EVSC100 - 4 - Stratospheric Ozone Depletion

dobson units

units of measurement used to measure ozone concentration in a column of air

ozone layer

layer in the stratosphere that filters out 99% of the harmful UV-B radiation from sunlight

ozone hole

an area in which ozone concentrations drop below the historical threshold of 220 dobson units

chlorofluorocarbons

CFC’s long lived chemicals that have been used in refrigerators and aerosol sprays, they cause ozone to break. Stable and safe in the lower atmosphere (earth)

ultraviolet light

\----- causes CFC’s to break apart and release chlorine, a very reactive atom that repeatedly catalyzes ozone destruction

chlorine

a very reactive atom that repeatedly catalyzes ozone destruction

Montreal protocol

treaty phasing out the production of ozone depleting chemicals

ozone

a chemical made of 3 oxygen atoms, mostly found in the stratosphere about 8-30 miles above earths surface

planetary boundary

only passed regionally over Antarctica in spring time (southern hemisphere)

atmosphere

thin layer of gas that surrounds earth, composed of several sub-layers

troposphere

which states at the surface of the earth and can extend up to 20km;gets colder the higher up you get

stratosphere

the section of the atmosphere found between 20km and 50 Km above earths surface, gets hotter the higher you get (because of ozone), comprised almost entirely of nitrogen and oxygen but has the highest level of ozone (90%)

tropopause

between troposphere and stratosphere

mesosphere

the section of the atmosphere found between 60km and 80 km above earths surface, gets colder the higher you get

stratopause

between stratosphere and mesosphere

thermosphere

section of the atmosphere found between 80km and 210km above earths surface, gets hotter the higher up you get

mesopause

between mesosphere and thermosphere

exosphere

between 210km to space; above earths surface

thermopause

between thermosphere and exosphere

ozone formation

when high energy ultraviolet radition from the sun breaks apart molecular oxygen, an oxygen atom combines with an oxygen molecule producing a new molecule with 3 atoms of oxygen

ultraviolet light

has smaller wavelengths than visible light so it can make more damage to humans, plants etc

UV-A

longest wavelengths of ultraviolet radiation, ozone absorbs 50% of this radition

UV-C

shortest wavelengths of ultra violet light, ozone absorbs all of this radiation and 90% of UV-B radiation this is the most harmful radiation to humans

CFC conditions

* UV radiation
* extremely low temperatures
* a surface on which the ozone destruction process can occur

polar stratospheric clouds

clouds that only form in extremely low temperatures, common in the south pole

residence time

CFC’s have a long------ which makes them stay in the stratosphere for long period of time

hydrofluorocarbons

manufactured to replace CFC’s, they do not have the same ozone depleting effects but they can lead to global warming, are being minimized by the Kigali amendment