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Latitudinal height couplings between single tropopause and 500 and 100 hPa within the Southern Hemisphere
Author(s) -
Yuchechen Adrián E.,
Bischoff Susana A.,
Canziani Pablo O.
Publication year - 2009
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.1914
Subject(s) - tropopause , empirical orthogonal functions , radiosonde , climatology , troposphere , depth sounding , stratosphere , quasi biennial oscillation , geopotential height , environmental science , lapse rate , diabatic , northern hemisphere , latitude , middle latitudes , atmospheric sciences , extratropical cyclone , southern hemisphere , geology , meteorology , geography , precipitation , physics , oceanography , geodesy , adiabatic process , thermodynamics
In order to provide further insights into the relationships between the tropopause and different mandatory levels, this paper discusses the coupling between standardized tropopause height anomalies (STHAs) and standardized 500‐hPa and 100‐hPa height anomalies (S5HAs and S1HAs, respectively) within the ‘climatic year’ for three sets of upper‐air stations located approximately along 20°S, 30°S and 45°S. Data used in this research consists in a radiosonde database spanning the period 1973–2007. The mandatory levels are supposed to be included in each radiosonde profile. The tropopause, on the other hand, is calculated from the significant levels available for each sounding using the lapse rate definition. After applying a selection procedure, a basic statistical analysis combined with Fourier analysis is carried out in order to build up the standardized variables. Empirical orthogonal functions (EOFs) in S‐mode are used to get the normal modes of oscillation as well as their time evolution, for STHA/S5HA as well as for STHA/S1HA coupling, separately, within the aforementioned latitudes. Overall, there are definite cycles in the time evolution associated with each EOF structure at all three latitudes, the semi‐annual wave playing the most important role in most of the cases. Nevertheless, 20°S seems to be the only latitude driven by diabatic heating cycles in the middle atmosphere. Certainly, EOF1 at this latitude has a semi‐annual behaviour and seems to be strongly influenced by the tropical convection seasonality. Apparently, the convectively driven release of latent heat in the middle troposphere affects the time evolution of the EOF1 structure. By contrast, the vertical propagation of planetary waves is raised as a possible explanation for the EOF1 and EOF2 behaviour at latitudes beyond 20°S, in view of the close connection existent between the semi‐annual oscillation (SAO) and the reversion in the direction of the zonal wind. Copyright © 2009 Royal Meteorological Society