An evaluation of the effect of volcanic eruption on the solar radiation at six Canadian stations

Hourly global and diffuse radiation data from the six Canadian stations at Edmonton, Montreal, Port Hardy, Resolute, Toronto and Winnipeg have been analyzed for evidence of the effect of volcanic eruption on the amount of direct beam radiation and diffuse radiation. A strong reduction of clear hour direct beam radiation is seen during 1983 due to aerosols in the stratosphere following the eruption of El Chichon in southern Mexico on 28 March and 3 and 4 April 1982. A corresponding increase in diffuse radiation and Angstrom turbidity coefficient is also seen during 1983. The effect of the aerosols from El Chichon is much reduced during 1984, but is still seen above levels from other sources. By combining all significant evidence found in these Canadian solar radiation data, the presence of an excess of volcanic aerosols associated with one or more of the series of volcanic eruptions occurring during the periods from about 1963 to 1968, near 1975, and just prior to the eruption of El Chichon is clearly seen. The amplitude of the effect of these series of eruptions on the data selected for examination here is approximately one-third the amplitude of the effect found for El Chichon. This study confirms that global radiation shows little change when volcanic aerosols in the stratosphere increase following an eruption.