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| Titel |
Scale-dependence of the Space-time Anisotropy of Tropical Rainfall |
| VerfasserIn |
Ram Ratan, Venugopal Vuruputur, Jai Sukhatme, Raghu Murtugudde |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135094
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| Publikation (Nr.) |
 EGU/EGU2016-15901.pdf |
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| Zusammenfassung |
| This work focuses on documenting the multiscale nature of the spatial coherence
of tropical rain, using TRMM satellite-retrieved rainfall observations at multiple
space and time resolutions. We take two different approaches, namely, a global and
local view. The global view attempts to quantify the conventional view of rain, i.e.,
the dominance of the intertropical convergence zone (ITCZ), while the local view
tries to answer the question: if it rains, how far is the influence felt in zonal and
meridional directions? In both approaches, the classical e-folding length for spatial
decorrelation is used as a measure of spatial coherence. The major finding in the global
view approach is that, at short timescales of accumulation (daily to pentad to even
monthly), rain over the Equator shows the most dominant zonal scale. It is only
at larger timescales of accumulation (seasonal or annual) that the dominance of
ITCZ around 7N is evident. The local view shows the expected dominance of the
zonal scale in the tropical ocean convergence zones, with an anisotropy value (ratio
of zonal to meridional scales) of 3-4. Over land, on the other hand, the zonal and
meridional scales are comparable in magnitude, suggesting that rain tends to be
mostly isotropic over continental regions. This latter finding holds true, irrespective
of the spatial and temporal resolutions at which rain is observed. Interestingly,
the anisotropy over ocean, while invariant with spatial resolution, is found to be a
function of temporal resolution: from a value of 3-4 at daily timescale, it decreases to
around 1.5-2 at 3-hourly resolution. We will also present preliminary results from
analysis of very high resolution GPM precipitation (0.1-degree, daily). Finally, we
discuss the ability of a suite of CMIP5 models to reproduce some of these observed
features. |
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