scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Statistics on coexisting large scale oscillations in the middle atmosphere and ionosphere
Borries Claudia
German Aerospace Center (DLR)
Signatures of planetary wave type oscillations (PWTO), with periods between 2 and 30 days
and wavelengths exceeding 10.000km, can be observed in the ionosphere. While up to 50% of
these PWTO can be allocated to variations in the solar radiation, others are supposed to be
forced by waves from below.
Hourly maps of the total electron content (TEC), covering the northern hemisphere from 50°N
to the North Pole, are used to analyse and describe PWTO in the ionosphere. Those PWTO
probably forced by solar variations can be reduced by applying a filter method based on the
wavelet transform. This paper presents statistics on the number of PWTO observed in the
filtered TEC, classified by period ranges and wavenumber in midlatitudes during 2002 to
2008. Additionally statistics on the coexistence of PWTO found in the filtered TEC and
planetary waves observed in NCEP stratospheric reanalyses are presented. It is found that
about one third of the observed PWTO occurs at about the same time as planetary waves in
the middle atmosphere. But, significance tests reveal that only few of the PWTO classes reach
a 95% significant number of coexisting waves. Thus, statistical analyses can give hints but no
evidence for atmosphere-ionosphere-coupling by planetary waves. Instead, case studies are
suggested for further analyses.