High pressure is created by rising air.

Isobar is a block of air with similar conditions of temperature and moisture.

Weather is any form of water falling from the sky

Air mass is is created by sinking air.

Precipitation is a line that joins places with equal air pressure.

Climate is the conditions of the atmosphere on a day to day basis.

Low pressure is the average rainfall and temperatures over the course of a year.

Theme 2 - Weather and Climate

Weather

Is the conditions of the atmosphere in the short term - over a day or a week. It is made up of temperature, rainfall, humidity, wind speed, wind direction, air pressure and other characteristics of the air around us.

Climate

Is the generalised conditions of the precipitation and temperature over a year. The figures are averaged out over a long period of time - this is normally a minimum of 30 years.

Weather is …

It includes …

It involves changes in the …

Climate is …

It includes …

It involves changes in the …

Condition High or Low Pressure

Cold and warm fronts

Sinking air

High level of condensation

Low precipitation

Sunny conditions in summer

Cold and frosty conditions in winter

Condition High or Low Pressure

Warm air rising over cold air

Thunderstorms in the afternoon in Summer.

Very stable conditions for a number of days or weeks

Low levels of condensation.

Rain, followed by few hours of dry, followed by heavy rain.

Storm conditions and isobars that are close together.

High or Low Pressure?

High

HighLow

HighHigh

LowHigh

HighHigh

Low

LowLow

Pm

Pc

TcTm

Am

The Importance of Air Masses

An air mass is a block of air that has similar temperature and moisture characteristics. Where the ‘air comes from’ has a big impact on our weather and climate.

The Importance of Air Masses

An air mass is a block of air that has similar temperature and moisture characteristics. Where the ‘air comes from’ has a big impact on our weather and climate.

Link - 1’10” in

Link 2 Link 3

War

m fr

ont

Cold front

War

m fr

ont

Cold front

War

m fr

ont

Cold front

Warm sector

Warm sector

Warm sector

Warm sector

Occluded Front

Symbol on a weather

map

What kind of weather will it bring?

Very cloudyHeavy rain - possiblyCold temperaturesHigh windsHumidity gradually falls.

Sandstorms in the Sahara Desert in Northern Africa collect and transport lots of sand and dust into the atmosphere. This is picked up by the wind moving clockwise in the high pressure.

Air in a high pressure (anticyclone) moves in a clockwise direction. This creates an air mass moving over the UK from the South.

The Tropical Continental Air Mass (Tc) is full of dust and sand which have been picked up from the storms in the Sahara

Air in a high pressure sinks creating very stable conditions. Wind speeds tend to be light and calm.

Sinking air with calm conditions means that levels of pollution in the atmosphere can build up. The air mass affecting the UK crosses some of the big industrial regions of Europe - Northern France, Belgium and Germany.

High Pressure

Stretch and Challenge•High pressure systems block other weather systems, especially low pressures and so can last for several days, even weeks. This means the weather conditions can remain similar for some time.•Isobars in High Pressure systems tend to be spread out; the pressure gradient is low.•Sinking air means the chance of condensation is low, and thus precipitation levels are low. This means there is little or no rainfall to wash pollutants and dust out of the atmosphere.•Microclimates in urban areas mean that high pressure conditions trap pollution emitted by transport and industrial sources in the local area. This combines with pollutants transported from further afield.

Why were pollution levels so high?

High pressureTc Air MassSand Storms in North AfricaTc Air crosses industrial regions

High pressure results in sinking airLow condensation and precipitationPollution is trappedAir is not washed clean

High pressure remains in place for several days.It is a ‘blocking anticyclone’ - it prevents other weather systems from affecting the UK.

What are the impacts?

Serious health risks.

High risk for elderly or people with lung or heart disease.

Smog - hazey conditions create poor visibility, and so increase the risk of accidents.

Using the ingredients you have been given explain the reason for high levels of pollution in the UK in early April 2014.

- combination of factors.- detailed knowledge- use of specialist vocabulary- Clear Point Evidence Explain structure

• Moves from East to West• Crosses three countries -

Philippines 26-27 September, Vietnam 29th September, and Laos/Cambodia on 30th September.

• Turns from a tropical depression, into a Tropical Storm, into Typhoon and then back into a Tropical Storm.

• Begins in the Philippine Sea, and moves west across the South China Sea.

• North of the Equator but South of the Tropic of Cancer.

• Highest number of deaths in the Philippines.

• Whereas lowest number of deaths in Cambodia.

• Deaths in Vietnam and Cambodia together are less than those in the Philippines.

• Damage is greatest in Vietnam.

• Damage is lowest in Philippines.

• Damage in the Philippines and Cambodia together is less than that in Vietnam.

• Homelessness is highest in Philippines.

• In contrast Cambodia has the lowest homelessness.

• Similarly Vietnam had a high level of evacuation - although this isn’t the same as homelessness.

Cause of floods:• Impermeable surfaces - lack of

infiltration, so rapid run-off.• Poor drainage in informal

settlements - rapid population growth led to poor level of infrastructure.

• High population density - lots of people affected in a small area.

Impact on Quality life• Economic:

• Social:

• Environmental:

People can’t get to work easily. Many businesses shut. People will see a fall in income which could increase poverty when people are already ‘on the edge’.

Emergency services cannot access those who need help - rise in diseases and ill health. Communities are cut off - people cannot access food and clean water.

Sanitation systems are flooded - dirty and contaminated water in many areas. Spreads disease very easily - young people, the sick and the old very vulnerable.

You’ve been given some case study revision notes about the impact of low pressure weather systems. However, they need improving - your challenge is to mark them and indicate where improvements need to be made, and to make them.

Check for:• Detailed information.• Specific evidence and facts.• Clear structure and small chunks of information.• Complex ideas and understanding - stretch yourself and apply ‘BIG’

ideas.

For a period of weather caused by high or low pressure.

• Name and locate the area affected by the weather.• Describe the main features of the weather.• Explain how the weather affected different groups of people.

[8 marks]Name:• UK - high levels of rain and flooding in 2012.

Describe:• Higher than average rainfall• Caused by higher air temperatures linked to Global Warming• Caused by change in the position of the Jet Stream - air masses created

conditions for high rainfall• Ground became quickly saturated - flooding in many drainage basins across the

UK• Higher populations on flood plains - more people at risk of flooding

Explain impacts on different groups:• Homeowners• Farmers• Insurance Companies• People in General

ChallengeWhat does warm air rise?

Your answer?

Describe

Explain

10oC, 8 oktas of cloud, drizzle, Force 5 Wind from the SSW.Located at the warm front. In the next few hours it will get warmer and the drizzle will stop.

Warm air is rising over cold air. As the air rises it cools, and this means water vapour condenses to form clouds. This causes the rainfall, along with the TM air that is warm and moist which comes from the SSW.

Describe

Explain

11oC, 8 oktas of cloud, rain, Force 5 Wind from the W.Located at the warm front. In the next few hours it will briefly get warmer and then it will rain heavily as the cold front arrives.Warm air is rising over cold air. As the air rises it cools, and this means water vapour condenses to form clouds. This causes the rainfall, along with the TM air that is warm and moist which comes from the W.

Describe

Explain

13oC, 3 oktas of cloud, rain, Force 3 Wind from the SW.Located in the warm sector. In the next few hours it will begin to rain heavily as the cold front arrives and temperatures will fall.In between the warm and cold fronts is a block of warm air. This creates an area of more stable and calmer weather. However as the cold front approaches, warm air will once again rise over cold creating the conditions for rainfall.

The weather at Point A is wet and windy. Temperatures are 9oC, and the wind is blowing from the South West, and is Force 4. There is quite a lots of cloud, and there is drizzle.

This is the warm front where a warm air mass is meeting a cold air mass. They don’t mix because they are different densities. Condensation leads to precipitation and this is why it is raining.

The weather at Point A is wet and windy. Temperatures are 9oC, and the wind is blowing from the South West, and is Force 4. There are 7 okras of cloud cover and it is drizzling.

This is the warm front. Warm air is being forced over cold air because it is less dense. As it rises it cools, which lets water vapour condense to form clouds. As the clouds build up eventually it will rain. This frontal system is a low pressure as the different air masses have different densities and one rises over the other.

Answer A Answer B