2.3 Weather processes and phenomena

Question 1

Adiabatic lapse rate

Answer 1

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

Question 2

Adiabatic processes

Answer 2

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

Question 3

Advection fog

Answer 3

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.

Question 4

Air mass

Answer 4

Large body of air with relatively similar temperature and humidity characteristics

Question 5

Altitude

Answer 5

Measurement in height usually given in meters above sea level.

Question 6

Clouds

Answer 6

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

Question 7

Condensation level

Answer 7

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

Question 8

Conditional instability

ask

Answer 8

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.

Question 9

Depression

Answer 9

Region of low atmospheric pressure.

Question 10

Dew

Answer 10

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

Question 11

How is dew formed?

Answer 11

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

Question 12

Dew point

Answer 12

Temperature at which relative humidity is 100 percent

Question 13

Environmental lapse rate (ELR)

Answer 13

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

Question 14

Evaporation

Answer 14

Process by which a liquid if transformed into a gas.

Question 15

Fog

Answer 15

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

Question 16

Front

Answer 16

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

Question 17

Humidity

Answer 17

Measure of the amount of moisture in the air.

Question 18

Absolute humidity

Answer 18

How much moisture there is in the air

Question 19

Relative humidity

Answer 19

How much moisture air at an specific temperature can hold

Question 20

Instability

Answer 20

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

Question 21

Lapse rate

Answer 21

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

Question 22

Mist

Answer 22

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

Question 23

Orographic (relief) rainfall

Answer 23

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

Question 24

Radiation fog

Answer 24

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.

Question 25

Rain shadow

Answer 25

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

Question 26

Stability

Answer 26

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

Question 27

Thunderstorm

Answer 27

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

Question 28

Dry adiabatic lapse rate (DALR)

Answer 28

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

Question 29

Saturated adiabatic lapse rate (SALR)

Answer 29

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