A2 Geography Weather and Climate

WEATHER AND CLIMATE

Definitions:

• Weather = The day to day changes in the atmosphere
• Climate = The overall pattern of weather usually based on an average over 30 years

Weather Covers these aspects:

• Precipitation
• Temperature
• Wind Speed
• Wind Direction
• Pressure
• Cloud Cover
• Humidity

Definition:

• A climatic hazard has to have short term fluctuations which effects people lives.

Such Hazards Are:

• Hurricanes, Cyclones, Droughts, Floods, Tornados, Lighting, Blizzards and High Winds

Weather and Climate and associated conditions effect:

• Tourism
• Transport
• Driving Conditions
• Health
• Obesity
• Education
• Economics
• Economy
• Farming/Industry
• Population
• Social
• Eco-Systems

1) Troposphere:

• Highest temperatures are found here, as solar radiation heats the earth,
• This is the most unstable layer due to containg the most water vapour and particulate matter
• Wind speeds increase the higher you go into this region due to less frictional drag
• Most Weather processes happen here.
• Between 0 and 7 miles above sea level

2) Stratosphere:

• Temperature starts cool but steadily warms the higher you go due to solar radiation being absorbed by the ozone layer
• The atmosphere is much thinner with a lower pressure with a lack of water vapour
• Wind Speeds increase again with height
• Between 7-30 miles above sea level

3) Mesophere:

• Rapid temperature decline to -90 degrees C,
• Strong winds upto 3,000km/h!
• No water vapour or dust to absorb radiation
• Between 30-51miles above sea level

4) Thermosphere:

• Temperature increases again due to the absorbtion of UV radiation by atomic oxygen at this level
• Between 51-90 miles above sea level

The areas between each level:

• Tropopause (Between the Troposphere and Stratosphere)
• Stratopause (Between the Stratosphere and Mesosphere)
• Mesopause (Between the Mesosphere and Thermosphere)

Earth recieves energy from the sun as short wave radiation

This means the earths surface (exept polar regions) has a net gain in energy

The Atmosphere however has a net defecit

This means that due to this difference heat is transferred from the surface of earth to the atmosphere by radiation, conduction and heat.

The main Factors are:

• Cloud Cover - Blocking and reflecting the suns energy energy out of the atmosphere preventing it reaching the earths surface

• Distance From the Sun - Insolation levels at the poles is less due to the suns rays being focused on a nuch wider area due to the curvature of the earth and less of the rays reaching these areas. Aswell as this the excentric orbit of earth around the sun can cause a 6% difference in the solar constant.

• Allitude/Angle of the sun in the sky - Equator recieves more insolation due to more radiation hitting the earth straight on meaning it is spread over a smaller ares

• Length of night and day - Due to the earths tilts it means some regions don't get any sunlight for 3 months of the years meaning no insolation.
• The Solar Constant (The normal average of energy the sun is giving out)

The greatest amount of energy coming into our solar system is from insolation

The amount of energy recieved by the sun depends on:

• Length of night and day
• Alltitude of the sun
• Distance from the sun
• The solar constant

Not all radiation hits the earth either some is absorbed by the ozone layer, water vapour, CO2, Dust and Ice Particles

During times of thick white clouds 90% of the suns energy is reflected away

Aswell as this during times of thick white cloud heat being released can also be reflected back down to earth (upto 80%)

The ratio of amount of radiation coming in and amount being reflected is called the albedo

The albedo for earth is approximately 4% on average

Only short wave radiation reaches the earths surface and turns to heat as long wave radiation gets trapped and finds it very hard to leave the atmosphere

These cells operate between the equator and 30degrees and north and the equator and 30degrees south

This cell produces winds in the form of tropical easterlies

It is an atmospheric circulation pattern in the tropics

Air rises at the equator (low pressure) and travels towards the poles and falls back down to earth around the sub-tropics (30degrees north/south) due to the air cooling, losing moisture causing high pressure at these regions)

The air then travels back round to the equator being warmed by the earths surface and picking up moisture causing it then to rise again at/around the equator

The air in the cell rises approximately 10-15km into the troposphere

At the equator aair flows along the earths surface towards the equator causing low pressure at the equator as this air starts to rise

This area of low pressure is known as the ITCZ

This produces winds which are turned westwards by the corrolis effect and become trade winds and tropical easterlies

Operates between 30-60 degrees north and 30-60 degrees south

Air flows eastward towards the poles along the ground

As it flows it flows from high pressure to low pressure

When it gets to 60degrees north or south it rises due to the air warming and gainging mositure over land

This causes an area of low pressure

As the air then rises it travels back round to 30 degrees north/south cooling and losing mositure before falling around the 30 degrees mark causing high pressure here

In the Fellel Cell their are warm south-westerlies for wind.

This cell operates between 60degrees north and the noth pole and vice versa

Cold dense air moves along the earths surface becoming less dense, warmer and wetter until the air reaches degrees north/south when it is now much warmer and starts to rise causing low pressure

This cell reaches a max height of 7.5km in the polar troposphere and moves towards the poles as the air travels and cools and condensing before the air starts to sink around the poles causing high pressure here

Definition:

An area of air which has similar properties of temperature, and humidity. Air masses develop over areas of similar geographical characteristics such as polar ice caps and hot deserts

The Tropical Maritime:

• Occours during a warm sector of a depression
• Very mild and wet with thick cloud cover in winter
• Normally Stratus Cloud
• No Frost
• Poor Visibility
• Warm in summer
• Lower layers stable but upper layers aren't
• Can give thunderstorms due to unstable layers
• Winds are moderate
• Very common over britan

Tropical Continental:

• Summer only when when sub-tropical high pressures move north
• Heat Waves
• Very stable in lower layers = droughts
• Upper layers can be unstable = Thunderstorms
• Gentle winds coming from the south
• Gentle Winds

Polar Maritime:

• Very common over Britain
• Cool conditions throughout the year
• Warms over the Atlantic and lower layers are unstable
• Heavy showers over highland areas separated by sunny intervals.
• Cumuloform Clouds
• Strong winds and gales
• Good Visibility
• Comes from the North West

Arctic Maritime:.

• Very cold in winter, mild in spring very rare in summer
• Slowly heats as it goes over the sea picking up water causing lower layers to be unstable
• Snow in Winter, Hail/heavy showers in Spring
• Good Visibility usually
• London temperatures just above freezing
• Limited precipitation in winter

Polar Continental: