formation of a depression
DESCRIPTION
Formation of a depression. Objectives. Be able to describe the formation of a depression weather system. Be able to describe the air movement within a depression weather system. Be able to identify the features of a depression upon a satellite image. . - PowerPoint PPT PresentationTRANSCRIPT
• Be able to describe the formation of a depression weather system.
Objectives
• Be able to describe the air movement within a depression weather system.
• Be able to identify the features of a depression upon a satellite image.
• Be able to identify the features of a depression upon a synoptic weather chart.
Polar Front
Cold artic or polar air
Tropical air
Somewhere over the
Atlantic…
Depressions form at the boundary between cold artic/polar air in the North and tropical air in the South.
Cold artic or polar air
Tropical air
The cold air is pushing south and the warm air is pushing north, this creates
a bulge along the polar front.
Can you identify the bulge along the polar front signifying the start
of a depression?
Cold artic or polar air
Tropical air
Due to the Coriolis Effect, caused by the rotation of the Earth, the air moves
around an area of low pressure in an anti-clockwise direction.
Cold artic or polar air
Tropical air
We can now see three fronts within the depression.
Cold Front
Warm Front
Occluded front
Identifying a depression on a synoptic chart. Can you identify?
Areas of low pressure
Isobars tightly packed
Characteristic fronts, warm,
cold and occluded
In order to be sustained, depressions need a source of warm
moist air. This is provided by the warm
conveyor.
Warm conveyor
This rises rapidly over the cold air in front of it.
As it does, the moisture within it cools and condenses to form a characteristic
area of clouds.
The cloud edge is sharp along the cold front.
Like humans, depressions are both born and mature over time…
A ‘cold conveyor’ bring cold air in along the warm front, which rapidly rises in
the centre of the system.
This forms a characteristic band of cloud and precipitation as air rises towards the
centre of the depression. This is called the emerging cloud head.
cold conveyor
This encourages the warm air along the warm conveyor to rise.
Behind the cold front, cold air descends from the upper atmosphere and spreads
out along the cold front.
Over time the depression begins to decay, the cold air cuts off the supply of warm moist air- leaving
the emerging head cloud along the cold conveyor.
Can you identify the cloud associated with the decaying
depression on this satellite image?
Depression or not?…
Which of the following would you associate with a depression?
Statement True FalseDepressions begin when two types of cold air meet.
Depressions are associated with low pressure.
The air moves in a clockwise direction within a depression.
Depressions usually bring rainfall.
In a depression we could expect to see isobars packed closely together.
There is usually no wind in a depression.