Aerosol Optical Depth Aerosol Optical Depth

measurements in the Azoresmeasurements in the Azores

Fernanda Carvalho1

Diamantino Henriques1

Paulo Fialho2

Vera Bettencourt1

1Instituto de Meteorologia2Universidade dos Açores

The José Agostinho Observatory, is located in Angra do Heroísmo town, is part of the regional station GAW network since 1992.

The very first global irradiance measurements in Portugal using conventional instruments and methods were done in this Observatory in 1937.

GAWGAW Global Atmosphere Watch

BSRNBSRN Baseline Station Radation Network

WMOWMO World Meteorological Organisation

In the scope of CLIMAAT project (Climate and Meteorology of Atlantic Islands), it was possible to fund and install an automatic system for solar and terrestrial radiation measurement.The results will provide a detailed characterization of atmospheric radiative properties.

Parameter Instrument Accuracy BSRN

Direct solar irradiance NIP Eppley 1% or 2 Wm-2

Diffuse radiation CM11 Kipp&Zonen 4% or 5 Wm-2

Global radiadion CM11 Kipp&Zonen 4% or 5 Wm-2

Longwave downwelling radiation flux

CG4 Kipp&Zonen 5% or 10 Wm-2

UV radiation Brewer Mark II 10%

Total ozone Brewer Mark II 1%

Aerosol optical depthMiddleton SP02BSRN

412, 500, 645, 862 nm

CG2 Kipp&Zonen

Sci-Tec 2AP

DTK 500

Parameter Precision Accuracy

Air temperature 0,1 ºC +/- 0,3 ºC

Dew point temperature 0,1 ºC +/- 0,5 ºC

Soil surface temperature 0,1 ºC +/- 0,3 ºC

Relative humidity 1% +/- 7%

Wind speed 0,5 ms-1 +/- 5% or 2 ms-1

Wind direction 5º +/- 10%

Total precipitation amount 0,2 mm Greather than +/- 0,2 mm or +/- 2% of total

Precipitation rate 0,2 mm h-1 Greather than +/- 0,2 mm h-1 or +/- 2%

Atmospheric pressure 0,1 hPa +/- 0,5 hPa

Visual direct observations

(cloudiness, present weather past weaher)

Ancillary meteorological information

Calibration, data processing and archive

• Sensor calibration - ISO 9846: 1993(E).

Under development:

• Application of QC/QA procedures;

• BSRN Station-to-Archive File Format.

BSRN Operations Manual, WMO/TD-No.879

Technical Plan for BSRN, WMO TD N.443

Aerosol Optical Depth (a,) computations

a, = -(1/m) ln( E / E0, ) - R, - O, - H2O

m =1./(cos(za*pi/180.)+0.15*(93.885-za)**(-1.253))mr=m*p/p0vdo=10000./cdo()

R, =mr*7.994*(vdo**4.)/(9.26799e18-1.07123e9*vdo**2.)

O, =ao3()*o3*mo3mo3=35.0/(1224.0*(cos(za*pi/180.)**2)+1.)**.5

H2O =0.3285*aH2O()*(w+(1.42-w)*.5)*m/(1.0+20.07*aH2O()*m)**0.45

Aerosol Optical Depth (a,) computations (Cont.)

Wavelength (nm) 412 500 675 862

Extraterrestrial const (E0) 3034 2477 2462 2565

O3 absorption coef. (aO3) 0.0000 0.0294 0.0391 0.0000

H2O absorption coef. (aH2O) 0.0000 0.0000 0.00037235 0.010629

•Precipitable water (w): 2.0 cm•Total ozone (o3): Brewer observed nearest value

Data acquisition and processing

Acquisition system: DTK500

Integration: 5 s (avg;std)

Filter: data with:•signal < night background (zero);•signal noise: std/ avg > 0.001•night readings (za >90)

should not be considered.•10 minute AOD averages computed only with n >= 30 readings

Results Results (August 2004-September 2005)Results Results (August 2004-September 2005)

AOD: 11-08-2004Angra do Heroísmo (SP02) and Horta (Cimel)

0

0.05

0.1

0.15

0.2

0.25

0.3

6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00

Time (UTC)

AO

D

340 nm (Cimel) 380 nm (Cimel)

412 nm (SP02) 440 nm (Cimel)

500 nm (SP02) 500 nm (Cimel)

675 nm (SP02) 670 nm (Cimel)

862 nm (SP02) 870 nm (Cimel)

1020 nm (Cimel)

Angra do Heroismo

Horta

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Jan-04 Fev-04 Mar-04 Abr-04 Mai-04 Jun-04 Jul-04 Ago-04 Set-04 Out-04 Nov-04 Dez-04

Data

AO

D

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Jan-05 Fev-05 Mar-05 Abr-05 Mai-05 Jun-05 Jul-05 Ago-05 Set-05 Out-05 Nov-05 Dez-05

Data

AO

D

Sun tracker failure

AOD @ 500 nmAngra do Heroismo

CimelSP02

AOD @500 nmAngra do Heroísmo: 7 Aug. 2004 - 17 Sep. 2005

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

5.00 7.00 9.00 11.00 13.00 15.00 17.00 19.00 21.00

Time (UTC)

AO

D

http://www.angra.uac.pt/paulo.fialho/investigacao/projectos/climaat-terceira-nare/

Observatório José Agostinho.htm

http://www.angra.uac.pt/paulo.fialho/investigacao/projectos/climaat-terceira-nare/

Observatório José Agostinho.htm

Acknowledments:

To WMO Secretariat for kindly funding this participation.To CLIMAAT project for funding part of the equipment.