Climate proxy events´ patterns and the rainfall variability over the Brazilian Amazon

Although the correlation between precipitation in the Brazilian Amazon and sea surface temperatures (SST) over the Pacific and Atlantic has been documented since the early twentieth century, the impact of each ocean variability on the frequency and intensity of the wet/dry season over Brazilian Amazon and the underlying mechanisms have remained unclear. The mechanisms of climate anomalies in the Amazon basin were explored from surface climatological time series. Interannual variability of seasonal rainfall in the Brazilian Amazon is examined in context of its relationship to El-Niño Southern Oscillation (ENSO), low frequency phenomena such as the Pacific Decadal Oscillation (PDO) and phases of the North Atlantic Oscillation (NAO). The regional rainfall has been related to high-frequency atmospheric phenomena, such as El Niño and La Niña events, of a statistically significant precipitation anomaly patterns. Non-linear correlations (response) reveal strong relationships, but rainfall patterns are of regional scale. Areas of rainfall exhibiting strong relationships with SST are confined to the equatorial region of the Brazilian Amazon. The best relationships are found either during the season of transition between wet and dry regimes, or entirely within the dry season. It is hypothesized, and results are shown in support, that during the transition seasons, an important contributor to the SST control on seasonal totals is its influence on the timing on the rainy season onset or end. That influence appears to be stronger than the SST influence on the rainy season. The analysis of Rainfall variability and sensitivity related to decadal and long-term anomaly patterns of rainfall has been carried out. Negative rainfall trends were identified for the entire Amazon basin, while at the regional level there is a negative trend in northern Amazonia and positive trend in southern Amazonia. Decadal time scale variations in rainfall have been discovered, with periods of relatively drier and wetter conditions, with different behaviour in northern and southern Amazonia. Spectral analyses show decadal time scale variations in southern Amazonia, while northern Amazonia exhibits both interannual and decadal scale variations. Shifts in the rainfall regime in both sections of the Amazon basin were identified and changes in the circulation and oceanic fields suggest an important function of the warming of the tropical central and eastern Pacific on the decreasing rainfall in northern Amazonia, due to more frequent and intense El Niño events during the relatively dry period. A complementary application was carried out correlating the rainfall database with the NCEP Reanalysis dataset. Scenarios for rainy station were considered consequence of located storms and they are associated with the Intertropical Convergence Zone (ITCZ) and its seasonal migration. Preliminary results of this research indicate that the precipitation over the Amazon Basin presents interanual variability associated to the ENSO phenomenon, with periodicity of about 20-25 years in frequency of subtropical highs, probably associated to the PDO. Besides, we have found strong anti-correlation, of about 60%, between the Outgoing Long-Wave Radiation (OLR) and annual cycle of precipitation amount over the region. There is an apparent association between SST anomalies in the tropical Atlantic and Pacific and the pentads of onset and end of the rainy season in the northern and central Amazon.Pages: 1545-155

Comparaçao de dados climatológicos modelados e observados utilizando a técnica dos quantis

Ponencia presentada en: XXVIII Jornadas Científicas de la AME y V Encuentro Hispano-Luso de Meteorología celebrado en Badajoz, del 11 al 13 de febrero de 2004.[PT]A técnica dos quantis foi utilizada na comparação de duas séries de dados de precipitação, uma climatológica modelada (Global Historical Climatology Network - GHCN) e outra incompleta, com dados observados (EMBRAPA). A série climatológica abrange um período de 50 anos e a série incompleta abrange o período entre 1973 e 1997. Através da técnica dos quantís pode ser observado que ambas as séries tendem para a normal climatológica da região, mesmo que os dados se apresentem modelados e que a série seja incompleta. Isto significa que ambas as séries provam o teorema fundamental da probabilidade, ou seja, obedecem a lei dos grandes números. A Lei dos Grandes números é um teorema que prova a probabilidade do modelo matemático, mostrando que ele é consistente com a interpretação da frequência de probabilidade.[en]The quantile technique was used to compare two precipitation datasets series, one climatological produced by Global Historical Climatology Network (GHCN) and other incomplete, with dataset observed (EMBRAPA). The climatological series embraces a 50 years period and the incomplete series embraces the period between 1973 and 1997. Through the quantile technique can be observed that both series trends to the normal climatological value to this area, even that the datasets presents modeled and the series is incomplete. This means that both series prove the fundamental theorem of the probability, they obey the law of the great numbers. The Law of Large Numbers, which is a theorem proved about the mathematical model of probability, shows that this model is consistent with the frequency interpretation of probability

Efeito do dia de ocupação sobre a produção leiteira de vacas mestiças em pastejo rotacionado de forrageiras tropicais

O trabalho foi conduzido para se observar as flutuações na produção leiteira de vacas mestiças em sistema de pastejo rotacionado de capim-elefante cv. Guaçu (Pennisetum purpureum Schum.) e capim-tanzânia (Panicum maximum Jacq.), de acordo com períodos de ocupação (dois dias de ocupação e 40 de descanso e três dias de ocupação e 33 de descanso, respectivamente), adubados com 200 kg de N/ha/ano. Foram estudados 19 piquetes de capim-elefante e 15 de capim-tanzânia. A análise estatística foi realizada considerando-se fase de lactação das vacas, piquete e dia de ocupação. Para o capim-elefante houve efeito da fase da lactação com interação com o dia de ocupação, mas não houve diferença para o dia de ocupação. As médias foram 10,3 ± 3,3 e 10,4 ± 3,2 kg de leite/vaca/dia para o 1º e 2º dia de ocupação, respectivamente. Para o capim-tanzânia, houve diferença significativa na produção de leite, conforme o dia de ocupação, e interação significativa para piquete e dia de ocupação. As médias foram 10,6 ± 3,0; 11,0 ± 3,1; 10,6 ± 3,2 kg de leite/vaca/dia, respectivamente, para o primeiro, segundo e terceiro dias de ocupação.The study was carried out to observe the fluctuation of milk yield of crossbred cows in two rotational grazing systems of elephant grass cv. Guaçu (Pennisetum purpureum Schum and Tanzaniagrass (Panicum maximum Jacq.), according of period of occupation (2 days of occupation with 40 days resting and 3 days of occupation with 33 days resting, respectively), fertilized with 200 kg of N/ha/year. Nineteen paddocks of elephantgrass and 15 of Tanzaniagrass were studied. The statistical analysis was performed considering lactation phase of cows, paddocks and days of occupation. For elephantgrass there was an interaction effect of lactation phase and days of occupation, but no difference was observed for days of occupation. Averages of daily milk yield were 10.3 ± 3.3 and 10.4 ± 3.2 kg/day for 1st and 2nd of days of occupation, respectively. For Tanzaniagrass there was a significant effect for milk yield, according to days of occupation and for interaction of paddocks and days of occupation. The averages of daily milk yield were 10.6 ± 3.0; 11.0 ± 3.1; 10.6± 3.16 kg/cow/day for 1st, 2nd and 3rd days of occupation, respectively