratosphere

A

Temperature constant up to 20km
Increases at 0.3degC/1000ft
Goes to 50km, where temp is 0degC

There is ozone 03 here. It is warmed from above and the creation of ozone means the UV radiation is turned into longwave, which warms this section.

First bit is “absolutely stable”

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9
Q

Describe differences in composition of Stratosphere compared with Troposphere

A

Same as troposphere, except 0.0003% ozone

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10
Q

Describe mesosphere

A

From 50km to 80-90km

From 0degC down to -290degC

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11
Q

Describe thermosphere

A

From 90km to about 700km

Very high temps, can be between 600degC and 2000degC depending on solar activity

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12
Q

Descibe ionosphere

A

Ionised layer, can affect radio transmissions, eg they can bounce off ionosphere.

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13
Q

Define air temperature

A

Measure of kinetic energy of air particles

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14
Q

List units of temp

A

degC, degF, K

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15
Q

Describe mean vertical distribution of temperature up to 20km.

A

+15 degC at surface
reduces at -1.98 degC/1000ft or -0.65 degC per 100m
to -56.5 degC at tropopause, at 11km or 36090ft
Steady temperature up to 20km

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16
Q

What are the general causes of cooling going upwards in troposphere?

A

Troposphere is warmed from the surface of the earth via conduction but mainly longwave radiation

This effect is lessened as you go upwards as there is more air down below.

Conduction affects up to 2000ft.

This is called the environmental lapse rate (1.98deC per 1000ft)

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17
Q

Learn to calculate temperature deviations

A

Calculate ISA temperature at the given height using 15-(Thousands of feet*2).

If it is above tropopause, then calc including deviation to tropopause level. Then take that value.

The temperature difference is the ISA deviation.

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18
Q

Explain how local warming or cooling results in transfer of heat

A

This describes conduction - where two bodies that touch transfer heat. If one bit of earth’s surface is hot, the air temp there is hot.

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19
Q

Describe radiation

A

This is the transfer of heat through electromagnetic waves.

20
Q

Describe solar radiation reaching the earth

A

Solar radiation is the primary cause of all weather.

Some absorbed by ozone, some some reflected by clouds and earths surface, major part is absorbed by earth.

Short wave insolation penetrates atmosphere
Long wave gets absorbed by the atmosphere

21
Q

Describe terrestrial radiation

A

This is the emmission of longwave radiation from the Surface.

Atmosphere is good at absorbing longwave, so this heats up the atmosphere

22
Q

Explain how terrestrial radiation is absorbed by some components of the atmosphere

A

Some gases are greenhouse gases.

Water vapour
Carbon Dioxide
Hydrogen
Methane
Ozone
Carbon Monoxide

These are efficient at absorbing longwave radiation

23
Q

Explain the process of conduction

A

Close to surface (-2000ft), the temp is impacted by conduction.

Thus the temperature can be higher or lower than that predicted by ISA.

If lower than temp above (at night) then get nocturnal inversion.

Windy, turbulent air increases conduction layer as more in contact with ground

24
Q

Explain the effect of absorption and radiation in connection with clouds

A

During day, clouds reflect a big proportion of solar radiation. So less insolation. Cooler max surface temp.

Night, water vapour is greenhouse gas so longwave from surface get absorbed and re-radiated back to ground, so slightly warmer than it would be.

Cloud cover reduces diurnal variation.

25
Q

Explain convection and its effect

A

Convection is vertical transfer of heat

Over surface, bits are warmer and cooler. Hot areas rise due to convection. Air becomes less dense so rises.

Can rise at 10000ft/min

26
Q

Explain advection

A

This is like sideways convection

If hotter in one place than another, then wind will blow it sideways.

As sea air is often hotter, coastal areas hotter than inland.

27
Q

Explain heating by turbulence

A

This is when hot air mixes with cold air and we get the average heat.

28
Q

Explain heating by transfer of latent heat

A

To do with state changes of water.

Water to gas means energy must be absorbed, so surroundings are COLDER.

Water to ice means energy must be expelled so it is HOTTER.

29
Q

What are the types of inversions?

What are the effects?

A 
Temperature inversion (umbrella term)
Ground inversion
Frontal Inversion
Subsidence Inversion
Tropopause Inversion

Effects: Nothing can get out. Smog and pollution are more dense so don’t go to where the temperature is higher.

Clouds will flatten and mushroom/

30
Q

Describe a ground inversion

A

At night, temp is low.

Conduction causes lower temp close to ground.

Can get inversion in valley where the air slides in

Fixes when sun warms the ground.

31
Q

Describe a frontal inversion

A

When a warm front meets cold air.

Causes a warm front slope -> inversion

32
Q

Subsidence inversion

A

When a body of air descends, the air pressure increases and thus pushes itself away, so what is left is the original cold air

33
Q

Tropopause inversion

A

When the temperature increases above the tropopause, where it should have stabilised up to 20km.

34
Q

Describe seasonal variations affect temp close to surface

A

Earth tilted at 23.5deg. So either northern or southern hemisphere is hotter or colder depending on which is closest to the sun.

So insolation depends on angle of inclination

35
Q

Sketch diurnal heating of surface of earth

A

Low is half hour after sunrise, as heat is still leaving the earth.

High temp is at 3pm due to lag in sun -> earth -> air.

Maximum insolation is at noon.

36
Q

How does nature of surface affect temperature?

A

Ice and snow - Energy is reflected or used for melting, so colder

Water - High spec heat cap, so energy used to heat water. Energy reflected or used for evaporation

Vegetation - Some absorbed for growing, some re-radiated

Cities - Energy easily absorbed and re-radiated, so quick to heat and cool (low spec heat cap)

Hot -> Cold
Cities, Veg, Water, Ice

37
Q

How do clouds and wind affect diurnal temperature

A

They make the range of temperature lower. Lower max, higher min.

38
Q

How does sea affect affect diurnal temp

A

Again, lower max and higher min.

39
Q

Distinguish effect of high/low thick/thin clouds

A

High clouds - cooler temp as re-radiation is less at low hight.

Thick cloud - higher temp as more radiated

40
Q

Explain the pressure variation with height.

What are the pressures at heights you must know?

A

Pressure decreases with height.

More change of pressure at lower height.
Less change of pressure at higher height

100hPa at 53800ft
200hPa at 38000ft
300hPa at 30000ft
500hPa at 18000ft  (50% of that at MSL)
700hPa at 10000ft
41
Q

What are the pressure lapse rates at 3 different heights?

A

Up to 10000 - 1 hPa per 27ft
10-18000 - 1hPa per 37ft
+18000ft - 1hPa per 50ft

42
Q

What is the density lapse rate at 4 different heights?

A

MSL - 1.225
10000 - 0.903 =75%
22000 - 0.609 =50%
40000 - 0.302 = 25%

43
Q

List what is in the ICAO standard atmosphere

A

ISA
Temp 15degC
Density 1.225 kg/m3 = 29.92 inches Hg
Pressure 1013.25hPa

44
Q

What do we use to measure ground temp? List some things about it

A

Stevenson’s Screen

4ft above ground
covered
dry and wet bulb

45
Q

What do we use to measure air temp?

A

Radiosonde

is weather ballon
measures temp, pressure, density
GPS and airspeed

Meteorology (1 decks)

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