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During a field campaign in 1991, the NASA Goddard Space Flight Center Scanning Raman Lidar measured, in the water vapor channel, Raman scattering from a low-level cloud in excess of saturation. The excess scattering has been interpreted to be spontaneous Raman scattering by liquid water in the cloud droplets. A review of theoretical and laboratory studies indicate that the technique may provide a remote method to observe cloud liquid water.

NASA/GSFC Scanning Raman Lidar measurements of water vapor mixing ratio, relative humidity, aerosol backscattering and extinction are used to investigate relationships between aerosol optical properties and water vapor.

A new technique to estimate profiles of mixing ratio and potential temperature through the depth of the Planetary Boundary Layer (PBL) over the ocean using airborne lidar and multi-channel radiometer data is presented. The technique utilizes lidar derived statistics on the height of cumulus clouds which frequently cap the PBL to estimate the lifting condensation level. Combining this information with radiometer derived sea surface temperature measurements, an estimate of the surface moisture can be obtained. Lidar derived statistics on convective plume height and coverage within the PBL are then used to infer the profiles of potential temperature and moisture with high vertical resolution. The RMS accuracy of derived average PBL moisture and potential temperature is less than 1 g/kg and 1 degree Celsius, respectively.

Three field missions were conducted at Wallops Island, VA in August and September 1995. The NASA Goddard Space Flight Center Scanning Raman Lidar participated in all three campaigns by measuring water vapor for ground truth comparisons. We present water vapor comparisons from 3 lidars, 2 in situ hygrometers, VIZ and Vaisala hygrometers, and an infrared interferometer. The comparisons agree to within 5–10% from the ground up to 7 km.

In this paper we describe a high resolution tunable Alexandrite laser system which we have used to make differential absorption lidar measurements of the atmospheric pressure profile. We also report on measurements of the spectral purity and line shape of the laser emission.

The development of energetic, tunable, narrowline pulsed lasers has made it possible to utilize numerous optical radar techniques for remotely probing the atmosphere; i.e., to measure constituents (H2O, O3, NO2, etc) and the thermal state. We describe progress on using the O2 A-band (760–770 nm) for lidar profiling of atmospheric temperature, pressure, and density [1]. First we illustrate the impressive capabilities expected for lidar systems, given equipment performance within reach of current technology. Second we outline a new body of high resolution spectroscopic data on the O2 A-band, data vitally needed for accurate interpetation of lidar observations that make use of this band. Third we indicate an ongoing problem of spectral purity for the narrowband lasers that are required to be tuned onto molecular absorption lines, for certain lidar methods to be successful.

This paper describes differential absorption lidar techniques for remotely measuring the atmospheric temperature and pressure profile, surface pressure, and cloud top pressure-height. The approach to the pressure measurements1 utilizes a high resolution measurement of absorption in the wings of lines in the oxygen A band where the absorption is highly pressure sensitive throug] the mechanism of collisional line broadening. The approach for temperature2 uses a measurement of the absorption at the center of a selected line in the oxygen A band which originates from a quantum state with high ground state energy. The population of the state depends strongly on temperature through the Boltzmann term which produces a highly sensitive temperature determination. Oxygen is used for these measurements since it is uniformly mixed in the atmosphere, which greatly simplifies the measurement approach, and has lines with appropriate strength and energy levels. Also, it is located in a spectral region (760 nm) easily accessible using tunable solid state and dye lasers and efficient detectors.