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Flashcards in Met Exam Deck (279)
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1

What is the average pressure at mean sea level??

1013.25hPa

2

Describe the composition of the atmosphere.

Nitrogen 78.09%

Oxygen 20.95%

Argon 00.93%

Carbon Dioxide 00.03%

3

What are the layers of the atmosphere from highest to lowest?

Thermosphere (Ionosphere is here)

Mesosphere

Stratosphere

Troposphere

4

What are the depths of the troposphere?

52,000ft/16km at the equator

36,000ft/11km at 50degrees north

30,000ft/9km at the poles

5

Describe the conditions of the stratosphere

Extends from the troposphere to 50km with a constant temp of around 0 degrees Celsius

6

What is the difference between official and unofficial met observations?

Official is provided by an appropriately trained person at a unit with the necessary equipment. Otherwise unofficial.

7

What are the conditions of the ISA?

International standard atmosphere

.pressure of 1013.25hPa

.air density 1225gm/m3

.temperature +15°C

. 1.98°C per 1000ft lapse rate up to 36,000ft, remains at -56.5°C thereafter up to 65,000ft

8

Where is most of the water, weather and flight in the atmosphere?

99% in the troposphere

Most flight happens here

9

What is the upper limit of the troposphere called?

The tropopause

10

How many feet of height does a hPa equal roughly?

30ft

11

What is insolation?

The incoming radiation from the sun warming the earth, as the air does not absorb the energy.

12

What is specific heat capacity?

The energy required to heat 1kg of a substance by 1°C

13

What factors affect diurnal variation?

Surface- variation is greater over land and sea.

Wind speed- wind causes turbulence that spreads the cooling effect through a greater depth of air.

Cloud- reduces heat loss.

14

How do inversions and isothermal layers affect the lapse rate?

Inversions cause the adiabatic effect to reverse and the air actually heats up as it rises. Isothermal layers are where the temperature remains the same in that layer and doesn't lapse.

15

What four ways may a parcel of air be cooled past its dew point?

Conduction

Evaporation

Mixing

Adiabatic cooling.

16

Define adiabatic

The change in temperature of a parcel of air as its density changes, normally cooling as the air expands when rising.

17

What are the adiabatic lapse rates for dry and saturated air?

SALR= 1.5 degrees/ 1000ft DALR= 3.0 degrees/1000ft

18

What is the ELR?

The environmental adiabatic lapse rate that exists within the atmosphere at a particular time. (ISA global average is 1.98 degrees per 1000ft)

19

Define stable and unstable air.

Stable air is air that doesn't rise and unstable rises.

20

Describe the Celsius Scale

Freezing point H20= 0°C

Boiling point H20=100°C

21

Describe the Kelvin scale

Theoretical Absolute zero= -273°C (0°K)

Freezing point H20= 273°K

Boiling point H20=373°K

Just add 273 to the celsius scale

22

Describe the Fahrenheit Scale

Freezing point H20= 32°F

Boiling point H20=212°F

23

How do you convert from Celsius to Fahrenheit?

(9x°C)/5+32

24

How do you convert from Fahrenheit to Celsius?

5x(°F-32)/9

25

What is terristerial radiation?

The earth reradiating the energy it received from insolation on a lower frequency which heats up the atmosphere.

26

What are the three main ways heat can be transferred in the atmosphere?

  1. Radiation
  2. Conduction 
  3. Convection (transfer of heat by vertical movement)

27

What is Diurnal Variation?

The daily variation in temperature

28

What happens to temperature as a parcel of air rises and what is this know as?

It cools

Adiabatic cooling.

29

Define latent heat.

The heat required to cause a change of state, the actual temperature does not change during the change of state as the energy is used to actually change the state.

A change from gas to liquid or liquid to solid will release energy into the environment and the opposite will absorb energy.

 

30

How does the temperature of the air affect its humidity/saturation? What is the point at which a piece of air that is cooling becomes fully saturated?

Warmer air holds more moisture so as a parcel of air warms its ability to retain water increases so it is less saturated and vice versa.

The dew point.