NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The Measurement of Aerosol Optical Properties Using Continuous Wave Cavity Ring-Down TechniquesLarge uncertainties in the effects that aerosols have on climate require improved in-situ measurements of extinction coefficient and single-scattering albedo. This abstract describes the use of continuous wave cavity ring-down (CW-CRD) technology to address this problem. The innovations in this instrument are the use of CW-CRD to measure aerosol extinction coefficient, the simultaneous measurement of scattering coefficient, and small size suitable for a wide range of aircraft applications. Our prototype instrument measures extinction and scattering coefficient at 690 nm and extinction coefficient at 1550 nm. The instrument itself is small (60 x 48 x 15 cm) and relatively insensitive to vibrations. The prototype instrument has been tested in our lab and used in the field. While improvements in performance are needed, the prototype has been shown to make accurate and sensitive measurements of extinction and scattering coefficients. Combining these two parameters, one can obtain the single-scattering albedo and absorption coefficient, both important aerosol properties. The use of two wavelengths also allows us to obtain a quantitative idea of the size of the aerosol through the Angstrom exponent. Minimum sensitivity of the prototype instrument is 1.5 x 10(exp -6)/m (1.5/Mm). Validation of the measurement of extinction coefficient has been accomplished by comparing the measurement of calibration spheres with Mie calculations. This instrument and its successors have potential to help reduce uncertainty currently associated with aerosol optical properties and their spatial and temporal variation. Possible applications include studies of visibility, climate forcing by aerosol, and the validation of aerosol retrieval schemes from satellite data.
Document ID
20020094297
Document Type
Conference Paper
Authors
Strawa, A. W. (NASA Ames Research Center Moffett Field, CA United States)
Owano, T. (NASA Ames Research Center Moffett Field, CA United States)
Castaneda, R. (NASA Ames Research Center Moffett Field, CA United States)
Baer, D. S. (NASA Ames Research Center Moffett Field, CA United States)
Paldus, B. A. (NASA Ames Research Center Moffett Field, CA United States)
Gore, Warren J.
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Environment Pollution
Meeting Information
American Association and Aerosol Research Conference (AAAR)(Charlotte, NC)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.