second sop0 workshop, exeter 15 may 2007 special issue amma sop0 lisa contribution 1) rajot et al.,...

Second SOP0 workshop, Exeter 15 May 2007

Special issue AMMA SOP0 LISA contribution

1) Rajot et al., General overview of Banizoumbou results

2) Formenti et al., Physico-chemical characteristics of aerosols over Western Africa (I): results from the AMMA dry season campaign

3) Alfaro et al., Spectral optical properties of mineral dust and biomass burning and their mixing

P. Formenti


1) What are the physico-chemical and optical properties of mineral dust in the Sahel ? (source regions)

2) How to predict dust optical properties knowing their physico-chemical properties ?

3) How to account for mixing with other aerosol species ?

4) How do mineral dust aerosols modify the solar and terrestrial radiation budgets at the local and the regional scales ?

Scientific questions within SOP0


SOP0 operation Timing

11/01 21/0114/01 27/01 16/0212/02

DJOUGOU

BANIZOUMBOU

M’BOUR

03/02

DABEX DODO

24/01 01/0213/01

ULM


Long term (2005-2008) + intensive observations (Jan-Fev et Jun-Jul 2006)

Banizoumbou


Sampling inlets

Laboratory "Belgique"

Banizoumbou ground-based station


Ground-based measurements at Banizoumbou (1 / 2)

On-line measurements (sampling interval)– Number and mass concentration, GRIMM OPC and TEOM (5-min)– Number size distribution, GRIMM OPC (5-min)– Spectral absorption coefficient, Magee Aethalometer (5-min)– Spectral scattering coefficient, TSI nephelometer (5-min)– Global, diffuse & direct radiation, MFRSR-7 shadowband radiometer (1-min)– Global and spectral downwelling radiation, ARM ancillary – Aerosol vertical profile, lidars (B. Heese and F. Cairo)– Ozone concentration (5-min)– Meteorology


Filter sampling and analysis

Aerosol sampling (sampling interval/frequency)Bulk

– Elemental Chemical composition (12-h + events, total + PM10)– Water soluble fraction (12-h + events)– Carbon content (24-h) – Mineralogy (12-h + events)– Single-particle composition and morphology (12-h + events)

Size-segregated– Chemical composition on 4- and 13-stage impactors (24-h) s


Sampling strategy: schematics

Lidars

TEOM

GRIMM GRIMMNEPHELOMETRE

TSI

AETHALOMETREMagee

Sampling inlets (physico-chemical and optical

measurements) ARM ancillary

Shadow-band


Ground-based, Banizoumbou

To the in

struments

To the buried instrumented

container

Air in


Filter collection onboard the UK BAe146

Air in Air in

Air out Air out

Quartz0.4-µm Nuclepore

90-mm SFU1:Inorganics

47-mm SFU2:Organic andElemental carbon

• Elemental Chemical composition (all)• Water soluble fraction (depends on concentration)• Mineralogy (depends on concentration)• Single-particle composition and morphology (selected events)


Collected samples

• About 500 bulk samples collected at the ground-based station• Dust and aged BB

• About 120 samples collected on the aircraft• SLR from ~ 170 feet to FL120• Various aerosol types (dust, fresh BB, aged BB, background, their mixing)


Status of analysis

ElementalWater-soluble fraction

MineralogyIron content speciation

Individual particle analysis

OC/BC

Bulk

Ground-based

Done July Done June July Done

Aircraft Done June July JuneJune (dust)

BB (TBD)Done

Size-segregated

Ground-based

June ---- ----- ------ ------ N/A


1

10

100

1000

13 Jan 18 Jan 23 Jan 28 Jan 02 Feb 07 Feb 12 Feb

Date

Un

co

rre

cte

d s

ca

tte

rin

g c

oe

ff,

Mm

-1

Dust aerosols are found at to the surface

BB

1

10

100

1000


Date

Un

co

rre

cte

d s

ca

tte

rin

g c

oe

ff,

Mm

-1

0

0.5

1

1.5

2

2.5

Co

lum

n A

OD


Episodes of dust and biomass burning

0.E+00

1.E+08

2.E+08

3.E+08

4.E+08


Nu

mb

er

(#/m

3 )

0

500

1000

Mass

(µg

/m3)

DustBB Banizoumbou, Jan 2006


Mineral dust from different source regions

0

0.2

0.4

0.6

0.8

1

1.2


Date

Ca/

Fe

rati

o

1

10

100

1000

Un

corrected

scatterin

g

coeffic

ient, M

m-1


Bulk composition of dust from ground-based and aircraft samples (DABEX) : Si vs Al

Si vs Al


Bulk composition of dust from ground-based and aircraft samples (DABEX) : Fe vs Al

Ongoing analysis to quantify the proportion of iron oxydes


Individual particle analysis of dust samples (B160, B161, B165)

Supermicronic composition flight B161 N3

Si, Al, Fe (Si/Al >2)53%Si, Al, Fe (Si/Al <2)

27%

Quartz13%

Salt particles3%

Carbonate (Ca)4%

Submicronic composition flight B161 N3

Si, Al, Fe (Si/Al <2)22%

Carbonate (Ca)8%

Quartz6%

Iron Oxyde4%Salt particles

16%

Si, Al, Fe (Si/Al >2)44%

Iron oxyde

• Iron oxydes observed in the fine fraction (4-5% by number), results of the mass analysis are still missing• "Uncontaminated" dust, soot particles less than 1% by number, although trajectories show that airmasses where dust plumes were sampled might have come in contact with pollution


Dust from Mauritania is enriched in minerals such as halite (Na-rich)

Confirmed by microscopy analysis

0

1

10

100

1000

Al Na Mg Si S K Ca Ti Fe

DABEXDODODODO (including dust storm B238)


Measuring the attenuation of the Al signal gives indication on particle size

0

1

2

3

4

5

6

0 1 2 3 4 5 6

Al PIGE (µg/cm2)

Al P

IXE

(µ

g/c

m2)

PIXE/PIGE = 0.83 ± 0.02

20% attenuation corresponds to aerodynamic VMD of ~ 2 µm (geometric 1.2 µm)

B238N3


The Ca-to-Fe elemental ratio as a marker of major source region

(DODO)

Niger (DABEX)

Local erosion


Mineralogy from ground-based samples S

OP

-0-4

SO

P-0

-5

SO

P-0

10

SO

P-0

-14

SO

P-0

-17

SO

P-0

20

SO

P-0

21

SO

P-0

23

SO

P-0

27

SO

P-0

29

SO

P-0

31

SO

P-0

-36

SO

P-0

-38

SO

P-0

-39

SO

P-0

-46

SO

P-0

-47

SO

P-0

-48

SO

P-0

-49

SO

P-0

-50

Gypse

Dolomite

Calcite

Feldspath

Plagio

Quartz

Kaolinite

Illite

smectite

BB

Clays

Quartz

Ca-rich


Mineral dust ubiquitous even in elevated BB layer

0.1

1

10

100

1000

2 6 10 14 18

X-ray energy (keV)C

ou

nts

/C

B158N6Fe

Zn

Br

Ti

0

50

100

150

200

250

300

0 1 2 3 4 5

X-ray energy (keV)

Co

un

ts/

C

B158N6

Al

Si

S

CaK


Tracers of biomass burning

Dust samplesy = 0.18x + 0.49

R2 = 0.99

Fresh BB samplesy = 0.16x + 2.41

R2 = 0.97

Old BB samplesy = 0.52x - 0.14

R2 = 0.89

0

5

10

15

20

0 20 40 60 80 100 120

Al concentrations, µg m-3 STP

K c

on

ce

ntr

ati

on

s, µ

g m

-3 S

TP

Banizoumbou

K vs Al

BB episode in Banizoumbou


Individual particle analysis of biomass burning samples

B158N4

• Coarse fraction dominated by mineral dust• Fine and coarse fraction are externally mixed


Conclusions

• Analysis still ongoing– won't be ready to submit in July– delaying some of your work (water-soluble fraction)

• Analysis is focusing on mineral dust– Biomass burning


Tracers of biomass burning

Old BB samplesy = 0.5x - 0.3

R2 = 0.58

Fresh BB samplesy = 2.5x - 6.5

R2 = 0.83

Dust samplesy = 4.9x - 5.4

R2 = 0.76

0

5

10

15

20

0 5 10 15

BC concentrations, µg m-3 STP

K c

on

ce

ntr

ati

on

s, µ

g m

-3 S

TP

SAFARI2000, aged smoke

K+/BC = 0.54


Aerosol optical properties in Niger during the dry season

Alfaro et al.

Objectives: Document and explain the temporal variability of the spectral dependence of scattering and absorption measured at ground

level in Banizoumbou.


DATA AVAILABLE from 13 Jan. to 12 Feb.

Optical propertiesat ground level

nephelometer TSI (3)aethalometer (Magee scientific, 7)

vertically averagedsunphotometer (AERONET)

Particulate concentrationsBulk mass concentration (TEOM microbalance)BC estimates derived from the aethalometerSize-resolved number(Grimm optical counter)


METHODOLOGY

Caracterization of spectral dependence

neph = C- abs = C-

and are the Angström’s exponents for scattering and absorption. They

are derived directly from nephelometer and aethalometer measurements.

In the case of the aethalometer, difference can be made between the values of

at short (sw) and long ( lw) solar wavelengths.


All data is used with particular emphasis on 3 case studies

-1

-0.5

0

0.5

1

1.5

1/13/06 0:00 1/18/06 0:00 1/23/06 0:00 1/28/06 0:00 2/2/06 0:00 2/7/06 0:00 2/12/06 0:00 2/17/06 0:00

0

0.5

1

1.5

2

2.5

3

3.5

4

Angstrom Cimel 440-675Angstrom

Angstrom neph 450-700 nm

AOT_440

Jan. 15 Feb.9Jan. 18


Examples of results

Dependence of to the BC mass fraction

-1

-0.5

0

0.5

1

1.5

0.10 1.00 10.00

%BC

An

gstr

öm

exp

on

en

t (s

catt

eri

ng

)


Absorption spectral dependence in the two wavelength ranges

lw is particularly stable whereas sw is much more variable and seems to be extremely sensitive to the presence of mineral dust

0

1

2

3

4

5

1/13 1/15 1/17 1/19 1/21 1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14

An

gstr

öm

exp

on

en

ts f

or

ab

so

rpti

on

SW/LW beta_LW


Sensitivity of sw/lw to the composition of the aerosol mixture

0

0.5

1

1.5

2

2.5

3

3.5

4

0.1 1.0 10.0

%BC

be

taS

W/b

eta

LW

sw/lw is - much larger when the proportion of dust increases- lower during BB advection than during local “pollution” events


Still to be done:

Assess the exact impact of aerosol size and composition (content in iron oxides) on the magnitude of sw


Radiative impact over source regions

Radiatif transfert

Emission model

Radiative impact over transport regions

Physico-mineralogicalcharacterization

Soil

Optical properties

Physico-chemical characterization

Optical model

Mineral dust aerosols Mineral dust aerosols (mixing)Transport

Aerosol

The mineral dust cycle


The Ca-to-Fe elemental ratio as a marker of major source region

Niger (DABEX)


LISA contribution to field observations

Dry season (Jan-Feb 2006, 6 weeks)Ground-based measurements in Banizoumbou + UK BAe146 operated in Niger and Senegal

Wet season (Jun-Jul 2006, 6 weeks)Ground-based measurements in Banizoumbou + F-ATR-42 operated in Niger and Benin

Wet season (Sep 2006, 2 weeks)UK BAe146 operated in Senegal


Aerosol inlets, orientable to the main wind direction

Banizoumbou, dry season


Air masses where dust plumes where found

B160N3 B165N7

Courtesy: M. Harrison


FL120 FL100 3200 feet3200 feet

FL100

FL120

B161 – 23 Janvier, nord of Niger


y = 0.47x + 13.5R2 = 0.71

0

20

40

60

80

100

120

0 50 100 150 200 250 300 350

OC, µg C

BC

, µg

C BB episoderatio BC/OC 0.24


y = 0.81x - 3.8R2 = 0.99

0

5

10

15

20

25

30

0 10 20 30 40

OC, µg m-3

BC

, µg

m-3

Flight B166, "fresh smoke"


0

2

4

6

8

10

12

14

0.1 1 10 100

Concentration, µg m-3

Alt

itu

de,

kft

AlOC


Air in

Air out

90-mm SFU1

PIXE PIGE

0.4 µm Nuclepore

Bulk elemental composition (Na…Pb)

IC/ICP CBDDRSEM

TEM

DRX

Water soluble fractionIron oxyde content and speciation

Bulk mineralogy

Individual particle characteristics

Analysis of inorganic fraction


Organic and elemental carbonAir in

Air out

47-mm SFU2

DRI

Quartz

BC/OC


This presentation

• Our scientific objectives for SOP0

• Our contribution to field observations within SOP0

• Status of data analysis: issues

• Some results relevant to publications in the SOP0 special issue


Rajot et al., General overview of Banizoumbou results

Aim of the paper1) Description of the sampling station2) Description of the temporal variability of the aerosol content and type as observed in Banizoumbou in Janvier-Fevrier 2006

DataTime series of 1) Number concentration2) Mass concentration3) Spectral scattering coefficient 4) Aerosol optical depth5) Basic meteorology


Formenti et al., Physico-chemical characteristics of aerosols over Western Africa (I): results from the AMMA dry season campaign

Aim of the paperDescribing the elemental and mineralogical composition and size distribution of mineral dust and biomass burning aerosols and their mixing

DataGround-based and airborne1) Filter samples2) OPC size distribution


Bulk composition of dust from ground-based and aircraft samples (DABEX) : Ca

vs Al

second sop0 workshop, exeter 15 may 2007 special issue amma sop0 lisa contribution 1) rajot et al.,...

Documents

dust optical properties

uncontaminated dust

surfacebbepisodes of

mineral dust aerosols

groundbased station

physicochemical properties

h mineralogy

aircraft samples dabex