Interannual variability of total and zonally asymmetric atmospheric fields / Variabilidade interanual de campos atmosféricos totais e zonalmente assimétricos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

Interannual variability of total and zonally asymmetric atmospheric fields is studied through analyses of variances and Empirical Orthogonal Function (EOF) patterns as well as using correlation maps between principal component time series and filtered anomalous time series of some variables for DJF and JJA periods. The period of study spans from 1979 to 1995. The domain of the study covers all longitudes but it is latitudinally limitated by the parallels 80oS and 80oN. Variance analyses (total, interannual and their ratios) were done for the total sea level pressure (SLP), zonal wind at 200 hPa, geopotential height at 500 hPa, vertical velocity in pressure coordinates at 500 hPa, outgoing longwave radiation (OLR) and temperature at 925 hPa and for asymmetric geopotential height at 500 hPa. These analyses suggest that the high variability in the tropics is related to El Niño-Southern Oscillation (ENSO) cycle. Seasonality is evident in the variance patterns for all variables, with the highest variability in middle and high latitudes of the winter hemisphere, except for OLR and vertical velocity. For these two variables, highest variability was seen in the tropics and during the austral summer. The first mode of the SLP shows a wavenumber one pattern in the tropical and extratropical regions, which describes features consistent with the extremes in the Southern Oscillation (SO). The correlation patterns for the other variables show seasonal differences possibly related to the periods when the extremes in the SO occur. The most important features are related to wave train pattern found for the total and asymmetric correlation fields of zonal wind at 200 hPa and geopotential height at 500 hPa. In DJF, the asymmetric of these variables show a wave train pattern in Atlantic/Africa region. In JJA wave pattern for asymmetric zonal wind at 200 hPa in the South Pacific is observed. The distinct features of the atmospheric patterns of asymmetric and total fields of zonal wind at 200 hPa and geopotential height at 500 hPa, suggest that possibly the asymmetric part of these variables plays an important role in the interactions of extratropical and tropical circulations.

ASSUNTO(S)

oscilação sul circulação assimétrica variação anual américa do sul atmospheric circulation annual variation el niño funções ortogonais

ACESSO AO ARTIGO

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