RESUMOO objetivo desta pesquisa foi verificar a importância dos fatores termodinâmicos na ocorrência de eventos extremos de precipitação em Belém (PA) e região metropolitana, no período de agosto de 2008 a dezembro de 2009. O estudo da termodinâmica da atmosfera foi realizado a luz das teorias da Energia Potencial Disponível para a Convecção (CAPE) e, da Energia de Inibição da Convecção (CINE). Para classificar os eventos extremos de precipitação foi utilizado o método dos decis, a fim de associá-los aos valores da CAPE e da CINE. Observou-se que a região estudada possui forte atividade convectiva durante todo o ano, e que nem sempre CAPE alta e CINE baixa produz precipitação. Esta situação determina convecção profunda, mas para haver precipitação existe a necessidade da forçante dinâmica, inclusive para a ocorrência de eventos extremos de precipitação no período chuvoso a forçante dinâmica é a ITCZ, e no período seco o que contribui é a Linha de Instabilidade (LI). Então quando o processo de precipitação dependeu, exclusivamente, da CAPE, foi necessário um valor alto para gerar convecção profunda e por consequência precipitação, enquanto, que no processo de precipitação com contribuição dinâmica não foi necessário um valor tão significativo da CAPE. Palavras-chave: CAPE, CINE, Precipitação, eventos extremos. ABSTRACT: IMPORTANCE OF THERMODYNAMIC CONDITIONS DURING EXTREME PRECIPITATION EVENTS OVER BELÉM CITY AND METROPOLITAN REGIONThe purpose of this research was to verify the importance of thermodynamic factors on the occurrence of extreme precipitation events in the city of Belém (PA) and its metropolitan area, during the period of August 2008 to December 2009. The study of the atmosphere thermodynamics was based on the theories of Convective Available Potential Energy (CAPE) and Convective Inhibition Energy (CINE). To classify the extreme precipitation events the decis method was used in order to associate them to the CAPE and CINE values. It was verified that the studied region has strong convective activity during all the year, and that not always high CAPE and low CINE determine precipitation. Those situations in fact determine profound convection, but to ensure precipitation, dynamic enforcement is required. For the occurrence of extreme precipitation events during the rainy season the ITCZ is the forcing dynamic and during the dry season the squall lines contribute to them. Then when the precipitation process is exclusively CAPE dependent, a high CAPE value is required in order to generate deep convection and, consequently, precipitation. Otherwise, for dynamic contribution precipitating process a significant value of CAPE is not needed.

The objective of this research was to verify the importance of thermodynamic factors in the occurrence of extreme precipitation events in Belém (PA) and metropolitan region, from August 2008 to December 2009. The study of the thermodynamics of the atmosphere was carried out in the light of theories of the Potential Available Energy for Convection (CAPE) and Convection Inhibition Energy (ISCED). In order to classify the extreme precipitation events, the decision method was used to associate them with the CAPE and the ISCED values. It was observed that the studied region has strong convective activity throughout the year, and that not always high CAPE and low ISCED produces precipitation. This situation determines deep convection, but to have precipitation there is a need for the dynamic forcing, even for the occurrence of extreme rainfall events in the rainy period, the dynamic forcing is ITCZ, and in the dry period what contributes is the Instability Line (LI). So when the precipitation process depended exclusively on the CAPE, it was necessary a high value to generate deep convection and consequently precipitation, whereas, in the process of precipitation with dynamic contribution, a significant value of CAPE was not necessary.