Weather Systems
- Created by: Charlie Davies
- Created on: 26-05-14 19:24
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- Weather Systems
- Depressions
- Form over Atlantic ocean then move East over UK usually tropical maritime and polar maritime meet
- HOW?
- 1. Warm air constantly moves out of topical areas towards poles. Warm front=leading edge of warm air mass
- 2. Cold air moves out of polar regions towards tropics. Cold front=leading edge of cold air mass
- 3. Where air mass meet warm air heading towards poles rises above cold air (warm air is less dense)
- 5. Strong winds blow areas of high pressure towards area of low pressure= system rotates and continues to rise
- 6. Cold fronts move more quickly than warm fronts so cold front catches up with warm front
- 4. Rising warm air means atmospheric pressure is reduced
- 7. When this happens warm air behind warm front is undercut by incoming cold front and is lifted away from ground
- it now sits above cold air= occluded front
- warm air rises into upper atmosphere and the depression dissolves
- it now sits above cold air= occluded front
- HOW?
- Weather
- distinct pattern of weather, which usually lasts for 2-3 days
- 1. Ahead of warm front its cool because cold air is overhead. Thin clouds form high up as warm air is pushed up
- 2. As warm front passes, conditions on ground get warmer. Warm air is pushed up over cold and condenses, forming low thick cloud and sustained drizzle
- 3. When warm air is overhead its warm. There's no cloud because warm air holds alot of water vapour
- 4. As cold front passes, cool air brings temp. down again. The cold dense air behind the cold front undercuts warm air mass in front
- this forces warm air to rise rapidly and condense, forming clouds and heavy showers.
- rapidly rising air makes it very wind at surface
- this forces warm air to rise rapidly and condense, forming clouds and heavy showers.
- 5. When cold front catches up with warm front, all of warm air has been squeezed upwards so there's no warm air left at bottom
- there's less rain because the uplift air has decreased
- there is little condensation, so cloud cover decreases
- wind speed decreases
- but air pressure rises as the dense cold air replaces uplifted air and depression dies out
- wind speed decreases
- there is little condensation, so cloud cover decreases
- there's less rain because the uplift air has decreased
- LOW PRESSURE WEATHER SYSTEM
- Form over Atlantic ocean then move East over UK usually tropical maritime and polar maritime meet
- Anticyclones
- HIGH PRESSURE WEATHER SYSTEM
- Areas of high atmospheric pressure caused by a large mass of falling air
- air falls from the upper atmosphere, and warms on its way down
- causes humidity to decrease because air masses can hold more moisture as they get warmer
- clouds don't develop and very dry
- causes humidity to decrease because air masses can hold more moisture as they get warmer
- in anticyclones there's not much difference in air pressure between centre and edges.
- because pressure is similar, winds are weak and flow gently outwards
- In UK wind flows clockwise around centre
- because pressure is similar, winds are weak and flow gently outwards
- WINTER WEATHER
- Low temp. during the day because sun is at low angle
- extremely cold overnight temps. with frost because clear skies allow loss of heat through radiation
- low level cloud and radiation fogs- radiation fog forms overnight.
- as ground cools, moisture in air close to ground condenses forming fog
- high levels of atmospheric pollution in urban areas
- pollutants are trapped by temp. inversions(when air at higher altitudes is warmer than air at lower levels)
- SUMMER WEATHER
- Absence of clouds leads to intense insolation which means its hot, sunny and no rain
- rapid radiation at night can cause temp. inversions, dew and morning mist
- coastal area may get fogs and strong breezes
- highlands may experience strong winds due to heating of valley sides=pressure gradient
- advection fog
- after several days risk of thunderstorm due to large amounts of rapidly rising warm air
- Depressions
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