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Dust-Climate Interactions in HadGEM2 Stephanie Woodward Met Office Hadley Centre

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Dust-Climate Interactions in HadGEM2 Stephanie Woodward Met Office Hadley Centre ([email protected]) ‏. A dust scheme for climate modelling needs to - work globally (including areas not currently sources) - respond to changing climate and so must

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Presentation Transcript
slide1
Dust-Climate Interactions

in HadGEM2

Stephanie Woodward

Met Office Hadley Centre

([email protected])‏

slide2
A dust scheme for climate modelling needs to

- work globally (including areas not currently sources)

- respond to changing climate

and so must

- work from model-generated fields

- be physically realistic

.

outline of hadgem dust scheme
Outline of HadGEM dust scheme

6 size bins of aerosol.03 – 30 um radius, treated independantly

Interactive emission scheme

Transport as 6 model tracers

Dry deposition through gravitational settling and turbulent mixing in BL

Wet deposition, scavenging coefficients from obs

Resistance analogue method of combining deposition processes

Radiative properties from medians of range of measurements

* Volken & Schumann 1993, Water, Air & Soil Pollution 68

emission scheme
Emission scheme

Soil:

9 size bins .06-2000um diameter

Horizontal flux :

Marticorena & Bergametti (bare soil fraction only)‏

U* corrected for scaling effects

U*t = U*t (dry,impact) x f (CorrectedSoilMoisture)

f - Fecan scheme, modified at high soil moistures

Vertical flux:

only .06-60 um range

total flux from log (F/G)=.134(%clay)-6 (M&B, based on Iversen data)‏

size distribution from that of horiz. flux below 60um

slide5
Emissions
  • Deposition
  • Load

(22Tg)‏

comparison with concentrations at u miami stations
Comparison with concentrations at U Miami stations

CGr KGI Maw

Pal Fun Nau

Nor ASm Mid

Ohu Chu Fan

EwtBar Ber

MaH Mia Iza

comparison with aeronet aods
Comparison with Aeronet AODs

Cap Verde

Solar village

Sede Boker

Banizoubou

Ougadougou

Ilorin

dust climate
Dust & Climate

Objective:To investigate feedbacks between climate and dust

Model: proto-HadGEM2-AO GCM (N96 38 levs), including proto-dust scheme

2 Experiments:

“A” – Active Dust – dust radiative effects included

“P” – Passive Dust – dust radiative effects excluded

Each experiment:

20 years spin up

allows climate (including ocean) to come to equilibrium

+10 years run

a concentrations aods vs observations
‘A’ concentrations & AODs vs. Observations

Cape Grim (concs) Funafuti (concs)‏

Midway (concs) Bermuda (concs)‏

Cape Verde (AOD) Solar Village (AOD)‏

slide11
A

A

P

P

  • P
humidity
Humidity
  • A
  • P
  • diff
summary
Summary

Dust scheme developed for HadGEM2

Good agreement with obs

Feedbacks on Dust production:

Positive in Sahara

Negative in moister regime

Shifts in circulation patterns

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