1. Smoke Aerosols, Clouds, Rainfall and Climate (SMOCC)
An EU Research Project, led by Prof. Meinrat O. Andreae
Max Planck Institute
for Chemistry, Mainz

2. How do aerosols influence climate?
I) Direct Effects (i.e., not involving cloud)
a) Backscattering of sunlight into space
 increased albedo  cooling

3. 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

4. Aerosol Mixing State of Black Carbon
Forcing
(W m-2, Jacobson, 2000)
External Mixing
Black Carbon Core +0.54
Internal Mixing

5. 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

6. IIa) First Indirect Effect
Ship tracks off the
Washington coast
Adding CCN makes clouds with more, smaller droplets.
These clouds are whiter, reflect more sunlight  net cooling

7. 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

8. 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!

9. 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

10. Large Scale Biosphere-Atmosphere Experiment over Amazônia
CLAIRE ‘98
Balbina, Amazonas
28 March - 15 April
EUSTACH ‘99
Rebio Jaru: forest
Nossa Senhora: pasture
Rondônia
7 April – 21 May
15 Sept. – 1 Nov.
Aircraft Experiment
2 – 14 September

11. Summary of CCN Spectra

12. Clear day
Visibility ~ ??? km
NCN ~ 500 cm-3
BC ~ 0.2 mg m-3
Smoke haze
Visibility ~ 800 m
NCN ~ cm-3
BC ~ 7 mg m-3

13. The “Green Ocean”: Maritime clouds over the Amazon
April - the wet and clean time of year: Note the shallow precipitating clouds, extensive
warm rainout, glaciation at T>-10oC, and few lightning events
VIRS T-Re
TRMM VIRS+PR, Amazon, :28

14. Clear day
Visibility ~ ??? km
NCN ~ 500 cm-3
BC ~ 0.2 mg m-3
Smoke haze
Visibility ~ 800 m
NCN ~ cm-3
BC ~ 7 mg m-3

15. The “Green Ocean” turns dry: Smoky clouds over the Amazon
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.
TOMS Aerosol Index
13 September 1998
VIRS+PR, Amazon, 1998
13 SEP 14:15
VIRS T-Re

16. When the “smoky clouds” become Cb, they spark lightning and high Z
VIRS T-Re
PR H-Z
VIRS+PR, Amazon, :16

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

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

20. SMOCC Objectives
1) Make field measurements of aerosol and supporting parameters in the Amazon Basin;
2) chemically characterize 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.

23. 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)

24. SMOCC Field Campaign: LBA-CLAIRE-2002
near Ji-Paraná, Rondonia: FNS pasture site
INPE Bandeirante
1 Sept. arrival, 7 Sept. fully operational
measurements as long as 30 Nov.
MPIC, MPI-BGC, USP, Bologna, Lund, Veszprem, Gent, ...