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Some considerations on the spectral features of meridional heat transport by transient eddies
Author(s) -
Messori G.,
Czaja A.
Publication year - 2013
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2224
Subject(s) - baroclinity , zonal and meridional , eddy , environmental science , climatology , atmospheric sciences , geology , meteorology , physics , turbulence
The present study analyses extreme events in meridional atmospheric heat transport due to transient eddies in the time–frequency domain. The data used are the European Centre for Medium‐Range Weather Forecasts ( ECMWF ) ERA ‐Interim reanalysis data, at the 850 mb pressure level and with daily, 0.7° latitude and longitude resolution. Fast‐growing atmospheric modes are associated with large heat transport, which would suggest a link between transport extremes and growing baroclinic systems (defined here as motions in the 2.5–6 day band). However, by analyzing wavelet power spectra of transport extremes and of the corresponding meridional velocity and moist static energy temporal anomalies, this is found not to be the case. In fact, baroclinic systems provide only a modest contribution to the integrated power of the extreme heat transport event spectrum. The transport extremes are driven by very precise phase and coherence relationships between the velocity and moist static energy anomalies, acting over a broad range of frequencies (2.5–30 days). Planetary‐scale motions ( k = 0–4) with periods beyond 6 days play a key role in this framework.