The objective of this study was to analyze the frequency of severe precipitation (PRP) to verify the impacts caused by severe precipitation in the city and population of Belém-Pará, Brazil, in the 30-year period between 1984 and 2013. For that, it was identified the possibility of occurrence of humidity convection through a Convective Available Potential Energy (CAPE) analysis. We used data from of DTCEA's radiosonde; analysis of the frequency of the precipitation (PRP), and occurrence of extreme precipitation events (EEPRP), precipitation measurements from the INMET’s stations. IBGE's demographic census, in the period of 1980 the 2010; and news articles from the main city's newspapers (between 1984 and 2013), and ready to overflow detected by the Civil Defense in Pará (PADCP). The CAPE is analyzed by reference values, which have associated conditions, and ranges in this study: a) CAPE less than 1000 J / kg, b) CAPE greater than or equal to 2500 and less than 1000 J / kg C) CAPE greater than or equal to 2500 and less than 4000 J / kg d) CAPE greater than or equal to 4000 J / kg, respectively CAPE were classifications 1, 2, 3 and 4. Growth trends (T) in the PRP and the EEPRP were observe, which were associates to the larger frequency of La Niña events. We observed that the local atmosphere presented favorable conditions for the development of deep humidity convection, as CAPE values higher than 1000 J/Kg (the limit for convective cloud formation), were the most frequent, being 65% of all radiosonde measurements. CAPE 2 and 3 classifications presented significant growth tendencies across the years, whereas CAPE 1 and 4 showed reduction. This is probably due to the increased of air temperature at the site, which has an impact on CAPE values. The results also did show the existence of a positive trend and correlation between population growth and increase of PRP, i.e., greater number of people are being affected, mainly due to the occurrence of EEPRP and PRP. The main problem facing the city and society quantified through the NJL, are overflow. The most susceptible neighborhoods to increased PRP and EEPRP were often NJL and detected by PADCP are: Agulha, Cremação, Guamá, Jurunas, Cidade Velha, Campina, Reduto, Marco, Pedreira, Canudos, Terra Firme, Curió Utinga e Fátima. It was observed that the overflows are not restricted to social classes with lower purchasing power, that because the city has deficiency and inefficiency of urban infrastructure, as well as a precarious sewage and draining systems.
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