Challenge of Weather and Climate Learning Objectives 1

Challenge of Weather and Climate Learning Objectives: 1) To know the characteristics of the UK climate- monthly temperatures, precipitation and sunshine hours 2) To understand the reasons for the climate and variations with the UK explained by its global positional- latitude, altitude, pressure, winds and distance from the sea.

Starter: Describe the climate graph for Nottingham How do we measure the weather?

• Temperatures are lower in winter but they are mild with an average 3° C in January • Summer temperatures are warm, reaching an average of 16 ° C, peaking in July and August • The annual temperature range is 13 ° C • Rain in Britain falls throughout the year and fluctuates with a slight winter maximum. • The highest rainfall is in January peaking at 85 mm • Total rainfall in Nottingham averages 810 mm a year

When describing the climate of an area you can include: The pattern of precipitation during the year The total precipitation for the year The average monthly temperature The range of temperature (the difference between the highest and lowest) Ø Average sunshine hours per moth, average wind speeds and direction Ø Ø

http: //www. bbc. co. uk/learningzone/clips/using-satellites-to-understand-weatherand-climate/7363. html http: //www. bbc. co. uk/learningzone/clips/weather-stations-collecting-climatedata/4317. html

Weather is the short term, day-to-day variations in features such as temperature, wind direction, cloud cover and sunshine. Climate is the average weather conditions such as temperature and precipitation, over a period of time, measured over at least 30 years. It includes the conditions that can normally be expected at a place, month by month during the year. The climate of the UK is largely influenced by it global position. It lies in an atmospheric battleground between warm tropical air and cold polar air. As the two distinctly different types of air battle one another for control over the mid-latitudes, the UK experiences contrasting and changeable weather conditions.

How would you describe the climate in the UK? We can describe the UKs climate as: Mild (or cool) wet winters and warm wet summers The name for this type of climate is temperate maritime Temperate means that the place experiences neither the heat of the tropics, nor the coldness of the poles Maritime means that the climate is strongly influenced by the sea. One effect of the sea is to reduce the temperature differences between winter and summer. Another is increased precipitation.

The global position of the UK also affects the relative position of the sun in the sky and the impact of the seasons. Unlike places nearer to the equator, we experience significant differences in the relative position of the sun during the year. During the summer the sun is high in the sky bringing long periods of potential warn sunshine. Occasionally the high temperatures can trigger convectional rainfall, resulting in thunderstorms. During the winter, our global position results in a much lower angled sun. This is less powerful and accounts for much lower winter temperatures.

Global influences on the UK climate Why is the UK climate mild and wet? Latitude is the most important. It greatly influences temperature, pressure and winds. Temperatures are highest in low latitudes in the tropics (nearer the equator) and lowest in polar latitudes. The gradual decrease in temperature between the Equator and poles is due to reduced insolation. The sun shines from a high angle in the sky in the tropics all year. As a result, the Sun’s light travels directly through the Earth’s atmosphere so that less is lost by reflection. Also, because the Sun’s rays are almost vertical, there is a smaller area of the Earth’s surface for each ray to heat up. In contrast, near to the poles the Sun’s rays approach the Earth’s surface at an oblique angle. This means that each ray has a larger surface area to heat up. As the rays have had a longer journey, less sunlight remains to be absorbed by the Earth’s surface.

At the North and South Poles, the greater curvature of the Earth means that the sun’s energy is spread over a larger area. This means colder temperatures. Ice forms there and reflects heat back into space making it even colder. The sun’s energy at the Equator is much more direct and concentrated than at the Poles. This means that the Earth is hottest here. http: //www. bbc. co. uk/schools/gcsebitesize/ge ography/weather_climate/climate_rev 3. shtml

Pressure and winds The UK lies within a zone of low pressure. Here the air is rising so that the weight of air at the surface becomes lower than average- hence there is low surface air pressure. Areas of low pressure associated with cloud and rain. As air rises, it cools; moisture in the air condenses and forms clouds. Water droplets increase in size in the clouds until they become too heavy to be held and fall as rain. Hot air that rises at the Equator sinks around 30° north of the Equator to form a zone of high pressure, which includes the Azores High. Winds blow from high to low pressure- air is transferred from where it is sinking towards are where it is rising. Southerly winds (winds blowing from South to North) are deflected by the Earth’s rotation from west to east and reach the UK as south-westerly winds. South-westerly winds are the prevailing winds in the UK- the winds that blow most often. They have a long sea journey across the Atlantic Ocean before reaching the UK.

Distance from the sea- maritime influence/ continentality The maritime influence from the sea on the UK’s climate is great, affecting both temperature and precipitation. As far as temperature is concerned, the sea has different thermal (heating) properties to the land. • During summer, when rates of insolation are highest, the sun heats up less quickly than the land. The Sun’s light penetrates below the water surface so that the Sun’s rays have more than the surface to heat up, and constant movement mixes warn and cool water. • In winter, the opposite happens. The sea retains its store of summer heat longer than the land. The result is that places near the sea have less hot summers and less cold winters than those further inland, where the continental effect dominates. In the UK the winter warming effect of the sea is magnified by the presence of a warm ocean current, the North Atlantic Drift, over which south-westerly winds cross before reaching the UK. Winds that take long sea journeys pick up lots of moisture and are always likely to bring rain. The interior of countries with large land masses, like the USA, have a continental climate. It is too far away from the sea to be influenced by it, and so they have very cold snowy winters, and hot dry summers.

Altitude Upland areas tend to record get more precipitation, so they are wetter because air is forced to rise over them (relief rainfall). Temperatures decrease by 1°C for every 100 metres of altitude (height above sea level) so mountainous areas are often cooler. http: //www. youtube. com/watch? v=95 Tt. XYj. OEv 4&feature=related http: //www. bbc. co. uk/schools/gcsebitesize/geography/weather_climate/climate_vid eo. shtml

Characteristics of the Climate of the UK Exam Tip: Be able to Describe how temperatures and rainfall vary in the UK Use specific data as evidence (°C or mm) Temperature in January • In winter, the warmest parts of the UK are to the west and the south where the North Atlantic Drift has a big influence • The coldest areas are in he north where the sun is at a lower angle in the sky. It is particularly cold over the mountains due to the effect of altitude. • Cold polar air moving south is likely to have a greater influence in the north of the UK than in the south • The sea warms up the coastal fringe of the UK

Temperature in July • In summer the warmest places are in the south, particularly in the South East. Here the sun is more powerful than in the north so as you move north temperatures fall • Warm air from southern Europe often nudges into the south if the UK during the summer. • Temperatures are also lower as you move westwards.

Explain why average July temperatures vary in different parts of the UK (4 marks) Ø Latitude which means that the angle of the sun is higher/ higher insolation is greater so rays travel through less of the atmosphere; rays are spread over a smaller area of land so warmer. Southern areas are warmer as the latitude is warmer. Ø Impact of the sea- in summer as the sea warms up more slowly than land it has a cooling effect in western areas Ø Continental influence in east- areas nearer Europe where air coming from here will be warmer due to continental influence as land warms up faster than water Ø Relief- areas that are higher, particularly in the north of England tend to be colder as the temperature falls at a rate of 1 degree per 100 metres increase in height.

Precipitation, or rainfall • The prevailing south-westerly winds explain the relatively high precipitation values in western areas. Upland areas also have an effect on rainfall. • The driest areas are in the east, sheltered by the uplands from the moist Atlantic winds.

Sunshine • The highest sunshine values are in the south and east, again sheltered from the relatively moist and cloudy south-westerly winds. • Anticyclones from the south that bring stable and cloud-free conditions often affect coastal areas in the south. • Upland areas tend to have less sunshine than lowland regions as air rising over the mountains cools to form clouds.

Average annual rainfall in the UK

Relief rainfall The prevailing wind in Britain is from the southwest and warm moist airs arrives from the Atlantic Ocean and rises over the mountains on the western side of Britain- the Cambrians, Pennines and Grampians. When it rises, it cools, condenses into cloud and starts raining. The mountain peaks can receive a lot of rain- up to 2000 mm a year. Once the air has passed over the mountains, it descends and gradually warms as it reaches lower ground. This creates drier conditions called the rain shadow. Therefore mountains in the UK tend to be wetter on their windward, western sides and drier on their leeward, eastern sides. http: //www. bbc. co. uk/learningzo ne/clips/reliefrainfall-newzealand/3088. ht ml

Convectional rainfall On sunny days air warms and rises. As it rises it cools and the water vapour in the air condenses to form clouds and rain. Convectional rainfall occurs less than the other two types of rain in Britain because it is caused by heat, but long summer days can leads to afternoon thunderstorms, especially in southeast England. http: //www. bbc. co. uk/learningzone/clips/convectional-rainfall-costa-rica/3089. html

Frontal rainfall Frontal rain develops along weather fronts which form where two air masses meet. Warm moist air meeting colder air at a warm front is forced upwards. As it rises it cools and the moisture condenses to form rain. Britain lies in an area where air masses frequently meet and so we get a lot of this type of rain. http: //www. bbc. co. uk/learningzone/clips/predicting-the-weather-frontalsystems/4319. html