- Created by: 8cburton
- Created on: 24-05-15 14:27
LATITUDE- mid latitude (50-55N) doesn't get very hot because the sun is never very high in the sky but never gets very cold as there is always daylight.
LOCATION IN ATMOSPHERIC CELLS- northern edge of ferrel cell (low pressure area)
MARITIME LOCATION- Surrounded by water (gains and loses heat slower than land) therefore warm winds in the winter and cool winds in the summer
LOCATED NEAR THE GULF STREAM- Makes UK warmer than many countries at the same latitude
Precipitation and wind
WETTER IN THE WEST= South westerly surface winds bring in warm wet wair from anlantic ocean. Air reached west coast and forced over the land making air cool and condense into rain clouds. The west is more mountainous so it rains there and the east is left with less moisture. This is called RAIN SHADOW
WINDY IN THE WEST= South westerly surface winds come over flat ocean so nothing to slow the winds down. More windy at higher altitudes due to fewer obstacles to slow them down. The prevailing wind is SOUTHWEST and strong gales are common in autumn due the the influence of low pressure weather systems. Eat winds being dry weather but are less common
5 air masses affecting the British Isles
Tropical continental only occurs in summer
Formation of a depression
1) Warm air from tropical maritime is a warm front
2) Cold air from polar maritime is a cold front
3) When they meet warm air rises, undercut by the cold air
4) Rising less dense air is removed by strong upper atmosphere winds (jet stream) which causes the atmospheric pressure to drop
5) Cold fronts move quicker than warm fronts so catch up and undercut the whole warm mass of air so that the warm air sits above the cold air in a occluded front.
Features of depressions
1) Ahead of a warm front it cools. Thin clouds form as warm air starts to rise
2) Warmer weather pushed above cold air and condenses to sustained drizzle
3) Warm, no clouds (warmer air holds more moisture)
4) Cold front passes and temp lowers and undercuts the warm air in front. Clouds condense and heavy showers occur + rapidly rising air + very windy
5) When the cold air catches up with the warm air it is completely lifted. Theres less rain as there is less rising air so less condensation. Cloud cover decreases. Wind speed also drops by air pressure rises as the depression dies outs (cold air disipates.
- Low atmostphereic pressure
- Isobars are close together producing steep pressure gradient winds
- Winds strong + blow inwards in anticlockwise direction
- Wind veers (changes direction from S to N)
- Wind backs (changes direction from SE to E)
The origin and nature of anticyclones
They are areas of relatively high pressure and move slowly/ may remain stationary over an area for days, weeks. Air falls, warming as it falls producing a decrease in relative humidity which leads to lack of cloud cover and dry conditions. Isobars far apart (little pressure different from centre to edge). Winds are weak and flow gently outwards in a clockwise direction in the N hemisphere and anticlockwise in the S hemisphere.
Low temperatures because the sun is at a low angle and extremely cold at night due to the clear skies allowing loss of heat through radiation. High levels of atmospheric pollution due to no wind and trapped by temperature inversion
Hot day and night, clear skies, hazy, early morning mists, heavy dew on the ground in the morning, thunderstormer many occur when the air had high relative humidity. Described as blocking anticlyclones due to them staying stationary over one area for a very long time.
RADIATION FOG= Forms under clear night skies when moist atmosphere cools through the radiation of the heat from the ground surface. Extends some distances off the ground and encouraged by light surface winds which allow mixing of the air. Air is cooled to its due point. Common in winter when long hours of night allow maximum cooling. Might persist all day but it dispersed by increased wind or warming of the air. Common under temperature inversions which often occur in valleys.
- In evening with clear sky and high humidity
- Air on upper slopes cool quicker than the valley bottom
- Cooling increases density of air so it falls downslope
- This pushes warm air upwards
- Cool air now reaches dew point and create dense fog that can last all day
Form when a mass of relatively warm air moves horizontally across a cooler surface. The air is cooled to its dew point and condenses. Most common around coasts and over the sea in summer. Such areas it is sometimes called a haar. As the fog moves inland it warms and evaporates.
Storms in the UK
GALES are a common of CTWM climate in autumn when the sea temp is still warm enough to fuel powerful low- pressure cells.
BEAUFORT SCALE can be used to categorise wind strength
- Moderate gale (moves trees)
- Fresh gale (breaks twigs off trees)
- Strong gale (slight damage to buildings)
- Whole gale (uprooting of trees and structural damage to buildings)
- Storm (widespread damage to buildings and infrastructure)
Storms in the UK are temperate storms and are caused by depressions
- Warm surface water in autumn evaporates causes warm+ moist air to rise. When air meets cold polar air it creates an area of low pressure and heavy rain
- Steep pressure gradient between 2 air masses drives strong winds which spiral around depression
- Strong temperature gradient means there is a stronger pressure gradient.