Smoke Aerosols, Clouds, Rainfall

and Climate (SMOCC)

Meinrat O. Andreae

Max Planck Institute

for Chemistry, Mainz

How do aerosols influence climate?

I) Direct Effects (i.e., not involving cloud)

a) Backscattering of sunlight into space

increased albedo cooling

Ib) Absorption of sunlight

• At surface: cooling

• In atmosphere: warming

• Effects:

reduced convection and cloudiness

reduced evaporation from ocean

reduced rainfall downwind

• The key parameter is the black carbon content of the aerosol and its mixing state

External Mixing +0.27

Black Carbon Core +0.54

Internal Mixing +0.78

Aerosol Mixing State of Black Carbon

Forcing(W m-2, Jacobson, 2000)

II) Indirect Effects

• Each cloud droplet needs a "seed" or nucleus to be able to form: "Cloud Condensation Nucleus” (CCN)

• For a given cloud, the more CCN in the air, the more droplets

• Since the water supply in a cloud is limited: more droplets means smaller droplets

IIa) First Indirect Effect

• Adding CCN makes clouds with more, smaller droplets.

• These clouds are whiter, reflect more sunlight net cooling

Ship tracks off theWashington coast

IIb) Second Indirect Effect

“Overseeding“: To produce rain, cloud droplets need to be bigger than ~ 14 µm radius. When there are too many CCN, this radius is not reached and rainfall is suppressed.

Therefore:

Adding CCN increases cloud lifetime and cloud abundance Cooling

• This rain-suppression applies only to "warm" clouds (those not containing ice)

• If there is enough latent heat available (tropics) the air will rise and rain-production mechanisms involving ice will take over.

• The result is a shift in the energy-release from lower levels (warm clouds) to upper levels in the troposphere.

• Since the tropics are the heat-engines of the atmosphere, this has far-reaching climatic effects!

Is there evidence that this is happening?

• Wet season data from Amazon basin indicate CCN are very low in “natural” state

“Green Ocean”

• Dry “smoky” season data show strong increase in CCN due to biomass smoke

More tall convection and lightning

Latent heat release at higher levels

Large Scale Biosphere-Atmosphere Experiment over Amazônia

CLAIRE ‘98CLAIRE ‘98

Balbina, AmazonasBalbina, Amazonas28 March - 15 April

EUSTACH ‘99EUSTACH ‘99

Rebio Jaru: forestRebio Jaru: forestNossa Senhora: pastureNossa Senhora: pasture

RondôniaRondônia7 April – 21 May15 Sept. – 1 Nov.

Aircraft ExperimentAircraft Experiment2 – 14 September

Summary of CCN Spectra

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.610

100

1000

******

**

**

Wet Season Pasture site Jaru Tower

(120 - 132) CLAIRE '98

Dry season Pasture site

Transition Jaru Tower

(134 - 143)

N

(cm

-3)

Sc (%)

Smoke hazeVisibility ~ 800 mNCN ~ 10000 cm-3 BC ~ 7 g m-3

Clear dayVisibility ~ ??? kmNCN ~ 500 cm-3 BC ~ 0.2 g m-3

April - the wet and clean time of year: Note the shallow precipitating clouds, extensive warm rainout, glaciation at T>-10oC, and few lightning events

TRMM VIRS+PR, Amazon, 1998 04 13 16:28

VIRS T-Re

The “Green Ocean”: Maritime clouds over the Amazon

Smoke hazeVisibility ~ 800 mNCN ~ 10000 cm-3 BC ~ 7 g m-3

Clear dayVisibility ~ ??? kmNCN ~ 500 cm-3 BC ~ 0.2 g m-3

VIRS+PR, Amazon, 1998

13 SEP 14:15

VIRS T-Re

TOMS Aerosol Index13 September 1998

September: The Fire Season

Note that clouds do not precipitate before reaching height of 6.5 km or –12oC isotherm, while containing ample cloud water.

The “Green Ocean” turns dry: Smoky clouds over the Amazon

VIRS+PR, Amazon, 1998 09 15 18:16

VIRS T-Re

PR H-Z

When the “smoky clouds” become Cb, they spark lightning and high Z

GCM simulation of the impact of biomass burning in the tropics on the global circulation in the extra-tropics. (Graf et al., 2000).

GCM simulation of the impact of biomass burning in the tropics on the global circulation in the extra-tropics. (Graf et al., 2000).

SMOCC Objectives

1) Make field measurements of aerosol and supporting parameters in the Amazon Basin;

2) chemically characterise the aerosols produced by biomass burning, with particular attention to the organic fraction;

3) determine the link between the aerosol’s chemical/physical properties and its hygroscopic and cloud-nucleating properties;

4) model the effect of biomass burning aerosol on cloud microphysics at the cloud and regional level;

5) investigate the effect of smoke aerosols on climate dynamics and the resulting large-scale climate effects; and

6) use satellite data to detect, validate and quantify the effect of smoke aerosol on cloud properties and precipitation processes.

Project planning and time table

2 0 0 1 2 0 0 2 2 0 0 3 2 0 0 4

N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O

Project Activities WP# 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Project co-ordination

Workshops all

EU reports all

Preparation and test of field instruments WP1,3

intercomparison & -calibration WP1,3

CNPq & customs documents WP1,3

Shipping and customs clearance WP1,3

Instrument set-up at field sites WP1,3

Field campaign WP1,3

Aerosol samples delivered WP1

Field data delivered WP1,3

Analytical methods development WP2

Aerosol chemical analysis WP2Parameterisation using simplified aerosolcomposition WP2

Lab data on hygroscopic and CCN activ-ity of selected compounds WP2,3

Models of hygroscopic and CCN activity asfunction of composition and surface tension WP3,4

Adaptation of 2D cloud model WP4Simulation of available data with 2Dmodel WP4

Construction of 3D model WP4Runs of 3D model for preliminaryevaluation WP4

Finalise 3D model analyses WP4Parameterisation of cloud droplet num-ber in GCM WP5

Models of CCN effects on rainfall effi-ciency WP4,5

Global and regional analysis of aerosoleffects on climate in GCM WP5

Model and remote sensing analysis ofobserved mesoscale convective systems WP5,6

Analysis of available aerosol and satellitedata WP6

Satellite data analysis for field campaign WP6

Validate results of the cloud models WP6

Data analysis and publication all

Training of Brazilian partners all

INSTITUTION PRINCIPALINVESTIGATOR

The Max Planck Institute for Chemistry (MPIC), Mainz, Germany M. O. Andreae

(Co-ordinator)

Istituto di Scienze dell’Atmosfera e dell’Oceano – Consiglio Nazionale

delle Ricerche (ISAO-CNR), Bologna, Italy

S. Fuzzi

Instituto de Fisica da Universidade de Sao Paulo (IFUSP), Sao Paulo,Brazil

P. Artaxo

Institute of Earth Sciences, Hebrew University of Jerusalem (HUJ), Jeru-salem, Israel

D. Rosenfeld

Department of Analytical Chemistry, Ghent University (RUG), Ghent,Belgium

W. Maenhaut

Division of Nuclear Physics, Lund University (LUND), Lund, Sweden E. Swietlicki

Max-Planck-Institute of Meteorology (MPG-IMET), Hamburg, Germany H. Graf

Department of Environmental Sciences (WI), Weizmann Institute of Sci-ence, Rehovot, Israel

Y. Rudich

Università di Bologna, Dipartimento di Chimica “G. Ciamician”(UNIBO), Bologna, Italy

E. Tagliavini

Laboratory of Bio-organic Mass Spectrometry, Department of Pharma-ceutical Sciences, University of Antwerp (UIA), Antwerp, Belgium

M. Claeys

Partner 1 – The Max Planck Institute for Chemistry (MPIC), Mainz, Germany

The role of Partner 1 is: to act as Co-ordinator for the proposed project;to act as Lead Contractor for WP1;to organise and conduct a field experiment in Amazonia, including a ground-based and an aircraft component (WP1); to collect and supply aerosol samples to WP2;to take aerosol measurements during the field campaign, including CCN spectra (WP3), and accompanying data, and provide them to WP3, WP4, and WP6;to analyse aerosol samples by GC-MS and EGA (evolved gas analysis)