A. Sarkissian et al., PSC AND VOLCANIC AEROSOL OBSERVATIONS DURING EASOE BY UV-VISIBLE GROUND-BASED SPECTROMETRY, Geophysical research letters, 21(13), 1994, pp. 1319-1322
Twilight sky colour measurements were made using ground-based UV-visib
le SAOZ spectrometers at four stations along the Arctic circle during
EASOE. The results show that volcanic aerosol from the Pinatubo erupti
on of June 1991 first appeared above the Arctic in September 1991. The
aerosol layer thickened progressively during the autumn and had sprea
d to all four stations, outside in the very low stratosphere, as well
as inside the polar vortex, by mid-January. For the rest of the campai
gn, to mid-March, little further change was seen. The aerosol would ha
ve masked any PSCs that may have occurred at altitudes less than 22 km
. However, PSCs at higher altitudes should have been detected, had the
ir optical thickness exceeded 0.01. Only one was recorded during EASOE
: on 28-29 December 1991, in contrast to their frequent occurrence in
January and early February 1990.