A decade of stratospheric sulfate measurements compared with observations of volcanic eruptions

Abstract

Sulfate aerosol concentrations in the stratosphere have been measured for 11 years (1971–1981) using portions of filters collected by the Department of Energy's High Altitude Sampling Program. Data collected seasonally at altitudes between 13 km and 20 km spanning latitudes from 75°N to 51°S are reported. These data are compared with the reported altitudes of volcanic eruption plumes during the same decade. From this comparison it is concluded that (1) several unreported volcanic eruptions or eruptions to altitudes higher than reported did occur during the decade, (2) the e‐fold removal time for sulfate aerosol from the stratosphere following the eruption of Volcan Fuego in 1974 was 11.2±1.2 months, (3) the volcanic contribution to the average stratospheric sulfate concentration over the decade was greater than 50%, and (4) there may be evidence for an anthropogenic contribution to stratospheric sulfate that increases at the rate of 6 to 8% per year.

Atmospheric injections of polonium-210 from the recent volcanic eruptions.

“…The 20 July 1978 eruption is not listed by Simkin et al (1981) and Sedlacek et al (1983) concluded that either the documen tation for the Dukono eruption is incomplete or another volcano has injected material but not been observed.…”

“…Livingston et al (1983) have reported the existence of a 'mistery' cloud over Japan and in the western United States shortly before the 28 March 1982 eruption of El Chi chon. Sedlacek et al (1983) reported on the oc currence of greatly elevated sulfate concentra tions at three altitudes (about 15, 17 and 19km) between 10°N and 20°N in samples collected on July 24 and July 25, 1978 (see a peak sulfate concentration which occurred in the middle of 1978 in Fig. 2).…”

“…If a region of greatly elevated sulfate con centrations existed at altitudes between 15 and 20km between 10°N and 20°N during the month of July 1978 as reported by Sedlacek et al (1983), and if the sulfates originated from a volcanic eruption, it is to be expected that the sulfate-rich aerosols were also rich in the volatile element 210Po. According to the Brewer-Dobson model of global circulation of air masses, the 21opo -rich aerosols are likely to be transported to the lower stratosphere in the northern tem perate zone and then brought down to the ground by the atmospheric precipitation ap proximately 6 months later during the months of January and February 1979.…”

“…2 that the 11 February 1979 eruption of Bezymianny volcano in Kamchatka did not cause a sharp increase in the sulfate concentration in the northern strato sphere. Sedlacek et al (1983) measured the sulfate concentrations during the period from April 5 to April 25, 1979, but they stated that a serious aircraft mechanical problem in Alaska prevented the sampling flight which might have intercepted material from the eruption of Bezymianny 2 months earlier. They measured the sulfate concentrations again from July 3 to August 1, 1979, and reported that a slight local enhancement at 17km between 45°N and 65°N may be residual material from the eruption of Bezymianny of 5 months ago.…”

Changes in stratospheric composition, chemistry, radiation and climate caused by volcanic eruptions

“…The flow of sulphur into the stratosphere is dominated by large explosive eruptions which account for about 60% of stratospheric sulphur E. J. HIGHWOOD budget (Sedlacek et al 1983). Pyle et al (1996) estimate that on average about 0.06-0.15 Mt/y of stratospheric sulphur (as SO2) is from nonvolcanic sources, while about 1 Mt/y arises from volcanic injection.…”