Weather

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.

https://es.tiching.com/link/15864?v=1

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

THERMOMETER

Fuente: 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 equator

Latitude 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 level

Temperatures decrease by 0,6 degrees

celsius for every 100 metres increase in

altitude. Mountainous areas are therefore

cooler.

Distance from the sea

Oceans 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 currents

The 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/secondary/students/airmasses.html

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=BVykQf

RC_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 winds

Widely 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 air

2. 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 Anticyclones

Summer 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 Anticyclones

Winter 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 FRONT

L L

L

L

H

L

L

C

WC

C

WW

COLD FRONTS

Heavy

rainrain 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) Anemometre

b)- 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&fe

ature=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_climat

e_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

CLIMATETEMPERATURES 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.

CONTINENT

AL

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.

MEDITERRA

NEAN

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

CLIMATETEMPERATURES

PRECIPITATION

SVEGETATION

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