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| Titel |
The UTLS ENSO signal from high resolution GPS radio occultation temperature profiles |
| VerfasserIn |
Barbara Scherllin-Pirscher, Clara Deser, Shu-Peng Ho, Chia Chou, William Randel, Ying-Hwa Kuo |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082208
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| Zusammenfassung |
| We investigate the vertical and spatial structure of the El Niño-Southern Oscillation
(ENSO) signal in the troposphere and lower stratosphere using radio occultation (RO)
temperature profiles. The unprecedented vertical resolution and global coverage of the
RO data do not only provide a detailed view of the full three dimensional ENSO
structure they also enable studying dynamical coupling between the troposphere and
lower stratosphere. Due to the strong confounding effects of the Quasi Biennial
Oscillation (QBO) and ENSO in the short RO record we only use RO data below
20Â km.
In the equatorial region we find that interannual temperature anomalies show a natural
decomposition into zonal-mean and eddy (deviations from the zonal-mean) components.
Both components are related to ENSO. In the tropical troposphere zonal-mean temperature
increases with height and reaches a maximum between 8Â km and 12Â km. Above the
tropopause, the warm phase of ENSO is associated with stratospheric cooling. This
zonal-mean response lags sea surface temperature anomalies in the eastern equatorial Pacific
(N3.4 region) by 3Â months. This lag can be attributed to exchange of fluxes at
the atmosphere-ocean interface and the atmospheric energy loss to space and to
mid-latitudes.
The eddy component, in contrast, responds rapidly (within 1 month) to ENSO forcing.
The corresponding pattern features a dipole between the Indian and Pacific Oceans at low
latitudes, with off-equatorial maxima centered around 20° to 30° latitude in both
hemispheres. Maximum amplitude of this signal in the troposphere occurs near 11Â km and
(with opposite polarity) in a shallow layer near the tropopause at approximately 17Â km. At
mid latitudes, the eddy ENSO signal tends to be out-of-phase with those at low latitudes in
both the troposphere and lower stratosphere. The fast eddy ENSO response as well as its
spatial pattern are consistent with Rossby and Kelvin wave circulations induced
by equatorial heating anomalies. Overall, this study underpins the high utility of
GPS RO data for studying atmospheric dynamics in the troposphere and lower
stratosphere. |
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