How do atmospheric conditions/systems cause heavy snowfall, intense cold spells, heatwaves and droughts and in what ways do they represent a hazard to people? Flashcards
What are the characteristics associated with anticyclones?
- Large area of slow-moving air
- High pressure – as air is sinking
- As air sinks it warms, causing temperature inversion
- As air is sinking it cant rise to form clouds so there are clear skies
- Winds are light, as gentle pressure gradient
- Winds blow outwards, usually clockwise, in the northern hemisphere
- Usually ends when uplift overcomes temperature inversion, leading to thunderstorms
What is the weather associated with high pressure in summer? (temp, cloud, precipitation, wind, sunshine, humidity and visibility)
Temperature:
- Hot in the day
- Chilly at night, as no cloud to trap heat
Cloud:
Little but cumulus may form during the day
Precipitation:
- Low - drought may end with a heavy thunderstorm
Wind:
- Little
Sunshine:
- Long hours of sunshine = sunstroke
Humidity:
- Varies with source of air. e.g if tropical then very humid
Visibility:
- Mist in early morning or over the sea
What is the weather associated with high pressure in winter? (temp, cloud, precipitation, wind, sunshine, humidity and visibility)
Temperature: • Cold in day • Freezing at night • Cold spells Cloud: - Little Precipitation: - Very low, but if it warms snow can occur Wind: - Little – calm but if wind blows then intense wind chill Sunshine: - Long hours of sunshine but if fog gets trapped under inversion layer it leads to anticyclonic gloom Humidity: - Low = very dry conditions Visibility: - Fog common, especially along coasts near warmer sea or collecting in hollows
Where do depressions form?
Along the polar front where cold northerly air meets/undercuts warm tropical air moving north
What are the characteristics of a depression?
- Relatively small area of fast moving air
- Low pressure, as air is rising
- Tend to move west to east across the UK
- As air is rising it forms clouds, so bringing rain
- Winds are strong, as steep pressure gradient
- Winds blow inwards, usually anti clockwise, in the northern hemisphere
- Rarely last more than a day but frequently one in a stream of depressions
- Depressions have cold and warm fronts, as the warm air is undercut by the cold
What is the weather associated with low pressure in summer? (temp, cloud, precipitation, wind, sunshine, humidity and visibility)
Temperature: - Mild in the day - Warm at night as cloud traps heat Cloud: - Heavy especially at the fronts Precipitation: High - often heavy thunderstorm producing intense downpours Wind: - Strong and gusty Sunshine: - Relatively little sunshine Humidity: - High as warm air holds a lot of moisture Visibility: - Good but poor in rain and can cause hill fog as clouds are level with summits
What is the weather associated with low pressure in winter? (temp, cloud, precipitation, wind, sunshine, humidity and visibility)
Temperature: - Mild in the day - Warm at night as cloud traps heat Cloud: - Heavy especially at the fronts Precipitation: High - Usually rain but can be snow over hills - with strong winds this causes blizzards Wind: - Strong and gusty so can cause wind chill Sunshine: - Little sunshine - dull and gloomy Humidity: - High as warm air holds a lot of moisture Visibility: - Good but hill fog common
What are the impacts on ecosystems from anticyclones?
- Drought
- Fires
- Heat
- Frost
What are the impacts on vegetation from anticyclones?
- Trees susceptible to drought (lose their leaves)
- Frost kills seedlings and buds (can’t reproduce)
- Trees wilt in heat, as increased transpiration means they need more water
What are the impacts on drainage from anticyclones?
- Bakes ground in drought so flash floods when it rains
* Rivers and lakes dry up
What are the impacts on soils from anticyclones?
• Dry and shrink - subsidence
What are the impacts on health from anticyclones?
- Poor due to heat/cold/fog and high pollen count
* Heatstroke
What are the impacts on housing from anticyclones?
Heat and cold damage fabric
What are the impacts on accidents from anticyclones?
Frost and fog cause poor driving conditions
What are the impacts on agriculture from anticyclones?
Need to irrigate, frost kills crops
What are the impacts on forestry from anticyclones?
Fires, droughts
