What is Weather? • Weather describes the conditions in the atmosphere and the air around us at a particular moment. • Weather is always changing.
Air Masses Influence Weather • Tropical maritime – • warm and moist • Tropical continental – • warm and dry • Polar maritime – • cold and (fairly) moist • Polar continental -cold and dry
What is Climate? • Climate describes what the weather is usually like at a particular place over a longer period of time
Britain’s Climate Britain’s Climate is: • Variable - it changes from day to day • Temperate – there are never extremes • e.g it is never too wet or too dry • Maritime- proximity to ocean affects our weather Britain is renowned for cool summers and mild winters.
Temperatures in Britain In SUMMER temperatures decrease with latitude, i.e. it becomes colder as you move from south to north Average JULYTemperatures across the UK
In WINTERtemperatures decrease with distance from the North Atlantic Drift. • It has a warming effect upon the coastlines it passes. • Winter temperatures decrease from west to east. • Average JANUARYTemperatures across the UK
Types of Precipitation There exist three types of precipitation, all of which Britain experiences. • Relief • Convection • Frontal
Relief Precipitation Stage 1.Warm wet air is forced to rise over high land. Stage 2.As the air rises it cools and condenses. Clouds form and precipitation occurs. Stage 3.The drier air descends and warms. Stage 4. Any moisture in the air (e.g. cloud) evaporates
Convection Precipitation Stage 1. The sun heats the ground and warm air rises. Stage 2. As the air rises it cools and water vapour condenses to form clouds. Stage 3.When the condensation point is reached large cumulonimbus clouds are formed. Stage 4. Heavy rain storms occur. These usually include thunder and lightening due to the electrical charge created by unstable conditions.
Frontal Precipitation Stage 1.An area of warm air meets and area of cold air. Stage 2.The warm air is forced over the cold air Stage 3.Where the air meets the warm air is cooled and water vapour condenses. Stage 4. Clouds form and precipitation occurs
Factors Affecting Climate • Latitude
Ocean Currents: -North Atlantic Drift warms up Britain’s West coast • Prevailing Winds: -Temperature of Wind depends on the surface over which it passes -If it blows from land it will be warm in summer but colder in winter -If blows from sea it will lower temperatures in summer but increase them in winter.
Altitude Temperature decreases on average by 1’C for every 100m in height
Depressions • Depressions are low pressure weather systems. • They bring clouds, rain, wind and unsettled weather-British Weather! • Depressions form where warm air meets cold air. • The boundary between the two air masses is called a front
Anticyclones • Anticyclones are high pressure weather systems. • They bring fine weather, usually in summer • Anticyclones form in places where air is descending
Fog • Fog and mist are made up of water droplets formed by condensation of water vapour. • Official definition: when visibility is reduced to less than 1000m • Two types of Fog: Radiation Fog Advection Fog
Radiation Fog: • Takes place at night when the ground loses heat and cools the air to saturation point. • Fog forms near to the ground because the air near the surface falls below its dew point Advection Fog: • Blown by wind • Moist air is cooled by travelling over a cold sea and becomes saturated. • Often forms in coastal areas in spring/summer.
Hurricanes/Tropical Storms • Intense low pressure: high winds, torrential rain • The ‘eye’ :Sky clear, winds light • Originate over warm oceans close to equator • Storm Surge
Human Influences • Industrialised urban areas generate ‘heat islands’ -buildings store heat during the day -central heating/energy leaks -wind speed: tall buildings -pollutants trap heat -reduced vegetation
Summary:To be done by you! • What is Weather? • What is Climate? • Name one factor that affects climate? • Name another factor that affects climate? • Name one type of precipitation? • What is a depression? • What is an anticyclone? • Name a natural hazard related to W&C? • Name the two types of fog? • Describe Britain’s climate?