Stratospheric chemistry

what is the Dobson unit

total column amount of O3 - if all O3 was compressed to 0oC and 1atm, how thick would it be. 3mm = 300DU

what is odd oxygen

Odd number of oxygen atoms, most reactive oxygen species. O and O3

Why do CFCs destroy O3

long lived species, so survive into the stratosphere, where they are then photolysed to generate Cl radicals which can rapidly destroy O3 in catalytic cycles

what is a null cycle

No net loss of O3

what are reservoir species

Stable and unreactive forms of the catalytic species, e.g. ClONO2, HCl, HNO3

methods of measuring O3 in stratosphere

sonde, LIDAR, satellite, flights, dobson spectrophotometer. Pros and cons??

what is a holding cycle

stores catalytic species which destroy O3 so in unreactive and stable compounds

Why are HOx/Nox/ClOx cycles not additive

They interact with each other in coupling cycles

which methods of O3 measurement give horizontal distributions?

satellite, other methods in different areas

Which methods of O3 measurement gives vertical distributions?

all

British vs American discovery of O3 hole

American data was ignored and corrected as it was thought to be a mistake

Conditions for formation of O3 hole over Antarctica

very cold, westerly circulating polar vortex to create PSCs, dark

why is most (O1D) formed in stratosphere collapsed back to O(3P)?

stratosphere is very dry - so little OH. formation

how does the ratio of O/O3 change with altitude

it increases - as doing R2=R3 steady state equation to check O/O3 ratio shows that [O2][M] are on the bottom of the equation - decrease with Z

why can the Br cycle occur at lower z

No O required - can occur where there are longer wavelengths of light loer down

why is the frost point lower in the stratosphere

it is very dry and low pressure

consequence of denitrification on PSCs

Less NOx available to form reservoir species with ClO

smoking gun experiment about ozone hole

flight measuring mixing ratios of ClO and O3 - patterns on the graph mirror each other exactly - as ClO increases, O3 decreases

why do volcanoes lead to a cooling effect in

sulfate aerosols form after SO2 is injected into the stratosphere, no rain to wash away the aerosols so they are long lived and spread around the globe, scattering UV from the sun so less reaches Earth

increase in CO2 from 1960-now

320 - 420 ppm

Change in patterns of pollutants from 1970-now in the UK

large decrease in SO2 due to less coal burning, smaller decrease in NH3 due to agriculture

deaths from air pollution

7 million globally annually, mainly due to NO2/O3/PM2.5