Results of Laser-Calibrated High-Resolution Transmission Measurements and Comparisons with Broadband Transmissometer Data: San Nicolas Island, California, May 1979.

摘要

Atmospheric transmission was measured along a 4.07 km overwater path in May 1979 at San Nicolas Island (SNI), California. A deuterium fluoride (DF) laser and a high-resolution Fourier transform spectrometer (FTS) system were used to generate high-quality transmission spectra of the 4.07 km path accurate to + or - 3 to 5% in absolute transmission. Details and procedures used and results obtained in the absolute transmission calibration of the spectra are presented. Path-integrated values for water vapor density have been derived from the FTS spectra and show good agreement with fixed-location dew-point hygrometer measurements. Comparisons of measured DF laser extinction coefficients with calculated molecular absorption values are presented which suggest modifications to existing water vapor continuum absorption models and which also provide a measure of infrared aerosol extinction. The aerosol extinction values thus derived have been found to show little correlation with concurrent measurements of visibility, windspeed, and relative humidity. Comparisons of spectral-band-averaged FTS data with Pacific Missile Test Center broadband transmissometer measurements show good average agreement with significant scatter in the data attributable in part to sizable fluctuations in transmission occurring during the time scales used to acquire the FTS data. (Author)