LO2-4 Flashcards
What is the cause of wind waves?
Wind.
What is the cause of swell waves?
Distant weather systems.
What is the cause of rogue waves?
A combination of local winds and swell when when in phase with one another/converging oceans.
(twice the height of the significant wave height.)
What temperature does seawater freeze at?
-2 degree/c
How is the significant wave height determined?
1/3 of the average wave heigh (many waves will actually be bigger)
What is water sky?
A dull neutral-coloured sky near the horizon caused by the reflection of the colour of the sea and so indicating open water when seen over an ice-covered sea
What does a Nomogram graph display?
The level of ice creation at different sea water temperatures.
What is the maximum travel distance of icebergs in the north Atlantic?
400 miles south east of Cape Farewell during April.
What do the three layers of the EGG code mean?
- Top row is how many tenths of that highlighted area is covered in ice.
- First row down is the division of that coverage into thick, medium and thin ice.
- Second row down is indicating what type of ice has formed at each thickness.
What is new ice?
- Recently formed ice which includes Frazil, grease, slush and Shuga ice.
- These types of ice are all composed of ice crystals which are only weak when frozen together and have a definite form only while they are afloat.
What is Nilas ice?
A thin elastic crust of ice up to 10 cm thick which is formed on the waters surface.
What is young ice?
- Formed during the transition of Nilas and first year ice (10-30cm thickness)
- Grey ice: less elastic than Nilas and breaks on swell and usually rafts under pressure (10-15cm thick).
- Grey-White Ice: Under pressure it is likely to ridge than raft.
What is first year ice?
Sea ice of not more than one winters growth, developing form young ice.
What is old ice?
Sea ice which has survived at least one summers melt.
What is frazil ice
Fine spicules plates of ice which are suspended in water.
What is grease ice?
A soupy layer on the waters surface which reflects little light giving the water a matte appearance.
What is Light Nilas?
More than 5cm thick and light in colour.
What is pancake ice?
Circular pieces of ice 30cm to 3m wide and 10cm thick.
What is grease ice?
- A later stage of freezing than frazil ice where crystals have coagulated to form a soupy layer on the surface.
- 10-15cm thick, less elastic than Nilas and breaks on swell. (usually rafts under pressure).
What is first year white ice?
- Sea ice of not more than one winters growth developing form young ice (30cm or greater).
- stage 1: 30-50cm
- Stage 2: 50-70cm
- Medium first year: 70-120cm
- Thick: 120+ cm
What is old ice?
- Ice that has survived at least one summers melt.
- Generally smoother than first-year ice and may be subdivided.
- Second year ice: Old ice which has survived only one summer’s melt. Thicker than first-year ice, it stands higher out of the water.
- Multi-year ice: Old ice which has survived at least two summer’s melt. Hummocks are smoother than on second-year ice and the ice is almost salt-free. Where bare, this ice is usually blue in colour.
What is a Polar front?
- Formed by the meeting of two very different air masses winds can be highly variable, blowing at times with great speed and intensity.
- When the cold air flowing out of the polar regions and the warmer air moving in the path of the westerlies meet, they do not mix well. The denser, heavier cold air pushes the warm air upward, forcing it to rise rapidly. The line along which these two wind systems meet is the polar front.
- The weather that results from the meeting of the cold polar air and the warmer air from the subtropics can be very changeable and at times stormy. Weather is very much influenced by the development of waves to the west that form into depressions that drive eastward and the intervening ridges of high pressure.
- (The front migrates north and south frequently as families of depressions).
What are general characteristics of a TRS?
- Organised convection such as thunderstorm activity.
- Winds at low levels circulating anti-clockwise (Northern Hemisphere)
- The system can reach up to 10km in height.
- Isobars are close to being true circles.
- Very steep pressure gradients.
What is required for the formation of a TRS?
- A source of warm, moist air derived from tropical oceans with sea surface temperatures normally in the region of 26 degree C +.
- Winds near the ocean surface blowing from different directions converging and causing air to rise and storm clouds to form.
- Winds which do not vary greatly with height (known as low wind shear). This allows the storm clouds to rise vertically to high levels.
- Sufficient distance from the equator for Coriolis to promote circulation.