March 14, 2011 NIST Aerosol Metrology Workshop

Optical Properties: The Global 

Atmosphere Watch (GAW) 

Aerosol Lidar Observation 

Network (GALION): Issues 

Involved with Obtaining Precise 

Optical Extinction Profiles for 

Climate Records 

Raymond Hoff

Gelsomina Pappalardo

AEROSOL:

Light scattering coefficient

AEROSOL:

AOD
Early GAW conclusions

GAW was bound to the surface

Global climatologies are difficult without 

involving satellite measurements

Correspondence with satellite 

measurements require understanding of 

the column and require precision AOD

AOD measurements are difficult to 

understand without the aerosol profile
Objectives for GALION

Supports Task 7.84 of GAW IP

1. Detection of long-term man-made trends in the 

concentration of greenhouse gases and aerosols 

2. Better environmental assessments

3. Better quantification of pollution sources and 

their atmospheric pathways

4. Reliable global concentration fields

5. Better prediction of UV intensities

6. Direct observation of plumes from major events

7. Improved regional forecasts of both weather 

and air quality
GAW Aerosol Lidar Observation 

Network (GALION)

ftp://ftp.wmo.int/Documents/Publi

cWeb/arep/gaw/gaw178-galion27-Oct.pdf http://www.wmo.int/gaw/galion/

2010

Geneva
Distribution of stations

ALINE, Latin America 

AD-Net, East Asia 

CIS-LINET, Commonwealth of Independent States 

EARLINET, Europe 

NDACC, Global Stratosphere 

CLN, Eastern North America 

MPLNET, Global, Micropulse Lidar 

Conceptually GALION fits GEOSS 

since it is a Network of Networks 

and GAW is GEOSS
AEROSOL PROPERTIES
Measurements

MEASUREMENTS POSSIBLE
Elastic lidar (eg. MPLNET)

Backscatter crosssection (m-1 sr-1)

Extinction crosssection (m-1)

S (sr) Colocated

Sunphotometer
(Multi λ) Raman Lidar

All the required parameters can be measured with a N2 Raman lidar 

(with a small assumption for the 355-387 nm Angstrom coefficient
Figure courtesy Aerosols-Clouds-Ecosystems Mission (ACE)
High Spectral Resolution Lidar
State of the art 

in lidar aerosol metrology

3β+2α+2δ (to come HSRL)

From Ansmann and Müller in Weitkamp (2005)

355

⊥

N2

387

532

⊥

N2

607

1064
Aerosol microphysics
Climatologies

Mattis et al, 2008

Pappalardo et al, 2010

Free tropospheric layers over Europe
DUST: Earlinet Assessment of Possible Pathways of 

Saharan Dust Transport over Europe (see A. Pappayanis, 

L. Mona papers in GALION Workshop)

1: ~20 %

2: ~ 35 %

3: ~ 30 %

4: ~ 5 %

5: ~ 10 %

4

3

5 1 2 3

EARLINET-ASOS-GALION Meeting, Geneva, 20-23 September 2010
DREAM Model (May 2000-April 2005) – Potenza station

EARLINET-ASOS-GALION Meeting, Geneva, 20-23 September 2010

2 3 4 5 6 7 8 9

0

10

20

30

40

50

60

Counts

Layer Center of Mass a.s.l. [km]

 Lidar

 Dream CoMLidar = (4.5 ± 1.2) km

CoMDream = (4.4 ± 1.1) km

Center of Mass (CoM)

2

4

6

8

10

0.0 5.0x10-5 1.0x10-4 1.5x10-4

0 20 40 60 80

Aerosol Concentration [ μg m-3]

Aerosol Extinction Coefficient @ 355 nm 

[m-1]

Altitude a.s.l. [km]

Aerosol concentration-Aerosol extinction (355 nm)
AT LC TH PO NA BA LA SF JU NEGPMU PL LE BE AB HH MI KB LK

0

20

40

60

80

100

120

140

160

180

200

220

240

N

u

m

b

er of d

u

st d

a

y

s

EARLINET Station

Observed

Forecasted

Papayannis et al., J. Geophys. Res., 113, D10204, 

doi:10.1029/2007JD009028, 2008 

EARLINET-ASOS-GALION Meeting, Geneva, 20-23 September 2010

(%) of observed to forecasted 

number of days
ARM Raman Lidar (CARL)

Ferrare et al., 2005
Unanswered GALION questions

Exactly how precise are the extinction 

profiles?

Still struggling with error assessment

Can an extinction climatology be 

derived and made into a climate record?

Hasn’t happened for ARM yet

Hasn’t happened for all of EARLINET yet

How do we validate the retrieved 

microphysical values, nr

, ni, N(r)?
Issues that could involve NIST

New technology 

(sources/detectors/filters, especially 

1.55 μm eyesafe lasers and APDs, notch 

filters)

Sources and detector characterization

Calibration on polarimetry channels

Validation of the inverse methods in 

3β+2α+2δ

Calibration of nighttime τfor fixed 

magnitude STARS experiment
Acknowledgements

WMO GAW Science Advisory Group on 

Aerosols

Contributors to the GAW report

And for the 2nd Workshop Support:

 Hal Maring, Radiation Sciences Program, NASA HQ

 Lawrence Friedl, Applied Sciences Program, NASA HQ

 Judd Welton, NASA GSFC

 UMBC Goddard Earth Sciences and Technology Center

 IMAA-CNR

 Atmospheric Research and Environment Program (AREP) 

WMO