atmosphere

the atmpsphere is a mixture of gases surroinding the earth

• nitrogen (78%) and oxygen (21%) are the most common

the upper limit of the atmosphere is thought to be between 100 and 120km

there are different layers in the atmosphere

• troposphere
• stratosphere
• mesophere
• thermosphere
• exosphere

the troposhpere is the lowest layer of the atmopshere and has most of its mass (75-80%)

it extends upwards about 10km above sea level

99% of the water vapour in the atmosphere is found in the troposphere

air pressure and temperature decrease as you go up the troposphere

the boundary between the troposphere and the next layer is the tropopause

the stratosphere is the second layer of the atmosphere

the bottom of the stratophere is about 10km and the top of the stratosphere is about 50km

the oxone layer is found in the statosphere (ozone is O3)

few clouds are found in this layer the only ones are Polar Stratospheric Clouds

• found in altidues of 15-25km and when the temperature is below -78 degrees C

lots of materials are found in the stratophere stay there for a long time due to the lack of vertical convection

temperature increases as you go up the stratosphere

the area between the stratosphere and the next layer is the stratopause

the mesosphere is above the stratosphere and extends from 50-85km above  the surface

the temperature decreases in the mesosphere and the coldest temperature in the atmosphere is found here (about -90 degrees C)

most of the meteors vaporize in the mesosphere, becuse of this it has a high consntration of iron and other metal particles

clouds called 'noctilucent clouds' and 'polar mesospheric clouds' form here

eletricl discharges are called sprites and ELVES

the air pressure at the bottom of the mesosphere is 1% of the pressure at sea level

the area between the mesosphere and the next layer is the mesopause

the thermosphere is above the mesosphere and extends about 90-500km above the surface

temperatures increase in the thermosphere and can get up top 500 degrees C

• the reason for the high temperature is the UV rays is absorbed there

the air density in the thermosphere is so low it is norrmally theought of as space

most statlites orbit in the thermosphere

the aurora (northern lights) occur in the thermosphere

the area between the thermosphere and the next layer is called the thermopause

the exosphere is considered by some scientists to be the final layer of the atmosphere

• air in the exosphere is actually leaking into space at a very slow rate
• the top of the exosphere is somewhere between 100000-190000km above the surface

the ionosphere is a region in the mesosphere and thermosphere

• it is where high-energy radiation from the sun makes molecules into isotopes by knocking lose electrons from their atoms and molecules

regional climate is the climate where you live - it is the average weather in a place for more than 30 years

the climate is effeted by the amount of sunlight that an area recieves, its altitude, the shape of the land and how close it is to sea level

global climate is a decription of the climate of the whole planet

the amount of solar radiation, chemistry of the atmosphere and the biosphere all effect the earths climate

the sun:

• the change in the cycle of the sun effects the climate 
• over tens of thousands of years the earths orbit around the sun changes effecting the amout of solar radiation absorbed by the earth

volcanic eruptions:

• when volcanoes erupt the release particles into the atmosphere- the main one effecting the climate is sulfer dioxide
• it gets into the atmosphere and refelects solar radiation - the effects is only temperary

greenhouse gases:

• make up less then 1% of the atmosphere but trap a lot of heat 
• over the last 150 years the amount of greenhouse gases has increased through the use of fossil fuels and changing landscapes

weather is different in different parts of the world and changes over time

the weather events are controlled by changes in air pressure.

• when there is high pressure the skys are normally clear
• when there is low pressure it tends to be cloudy 

meteorologisits predict the weather through monitoring changes in pressure and weather conditions in the surrounding area

it is hard to predict the weather far in the future becuase of the chaotic nature of the atmosphere

air pressure varies on the earths surface. areas where the air is warmed often have low pressure are are called low pressure systems. areas with high pressure are called high pressure systems

low pressure systems:

• winds blow towards areas of low pressure
• as the air rises, the water vapour condencing forming clouds and precipitation
• the coriolis effect causes low pressure to to turn anti-clockwise in the northern hemisphere

high pressure systems:

• wind blows away from high pressure systems
• air from higher in the atmosphere sinks down to fill the space left as the air is blown outwards

clouds form when the air cools below dewpoint, and the air cannot hold much water vapour

clouds are made of water droplets or ice crystals that are so light that are able to stay in the air

some clouds form when air heated by the ground rises. when it gets to a certain altitude the water vapour condences to form a cloud. he types of cloud formed are cumulus, cumulonimbus, mammatus and srtatocumulums clouds

another way that clouds form is when wind is forced upwards when it hits a mountain. as the air rises the water vapour condences forming clounds. the types of cloud formed are lenticular, stratus and cumulus clouds

at a warm front clouds form when the less dence warm air is foced above the cold air mass forming clouds. the types formed are are altocumulus, altostratus, high cirrus, cirrocumulus, cirrostratus, cumulonimbus and nimbostratus clouds

air in the atmosphere moves around in a pattern called the global atmospheric circulation

it forms 3 main cells on each side of the equator 

• the hadley cell
• the ferrel cell
• the polar cell

the hadley cell is at the equator until about 30degrees north of south

the ferrel cell is from 30 degrees until 60 degrees

the polar cell is from 60degrees until the poles