 |
| Titel |
Spectral signatures of Earth's climate variability as observed from space and diagnosed from reanalyses |
| VerfasserIn |
Helen Brindley, Richard Bantges, Jacqueline Russell, Jonathan Murray, John Harries |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110677
|
| Publikation (Nr.) |
 EGU/EGU2015-10704.pdf |
|
|
|
|
|
| Zusammenfassung |
| Measurements of the Earth’s spectrally resolved outgoing longwave radiation have the
intrinsic information content and link to the overall energy budget that implies that they are
ideal candidates to monitor the climate and detect and attribute change. Theoretical studies
have shown how distinct longwave spectral signals from different climate forcing and
feedback mechanisms may be derived and appear to combine with a high degree
of linearity. However, an open, important question which has not yet been fully
addressed concerns the exact level of short-term variability seen in observed longwave
spectra.
We investigate this here by exploiting the emerging radiance record available from the
Infrared Atmospheric Sounding Interferometer (IASI) on the Metop-A satellite. We use
five years of IASI data to assess the level of interannual variability seen in all-sky
spectra at different spatial scales. Maximum variability is seen at the smallest scales
investigated (10Ë Âzonal means) at northern and southern high latitudes across the centre
of the 15Âμm CO2Âband. As spatial scale increases, the overall magnitude of
interannual variability reduces across the spectrum and the spectral shape of the
variability changes. We show that the interannual variability manifested across the
IASI spectra is less than 0.17 K in brightness temperature in the all-sky global
annual mean, collapsing to a value of less than 0.05 K in the atmospheric window, a
spectral region whose variability is dominated by fluctuations in surface and cloud
properties. Spectrally integrating the IASI measurements to create pseudo broadband
and window channels indicates a variation about the mean that is higher for the
broadband than the window channel at the global and quasi-global scale and over the
Southern Hemisphere. These findings are in agreement with observations from
CERESÂTerraÂover the same period and imply that at the largest spatial scales, over
the period considered here, fluctuations in mid-upper tropospheric temperatures
and water vapour, and not cloud or surface temperature, play the dominant role
in determining the level of interannual variability in all-sky outgoing longwave
radiation.
This pattern of behavior is not seen in spectra simulated using reanalysis fields that have
been sub-sampled to match the Metop-A satellite track. Possible reasons for this discrepancy
will be discussed in this paper. |
|
|
|
|
|
|