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| Titel |
Statistical Study of Concentric Gravity Waves in the Mesopause by using the IMAP/VISI Data |
| VerfasserIn |
Septi Perwitasari, Takeshi Sakanoi, Yuichi Otsuka, Atsushi Yamazaki, Yasunobu Miyoshi, Yuta Hozumi, Yusuke Akiya, Akinori Saito |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109323
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| Publikation (Nr.) |
 EGU/EGU2015-9226.pdf |
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| Zusammenfassung |
| Concentric gravity waves (CGWs) have been intensively studied in the past few
years because of its unique characteristic that shows the direct coupling between
lower and upper atmosphere. The past studies, both by using the ground-based and
space-based observations, have revealed the general properties of these CGWs, such as;
source and effect of the background profile. However, they were mostly a single
event studies and gave only limited information locally. Therefore, a statistical
study on global distribution of the CGWs is needed to get more comprehensive
understanding. To address this issue, a space-based observation is more preferable since it
covers wider area. Until recently, IMAP/VISI is the only space-based instrument that
capable of imaging gravity waves above in the MLT region in the nadir direction.
The Visible and near-Infrared Spectral Imager (VISI) of the IMAP mission was
launched successfully on July 21, 2012 with H-IIB/HTV-3 and installed onto the
International Space Station (ISS). IMAP/VISI is now operated in the night side
hemisphere with a range of +/- 51 deg. GLAT. IMAP/VISI is measuring three airglow
emissions of OI (630 nm), OH Meinel (730 nm) and O2 (762 nm) with the typical
spatial resolution of 16 – 50 km in the nadir direction. Since the start of nominal
operation in October 2012, IMAP/VISI has been operated with approximately 15
paths/day.
In this study, we analyze the CGWs events from IMAP/VISI data of 2013. We found total
172 CGWs events in the O2(762nm) airglow emissions out of 4853 data paths. The monthly
distribution of the CGWs occurrence shows a clear seasonal dependence with the peak
around March-April and August-September. The weak background winds in the middle
atmosphere during the March and September equinox are likely responsible for the seasonal
dependence. We determined the source of CGWs by estimating the center of the circular
pattern. In the northern hemisphere, the sources were mostly found to be convective
activity (convective plum, tropical storm and typhoon), which was identified from the
meteorological satellite data. In the southern hemisphere, the high occurrence region is
co-located with the jet streams flow region. Therefore, we suspect that the source
in the southern hemisphere is likely related with the jet stream activity. We have
calculated the wave parameters for two months (March and April) and found that
the small-scale waves (horizontal wavelength |
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