Global Simulation of the Indirect Aerosol Effect With the ECHAM5 GCM

III LBA Scientific Conference

Brasilia 28/07/2004

P. Stier (1), J. Feichter (1), S. Kinne (1),

U. Lohmann (2), J. Zhang (2), G. R. van der Werf (3)

(1) Max Planck Institute for Meteorology, Hamburg, Germany

(2) Dalhousie University, Halifax, Canada

(3) NASA Goddard Space Flight Center

• Sink processes global aerosol distribution

• Direct radiative effects

• Aerosol-cloud interaction

mixing statesize distribution composition

Requirements for Aerosol Models

To Simulate Radiative Effects

ECHAM5( Roeckner

et al., 2003)

Size-Dependent Dry- and Wet-Deposition(Ganzeveld et al., 1998; Slinn and Slinn, 1982; Feichter et al., 1996; ...)

Online emissions of Dust, Sea Salt and DMS(Tegen et al., 2002; Schulz et al., 2002; Kettle and Andreae, 2000;...)

Sulfur Chemistry MOZART Chemistry(Feichter et al., 1996) (Horowitz et al., 2003)

Aerosol Microphysics M7 (Vignati, Wilson, and Stier, JGR, accepted)

• Nucleation of sulfate particles• Condensation of sulfate on existing particles• Coagulation• Transfer from insoluble to soluble modes• Thermodynamical equilibrium with water vapour

Stratiform Cloud Microphysics - Aerosol Activation(Lohmann et al., 1999; Lohmann, 2002; Zhang et al., submitted;Lin and Leaitch, 1997; A.-Razzak and Ghan, 2000)

Radiation Module(Boucher and Stier)

The ECHAM5-HAM Aerosol Model

Aerosol-Cloud Coupling in HAM

Alternative schemes for aerosol activation:

• Empirical approach (Lin & Leaitch, 1997)

• Explicit activation (Abdul-Razzak et al., 1998; Abdul-Razzak and Ghan, 2000):

- Caveats: uncertainties of composition, e.g. for organics

Evaluation in SCM Mode

Single column studies with Lin and Leaitch (1997) approach

for Atmospheric Radiation Measurement Programme

intensive observation period in March 2000

Pre

ssu

re (

hP

a)

Pre

ssu

re (

hP

a)

Aerosol- and standard-version

agree well with the observations

Evaluation in SCM Mode

Global Simulations

• Global simulations with Lin and Leaitch (1997) activation scheme

in T63 resolution ( 1.8 x 1.8 on Gaussian grid) with 31 vertical levels

• ECHAM5-HAM nudged to ECMWF meteorology for year 2002

• Two simulations: with and without wildfire emissions

• Tropical wildfire emission inventory GFED for year 2002

based on methodology of van der Werf et al. (2003)

Emissions

Seasonal distribution of GFED wildfire emissions for South America

Emissions

Including Wildfires Excluding Wildfires

Emissions

0.10 1 10 [ g m-2 yr-1 ] 0.10 1 10

0.20 2 20 0.20 2 20 [ g m-2 yr-1 ]

Including Wildfires Excluding Wildfires

ECHAM5-HAM Optical Properties

Including Wildfires Excluding Wildfires

Optical Thickness

ECHAM5-HAM and MISR AOT (550 nm)

Difference in solar surface flux (with Wildfires - without Wildfires)

Effect on Solar Radiation Flux

[ W m-2 ] [ % ]

Discussion

Introduction of a global coupled aerosol-cloud climate model

• Prognostic treatment of CDNC and ICNC

• Aerosol activation schemes of intermediate and higher complexity available

Single column studies:

• Coupled aerosol-cloud model shows good forecasting skill

for observed hydrological parameters

Global simulations with focus on South American biomass burning season:

• Simulated AOT in good agreement with satellite measurements

• Wildfires dominant contributor to optical thickness and absorption

• Locally, wildfires decreases the solar surface flux by up to 20%

Outlook

Model development:

• Convective cloud scheme including microphysics and aerosol coupling

• Extended chemical composition and thermodynamics EQSAM/M7

• Extended parameterisation for organic carbonaceous compounds

Ongoing model evaluation:

• LBA measurements of great interest

Case studies:

• e.g. usage of measured activation spectra or CCN efficiencies

• single column studies

• Elisabetta Vignati and Julian Wilson, EC-JRC, Italy

• Erich Roeckner and the ECHAM developers team, MPI-Met, Germany

• Judith Hoelzemann, MPI-Met, Germany

• Part of this work was performed within the

EU project PHOENICS

PHOENICS Partners:

- University of Crete, Greece

- European Commission Joint Research Centre, Italy

- Max Planck Institute for Meteorology, Germany

- Max Planck Institute for Chemistry, Germany

- LSCE, France

- CNRS-LOA, France

- University of Utrecht, The Netherlands

- CNR, Italy

Acknowledgements

Precipitation

Cloud cover and lifetime

+

+

_

Aerosols

+Emissions

Cloud albedo

Cloud droplets

Cloud nuclei

+

+

+

Warm Indirect Aerosol

Effects

+

+Mixed particles Ice crystals

Ice nuclei

++

+

_

_

Glaciation Indirect Aerosol Effect

Aerosol-Cloud Interaction

Aerosol Microphysics Chemistry

Aerosol Dynamics

Lohmannet al. (1999)

Lohmann (2002)

Evaluation of Number Concentrations

Measurement data by courtesy of Andreas Petzold and Andreas MinikinGerman Aerospace Center (DLR)

Campaign-composite vertical profiles of aerosol number-concentrations

HAM

Size

Refractive Index

ECHAM5 RadiationRadiative Properties

Mie Calculation - Lookup Table

Composition

Diagnostics

ECHAM5 Physics

Radiation Module

Resolve aerosol distribution by 7 log-normal modes

Each mode is described by three moments:

Number, Median Radius Mass, Standard Deviation (fixed)

Mixing State:

AITKEN(0.005 µm < r < 0.05 µm)

ACCUMULATION(0.05 µm < r < 0.5 µm)

SOLUBLE / MIXED

COARSE(0.5 µm < r )

INSOLUBLE

1 N1, MSO4

5 N5, MBC, MOC

6 N6, MDU

7 N7, MDU

2 N2, MSO4, MBC, MOC

3 N3, MSO4, MBC, MOC , MSS , MDU

4 N4, MSO4, MBC, MOC , MSS , MDU

NUCLEATION(r < 0.005 µm)

MODES IN M7

HAM - Aerosol Representation