Raman Lidar Technique Research Articles

Applications of Kalman Filtering to Derive Water Vapor Profiles from Raman Lidar and Microwave Radiometers

Water vapor profiles are derived from data provided by a Raman lidar and a microwave radiometer, as well as other instruments. The authors demonstrate that this system can provide accurate profiles at altitudes above which the Raman lidar technique is limited.

Combined raman elastic-backscatter LIDAR for vertical profiling of moisture, aerosol extinction, backscatter, and LIDAR ratio

A combined Raman elastic-backscatter lidar has been developed. A XeCl excimer laser is used as the radiation source. Inelastic Raman backscatter signals are spectrally separated from the elastic signal with a filter or grating polychromator. Raman channels can be chosen to register signals from CO2, O2, N2, and H2O. Algorithms for the calculation of the water-vapor mixing ratio from the Raman signals and the particle extinction and backscatter coefficients from both elastic and inelastic backscatter signals are given. Nighttime measurements of the vertical humidity distribution up to the tropopause and of particle extinction, backscatter, and lidar ratio profiles in the boundary layer, in high-altitude water and ice clouds, and in the stratospheric aerosol layer are presented. Daytime boundary-layer measurements of moisture and particle extinction are made possible by the improved daylight suppression of the grating polychromator. Test measurements of the CO2 mixing ratio indicate the problems for the Raman lidar technique in monitoring other trace gases than water vapor.

Atmospheric temperature measurements using a pure rotational Raman lidar

A Raman lidar technique for measuring atmospheric temperature using pure rotational Raman spectra of N2 and O2 is discussed in detail. The use of a double-grating monochromator in the lidar for isolating two portions of the pure rotational Raman spectrum (PRRS) of N2 and O2 and suppressing the line of aerosol light scattering is experimentally shown to be very efficient. The feasibility of the method is convincingly illustrated by the results of laboratory experiments, as well as with measurements of air temperature carried out in the atmosphere. The accuracy of temperature measurements using the ratio of intensities of two portions of PRRS of N2 and O2 was ∼±0.74 K in laboratory experiments. The accuracy of the atmospheric temperature profile measurements using the lidar varied from 0.8 K at altitudes up to 300–400 mto, and slightly exceeded, ±1.5 K at 1-km height. Lidar temperature data are in good agreement with radiosonde data.

Air Pollution Field Studies with a Raman Lidar

Raman Lidar techniques have been discussed theoretically and sensitivities for various pollutants have been predicted. The results of the present real Raman Lidar indicates pollutant levels between 40-700 ppm is the present sensitivity but very realistic projections based on this data suggest sensitivities between 0.4 - 7 ppm could be reached if nondispersive detection techniques were used.