Data Rescue
Measuring in-situ the stratospheric aerosol layer became an urgent priority in the 1950s to monitor the progression of radionuclide concentrations from thermonuclear tests in the Pacific and mid-latitudes (Telegadas et. al., 1964), due to the potential biological hazard from fallout of long-lived fission products such as strontium-90 transported within aerosol particles (Martell, 1966).
Landmark papers analyzing aerosol measurements from high-altitude balloon (Junge et. al., 1961) and aircraft (Junge et. al., 1961), established much of today’s understanding of the vertical distribution of stratospheric aerosols (Junge et. al., 1961; Friend, 1966). The major volcanic aerosol cloud from the tropical 1963 Agung eruption was also measured from in-situ (Mossop, 1964; Rosen, 1964; Rosen, 1968) and active remote sensing instruments (Elterman et. al., 1969; Grams et. al., 1967).
These measurements provide invaluable information on the 1960s stratospheric aerosol layer and, crucially for climate models, new constraints for the vertical extent and longevity of the Agung aerosol cloud. However, in this early period, the majority of these measurements are only available in journal papers and project reports, and although there is extensive documentation of the datasets, these have not yet been gathered together for the scientific community.
In this new SSiRC data rescue activity we will provide information and links to these observations and establish guidance documents to enable them to be interpreted consistently with today’s stratospheric aerosol measurements and link to the more recent observational data record. We aim to stimulate new research to add new scientific knowledge of the stratospheric aerosol layer and volcanic radiative effects during this key baseline period.
We seek to foster new collaborations between scientists to recover, re-digitize and re-calibrate other historic stratospheric aerosol data sets, and invite scientists to contribute to this activity and to provide advice and expertise on how best to recover other incomplete long term observations of stratospheric composition.
Rather than providing a new data archive for historic data sets we suggest that these measurements are to be hosted by an existing data center such as NASA’s Atmospheric Science Data Center. The SSiRC data rescue webpage will then provide sign-post information on where to find the pre-satellite stratospheric aerosol measurement data sets in existing archives, publications and reports.
The initial focus of the data rescue initiative is on the 1950s/1960s stratospheric aerosol measurements from lidars, particle counters and searchlight observations. The data sources from most of these observations have already been archived within reports or PhD theses, some fully tabulated. In some cases however, the only sources may be Figures included in reports, journal papers and other documents, in which case these will be digitized and recovered. A key step of the SSiRC data rescue initiative will involve registering each data set with a DOI (Digital Object Identifier) to publish the data set in an open access data repository.
Here we provide an initial list of stratospheric aerosol datasets the SSiRC data rescue activity will focus on, and provide links to existing documentation and references. For the Minneapolis balloon measurements, the PI (James Rosen) has already produced a detailed description document and the data are already available on the NASA ASDC archive. The activity will involve consulting with each PI, and providing links to documentation that will similarly describe each of the data sets. Where data is re-digitized from publications we will also clearly describe the methodology used.
An extra focus of the initial SSiRC data rescue is to gather datasets to characterize the progression of the aerosol cloud during the initial months after the 1991 Pinatubo eruption and we include an initial section on these early post-Pinatubo period data sets. The datasets available are:
Details on 1950s/60s stratospheric aerosol measurements
Measuring in-situ the stratospheric composition became an urgent priority in the 1950s to monitor the progression of radionuclide concentrations from thermonuclear tests in the Pacific and in mid-latitudes (Telegadas et. al., 1964). Existing US Air Force and Atomic Energy Commission high-altitude balloon-borne and U-2 aircraft monitoring capabilities began to measure aerosol in 1960 (Friend, 1966)(e.g. Friend, 1961), and the program continued to 1966 (Feely et. al., 1967).
Christian Junge and co-workers analyzed stratospheric aerosol measurements from high-altitude balloon (Feely et. al., 1967) and aircraft (Junge et. al., 1961), establishing the basis of today's understanding of the vertical distribution of stratospheric aerosols (Junge et. al., 1961; Friend, 1966).
Junge et. al., 1961 analyzed balloon flights made in 1958 and 1959, measuring increasing concentrations of particles larger than 100nm, up to a maximum at 20km, the layer subsequently becoming known as the Junge layer. In contrast, smaller Aitken particles, measured by expansion- type nuclei counters decreased above the tropopause, up to 25km. These measurements combined existing aerosol measurement technologies (Junge, 1935) with new sampling methods (Chagnon, 1957) for stratospheric conditions.
The initial aerosol samples from U-2 flights (Mar-Nov 1960) spanned 63°S to 72°N (Junge et. al., 1961), and established the dominant sulfate aerosol composition, with also trace metals including magnesium, silicon and iron with lower concentrations of calcium and potassium.
The high-altitude sampling program of aircraft and balloon measurements continued through much of the 1960s(Feely et. al., 1967). Instruments on the U-2 flights measured the volcanic aerosol cloud from the 1963 Agung eruption, including the morphology of volcanic aerosols (Mossop, 1963; Mossop, 1964; Mossop, 1965). Balloon-borne particle counters developed at the University of Minnesota (Rosen, 1964), together with a 4-wavelength solar extinction instrument developed by Ted Pepin (Pepin, 1969) were used to measure the full vertical extent of the volcanic aerosol concentrations, and provide information on the temporal variation of the stratospheric aerosol layer in mid-latitudes.
The eruptions of Taal, Philippines in September 1965, Awu, Indonesia in August 1966, and Fernandina, the Galapagos Islands in June 1968 were each explosive enough to inject aerosol material into the stratosphere (see Newhall et. al., 1982). The Mauna Loa transmissions record (Mendonca et. al., 1978) shows how the volcanic dimming from Agung was prolonged through to the late 1960s. In addition to the Minneapolis balloon measurements, a field campaign in Panama in September 1966 measured the Awu aerosol cloud using ballon-borne OPC instruments (Rosen, 1968) and solar extinction measurements (Pepin, 1969).
Several observational synthesis papers at the end of the 1960s brought together wide range of different data sets. For example Rosen, 1969 analysed both in-situ and active remote sensing measurements to understand aerosol formation processes, and Dyer et. al., 1968 present a comprehensive synthesis of ground-based radiation measurements, then leading to our current understanding of the dispersion of the Agung aerosol cloud (Dyer, 1970).
With the development of active ground-based remote sensing techniques in the early 1960's, the Agung plume was also measured by searchlight (Elterman et. al., 1964) and lidar (Clemesha et. al., 1966; Grams et. al., 1967). Together with information documented in reports that were recovered from that time (Elterman, 1966; Feely et. al., 1967; Grams, 1966), these measurements provide information of the Northern Hemisphere altitude progression of the major volcanic aerosol cloud.
Further advances in particle counter technology in the 1970s (Käselau et. al., 1974; Haberl, 1975; Rosen et. al., 1977) led new knowledge of the existence of the Aitken-sized stratospheric aerosol (Rosen et. al., 1975; Cadle et. al., 1976; Cadle et. al., 1977). Together with the long term record of in-situ aerosol measurements from Wyoming (Hofmann et. al., 1975) which span the 1974 Fuego period (Hofmann et. al., 1977), our understanding of volcanic effects progressed further.