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Lidar observations of the stratospheric aerosol: California, October 1972 to March 1974
Author(s) -
Russell P. B.,
Viezee W.,
Hake R. D.,
Collis R. T. H.
Publication year - 1976
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710243313
Subject(s) - lidar , atmospheric sciences , stratosphere , aerosol , scattering , volcano , environmental science , particulates , wavelength , backscatter (email) , twilight , meteorology , geology , remote sensing , optics , physics , chemistry , organic chemistry , astronomy , computer science , wireless , telecommunications , seismology
Thirty night‐time observations of the stratospheric aerosol 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 backscattering. 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 search‐light 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.