Padrões Climáticos da Razão de Mistura do Ar em Minas Gerais/Brasil (Weather Patterns of Air Mixing Ratio in Minas Gerais/Brazil)

Padroes espaco-temporais da razao de mistura no estado de Minas Gerais serao definidos neste trabalho. Para isso, foram empregadas as tecnicas multivariadas de Analise de Componentes Principais e de Agrupamentos aos dados mensais de razao de mistura de 39 estacoes climatologicas com 30 anos comuns de observacoes. O emprego da ACP mostrou a existencia de dois padroes dominantes da razao de mistura que explicaram aproximadamente 98% da variância total dos dados. O primeiro, relacionado a maior concentracao de umidade, mostra a atuacao da ZCAS, dos sistemas frontais e influencia orografica. O segundo esta associado ao ASAS. As tres regioes homogeneas de razao de mistura, utilizando o metodo hierarquico de Ward, identificaram bem a sazonalidade dessa componente termodinâmica. Portanto, os resultados obtidos evidenciaram que as chuvas de verao e outono sao influenciadas pelas ZCAS e pelos sistemas frontais. No inverno, esses sistemas enfraquecem e a intensidade das chuvas diminui na regiao. A B S T R A C T Space-time standards of mixing ratio in the state of Minas Gerais will be defined in this work. For this, we used multivariate techniques of Principal Component Analysis and Cluster Analysis to monthly data of mixing ratio of 39 weather stations with 30 years of common observations. The use of PCA showed the existence of two dominant patterns of mixing ratio that accounted for approximately 98% of the total variance. The first, related to higher moisture concentration, shows the performance of the SACZ, of the frontal systems and orographic influence. The second is associated with Subtropical Anticyclone of the South Atlantic (SASA). The three homogeneous regions of mixing ratio, using the hierarchical method of Ward, identified seasonality of this thermodynamic component. Therefore, the results showed that the summer rains and autumn are influenced by SACZ and the frontal systems. In winter, these systems weaken and the intensity of rainfall decreases in the region. Keywords: multivariate techniques, weather systems and climate variability.