Abstract
The Onset and Demise of the rainy season (ONR and DER, respectively) are found in Minas Gerais (MG) for the 1998-2012 period with two methodologies: one using daily rainfall data and another that using daily data of antisymmetric equatorially outgoing longwave radiation (AOLR). The ONR (DER) is indicated by a sign change from positive-negative (negative-positive) of the AOLR spatial averages, as in Garcia and Kayano (2009GARCIA, S. R.; KAYANO, M. T. Determination of the onset dates of the rainy season in Central Amazon with equatorially antisymmetric outgoing longwave radiation. Theoretical and Applied Climatology, v. 97, p. 361-372, 2009.; 2013GARCIA, S. R.; KAYANO, M. T. Some considerations on onset dates of the rainy season in Western-Central Brazil with antisymmetric outgoing longwave radiation relative to the equator. International Journal of Climatology, v. 33, p. 188-198, 2013.), whereas for the Liebmann et al. (2007)LIEBMANN, B.; CAMARGO, S. J.; SETH, A.; MARENGO, J. A. et al. Onset and end of the rainy season in South America in observations and the ECHAM 4.5 atmospheric general circulation model. Journal of Climate, n. 20, p. 2037–2050, 2007. method that date is determined by the minimum (maximum) of the anomalous accumulation of daily precipitation. For comparison, the daily precipitation series in the region are also analyzed. The ONR dates found by both methods are closer to each other compared to the DER, which has greater variability in both methods. Both methods detect the ONR and DER dates in MG with quality and the main differences between them are discussed in the text. It is worth noting that the Garcia and Kayano (2009GARCIA, S. R.; KAYANO, M. T. Determination of the onset dates of the rainy season in Central Amazon with equatorially antisymmetric outgoing longwave radiation. Theoretical and Applied Climatology, v. 97, p. 361-372, 2009.; 2013GARCIA, S. R.; KAYANO, M. T. Some considerations on onset dates of the rainy season in Western-Central Brazil with antisymmetric outgoing longwave radiation relative to the equator. International Journal of Climatology, v. 33, p. 188-198, 2013.) method is relatively more advantageous when compared to the method of Liebmann et al. (2007)LIEBMANN, B.; CAMARGO, S. J.; SETH, A.; MARENGO, J. A. et al. Onset and end of the rainy season in South America in observations and the ECHAM 4.5 atmospheric general circulation model. Journal of Climate, n. 20, p. 2037–2050, 2007., because it depends solely on the OLR data, which are available on near real-time basis, different of the indices based on precipitation; and also to be independent of the analyzed period, which is characteristic of the Liebmann et al. (2007)LIEBMANN, B.; CAMARGO, S. J.; SETH, A.; MARENGO, J. A. et al. Onset and end of the rainy season in South America in observations and the ECHAM 4.5 atmospheric general circulation model. Journal of Climate, n. 20, p. 2037–2050, 2007. method.
Keywords:
precipitation; monsoon; outgoing longwave radiation; southeast of Brazil
