First height comparison of noctilucent clouds
and simultaneous PMSE
On the night of August 9-10, 1991, three rocket payloads were launched
into simultaneously occurring noctilucent clouds (NLC) and polar
mesospheric summer echoes (PMSE) above Esrange, Sweden as part of the
NLC-91 campaign. This success should lay to rest any lingering doubts
that the two phenomena are related to each other. Give this result, a
second aim of this experiment was to compare the vertical structures
and locations of the NLC and PMSE events. To this end, in situ optical
photometers and particle impact sensors were used to measure the
altitude and vertical structure of the NLC layer, while the Cornell
University portable radar interferometer (CUPRI) was used to probe
PMSE. Although this comparison is complicated by the horizontal
separations between the in situ measurements and the radar volume, and
low electron densities which reduced the overall radar reflectitivity,
we conclude that the PMSE layer in the CUPRI radar volume remained
above the NLC layer detected by the in situ instruments by 300 to 1000
m throughout the experiment. We interpret this result as supporting
the view that PMSE are more likely to result from the presence of
aerosols smaller than the ones optically detectable as NLCs.
Send e-mail to gwitt@misu.su.se for a
copy of the complete article.
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