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Title
Mesures physiques et signatures en télédétection

75
MULTI-BAND AUTOMATIC SUN AND SKY SCANNING RADIOMETER
SYSTEM FOR MEASUREMENT OF AEROSOLS
B.N. HOLBEN
Code923, NASA/Goddard Space Flight Center, Greenbelt, MD 20771
T.F. ECK
Huges STX Corporation, Code 923, NASA/GSFC, Greenbelt, MD 20771
I. SLUTSKER
Science Systems and Applications Inc., Code 923, NASA/GSFC, Greenbelt, MD
D. TANRÉ
Lab. d'Optique Atmosphérique, U.S.T. de Lille, 59655-Villeneuve d'Ascq,France
J.P. BUIS
CIMEL Electronique, 5 cité de Phalsbourg, Paris, France
A. SETZER
Instituto de Pesquisas Espaciáis, Sao José dos Campos, SP,Brazil
E. VERMOTE
Univ. of MD, Code 923, NASA/GSFC,College Parle, MD
J. A. REAGAN
Univ. of Arizona, Tucson, AZ
Y.A. KAUFMAN
Code 913, NASA/Goddard Space Flight Center, Greenbelt, MD 20771
ABSTRACT:
A weather resistant automatic scanning sun photometer system is assessed and demonstrated as practical for
measurements of aerosol concentrations and properties at remote sites. Interfaced with a transmitter using
the Geostationary Data Collection System, the data are processed in near real-time. The processing allows a
time dependence of the aerosols and water vapor and an ongoing assessment of the health and calibration of
the instruments. The systems automatic data acquisition, transmission and processing offer immediate
application to atmospheric monitoring and modeling on a regional to global scale and validation of Satellite
retrievals. We estimate that under normal circumstances the retrieved aerosol optical thickness has a
network wide accuracy of ±0.02 from 340 nm to 1020 nm, water vapor ±0.2 cm and size distribution from
0.1 to 3. |i.m.
KEY WORDS: Sun Photometry, Aerosols, Optical Thickness, Radiometer
1 - INTRODUCTION
Ground based atmospheric aerosol measurements using sun photometry has changed little since
Voltz (1959) introduced the first handheld more than three decades ago. Modem units can collect data more
accurately and quickly but the method remains largely the same, that is a filtered detector measures the
extinction of direct beam radiation according to Beers Law:
V = V 0 exp-(Tm) (1)
where: V=Digital voltage
Vo=extratrestrial voltage
m=optical airmass
T=total optical thickness
Other strategies have been developed and are commercially available. The shadow band radiometer
measures spectral total and diffuse radiation to obtain the direct component from which aerosol optical
thickness is computed. The instrument has been shown to be reliable over long periods of time and is