DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE ... · dragon advanced training course in atmosphere remote sensing ... dragon advanced training course in atmosphere remote sensing

D2 – L1 Basics about the atmosphere - Hennie Kelder 1

DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSING

Basics on the atmosphere



Overview• Climate and enhanced greenhouse effect• Stratosphere

– Background ozone chemistry– Polar ozone depletion – the ozone hole

• Troposphere– Ozone formation and destruction– Ozone budget– Air pollution



Atmospheric temperature distribution

Composition

N2 (~80%) and O2 (~20%)

trace gases < 0.03 % essentialrole in radiation budget and atmospheric chemistry

•



Temperature distribution: radiative balance earth-atmosphere system

Incoming solar radiation342 Wm-2

Reflected solar radiation102 Wm-2 (circa 30%)

Outgoing infrared radiation 240 Wm-2Te = 255 K, A = 0.30With atmosphere, Ts = 288 K, 15 C Difference 33 K due to natural greenhouse effect



Climate, climate changes due to natural variability and externalcauses

1. Vulcanic eruptions

2. Solar activity


DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSINGIncrease of greenhouse gasesThe greenhouse effect



Temperature on earth has increased globally



Increase of temperature in last decades mainly caused by enhanced greenhouse effect


DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSINGRadiative forcing



Where in the atmosphere is the ozone?



What is ozone?

OxygenAtom (O)

OxygenMolecule (O2)

OzoneMolecule (O3)



How ozone is formed?



Why is the ozone layer important?


DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSINGUV-radiation DNA-damage

Skin cancer



How is ozone distributed over the world?



Life is due to the ozone layer and the ozone layer is due to life


DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSINGThe ozone hole aboveAntarctica



Ozone destruction above the North pole



Ozone destruction at the north- and south polar region



Ozone destruction

emissions accumulation transport

removal Chemicalreactions

transformation

Uitstoot Ophoping Transport

Omzetting

Chemische reactie

Verwijdering

CFC’s

Wat is hetozongat?



Emissions

Ozonafbraak



Polar stratospheric ozoneWhere do Cl and Br come from?

Stable compounds (CFCs) are photolyzed by UV in the stratosphere



Accumulation

Ozonafbraak

CFC’s are inert in the troposphere

Long lifetime (~100 Year)

Total amount

“effective chlorine”



Transport

Ozonafbraak

yearly ca. 5% of all air exchanged between the

the troposphere and the stratosphere



transformation

Ozonafbraak

In the stratosphere CFC’s are destructed through the intense UV-radiation producing Cl and ClO



Chemical reactions

Ozonafbraak



Removal

Ozonafbraak

By the atmospheric circulation Cl is transported from the stratosphere to the troposphere;

By clouds and precipitation Cl is removed from the atmosphere.



How is the ozone hole created?Necessary:

1) Low temperature (< -78 ºC); → polar stratospheric clouds

2) Chlorine

3) Sunlight

This happens at the end of the polar winter



Polar stratospheric ozone Role of PSCsCl and Br in stable reservoirs: HCl, ClONO2 , BrONO2 and HBr.

But on polar stratospheric clouds (PSCs):

ClONO2solid+ HClsas Cl2gas + HNO3solid

Cl2 + hν 2Cl sunlight !

PSCs form at sufficiently low T as ice or NAT (HNO3.3H2O)

Detailed microphysics still not completely understood!

Reformation of the reservoirs after PSCs re-evaporate:HNO3 + hν NO2 + OH

ClO + NO2+ M ClONO2 + M

Re-evaporation may occur after sedimentation !


DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE SENSINGThe future of the ozone layer



The future of the ozone layer: CFC’s



Observed temperature trend (1961-96)

Troposphere is warming up, butOzone layer is cooling!



Global mean temperature in the stratosphere,1960-2000



Causes cooling stratosphere-lower part: mainly increase in ozone-upper part: mainly increase in greenhouse gases

20 km

30 km

50 km



Hence:More greenhouse gases →lower temperature stratosphere →more polar stratospheric clouds →more ozone destruction above polar regions → delay in recovery of the ozone layer



Tropospheric ozone increase related to emissions



Tropospheric ozone budget

23.6 daysLifetime344 TgBurden

508 Tg/yrInflux from stratosphere

720 Tg/yrSurface deposition

212 Tg/yrNet chemical production

4594 Tg/yrChemical loss

4806 Tg/yrChemical production

TM resultsProcess

Zonal mean ozone (ppbv)



Air Pollution: Global Tropospheric NO2 from SCIAMACHY



Spatio-temporal variability

tropospheric NOx is high

EMEP emissions

SCIAMACHY cloud-free 2003

Model 2003



Summary

• Overview of the enhanced greenhouse effect• Introduction to the stratosphere

- Background ozone chemistry– Polar ozone depletion – the ozone hole

• Tropospheric composition– Ozone budget– Ozone in a changed climate– Air pollution

DRAGON ADVANCED TRAINING COURSE IN ATMOSPHERE REMOTE ... · dragon advanced training course in atmosphere remote sensing ... dragon advanced training course in atmosphere remote sensing

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