stratospheric ozone

stratosphere

temperature goes up due to ozone layer convection

UVC

ozone layers absorbs 100% of UVC, whcih is the highest energy

UVB

90% of UVB is absorbed by the ozone layer

UVA

50% of UVA is absorbed by the ozone layer

ways to track ozone

satellites, high and low altitude aircraft, ground based systems

stratosphere ozone formation

oxygen plus UV results in two oxygen radicals, which form with oxygen to create ozone

Polar stratospheric clouds

sunlight breaks CFCs apart, releasing chlorine ready to destroy ozone in cold temps (when chlorine compounds are active), so it happens in PSCs

1957

global ozone observing system

1973

first observations of CFCs

1985

ozone hole reported over antarc

ozone cycling

once ozone is formed, UVB reacts with it, creating oxygen and an odd oxygen radical, which creates more ozone

catalytic ozone loss by OH

OH and ozone create hydroperoxyl radical and oxygen - hydroperoxyl radical and ozone create OH and oxygen 

seasonality

more ozone in northern hemisphere spring, tropics tend to have lower ozone than poles, antarctic ozone hole bad in southern hemisphere spring

trends overtime

southern midlatitudes with greatest decrease, relatively stable in tropics

chlorofluorocarbons

carbon molecules that contain halogens (chlorine, fluorine, bromine)

trichlorofluoromethane 

CFC 11 and Freon 11: refrigerant, aerosol propellant,foam blowing agent invented in 1930s

Nitrous oxide

“laughing gas”, created by soil microbes with natural and human sources, increased emissions from fertilizer use,

substitution chemicals

CFCs have gone down, carbon dioxide, methane, and nitrous oxide have gone up

amplifying factor of chlorine

1 chlorine can destroy a ton of ozone molecules

chlorine monoxide

CIO

chlorine catalytic cycle

one type of halogen catalysis, CI + ozone = CIO and O2, O plus ozone to O2 overall

halogen source gases

ozone depleting substances, short lived substances (CFCs, HFCs,

largest reservoirs

hydrogen bromide, chloride and chlorine and bromine nitrate

reactive

chlorine and bromine monoxide and chlorine and bromine atoms

PSC

antarctic is super cold, allowing for polar stratospheric cloud formation, chlorine source gases form into hydrogen chloride, PSC taps into this hydrogen chloride, they react on cloud surface, reducing ozone 

antarctic ozone hole

largest depletion in late winter, nitric oxide and chlorine monoxide play large role 

montreal protocol 1987

based on 1974 CFC ozone depletion hypothesis, banned substances that deplete the ozone layer

montreal results

CFC emissions dropped in 1990s with gradual decline into the present

montreal steps

1. identification of problem

2. engagement with policy makers

3. continued scientific assessments

montreal science and policy

science can inform policy and then policy is reinforced with more scientific knowledge (1990 London amendment)

climate change

bromine has high ozone depletion potential, and HFC, CFC, and bromine all have high global warming potential

nitrous oxide

important greenhouse gas, glaciers trap bubbles, result of disruptions in the nitrogen cycle, agriculture, natural soils, open oceans, industries, shows that it is going to be a problem that we will need to handle