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Mudancas climaticas e ambientais do ciclo hidrologico da America do Sul sao amplamente investigadas, mas ainda existem indagacoes devido a complexidade do ciclo. Para identificar padroes espaco-temporais dessas mudancas analisou-se a variabilidade climatica da precipitacao, em 32 estacoes meteorologicas, e da razao isotopica do oxigenio dezoito (δ 18 O) do testemunho de gelo do Nevado Illimani-Bolivia, entre 1929-1998. Calcularam-se as anomalias da precipitacao, que sao obtidas pela subtracao da media mensal das amostras. As series foram divididas em dois periodos, antes e depois de 1970, pois e nessa decada que o clima global apresenta uma ruptura no balanco termico. Para as analises utilizou-se estatistica descritiva e inferencial. As medias mensais da precipitacao tropical podem variar entre ~50 mm e ~450 mm, mas as anomalias podem atingir 100% dessas magnitudes. O desvio padrao evidencia um aumento do mesmo apos 1970 (em 84% das estacoes), existindo uma menor certeza de ocorrencia do padrao sazonal das chuvas. Ja os dados paleoclimaticos evidenciam maior amplitude de variacao do δ 18 O apos 1970, sendo relacionado as maiores variacoes do processo de evaporacao e precipitacao da agua sobre o continente. As linhas de tendencia evidenciaram um aumento das chuvas entre 1929-1998 em 81% das estacoes, principalmente as que se localizam sobre as zonas de convergencia tropical. Ja nas bordas dessas zonas observam-se tendencias negativas da precipitacao. A variabilidade climatica na regiao tropical do continente pode estar associada a fatores remotos e locais como, o aumento da temperatura global e a mudanca no uso do solo (savanizacao da Amazonia).  A B S T R A C T Climate changes and hydrological cycle variability of South America have been widely researched, but there are still affairs owing the complexity of the cycle and relationship between biosphere, lithosphere and atmosphere. Wherefore, the climatic variability of precipitation (1929-1998) observed in 32 meteorological stations and the ratio of stable isotopes oxygen-18 (δ 18 O) of the Nevado Illimani-Bolivia, are analyzed to identification spatial-temporal patterns of climate change. The precipitation anomalies were calculated, with subtraction of the monthly mean of samples. The time series analysis was divided in two periods, before and after 1970´s, because this decade exhibit global thermal balance rupture and used descriptive statistics (mean and standard deviation) and inferential statistics (linear regression) to quantify the precipitations variability. The tropical precipitation monthly varies between ~ 50 mm and ~ 450 mm, and the anomalies can attain 100% of these magnitudes, but after 1970´s increase uncertainty of rainfall seasonal pattern occurrence (in 84% of the meteorological stations). The paleoclimatic data evidenced lager variations evaporation-precipitation process on America South Continent because the more amplitude of δ 18 O variation after 1970. The trend line analysis show an increase in rainfall on convergence tropical zones between 1929 and 1998 (81% of the meteorological stations) and decrease in precipitations on zones convergence periphery. The tropical precipitations variability on South America can be associated the remote and local factors, for example, global warning and land use change (Amazonian savannization process). Keyword: climate; water, ice core.

revista brasileira de geografia física

Análise dos Registros Históricos e Paleoclimáticos da Variabilidade da Precipitação na Região Tropical da América do Sul (Historical and Paleoclimatic Register Analysis of Precipitation Variability in the South American Region)