Determinação de regiões homogêneas do Índice de Precipitação Normalizado (SPI) no Estado do Pará por meio da análise multivariada.

Abstract

The spatial and temporal patterns, the homogeneous precipitation regions and Normalized Precipitation Index (SPI) have been determined through the Principal Components Factor analysis (PCA) and Cluster. For this we used monthly data from 72 rain gauge stations distributed in the State of Pará. The first three CPs explained 92.91% of the total variance of monthly data. The technique of cluster ha divided State of Pará into three homogeneous regions of precipitation when applied to the main common factors. The Rh-1 located to north of the state, with rainfall influenced mainly by the north-south movement of the ITCZ, the Rh-2 located to central where the main rain-producing weather are systems location convection and SACZ and the Rh-3 located to south where the rains have influences from frontal systems and systems location convection. Next we determined the SPI in the time scales of 3 and 6 months. The implementation of ACP and Groupings for SPI resulted in three homogeneous regions of SPI-3 and SPI-6. The regions of SPI-3 are Rh-1 (Coastal), Rh-2 (central / north-northwest) and Rh-3 (south). For each homogeneous region of SPI, became the histogram of frequencies for the 9 categories of dry and wet events. The Rh-1 to SPI-3 was classified with 26 and 21 dry and wet events (respectively), the Rh-2, 19 dry events and 29 rainy events and Rh-3 19 dry events and 32 wet events. For SPI-6, the regions were equals though some categories were different of the SPI-3, resuming the Rh-1 showed 15 dry and 10 rainy events, the Rh-2 with 10 dry and 15 rainy events and the Rh-3 with 10 dry and 15 rainy events. The coastal region had showed events drier than wet with minor occurrences for SPI-6. In the other regions (central / north-northwest and south) the situation is reversed, there are more rain events, but with short duration.