Contribuição das chuvas do período da tarde em Belém do Pará para os totais mensais e possíveis relações com a média climatológica.

Abstract

The contributions of afternoon precipitation in Belém and the homogeneous precipitation regions were determined by means of statistical analysis and clustering. We used hourly and monthly data from 25 rainfall stations distributed in the state of Pará. In general, the results showed that afternoon precipitation in Belém contributed an average of 17% of the annual total. The annual cycle of the march showed that the contributions are different for each month of the year. In the less rainy months, this percentage is around 30%. Precipitation rates showed maximum peaks in the local time of 16 hours, influenced directly by the ITCZ, the main mechanism generating rainfall in Belém and LI and local systems. It is suggested that the interannual oscillations of the seasonal precipitation are mainly due to the climatic variability associated to the events of the South Oscillation Index and the Atlantic Dipole. The applied cluster analysis technique divided Pará into three homogeneous regions of precipitation: Group 1 located in the northwest, with rainfall regime influenced mainly by the north-south displacement of the ITCZ; Group 2 is located in the northeastern part of the state where local convection, MLF, LI and ITCZ are the main atmospheric systems that produce rainfall and Group 3 is located in the center-south of the region, where rainfall is subject to frontal influence systems together with local convection and SACZ. Group 2 was analyzed, where the municipalities with similar rainfall were identified with the city of Belém and the hourly data of these stations were analyzed and the results obtained were that Belém has a rainfall regime that differs from other municipalities, being the only municipality to have an increase in rainfall in the afternoon in each month.