Cloud Condensation Nuclei Concentrations in the

Amazon Basin

G P Frank, G Roberts, E Swietlicki, P Artaxo,

L Rizzo, P Guyon, O L Mayol-Bracero, A Vestin, J Rissler, J Zhou, M O Andreae

CCN measurements(ground-based)

Project Dates SeasonCLAIRE-98 March-

April 1998Wet

EUSTACH-99-1

April-May 1999

Transition wet-dry

EUSTACH-99-2

September-October 1999

Transition dry-wet

CLAIRE-2001

July 2001 Dry

CLAIRE/ SMOCC-2002

September-November 2002

Transition dry-wet

CCN measurements(aircraft)

Project Dates SeasonCLAIRE-2001

July 2001 Dry

CLAIRE/ SMOCC-2002

September-October 2002

Transition dry-wet

Ground site at Fazenda Nossa Senhora (FNS), Rondônia

SMOCC Aircraft

Experiment/Season/Period

(ground-based)

Total aerosol particle concentration (CN)

(part/cm3)CLAIRE-98

Wet season 450

CLAIRE-2001

Dry season, clean period 640

CLAIRE-2001

Dry season, influence from fresh biomass burning

1300

SMOCC

Transition dry-wet, semi-clean period 2000

SMOCC

Transition dry-wet, transition period 5500

SMOCC

Biomass burning period 11000

Experiment/Period

(aircraft)

Total aerosol particle concentration (CN)

(part/cm3)SMOCC

Biomass burning period

Regional haze (altitude ~500-1500 m)3600

SMOCC

Biomass burning period

Cloud-processed smoke (altitude ~2000-4500 m)1300

CCN concentrationsBalbina (near Manaus)

Supersaturation, %

0.0 0.5 1.0 1.5 2.0 2.5

CC

N c

onc

ent

ratio

n,

#/c

m3

0

200

400

600

800

1000

1200

1400

1600

CLAIRE-2001 BackgroundCLAIRE-2001 Fresh biomass burningCLAIRE-98 Background

Error bars are ± 1 of the averages

CCN concentrationsSMOCC (ground-based, FNS)

Supersaturation, %

0.0 0.2 0.4 0.6 0.8 1.0 1.2

CC

N c

once

ntr

atio

n,

#/c

m3

0

5000

10000

15000

20000

25000

Biomass burning period (estimated)Transition periodSemi-clean period (November)

Error bars are ± 1 of the averages

From Reid et al. 1998, JGR, 103, D24, 32059 (SCAR-B)

1-2 km

Schematic

CCN concentrationsSMOCC aircraft (biomass burning period)

Supersaturation, %

0.0 0.2 0.4 0.6 0.8 1.0 1.2

CC

N c

onc

ent

ratio

n,

#/c

m3

0

500

1000

1500

2000

2500

Cloud-processed smoke (2000-4500 m)Regional haze (500-1500 m)

Error bars are ± 1 of the averages

Size distribution of the SMOCC smoke aerosols

20 30 40 50 60 70 80 90100 200 300

0.0

5.0x104

1.0x105

1.5x105

2.0x105

2.5x105

SMOCC 0901 Oct 2002

dN/d

logD

p (#

/cm

3 /nm

)

Particle diameter Dp (nm)

Fresh smoke Detrained smoke

CCN efficiencies as CCN/CN ratios

Supersaturation, %

0.0 0.2 0.4 0.6 0.8 1.0 1.2

CC

N/C

N r

atio

0.0

0.2

0.4

0.6

0.8

1.0

SMOCC biomass burning period. Cloud-processed smoke (altitude ~2000-4500 m)SMOCC biomass burning period. Regional haze (altitude ~500-1500 m)CLAIRE-98, backgroundSMOCC, FNS, Transition periodSMOCC, FNS, Semi-clean

Aerosol particle size distributions (CN)

Particle diameter, nm

1 10 100 1000

dN

/dlo

gDp

, #

/cm

3

0

2000

4000

6000

8000

10000

12000

14000

16000

SMOCC biomass burning period. Cloud-processed smoke (altitude ~2000-4500 m)SMOCC biomass burning period. Regional haze (altitude ~500-1500 m)CLAIRE-98, backgroundSMOCC, FNS, Transition periodSMOCC, FNS, Semi-clean SMOCC, FNS, Biomass burning period

Conclusions

CCN efficiencies of the aerosols can partly be explained by the size and partly by

the chemical composition

1. The background aerosol (CLAIRE-98) are efficient CCN, although they are small (the number of particles below 100 nm in diameter are relatively high). The higher efficiency can be explained by the fact that they are more hygroscopic (Zhou et al., 2002).

2. The smoke aerosol at the ground during the biomass burning and transition periods are efficient CCN. These particles have a peak in the size distribution above 100 nm, and a relatively low fraction of smaller particles. The particles are not very hygroscopic, but anyway efficient due to their large size.

3. The aerosol particles in the regional haze have a lower CCN efficiencyThe size is nearly the same as for the particles at ground during the biomass burning period, although the concentration of particles below 100 nm are slightly higher relative to the larger particles. Possible explanations of the low efficiency:

– Gas-to-particle conversion can change the hygroscopic properties. The gas-to-particle conversion might not be so important at the ground, but more in the regional haze.

– The number of nucleation mode particles might be relatively higher (not measured).

4. The cloud-processed smoke particles are effective CCNThis smoke consists mainly of large particles (relatively few particles below 100 nm). The cloud-processing might also change the chemical composition.

5. The aerosol at the ground during the semi-clean period are less efficient CCN

This aerosol contains most likely of a mix between some biomass burning smoke, natural aerosol and local pollution, such as traffic, industry (e.g. char-coal factories) and energy production. Most particles are below 100 nm in diameter and not very hygroscopic, which can explain the low efficiency. They also probably contain residual particles after washout, which are poor CCN.