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

We report the rescue and processing completion of the first multiyear set of stratospheric aerosols lidar measurements. They were conducted at Lexington, MA between January 1964 and August 1965 and some additional measurements conducted at Fairbanks, AK between July and August 1964. The processing of the rescued lidar scattering ratio profiles was aimed to determine the stratospheric aerosols extinction profiles (sAEP) and the stratospheric aerosols optical depth. Contemporary nearby measurements of atmospheric variables were used with that aim (sAOD). Atmospheric soundings of temperature, and pressure were used to determine the molecular backscattering profiles and ozone soundings to determine the ozone absorption profiles. Those former profiles served to determine the molecular and ozone two way transmittances corrections profiles. Stratospheric aerosols two way transmittances corrections profiles were determined by a cyclic processing combining the sAEP and the total aerosols turbidity measurements. A comparison was conducted between the sAEP and sAOD calculated using the soundings and the 1962 US standard atmosphere. The two way transmittance corrections were not applied in this case, resulting in slightly lower values of both variables in the case of soundings. The two way transmittance correction was applied to the sAEP based in the fact that it was not applied in the originary processing producing the lidar scattering ratio profiles we rescued. It was reason to consider that the aerosols backscatter derived directly from it were in fact the aerosol attenuated backscatter. The magnitudes of the differences in the aerosols extinction between the corrected and uncorrected two way transmittances results show an increase of 72 % for Lexington and 26 % for Fairbanks. For the sAOD the increase is 66 % and 26 % respectively. The comparison of 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 variables. At Lexington the sAEP cross- sections and the sAOD vs time plot show the presence of three maximums between January 1964 and August 1965, with the last having higher magnitudes of the aerosol extinction and sAOD in contradiction what it would be expected for the Mt Agung decaying stratospheric aerosols. In search for an explanation we found contemporary and updated references to other two volcanic eruptions the Trident volcano in Alaska and the Vestmannaeyjar volcano south of Iceland, both with plumes above the tropopause.. The first reported to have erupted in April and October- November 1963 and also in May 1964. The second between November 1963 and the middle of 1964. A detailed analysis of the uncertainties of the several intermediate variables involved in the processing conducting to derive the sAEP for each site was conducted. The two way transmittance uncorrected aerosols extinction values relative error magnitudes were 54 % for Fairbanks and 44 % Lexington. The corrected aerosols extinction values relative error magnitudes were 61 % and 64 % respectively. The analysis of the uncertainties pointed to the variables that, upon an extended rescue process and further reprocessing may improve the reported relative error levels.