Nonlinear-approximation technique for determining vertical ozone-concentration profiles with a differential-absorption lidar
- National Exposure Research Laboratory, U.S. Environmental Protection Agency, P.O. Box 93478, Las Vegas, Nevada 89193 (United States)
A new technique is presented for the retrieval of ozone-concentration profiles (O{sub 3}) from backscattered signals obtained by a multiwavelength differential-absorption lidar (DIAL). The technique makes it possible to reduce erroneous local fluctuations induced in the ozone-concentration profiles by signal noise and other phenomena such as aerosol inhomogeneity. Before the O{sub 3} profiles are derived, the dominant measurement errors are estimated and uncertainty boundaries for the measured profiles are established. The off- to on-line signal ratio is transformed into an intermediate function, and analytical approximations of the function are then determined. The separation of low- and high-frequency constituents of the measured ozone profile is made by the application of different approximation fits to appropriate intermediate functions. The low-frequency constituents are approximated with a low-order polynomial fit, whereas the high-frequency constituents are approximated with a trigonometric fit. The latter fit makes it possible to correct the measured O{sub 3} profiles in zones of large ozone-concentration gradients where the low-order polynomial fit is found to be insufficient. Application of this technique to experimental data obtained in the lower troposphere shows that erroneous fluctuations induced in the ozone-concentration profile by signal noise and aerosol inhomogeneity undergo a significant reduction in comparison with the results from the conventional technique based on straightforward numerical differentiation. {copyright} {ital 1996 Optical Society of America.}
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 397388
- Journal Information:
- Applied Optics, Journal Name: Applied Optics Journal Issue: 24 Vol. 35; ISSN APOPAI; ISSN 0003-6935
- Country of Publication:
- United States
- Language:
- English
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