18. Polar Front Depression Part 1 Flashcards
Polar Front Depression Pt 1
What is the name, latitudes, and air type of the 3 air circulation cells
Polar Front Depression Pt 1
- The pressure system along the ITCZ is a HIGH or LOW
- The pressure system around the Horse Latitudes is HIGH or LOW
- The pressure system around the Polar front is HIGH or LOW
- LOW
- HIGH
- LOW
- The definition of a low pressure system is that high pressure air will flow towards it and want to rise up to lower pressure areas
- Therefore think about where each of the cells meet. Starting from the ITCZ (equator) this is a Low pressure system
- Air must therefore rise and diverge aloft
- The air meets where the Hadley and Ferrel cells converge and starts to sink again, making it a high pressure system.
- This happens at the horse latitudes, a name given to around 30° Latitude, calm winds, very little precipitation
- At the horse latitudes at the surface, air divereges towards the equator and towards the pole
- Where the air diverges towards the pole, it meets the polar cell air at the polar front
- This is a low pressure system so air rises again
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Polar Front Depression Pt 1
On the surface of the Earth, winds will respond to the surface pressure gradient and turn according to the coriolis effect. in the Northern Hemisphere;
- Winds converging on the equator will be from ____
- Winds flowing towards the pole out of the sub-tropical highs will be from ____
- Winds flowing out of the polar high will be from ____
- NORTH EAST
- SOUTH WEST
- NORTH EAST
- Winds converging on th e equator will be from the NE
- Winds flowing towards teh pole out of the subtropical hights will turn and become SW at around 40° Latitude
- Winds flowing out of the polar high will turn and become NE at 60° latitude
3
Polar Front Depression Pt 1
- In winter, the North Atlantic Polar Front sits between ____ (America) and ____ (France)
- In summer, the North Atlatnci Polar Front sits between ____(Canada) and ____ (Scotland)
- FLORIDA and BRITTANY
- NOVA SCOTIA and SCOTTISH ISLES
4
Polar Front Depression Pt 1
Refer to the diagram. What is represented by this on a weather chart
QUASI-STATIONARY FRONT
- An example of this happening is at the Polar Front where the Polar High air is coming from a NE direction and the Sub Tropical High air is coming from a SW direction
- The cold and warm air have an airflow direction opposing each other
- With no disruption, they will sit side by side - EXAMPLE
4
Polar Front Depression Pt 1
Where the Cold Polar High air and the Warmer Sub Tropical Air meet at the polar front, the air travels in opposing directions to each other causing a stationary front (EXAMPLE). Kinks or waves in the front will cause a depression.
- Between what length in KM does the kink/wave need to be to continue to deepen to create a depression, ____km and ____km
500 km to 1600 km
Polar Front Depression Pt 1
- The polar front depression moves along the front line at approximately the speed of the ____ft wind
- The polar front depression will move in what direction
- The ‘ripple’ in the polar front is known as a ‘____’ wave
- 2000 ft
- NORTH EAST
- WESTERLY WAVE
- The Sub-tropical air overlies the polar air
- The wind at 2000 ft over the surface position of the depression is therefore sub-tropical wind
- The sub-tropical wind is blowing from a South Westerly direction, meaning it is moving the depression in a North Easterly direction
POLAR FRONT DEPRESSION - SIDE PROFILE
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Polar Front Depression Pt 1
Once a Polar Front Depression has formed and the warm air sector is now intruding into the polar air, there will be a warm front at the front of the westerly wave, and a cold front at the rear.
- The warm front moves FASTER or SLOWER than the cold front
- What is formed when the fronts catch up with each other
- SLOWER
- OCCLUSION
- The cold front moves faster than the warm front
- The warm front is held back by surface friction
- When the cold front catches up with the warm front, it will form an occlusion
- This process squeezes out the warm air, cutting off the warm air feed and signfies the end of the depression
7
Polar Front Depression Pt 1
In the formation of an occlusion;
- If cold air catches up with cooler air, this will create a WARM or COLD occlusion
- If cool air catches up with colder air, this will create a WARM or COLD occlusion
- COLD
- WARM
Polar Front Depression Pt 1
What are the 4 stages of a polar front depression formation
- INITIAL STAGE
- MATURE STAGE
- OCCLUDED STAGE
- DYING STAGE
Polar Front Depression Pt 1
When a polar front depression is fully formed, another depression can start to form near the main depression. This is known as a what depression
SECONDARY DEPRESSION
- The secondary depression move around the main depression with a cyclonic rotation (anti clockwishe in NH).
- Secondary depressions often grow to be deeper and more violent than main depressions
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Polar Front Depression Pt 1
A blocking cyclone can bring;
- What sort of weather conditions in summer
- What sort of weather conditions in winter
- Which jet stream can blocking cyclones affect
A blocking cyclone is also known as an Omega blocking cyclone. This is because it looks like an omega sign ( Ω )
- HEAT WAVES
- LONG COLD WINTERS
- SUB TROPICAL JETSTREAM
Polar Front Depression Pt 1
The low pressure zone of a polar front depression will move in the direction of the isobars in the WARM or COLD sector
WARM SECTOR
- The low pressure system will be moving in the direction of the warm sector isobars
- It will be travelling approximately the speed of the isobar spacing closest to the tripple point
10
Polar Front Depression Pt 1
To measure the speed of a front on a pressure chart using the compass, measure the space between the isobars and compare to a geostrophic wind scale.
- For a cold front, the speed is FULL VALUE or ⅔ of the measurement
- For a warm front, the speed is FULL VALUE or ⅔ of the measurement
- FULL VALUE
- ⅔
