AERONET Processing AERONET Processing Algorithms RefinementAlgorithms Refinement

AERONET WorkshopAERONET Workshop May 10 - 14, 2004, El Arenosillo, SpainMay 10 - 14, 2004, El Arenosillo, Spain

AERONET Data FlowsAERONET Data Flowshttp://aeronet.gsfc.nasa.govhttp://aeronet.gsfc.nasa.gov

Flux measurementsFlux measurementsDirect - Direct - =340, 380, 440, 500, 670, 870, 940, 1020 nm=340, 380, 440, 500, 670, 870, 940, 1020 nmDiffuse - Diffuse - =440, 670, 870, 1020 nm (alm, pp, pol)=440, 670, 870, 1020 nm (alm, pp, pol)

Calibration and processing informationCalibration and processing information

Aerosol optical depth and Aerosol optical depth and precipitable water computationsprecipitable water computations

Holben et al.RSE, 1998

Holben et al.JGR, 2001

Holben et al.RSE, 1998

Holben et al.JGR, 2001

Smirnov et al.RSE, 2000

Smirnov et al.RSE, 2000

Dubovik and KingJGR, 2000

Dubovik et al.JGR, 2000

Dubovik and KingJGR, 2000

Dubovik et al.JGR, 2000

Cloud screening and quality controlCloud screening and quality control

Eck et al.JGR, 1999

Eck et al.JGR, 1999

Inversion productsInversion products

Volume size distribution (0.05<R<15 mm),Volume size distribution (0.05<R<15 mm),refractive index, single scattering albedorefractive index, single scattering albedo(l=440, 670, 870, 1020 nm)(l=440, 670, 870, 1020 nm)

AERONET Data Flows

Current andCurrent and futurefuture additionsadditions

Flux measurementsSun - =340, 380, 440, 500, 670, 870, 940, 1020 nm +1640 nm (412, 532, 555 nm)+1640 nm (412, 532, 555 nm)Sky - =440, 670, 870, 1020 nm ++ 500, 1640 nm500, 1640 nm + ? 340, 380 nm? 340, 380 nm

Calibration and processing information HH22O, COO, CO22, CH, CH44

Aerosol optical depth and precipitable water computations (1020, 1640, 940 nm) + extra (1020, 1640, 940 nm) + extra aa(1020 nm)(1020 nm)

Cloud screening and quality control

Inversion productsAlmucantar retrievals - spherical and spheroid models (4 wavelengths), level 2Almucantar retrievals - 6 wavelengths6 wavelengths + + ? 340, 380 nm? 340, 380 nmPrincipal plane retrievals -Principal plane retrievals - 4 wavelengths, level 2;4 wavelengths, level 2; ? 6 wavelengths ? 6 wavelengths? Combined retrievals (almucantar and principal plane)? Combined retrievals (almucantar and principal plane)

Current Processing AlgorithmCurrent Processing Algorithm Extraterrestrial Solar Flux - Neckel and Labs

1981; and Frohlich and Wehrli 1981 Rayleigh optical depth - Edlen 1966 Ozone amount - LUT (5ºx 5º Lat Long) -

London et al. 1976 Water vapor content - Bruegge et al. 1992;

Reagan et al. 1992 Water vapor correction for AOD (1020 nm) -

none CO2, CH4, WV for AOD (1640 nm) - N/A

Processing Algorithm RefinementProcessing Algorithm Refinement Extraterrestrial Solar Flux - Woods et al. 1996 Rayleigh optical depth - Bodhaine et al. 1999 Ozone amount - LUT (1ºx 1º Lat Long) -

TOMS data 1979-2002 Water vapor content - Michalsky et al. 1995;

Schmid et al. 1996 Water vapor correction for AOD (1020 nm) -

LBLRTM CO2, CH4, WV for AOD (1640 nm) - LBLRTM

Extraterrestrial Solar Flux

www.astm.org

600

800

1000

1200

1400

1600

0.365 0.375 0.385 0.395

US Standard (E-490)EU Standard (Wehrli 1985)Gueymard 2003Thekaekara & Drummond 1973ATLAS 3

Irradiance, W/m

2 /μm

, wavelength μm

Courtesy Dr. Jay Herman,

code 916, NASA/GSFC

-0.001

0.000

0.001

0.002

0.003

0.004

0.005

75o

60o

45o

40o

23o

10o

0o

340 nm380 nm440 nm500 nm675 nm

R( ) -new

τR

(current)

Latitude, deg

Rayleigh Optical DepthRayleigh Optical Depth

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007 340 nm380 nm440 nm500 nm675 nm

75o

60o

45o

40o

23o

10o 0

o

Latitude, deg

R( ) -new

τR

(current)

Rayleigh Optical DepthRayleigh Optical Depth

Tw = exp(-A(mu)B)

Ln V() + m[a()+r()]=

= Ln [V0()d-2] - A(mu)B

V() = V0()d-2 exp{-m[a()+r()]}Tw()

Tw() = ∫ E0()S()exp[-mw()] d

/ E0()S()d

Parameters A and B for various filter batches

0.55

0.60

0.65

0.70

0.75

0.80

0 50 100 150 200 250 300

B(2001)B(1997-1)B(1997-2)B(1998-1)B(1998-2)

filter number

B=0.574

0.55

0.60

0.65

0.70

0.75

0.80

0 50 100 150 200 250 300

A(2001)A(1997-1)A(1997-2)A(1998-1)A(1998-2)

filter number

A=0.6548

Optical Depth Correction at 1020 nmOptical Depth Correction at 1020 nm

0.000

0.005

0.010

0.015

0.020

0 2 4 6 8

Abs OD (1020 nm)

water vapor content (cm)

abs

(1020 )= 0.0023* +0.0002nm wvc

2% 5%=475 n filters

Optical Depth Correction at 1640 nmOptical Depth Correction at 1640 nm

0.000

0.005

0.010

0.015

0.020

0 2 4 6 8

Water vapor Abs OD (1640 nm)

water vapor content (cm)

abs

(1640 )= 0.0014* -0.0003nm wvc

=50 n filters 5% 2%

abs

(CO2)=0.0036

abs

(CH4)=0.0089

4.5%

AERONET Precipitable Water ComparisonAERONET Precipitable Water Comparison

0

1

2

3

4

5

6

0 1 2 3 4 5 6

water vapor content (new), cm

water vapor content (current), cm

wvc(new)=0.85wvc(current)-0.05, R=0.99

AERONET-GPS Precipitable Water ComparisonAERONET-GPS Precipitable Water Comparison

0

1

2

3

4

5

0 1 2 3 4 5

water vapor content (new), cm

water vapor content (GPS), cm

wvc(new)=0.92wvc(GPS)+0.15, R=0.99

AERONET-GPS Precipitable Water ComparisonAERONET-GPS Precipitable Water Comparison

0

1

2

3

4

5

6

0 1 2 3 4 5 6

water vapor content (GPS), cm

water vapor content (current), cm

wvc(current)=1.09wvc(GPS)+0.11, R=0.99

What to do next

Recalibrate Master instruments (water vapor channel only)

Recalculate calibration constants (water vapor channel only) for all instruments in the network

Update database on water vapor content Quality assure PW (WVC) database Compare QC/QA PW with GPS and MWR

retrievals