Weather & Climate By Sarah Waters & Therese Daly

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 Average JULY Temperatures across the UK In SUMMER temperatures decrease with latitude, i.e. it becomes colder as you move from to north In SUMMER temperatures decrease with latitude, i.e. it becomes colder as you move from south to north

In WINTER temperatures 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 JANUARY Temperatures 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

UK Weather Systems

Depressions and Anticyclones

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

MEDCLEDC Advance warning systems Warnings limited in rural areas Evacuation procedures in place Lack of evacuation procedures Emergency services well developed Poor transport systems hinder evacuation Building standards set to cut human risk Poor quality housing located in vulnerable xareas Individuals given information on precautions xto take Preparation by individuals limited Insurance cover Little insurance against disaster Government funds available for recovery and xrepair Very limited government funds available Responses to Hazards

Climate Change

Effects of Global Warming

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?