Shipborne lidar measurements showing the progression of the tropical reservoir of volcanic aerosol after the June 1991 Pinatubo eruption
Authors: Antuña-Marrero Juan-Carlos , Mann Graham W. , Keckhut Philippe , Avdyushin Sergey , Nardi Bruno , Thomason Larry W. 
Published: November 2020

Abstract. A key limitation of volcanic forcing datasets for the Pinatubo period is
the large uncertainty that remains with respect to the extent of the optical
depth of the Pinatubo aerosol cloud in the first year after the eruption,
the saturation of the SAGE-II instrument restricting it to only be able to
measure the upper part of the aerosol cloud in the tropics. Here we report
the recovery of stratospheric aerosol measurements from two shipborne
lidars, both of which measured the tropical reservoir of volcanic aerosol
produced by the June 1991 Mount Pinatubo eruption. The lidars were on board
two Soviet vessels, each ship crossing the Atlantic, their measurement
datasets providing unique observational transects of the Pinatubo cloud
across the tropics from Europe to the Caribbean (∼ 40
to 8∘ N) from July to September 1991 (the Professor Zubov ship) and from
Europe to south of the Equator (∼ 40∘ N to 8∘ S)
between January and February 1992 (the Professor Vize ship). Our philosophy with
the data recovery is to follow the same algorithms and parameters that appear
in the two peer-reviewed articles that presented these datasets in the same
issue of GRL in 1993, and here we provide all 48 lidar soundings made from
the Professor Zubov and 11 of the 20 conducted from the Professor Vize, ensuring we
have reproduced the aerosol backscatter and extinction values in the
figures of those two papers. These original approaches used thermodynamic
properties from the CIRA-86 standard atmosphere to derive the molecular
backscattering, vertically and temporally constant values applied for the
aerosol backscatter-to-extinction ratio, and the correction factor of the
aerosol backscatter wavelength dependence. We demonstrate this initial
validation of the recovered stratospheric aerosol extinction profiles,
providing full details of each dataset in this paper's Supplement S1, the
original profiles of backscatter ratio, and the calculated profiles of aerosol backscatter and extinction. We anticipate these datasets will provide potentially important new observational case studies for modelling analyses, including a
1-week series of consecutive soundings (in September 1991) at the same
location showing the progression of the entrainment of part of the Pinatubo
plume into the upper troposphere and the formation of an associated cirrus
cloud. The Zubov lidar dataset illustrates how the tropically confined
Pinatubo aerosol cloud transformed from a highly heterogeneous vertical
structure in August 1991, maximum aerosol extinction values around 19 km for
the lower layer and 23–24 for the upper layer, to a more homogeneous and
deeper reservoir of volcanic aerosol in September 1991. We encourage
modelling groups to consider new analyses of the Pinatubo cloud, comparing
the recovered datasets, with the potential to increase our understanding
of the evolution of the Pinatubo aerosol cloud and its effects. Data
described in this work are available at https://doi.org/10.1594/PANGAEA.912770 (Antuña-Marrero et al.,
2020).