Lidar observations of the stratospheric aerosol: California, October 1972 to March 1974

Abstract

SUMMARYThirty night-time observations of the stratosphericaerosol were made between October 1972 and March 1974, using a ground-based ruby lidar (laser radar) at Menlo Park, California (37.5"N 122.2"W). Vertical profiles of scattering ratio and particulate backscattering coefficient were obtained by reference to a level of assumed negligible particulate backscattering.The observation period preceded the major stratospheric penetration of the Fuego volcanic eruption and was evidently one of minimal volcanic influence. Nevertheless, there was appreciable variation among observations, including significant vertical movement of the scattering ratio peak near the time of the 1973 stratospheric warming. Maximum scattering ratios ranged between 1.08 and 1.19, indicating a decline in particulate backscattering by approximately an order of magnitude since the maximum observed shortly after the 1963 eruption of the Agung volcano. This decline in backscattering is shown to agree with the overall trend in twilight scattering and particle data, from balloons, during the same period. On a single night, sequential observations with ruby (694 nm) and dye (589 nm) laser transmitters were made, showing significant scattering-ratio differences, due primarily to the wavelength dependence of molecular back-scattering.An optical model, consistent with a number of stratospheric measurements made in the early 1970s by a variety of techniques, is used to convert the lidar-measured backscattering values to other quantities. In this manner, good agreement is demonstrated between particle mass values inferred from lidar and aircraft filter measurements made on the same date. Values for turbidity and particulate optical thickness are similarly derived from the lidar data, giving values considerably smaller than those measured by searchlight in 1964-1965. To assist in radiative transfer calculations for the nonvolcanic period, a table of these optical thickness values is provided. Between 10 and 30 km, the lidar-derived nonvolcanic particulate optical thicknesses are 0.005 and 0.004 for wavelengths of 550 and 700 nm, respectively.

The transport and spacial scale of Asian dust-storm clouds: a case study of the dust-storm event of April 1979

“…The analytical procedure for evaluating the back-scattering coefficient of particulate matter from the back-scattered signal obtained from an air parcel has been discussed by many investigators (e.g., Russell et al, 1976).…”

Determination of the complex refractive index and size distribution of atmospheric particulates from bistatic‐monostatic lidar and solar radiometer measurements

“…Most of the aforementioned problems may be avoided by applying remote sensing techniques which permit sensing of the particulates in their natural surroundings. While remote sensing methods do present their own interpretation problems, a number of particulate remote sensing applications have already been demonstrated with apparently good success [e.g., Yamamoto and Tanaka, 1969;FernaM et al, 1972;Ward et al, 1973;Russell et al, 1976;Twitty et al, 1976;Reagan et al, 1977a;$pinhirne, 1977;$pinhirne et al, 1980;King et al, 1978;King, 1979].…”

A survey of light‐scattering techniques used in the remote monitoring of atmospheric aerosols

“…The results obtained by Russell et al [1976] appear to be quite plausible, so far as they go, considering the methodology and assumptions spelled out in their paper. They manage to resolve the problem of discriminating between the factors in the product fisMPM by simply adopting a well-defined aerosol model for the local stratosphere, including both composition and size distribution (the so-called haze H model.)…”

“…Some of the SRI's reduced data yield values of Rs(h) < 1 somewhere between 10 and 15 km above sea level, contrary to the implication of (4), where the aerosol contribution is assumed to be always positive. This may be attributed either to experimental error or to lower molecular densities than the standard atmosphere values adopted by Russell et al [1976]. There may, however, be another explanation which admits the observed Rs < 1 values and molecular densities equal to or less than the adopted standard ones; that is to say, the presence of aerosols may yield weaker lidar returns than those from an (optically) equivalent purely gaseous layer.…”