03 Nov 2020

03 Nov 2020

Review status: this preprint is currently under review for the journal ESSD.

Recovery of the first ever multi-year lidar dataset of the stratospheric aerosol layer, from Lexington, MA, and Fairbanks, AK, January 1964 to July 1965

Juan-Carlos Antuña-Marrero1, Graham W. Mann2,3, John Barnes4, Albeth Rodríguez-Vega5, Sarah Shallcross2, Sandip Dhomse2,3, Giorgio Fiocco, and Gerald W. Grams Juan-Carlos Antuña-Marrero et al.
  • 1Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47002, Spain
  • 2School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 3National Centre for Atmospheric Science (NCAS-Climate), University of Leeds, Leeds, UK
  • 4NOAA ESRL Global Monitoring Division, Colorado, US
  • 5Grupo de Óptica Atmosférica de Camagüey, Centro Meteorológico de Camagüey, INSMET, Cuba
  • deceased

Abstract. We report the recovery and processing methodology of the first ever multi-year lidar dataset of the stratospheric aerosol layer. A Q-switched Ruby lidar measured 66 vertical profiles of 694 nm attenuated backscatter at Lexington, Massachusetts between January 1964 and August 1965, with an additional 9 profile measurements conducted from College, Alaska during July and August 1964. We describe the processing of the recovered lidar backscattering ratio profiles to produce mid-visible (532 nm) stratospheric aerosol extinction profiles (sAEP532) and stratospheric aerosol optical depth (sAOD532) measurements, utilizing a number of contemporary measurements of several different atmospheric variables. Stratospheric soundings of temperature, and pressure generate an accurate local molecular backscattering profile, with nearby ozone soundings determining the ozone absorption, those profiles then used to correct for two-way ozone transmittance. Two-way aerosol transmittance corrections were also applied based on nearby observations of total aerosol optical depth (across the troposphere and stratosphere) from sun photometer measurements. We show the two-way transmittance correction has substantial effects on the retrieved sAEP532 and sAOD532, calculated without the corrections resulting in substantially lower values of both variables, as it was not applied in the original processing producing the lidar scattering ratio profiles we rescued. The combined transmittance corrections causes the aerosol extinction to increase by 67 % for Lexington and 27 % for Fairbanks, for sAOD532 the increases 66 % and 26 % respectively. Comparing the magnitudes of the aerosol extinction and sAOD with the few contemporary available measurements reported show a better agreement in the case of the two way transmittance corrected values.

The sAEP and sAOD timeseries at Lexington show a surprisingly large degree of variability, three periods where the stratospheric aerosol layer had suddenly elevated optical thickness, the highest sAOD532 of 0.07 measured at the end of March 1965. The two other periods of enhanced sAOD532 are both two-month periods where the lidars show more than 1 night where retrieved sAOD532 exceeded 0.05: in January and February 1964 and November and December 1964. Interactive stratospheric aerosol model simulations of the 1963 Agung cloud illustrate that although substantial variation in mid-latitude sAOD532 is expected from the seasonal cycle in the Brewer-Dobson circulation, the Agung cloud dispersion will have caused much slower increase than the more episodic variations observed, with also different timing, elevated optical thickness from Agung occurring in winter and spring. The abruptness and timing of the steadily increasing sAOD from January to July 1965 suggests this variation was from a different source than Agung, possibly from one or both of the two VEI3 eruptions that occurred in 1964/65: Trident, Alaska and Vestmannaeyjar, Heimey, south of Iceland. A detailed error analysis of the uncertainties in each of the variables involved in the processing chain was conducted, relative errors of 54 % for Fairbanks and 44 % Lexington for the uncorrected sAEP532, corrected sAEP532 of 61 % and 64 % respectively. The analysis of the uncertainties identified variables that, with additional data recovery and reprocessing could reduce these relative error levels. Data described in this work are available at (Dataset in Review) (Antuña-Marrero et al., 2020a).

Juan-Carlos Antuña-Marrero et al.

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Juan-Carlos Antuña-Marrero et al.

Data sets

Mt Agung 1963 attributed, stratospheric aerosols lidar dataset from Lexington, MA, and Fairbanks, AK Antuña-Marrero, Juan-Carlos, Mann, Graham W., Barnes, John, Rodríguez-Vega, Albeth, Shallcross, Sarah, Dhomse, Sandip, Fiocco, Giorgio, and Grams, Gerald W.

Juan-Carlos Antuña-Marrero et al.


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Short summary
The first ever set of stratospheric aerosols measurements with lidar was rescued and reprocessed. It consists of observations 1964 and 1965 at Lexington, MA, and July–August 1964 at Fairbanks, AK. At Lexington, high values of stratospheric aerosol optical depth with three peaks, the last the highest (0.07), initially attributed solely to the 1963 Agung volcanic eruption. Last peak, in mid-1965 is explained by contributions from two volcanos which erupted in 1964/1965 in high latitude NH.