2.3 Weather processes and phenomena Flashcards Preview

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Flashcards in 2.3 Weather processes and phenomena Deck (29)
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1

Adiabatic lapse rate

Change of temperature caused by the air changing internally. i.e rising and falling in height

2

Adiabatic processes

Change in temperature of a parcel of air caused by its ascent or descent. Changes are internal.

3

Advection fog

It is formed by warm air flowing over a cold surface, being chilled, reaching dew point , and condensation taking place, close to the ground's surface.

4

Air mass

Large body of air with relatively similar temperature and humidity characteristics

5

Altitude

Measurement in height usually given in meters above sea level.

6

Clouds

Water vapour condensed into millions of minute water particles that float in masses in the atmosphere.

7

Condensation level

Altitude at which relative humidity is 100 percent, when clouds form.

8

Conditional instability
(ask)

When the ELR is lower than the DALR (dry adiabatic lapse rate) but higher than the SALR (saturated adiabatic lapse rate). The air in unstable so dew point is reached.

9

Depression

Region of low atmospheric pressure.

10

Dew

Precipitation in the form of moisture that collects on the ground.

11

How is dew formed?

It is formed after temperature of the ground has fallen below dew point of the air in contact with it.

12

Dew point

Temperature at which relative humidity is 100 percent

13

Environmental lapse rate (ELR)

Normal decline of temperature with altitude; usually about 6/1000m

14

Evaporation

Process by which a liquid if transformed into a gas.

15

Fog

Cloud at ground level, composed of water vapour that has condensed on particles of dust in the atmosphere.

16

Front

Boundary between a warm air mass and a cold air mass that results in frontal (cyclonic) rainfall

17

Humidity

Measure of the amount of moisture in the air.

18

Absolute humidity

How much moisture there is in the air

19

Relative humidity

How much moisture air at an specific temperature can hold

20

Instability

Refers to unstable atmospheric conditions (rising air) likely to cause cloud formation and precipitaion

21

Lapse rate

Rate of change of atmospheric factors (temperature and humidity) with changing altitude

22

Mist

Low cloud caused by condensation of water vapour in lower part of the atmosphere. (less thick than fog)

23

Orographic (relief) rainfall

Rainfall that occur when an airstream is forced to rise over a mountain range

24

Radiation fog

Fog forms on clear, calm nights when the land surface loses heat capacity the air above is cooled to below dew point and condensation takes place.

25

Rain shadow

Leeward side of hills, which has a relatively light rainfall compared to the windward side.

26

Stability

Refers to pressure conditions; air is unable to rise above a low level, calm , dry conditions.

27

Thunderstorm

Usually carried by intense heating of ground surface during the summer.

28

Dry adiabatic lapse rate (DALR)

Adiabatic cooling and warming in dry unsaturated air occurs at around 10/km

29

Saturated adiabatic lapse rate (SALR)

Air in which condensation is occurring. Between 4/km and 9/km