The Atmosphere

Question 1

Describe vertical variation of atmosphere, regarding temperature with height

Answer 1

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

Question 2

List different layers

Answer 2

Troposphere
Stratosphere
Mesosphere
Thermosphere

Question 3

Describe troposphere

Answer 3

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

Question 4

Describe proportions of most important gases in troposphere

Answer 4

78% Nitrogen
21% Oxygen
1% Other

4% by vol is water vapour

Question 5

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

Answer 5

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

Question 6

Describe breaks in tropopause

Answer 6

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

Question 7

Variation of tropopause with seasons and atmospheric pressure?

Answer 7

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

Not sure about the pressure bit

Question 8

Describe the stratosphere

Answer 8

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”

Question 9

Describe differences in composition of Stratosphere compared with Troposphere

Answer 9

Same as troposphere, except 0.0003% ozone

Question 10

Describe mesosphere

Answer 10

From 50km to 80-90km

From 0degC down to -290degC

Question 11

Describe thermosphere

Answer 11

From 90km to about 700km

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

Question 12

Descibe ionosphere

Answer 12

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

Question 13

Define air temperature

Answer 13

Measure of kinetic energy of air particles

Question 14

List units of temp

Answer 14

degC, degF, K

Question 15

Describe mean vertical distribution of temperature up to 20km.

Answer 15

+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

Question 16

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

Answer 16

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)

Question 17

Learn to calculate temperature deviations

Answer 17

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.

Question 18

Explain how local warming or cooling results in transfer of heat

Answer 18

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.

Question 19

Describe radiation

Answer 19

This is the transfer of heat through electromagnetic waves.

Question 20

Describe solar radiation reaching the earth

Answer 20

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

Question 21

Describe terrestrial radiation

Answer 21

This is the emmission of longwave radiation from the Surface.

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

Question 22

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

Answer 22

Some gases are greenhouse gases.

Water vapour
Carbon Dioxide
Hydrogen
Methane
Ozone
Carbon Monoxide

These are efficient at absorbing longwave radiation

Question 23

Explain the process of conduction

Answer 23

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

Question 24

Explain the effect of absorption and radiation in connection with clouds

Answer 24

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.

Question 25

Explain convection and its effect

Answer 25

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

Question 26

Explain advection

Answer 26

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.

Question 27

Explain heating by turbulence

Answer 27

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

Question 28

Explain heating by transfer of latent heat

Answer 28

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.

Question 29

What are the types of inversions? What are the effects?

Answer 29

``` 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/

Question 30

Describe a ground inversion

Answer 30

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.

Question 31

Describe a frontal inversion

Answer 31

When a warm front meets cold air. Causes a warm front slope -> inversion

Question 32

Subsidence inversion

Answer 32

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

Question 33

Tropopause inversion

Answer 33

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

Question 34

Describe seasonal variations affect temp close to surface

Answer 34

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

Question 35

Sketch diurnal heating of surface of earth

Answer 35

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.

Question 36

How does nature of surface affect temperature?

Answer 36

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

Question 37

How do clouds and wind affect diurnal temperature

Answer 37

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

Question 38

How does sea affect affect diurnal temp

Answer 38

Again, lower max and higher min.

Question 39

Distinguish effect of high/low thick/thin clouds

Answer 39

High clouds - cooler temp as re-radiation is less at low hight. Thick cloud - higher temp as more radiated

Question 40

Explain the pressure variation with height. What are the pressures at heights you must know?

Answer 40

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 ```

Question 41

What are the pressure lapse rates at 3 different heights?

Answer 41

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

Question 42

What is the density lapse rate at 4 different heights?

Answer 42

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

Question 43

List what is in the ICAO standard atmosphere

Answer 43

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

Question 44

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

Answer 44

Stevenson's Screen 4ft above ground covered dry and wet bulb

Question 45

What do we use to measure air temp?

Answer 45

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