Anticyclones Flashcards
What are anticyclones?
Areas of high atmospheric pressure caused by a large mass of falling air
What happens as the air falls down from the upper atmosphere?
The air warms on its way down
Why does the air falling from the upper atmosphere cause humidity to decrease?
Air masses can hold more moisture as they get warmer. This means clouds don’t develop, and conditions are very dry
Why is there not much difference in air pressure between the centre and edges of anticyclones?
The pressure is similar, the winds are weak, and flow gently outwards
What are daytime temperatures like during a winter anticyclone?
Low temperatures during the day (below freezing to 5°C), because the sun is at a low angle
What are overnight temperatures like during a winter anticyclone?
Extremely cold overnight temeratures (below freezing) with frosts, because clear skies allow loss of heat through radiation
What is cloud and fog like during a winter anticyclone?
Low level cloud and radiation fogs - radiation fogs form overnight. As the ground cools, moisture in the air close to the ground condenses, forming fog
What is atmospheric pollution like during a winter anticyclone?
High level of atmospheric pollution in urban areas - pollutants are trapped by temperature inversion. A lack of wind means pollutants aren’t dispersed
What are temperature inversions?
When the air at higher altitudes is warmer than the air at lower levels
During a summer anticyclone, what does the absence of clouds lead to?
Intense insolation, which means its hot, sunny and there’s no rain
During a summer anticyclone, what can rapid radiation at night cause?
Temperature inversions, dew and morning mist
During a summer anticyclone, what may coastal areas and highlands experience?
Coastal areas - fogs and strong breezes
Highlands - strong winds due to heating of valley sides, which causes a pressure gradient
After several days of a summer anticyclone what is there a risk of?
Thunderstorms, due to large amounts of rapidly rising warm air
What are blocking anticyclones?
Anticyclones that sit over the UK and remain there for many days
What are weather conditions like with a blocking anticyclone?
Extreme, e.g. heatwaves in summer and dry, freezing weather in winter
