13.4 Atmosphere read pp 510-513 The blanket of air and moisture that surrounds the Earth density of the atmosphere decreases with elevation air of lower atmosphere is dense due to the weight of overlying air
Exosphere Thermosphere Mesosphere Stratosphere Troposphere
Atmospheric Composition Nitrogen 78% Oxygen 21% Argon 0.9% Carbon Dioxide 0.03% traces of other gases
Atmospheric Composition Water vapour : considered a variable gas, can make up 4% of the volume of the air solids are also present: smoke, dust, volcanic ash, soil etc.
Troposphere 8-16 km altitude thicker at equator most of atmospheric moisture and weather temp decreases with altitude tropopause
Stratosphere highest [O3] temp rises above tropopause because ozone absorbs UV ~12-50 km very dry
Mesosphere 50 - 80 km temperature and density extremely low
Thermosphere Exosphere: space? or ionosphere density still low but very energetic molecules thus high temperatures auroras Exosphere: space?
structure of atmosphere video
Atmospheric Pressure: Force which air exerts as a result of gravity
Pressure Gradient: amount atmospheric pressure changes across a set distance fig 4a and 4b p.512
Isobars are lines of equal pressure when isobars are close together the gradient is higher, usually indicating strong winds check weather maps
Drawing Isobars video
Temperature Gradient: change in temperature over a distance in the troposphere this gradient is -6°C per 1000 m, i.e. the temperature drops 6°C for every 1000 m of elevation
Supporting Life the atmosphere is necessary to life… O2 is necessary for breathing N is essential for plant growth CO2 is used by plants O3 filters out UV
Supporting Life con’t plays a role in the water cycle absorbs meteroids regulates temperatures
Atmospheric Pressure measured in kilopascals 1 kPa = 1000 Pa fig 5, p 512 aneroid barometer
Low pressure areas have less atmospheric mass above their location, high pressure areas have more atmospheric mass above their location. Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation.
Weather Balloons Radiosonde: instrument with electronic sensors which transmit temperature, air pressure, water vapour to ground stations radar tracking gives wind speed and direction
UC questions p 513 2, 3, 6