ATMOSPHERE

The atmosphere is the layer of gases that surrounds the Earth and makes life possible on the planet. It extends for thousands of kilometres. Its composition is mainly nitrogen and oxygen, but also argon, carbon dioxide and other gases (hydrogen, ozone, methane and water vapour).

The atmosphere is divided into layers. These layers include the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The temperature, thickness and composition of each layer is different.

http://cienciasnaturales.es/2M1ESO.swf

Animation

LAYERS OF THE ATMOSPHERE

Weather describes the condition of the atmosphere. It might be sunny, hot, windy or cloudy, raining or snowing.

Climate means the average weather conditions in a particular location based on the average weather experienced there over 30 years or more.

The weather takes into account the temperature, precipitation, atmospheric pressure and wind of the part of atmosphere (air) closest to the surface of the earth.

TEMPERATURE

THERMOMETERFuente: Banco de imágenes del

CNICE

• It is the amount of heat in the atmosphere

• We measure it with the thermometer.

• It is expressed in degrees centigrade.

Factors affecting temperature are:

Latitude or distance from the equatorLatitude is the main factor affecting global climate - the further you go from the equator, the cooler it gets. This is because the earth in curved which means that the sun's energy is more concentrated at the equator. This, and the thinner atmosphere at the equator, means that the earth gets hotter here.

Altitude or height above sea levelTemperatures decrease by 0,6 degrees celsius for every 100 metres increase in altitude. Mountainous areas are therefore cooler.

Distance from the seaOceans heat up and cool down much more slowly than land. This means that coastal locations tend to be cooler in summer and warmer in winter than places inland at the same latitude and altitude. Glasgow, for example, is at a similar latitude to Moscow, but is much milder in winter because it is nearer to the coast than Moscow.

Prevailing winds and ocean currentsThe prevailing wind is the most frequent wind direction a location experiences. Winds take on the characteristics of their source region. Ocean currents can be warm or cold, and they affect the temperature of coastal areas.

Air Masseshttp://www.metoffice.gov.uk/education/teachers/videos/what-are-air-masses

DISTRIBUTION IN THE EARTH

RAINFALL

pluviometer

• It is water from the atmosphere that falls into the Earth´s surface in the form of rain, snow, sleet or hail.

• We use a rain gauge or pluviometer to measure the precipitation

• The amount of precipitation is expressed in mm.

The atmosphere contains water vapour. The amount of water vapour in the air is called the humidity. Low humidity means that the air is dry and high humidity means that the air is moist.

When humid air rises, it cools and it produces condensation, forming small droplets of water, which form clouds. For precipitation to occur, the droplets must become bigger and heavier. When this happens, thet fall (precipitation) onto the Earth´s surface.

http://www.curriculumbits.com/prodimages/details/geography/types-of-rainfall.html

Cloud (liquid water)

Water vapour

Condensation level

Altitude at which temperatures reach dew point and therefore air starts to condensate

Warm, moist air rises and it cools. As cool air can't hold as much water vapour as warm air, the water vapour condenses and turns into water droplets.

We get rain because of rising air.

The amount of precipitation varies from one zone to another, depending on factors as latitude, altitude, and proximity to the sea.

Relief Rainfall

With relief rainfall, it is the presence of hills or mountains that leads to the warm aid rising. The winds pick up moisture from the sea as they pass over it, and this makes the air moist. As the air rises to pass over the higher land, it cools and the water vapour condenses, forming clouds. The droplets then fall as rain, sleet, hail, or snow, depending on the atmospheric conditions.

On the leeward side of the mountain (the side not facing the wind), it is much drier. This area is said to be in the 'rainshadow'. There is little rain here as the air is descending and warming up.

http://www.youtube.com/watch?v=BVykQfRC_aI&feature=player_embedded

Convectional Rainfall

This is very common in areas where ground is heated by the hot sun, such as the Tropics.The sun heats up the ground, which heats the air above it. This then rises and cools, and the water vapour condenses into water droplets, forming clouds. The droplets falls as rain under the influence of gravity.

http://www.youtube.com/watch?v=RkgThul2El8&feature=player_embedded

Frontal Rainfall

Frontal rainfall is associated with depressions. It happens when two air masses (a warm one and a cold one) meet. The warm air is pushed upwards over the cold air, and, as it rises, it cools down. The water vapour condenses to form clouds, which give rain.

http://www.youtube.com/watch?v=D88dYNFyBq8&feature=player_embedded

• Air pressure is the force exerted by air particles. The air around us pushes on us and every other thing (but our bodies and objects push back with equal force so we don't notice it).

• We measure pressure with a barometer

• Pressure is expressed in milibars (mbar). Normal pressure at sea level is 1013 mbar.

AIR PRESSURE

A low pressure system, or "low," is an area where the atmospheric pressure is lower than that of the area surrounding it.

A high pressure system, or "high," is an area where the atmospheric pressure is greater than that of the surrounding area.

Cold front represented with blue triangles (cold sector)

Warm front represented with red semicricles (waarm sector)

L H

Lows are usually associated with high winds, warm air, and air rising. Because of this, lows normally produce clouds, precipitation, and other bad weather such as tropical storms and cyclones.

They are associated with dry, bright and settled weather.

http://www.juicygeography.co.uk/downloads/flash/lowpressure.swf

http://www.juicygeography.co.uk/downloads/flash/highpressure.swf

Areas of equal pressure are connected using isobars. They never cross.

Lows: inspiraling, upspiraling,counter-clockwise in north, clockwise in south; stormy weather

Highs: outspiraling, downspiraling, clockwise in north, counter-clockwise in south; fair weather

Isobars also show us the direction of the air.

H

H

L

Air moves from a high pressure area toward a low pressure area.

Closely-spaced isobars = strong windsWidely spaced isobars = light winds

Pressure-Gradient Force

How depressions form?

• Depression is a low-pressure system.• A depression forms when cold polar air meets warm tropical air at a front. The

less dense warm air starts to rise over the colder air, and this starts to lower the air pressure.

The boundary between the two masses is called a front. There are 2 fronts in a typical depression:

1. the warm front - this passes first, and has the warm air behind it (i.e. it is the front of the warm air). It is where the advancing warm air is forced to rise over the cold air2. the cold front - this follows, and has the cold air behind it (i.e. it is the front of the cold air). This is where the advancing cold air undercuts the warm air in front of it. http://www.phschool.com/atschool/phsciexp/active_art/weather_fronts/

• Describe the weather through a depression

On a weather map, the warm front is shown as red semi-circles and the cold front as blue triangles.

How anticyclones form?

• Anticyclones are areas of high pressure caused by air sinking towards the ground.

• Once anticyclones develop, they tend to remain for several days, bringing dry, bright and settled weather.

This image shows an anticyclone over Spain on 31st January 1999.

Summer AnticyclonesSummer anticyclones bring hot and sunny weather due to clear skies (because of the descending air). The days are long and the sun high in the sky, which gives plenty of opportunity for the land to be heated up. These conditions could therefore lead to convectional rainfall occurring.

Winter AnticyclonesWinter anticyclones bring clear days too. However the sun is low in the sky and the days are short, meaning you get cool days. Clear skies on a winter’s night will allow frost to form. The land quickly loses heat during the night, as there is no cloud cover to act as insulation. The rapidly cooling ground cools and condenses any moisture in the air above it, forming droplets of ice when the temperature falls below freezing. This is frost.Fogs are also caused by clear winter nights. The ground loses heat. This cools the air above it causing moisture to condensate around dust particles in the layer of air closest to the ground surface. This is fog.

Winter Summer

Pressure High High

Temperature Very cold Very warm

Clouds/Rainfall No No

Wind Calm Calm

Other weather conditions

Frost/fog Heat waves/drought

• Two different views of a depression NW of UK with an anticyclone to the SE

https://www.youtube.com/watch?v=bd7DcVnrSL8

ISOBAR

WARM FRONTS

OCCLUDED FRONTL L

L

L

H

L

L

C

WC

C

WWCOLD FRONTS

Heavy rain

rain Heavy rain

rain

Heavy rain rain

rain

WIND

• It is the movement of air from areas of high pressure to areas of low pressure.

• We measure wind with the wind gauge (anemometer) in metres per second m/s or km/hour. A weather vane shows the direction of the wind.

a) Anemometreb)- Weather vane

Most common types of winds

PREVAILING WINDS

Prevailing winds always blow in the same direction. For exmple, trade winds always blow from the tropics toward the equator.

http://cienciasnaturales.es/CIRCULACIONATMOSFERICA.swf

Trade winds

Westerlies

East winds

PERIODIC WINDS, such as the monsoons in south and south-east Asia.

Monsoons change direction seasonally. In summer, they blow from the Indian Ocean towards the continent and bring abundant rain. In winter, monsoons blow from the continent towards the sea and bring dry stable weather.

SYNOPTIC WINDS, change daily, such as sea breezes

Sea breezes blow from the sea towards the land by day. At noght, they blow from the land towards the sea.

BREEZE

BREEZE

COOLER

WARM

WARM

COOLER

How do weather and climate affect peoples' lives?

Weather and climate can have a major effect on people's lives, for example:

Farming –there is a direct link between the type of agriculture and climate. For example, inland Spain has a drier climate than coastal, with more contrasted temperatures between winter and summer. Northern Spain has a much wetter climate. Arable crops tend to be rain-fed in centered areas, and pastoral farming dominates in the north. Irrigated crops grow in the east.

Housing – in particularly hot climates, buildings may be painted white to reflect the heat. Houses in cold climates are often built on stilts to insulate them from the freezing ground.

Sources of energy – particularly windy areas have plenty of potential for wind farms.

Sport and leisure opportunities – The Jamaican bobsled team of the film Cool Runnings weren't too successful! Why might this be? http://www.youtube.com/watch?v=aaov7DNICPg&feature=player_embedded

Water supply – for example, most of the UK´s population live in the south and east, which is relatively dry. Water has to be transferred from reservoirs in the wetter west.

Snow and Ice - in areas where snow and ice are rare, even a small snowfall can lead to chaos on the roads. Schools may even be closed for the day!

How do weather and climate affect peoples' lives?

Tourism

Holidays in the Mediterranean

The graph shows the percentage of outbound visitors to visit the top 10 destinations in 2003.

This graph shows the average temperatures in the UK and Costa Blanca, and the average number of hours of sunshine. To what extent do you think UK travel agents are justified in using the slogan 'Come to Benidorm for your winter break!'. How does the Mediterranean climate differ from the UK climate?

Unit of measurement is Celsius

Temperatures are represented with the red line and can be read in this axis

Precipitation in August is 5 mm. We can say the climate in this place is very dry.

Rainfall is represented with blue columns and can be read in this axis

Where do we find temperatures? Where do we find rainfall?

Example to read the rainfall in August.

Example to read the temperatures in August.

dryness

Temperature in August is 27ºC. This month is the hottests month of the year.

When the line of temperature is above the columns of rainfall, it marks a period of dryness, as it is shown in this graph.

Climate graphs are a combination of a bar graph and a line graph. Temperature is shown on a line graph, with the figures being shown on the right side of the graph. Rainfall is shown by a bar graph, with the figures being shown down the left side of the graph.

The climate graph below shows average annual rainfall and temperature throughout the year for a particular area.

Climate Graphs

Interpreting climate graphs

Temperature data Is the temperature the same all year round? If it is different, how many seasons does the location experience?Which season is the warmest? Is it warm (10 to 20°C), hot (20 to 30°C) or very hot (above 30°C)?Which season is the coolest? Is it mild (0 to 10°C), cold (-10 to 0°C) or very cold (below -10°C)?What is the range of temperature? (Subtract the minimum temperature from the maximum temperature).Rainfall data Does the rainfall occur all year round?What is the pattern of the rainfall? Check which season(s) is/are drier or wetter than others.What is the total annual rainfall? Add each month's total together to get the annual total.Then put the rainfall and temperature information together - what does it tell you about this area?

Describe the patterns in temperature and rainfall, including how they relate to each other. You now have a description of the climate.

http://www4.uwsp.edu/geO/faculty/ritter/interactive_climate_map/climate_map.html

TYPE OF CLIMATE TEMPERATURES PRECIPITATIONS VEGETATION

EQUATORIALTemperatures are high

throughout the year (around 26 °C in January

and 24 °C in July)Low temperature range

from 3 to 5 ºC

Abundant throughout the year, + 1.500 mm annually. There is no

dry season.

Rainforest. Dense forest of evergreen trees

TROPICAL

Average temperatures + 18ºC

Low temperature range from 5 to 10 ºC

There are two seasons humid/dry

(750-1.500 mm annually)

Savannah. Very tall grass in the rainy season,

which dries up in the dry season.

Steppes (short thinly scattered grass) in the areas where the dry season lasts longer.

DESSERT Temperature range + 10 ºC

Temperatures very high (+25ºC)

Precipitation is very rare. (less than 250

mm annually)

Short, widely spaced grass, thorny shrubs,

cactus. In the oases there are palm trees.

TYPE OF CLIMATE

TEMPERATURES PRECIPITATIONS VEGETATION

MARITIME Moderate throughout the year, mild in winter, cool in summer. Temparature range 10ºC

Abundant thoughout the year. (+ 1.000 mm annually)

Deciduous forest (beeches, oaks, lime trees, etc) that lose their leaves in autumn and winter. Moors in non-forested areas and grasslands.

CONTINENTAL

Very contrasting temperatures (cold winters, and hot summers )Temperature range + 20ºC

Between 300-1000 mm annually, mainly in summer

Coniferous forest (taiga) with trees like pines and firs, grasslands and steppes.

MEDITERRANEAN

Temperatures are mild in winter and hot in summer.

Summers are very dry. Precipitation more abundant in spring and fall (300-1.000 mm)

Maditerranean forest (holm oaks and cork oaks) and scrubland. Also pines.

TYPE OF CLIMATE

TEMPERATURES PRECIPITATIONS

VEGETATION

POLAR Very cold thorughout the year(not exceeding 0ºC)

Precipitation is very rare (less than 250 mm a year)

Tundra, moss, lichen and dwarf shrubs

ALPINE Temperature falls with altitude. Winters cold, summers cool

Precipitation increases with altitude(+ 1000 mm annually)

Varies with altitude

HOT CLIMATES

TEMPERATE CLIMATES

COLD CLIMATES

• POLAR • ALPINE

Low-latitude Landscapes:

RAINFOREST SAVANNAH DESERT

Mid-latitude Landscapes :

High-latitude Landscapes :

TAIGA TUNDRA ALPINE

MEDITERRANEAN STEPPEDEIDUOUSFOREST