Determination of aerosol components from multiwavelength/depolarization

measurements

Nobuo SUGIMOTO,Tomoaki Nishizawa, and Atsushi Shimizu

National Institute for Environmental Studiesnsugimot@nies.go.jp

GALION WS, 20-23 Sep 2010, Geneva

Lidar

Chemical Transport Model

signal intensity (depolarization)

Which parameter shall we compare with models?

dust extinction coefficient

extinction coefficient

dust density

S1

assumption on external mixing

mass/extinctionconversion factor

distribution and characteristics of other aerosols

optical characteristics of dust

Method for estimating contributions of dust and air pollution

€

R=δ2'+δa(1−δ2')(δ2'−δ1')(δa+1)=(δa−δ2)(1+δ1)(1+δa)(δ1−δ2)

The mixing ratio of dust, R, can be estimated from the observed aerosol depolarization ratio, a.

where 1 and 2 are depolarization ratio of dust and other aerosols. We used 1~0.35 and 2~0.05 empirically determined from the histogram of observed aerosol depolarization ratio.

[Sugimote et al. 2003; Shimizu et al. 2004]

Dust

Spherical aerosols

March 21-31, 2004 Beijing

Method for estimating the extinction coefficients of dust and spherical aerosols using the depolarization ratio

Dust

Air pollution

Lidar dust and spherical extinction coefficients & OPC

0.3-1 m1-22-33-44-5> 5

OPC data

Volume concentrationSize

http://sprintars.riam.kyushu-u.ac.jp/indexe.html

BC, OM, sulfate, sea salt, soil dust

Development of data analysis methods

1β+1δ method to estimate dust and spherical aerosols (Sugimoto et al., 2003; Shimizu et al., 2004)

2β+1δ(switch) method to estimate dust (or sea-salt) and water soluble* (Nishizawa et al., 2007)

2β+1δ method (using spheroid model) to estimate dust, sea-salt and water soluble (Nishizawa et al.)

1α+2β+1δ(switch) method to estimate (dust or sea-salt), water soluble and black carbon (Nishizawa et al., 2008)

1α+2β+1δ to estimate dust, water soluble, black carbon or sea-salt (for EarthCARE ATLID, Nishizawa et al.)

2α+3β+2δ method to estimate dust, sea-salt, water soluble, black carbon and particle size of water soluble (being developed)

*Water-soluble aerosol: a mixture of sulfate, nitrate, and organic carbon

The algorithm consider external mixing of aerosol components and prescribe the optical properties for each component

NIES aerosol classification algorithms using 2+1 Mie lidar

532,||

532,

Spherical

DS

Spherical + DustSugimoto et al. [2003]

1 + 1

532

1064

SSWS

DS

2

Water-soluble + Dust (>0.1)or

Water-soluble + Sea-salt (<0.1)Nishizawa et al. [2007]

WS: water-soluble particlesSS: Sea-saltDS: Dust

532,||

1064

532,

SSWS

DS

Water-soluble + Dust + Sea-salt

WS: water-soluble particlesSS: Sea-saltDS: Dust

WS SS DS

rm 0.13 3.0 2.0

S 55 20 48

0 0 0.3

Assumptions・ Log-normal size distribution・ Mode radius, standard deviation, refractive indexes are prescribed・ Spheroid particles for dust

2+1 algorithm

Spheroid model

Axis Ratio = a/b

ab

Lidar ratio

[Mishchenko et al. 1997]

Depolarization ratio

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λ = Cλ (r,ε,m)dV (r)

d ln r

dn(ε)

d lnεr

∫ d ln rd lnεε

∫

[Dubovik et al. 2006]

1 + 2 algorithm

532

532

1064

BC

WS

DS

Water-soluble + Dust + BC

1(532) + 2(532,1064)

rm

[um]

m (532nm) S (532nm)

[sr]

WS 0.18 1.44 3×10-3i 58

DS 3.0 1.53 6×10-3i 50

BC 0.05 1.75 0.4i 101

Assumptions・ Log-normal size distribution・ Mode radius, standard deviation, refractive indexes are prescribed

Set S=50sr to consider the non-sphericity of dust

Comparison with Skyradiometer

2

Water-soluble

Dust

Sea-salt

Total

AOT (532) Angstrom

60% overestimation

Water-soluble

Dust

Sea-salt

Total

AOT (532) Angstrom

Agreement within 5%

2+1

Algorithm for ATLID

*Water-soluble aerosol: a mixture of sulfate, nitrate, and organic carbon

The algorithm consider external mixing of aerosol componentsand prescribe the optical properties for each component

1+1+ 1 algorithm: Absorption + Depolarization Water-soluble* + Dust + Black carbon Water-soluble* + Dust + Sea-salt

Depolarization / absorption

properties

NIES 1 + 1 + 1 algorithm

Over Land

355

355,||

355,

BCWS

DS

Water-soluble + Dust + Black carbon

Over Sea

355

355,||

355,

SS

WS

DS

Water-soluble + Dust + Sea-salt

S < Sth

S > Sth

1+2 algorithmWater-soluble

Dust

Soot

Demonstration of 1 + 1 + 1 algorithm

Water-soluble

Dust

Soot

1+1+1 algorithm

• 1(532)+2(532,1064)+1(532) data measured with HSRL and MSL on Apr. 8 2005

were used in the analysis. • The aerosol properties at 532 nm used in 2+1 algorithm were used in the analysis using 1+1+1 algorithm