| 02 Apr 2026
Extending the late 1963 to 1964 Mt Agung rescued searchlight aerosol profiles dataset at 32º N, from early 1963 to 1976
Abstract. A set of 11 aerosol turbidity profiles (ATP) and 2 aerosol extinction profiles (AEP) at λ = 0.55 µm, observed with searchlight in New Mexico at 32° N, has been digitized from plots in scientific articles. They cover the period February to June 1963 and September 1965 to May 1975, complementing the already rescued and previously published 105 individual AEP, corresponding to 36 days, between December 1963 and December 1964. Eleven AEP are calculated (AEPc) from the ATP, and the corresponding stratospheric aerosol optical depth (sAOD) between 12 and 25 km is also derived. Estimates of the digitization’s errors for the AEPc and the sAOD are also calculated using information available in the literature. The combined set of rescued AEP reported here and the earlier rescued set of AEP from searchlight observations, are the only AEP dataset covering the period between the 1963 Mt Agung and the 1974 Fuego eruptions at northern midlatitudes. In this regard two relevant features identified in the AEP and the sAOD are described here. The first, using AEPc from March and April 1963 identified what could be the date of arrival of the stratospheric aerosols from the Mt. Agung first eruption on March 17th 1963. This fact challenges the accepted criteria that the arrival of the stratospheric aerosols from Mt Agung arrived at the northern hemisphere midlatitudes in the second half of 1963. The second feature evidences two anomalous increases of the sAOD during a period supposed to be the decay of the sAOD from Mt. Agung eruption. They show our limited knowledge and understanding of the 1963 Mt Agung volcanic stratospheric aerosol transport. Finally, we describe evidences found in the literature pointing to the possible existence of the original searchlight raw signals and its processing software. The dataset described in this work is available at: https://issues.pangaea.de/browse/PDI-43217, (Antuña-Marrero et al., 2026).
Review for Antuña-Marrero: "Extending the late 1963 to 1964 Mt Agung rescued searchlight aerosol profiles dataset at 32N, from early 1963 to 1976."
The 1963 Mt. Agung eruption was one of the most significant volcanic events of the 20th century, yet its long-term climate impact remains poorly understood because very little is known about the transport and vertical distribution of its stratospheric aerosols. Before the satellite era, most publications relied heavily on indirect measurements such as ice core data and astronomical observations of starlight attenuation. This lack of high-resolution vertical profiles means current climate models often rely on poorly constructed datasets for evaluation; hence, there is a limited understanding of how these aerosols evolved over time. The rescued searchlight data presented in this manuscript addresses this critical gap for both the 1963 Agung and 1974 Fuego eruptions.
The manuscript identifies two critical features in the rescued dataset. First, observations from March and April 1963 reveal an early arrival of stratospheric aerosols at 32N, directly contradicting the accepted view that these aerosols only reached northern midlatitudes in the second half of 1963. Second, the joint series shows anomalous increases in stratospheric aerosol optical depth during late 1964, a period previously thought to be characterised by a simple decay phase. The authors also estimate the optical depth values at 0.019 and 0.040 before and after the arrival of the aerosol cloud, respectively. These findings demonstrate that the post-Agung stratosphere was significantly more complex than existing understanding suggests. Consequently, this research is an important component of the SSiRC Data Rescue Activity. Integrating these rescued searchlight profiles with lidar records provides the necessary synergy for a robust foundation for quantifying volcanic forcing. Most of the modelling studies (e.g. Dhomse et al. (2020)), highlighted difficulties in identifying consistent aerosol optical depth datasets across multiple instruments. Overall, it is a well-written manuscript describing an important dataset, and I recommend it for publication.
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