Lecture 7/8 - Anticyclones & Waves

Question 1

What are anticyclones?

Answer 1

Anticyclones are the opposite of depressions - they are an area of high atmospheric pressure where the air is sinking.

Question 2

What are features of anticyclones?

Answer 2

Slow moving with little/no fronts
Little density change
Surface divergence
Temperature inversions

Question 3

What are the two forms of anticyclones?

Answer 3

Warm core and cold core

Question 4

What are the features of a warm core anticyclone?

Answer 4

Slow moving, occupy at great depth, large geographical extent, sub-tropical and features of the general circulation. Set up major oceanic gyres.

Question 5

What are the features of a cold core anticyclone?

Answer 5

Mobile features, associated with trough ridge systems, cold descending air behind depression.

Question 6

What is the weather associated with anticyclones like?

Answer 6

Cloud free in the centre, fine and dry in summer. Haze trapped under inversions. Cold in winter - fog/frost.
Can get extensive sheets of Sc (strata-cumulous) cloud.

Question 7

What is the importance of waves to coastal processes and maritime operations? (2)

Answer 7

1. ) Erosion, transportation of material

2. ) Effect of waves on ships, harbours etc

Question 8

Long period and low frequency waves usually result in… (3)

Answer 8

Tsunamis, Seiches or Storm Surges

Question 9

How are surface waves formed?

Answer 9

Caused by the effect of the wind on the sea surface, through:
Frictional stress between the air and sea
Transfer of energy from air to sea

Question 10

What is the sequence of wave generation?

Answer 10

Small ripples begin to form and grow, energy is transferred into the ocean to form a current.
Energy lost to friction, large waves break leaving white caps.

Question 11

Give unlimited fetch, time and constant time and what is formed?

Answer 11

A fully developed sea. Generally speaking the characteristics of a fully developed sea do not change (but a rare ideal).

Question 12

How is wave speed in deep water measured?

Answer 12

Wave speed in deep water governed by V = f.L

Waves in shallow water move slower

Question 13

Waves in Shallow Water

Answer 13

Proportion to wavelength and depth
V shallow prop to depth only
Low depth low speed

Question 14

What are the methods of measuring waves? (5)

Answer 14

Mechanically by buoys
By eye
Satellite
Measure combined sea and swell e.g. total height
General paucity of good data

Question 15

Characteristics of tsunamis

Answer 15

Ocean wave of very great wavelength but low height, Caused by some seismic or other submarine force,
Wavelength in 100s of Kms, travels at great speed,
Creates very large waves when landfall occurs 20m recorded

Question 16

Characteristics of seiches

Answer 16

Standing wave which occurs in bays, lakes etc.
Dangerous to vessels in such harbours
Oscillations set up by squalls or local storms etc

Question 17

Characteristics of storm surges

Answer 17

Depression travels at same speed as waves
Constant transfer of energy
Coupled with tide
Low pressure raises local sea level
North Sea surge inc levels by 4m
London Thames Barrier as a precaution

Question 18

Effect on Maritime Environment/Operations (6)

Answer 18

• Sea sickness
• Boat handling difficult
• Turning large ships in heavy sea/swell
• Transport of material along beaches
• Dispersal of pollutants
• Waves on shore, destruction etc