Abstract

The NOAA Doppler lidar has been recently upgraded with a 2-J/pulse injection-lock laser that provides a 13-dB increase in energy over the previous hybrid design. Frequency stability of the new laser is demonstrated by the consistencies in sequentially recorded wind profiles to better than 0.1 m/s when scans are made within 1 min of each other. Comparison with tower anemometers also agrees well to within 0.2 m/s. Backscatter profiles at 10.6 μm show occasional, very clean layers in the upper troposphere where the scattering coefficient, beta, is <1.0E-11 l/(m sr). These layers have been confirmed using a ruby lidar, where scattering ratios of 1.1 compared to Rayleigh are measured. The sparse population of large aerosols in these clean layers does not compare well with much higher turbidity measured in 1981, 1982, and 1983 with the hybrid lidar. We conclude that there is great variability from one year to the next in large aerosol population in the upper troposphere. Possibly the El Nino climate anomaly in 1982 and 1983 caused a more dusty atmosphere than normal.

© 1986 Optical Society of America