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| Titel |
The low frequency variability of CAPE and CIN, and the interpretation of its forcing mechanisms |
| VerfasserIn |
K. Riemann-Campe, K. Fraedrich, R. Blender |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023794
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| Zusammenfassung |
| CAPE (Convective Available Potential Energy) is a promising parameter to determine the
variability of convective precipitation. The potential occurrence of convection is
restricted by CIN (Convective INhibition), which is determined in the lower boundary
layer. CAPE and CIN are based on the vertical profiles of temperature and specific
humidity. We compare daily high resolution ERA-40 reanalysis data (T106) with
general circulation models: ECHAM5/MPI-OM (T63), Planet Simulator (T42 and
T21).
The variability is determined on intra-annual and inter-annual (low frequency variability)
time scales using the Detrended Fluctuation Analysis (DFA), spectral and correlation
analyses. The global memory properties of CAPE and CIN are attributed to the contributions
of temperature and specific humidity. The memory increases towards the tropics where it
reaches nonstationary 1-f scaling in all ocean basins on time scales extending from days to
several years.
The variability of CAPE, CIN, and convective precipitation is interpreted in terms of
Hoskings infinite memory fractionally differenced processes (FD) characterised by the Hurst
exponent, which is obtained by DFA. The FD processes describe the observed scaling
behaviour of the low frequency variability as an amplification of a presumed white
noise forcing. Our results suggest that the high frequency forcing is located in the
tropics aligned along the ITCZ with a double ITCZ structure in the Indian Ocean. |
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