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Title: Seasonal/latitudinal variations in the satellite observed aerosol properties in the stratosphere and upper troposphere during the eruption of Alaid and Pagan
Authors: Raja, P Ernest
Devara, P C S
Issue Date: Oct-1997
Publisher: NISCAIR-CSIR, India
Abstract: Aerosol extinction data at two wavelengths from SAGE satellite measurements made during the period January to November 1981 has been used to study seasonal/latitudinal variations of aerosol size distributions in the stratosphere and upper troposphere. As the volcanic eruptions from Alaid (50.8° N, 155.5° E) on 27 April. 1981 and Pagan (18.1° N, 145.8°E) on 15 May 1981 occurred during the observations period, the effects of volcanic injection of material have been investigated in particular. The latitudinal variation of aerosol optical depth shows a broad maximum in the tropical region and again larger values in the high latitudes with midlatitude minima around 25°-30° in both the hemispheres. At the equatorial latitudes, mode radius, computed from extinction data at two wavelengths, is large in the upper troposphere and decreases rapidly with increasing altitude. An interesting latitudinal variation is seen in the mode radium which is almost the same in all the three seasons of spring, summer and fall. At altitudes below 22 km, mode radius shows an equatorial maximum with smaller values at middle and higher latitudes in both the hemispheres. But at altitudes above 22 km, a reverse latitudinal variation is seen. During northern summer, smaller-sized particles are more prevalent in the northern high latitude stratosphere and relatively bigger aerosol particles are obtained at the southern high latitudes. The effect of volcanic injection of particulate material into the stratosphere can be seen as an increase in mode radius immediately and an increase in aerosol number density for several months after the eruption. Plausible explanations about the variations of stratospheric aerosol properties are given.
Page(s): 256-263
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.26(5) [October 1997]

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