Abstract The relationships among humidity, air temperature, wind, and vertical velocity with formation and propagation of Amazonian squall lines (ASL) is analyzed in this study. One year of data (2005) is verified by counting ASL cases according to their classification (propagated and non-propagated) to understand more clearly how the variation of these variables over this year influences their environment of formation. The results show an increase in humidity on days with ASL, with the highest occurrence during the wettest months. Furthermore, system propagation toward the interior of continent seems to be strongly related to the moisture content that reaches the coast, through the winds that blow from the ocean from both by the Northeast Trade Winds, of the North Atlantic Subtropical High, and by the Southeast Trade Winds, of the South Atlantic Subtropical High. Higher moisture content from the sea corresponds to a higher wind intensity toward the coast. A relationship between continent/ocean temperature gradient and the ASL amount and types formed is also demonstrated. Such information is extremely relevant because of the great importance of these systems in the extreme north and northeast regions of Brazil, particularly at the Amazon, given the difficulty of predicting them due to their complexity.

Neste artigo investiga-se numericamente a interação entre brisas marítima-terrestre e de vale-montanha, que ocorrem no nordeste brasileiro devido à presença do Planalto da Borborema, aplicando o trabalho de expansão associado ao ramo inferior das circulações. Resultados da teoria da máquina térmica são comparados aos resultados 3D, obtidos com a versão brasileira do modelo RAMS. Os resultados indicaram que o efeito do contraste de temperatura no trabalho ligado às circulações (Wa), isoladamente, contribui para a formação de brisas marítimas mais intensas e de brisas terrestres menos intensas. Na realidade, o que se observa são brisas terrestres com intensidades iguais ou até maiores que das brisas marítimas. Assim, a contribuição da montanha para a intensidade das circulações de brisa no período noturno mostra-se extremamente não-linear. O trabalho de expansão que realmente está ligado às circulações, contribui em apenas 7% para o trabalho total. Dessa forma, a maior parte do trabalho total está associada ao trabalho de compressão que a atmosfera realiza para compensar a perda por resfriamento radiativo, e muito da energia disponibilizada para as circulações é gasta para vencer os processos dissipativos.

The purpose of this work is to further understand the interactions between sea-land breeze and valley-mountain breeze that occur at the coast of Northeast Brazil due to the presence of the Borborema plateau, using the associated expansion work at the lower branch of these circulations. Results of the thermal machine theory are compared to the 3D results obtained from the Brazilian RAMS model version. The results indicate that the sole effect of temperature contrast on the work associated with circulations (Wa) is more intense sea breezes and weaker land breezes. Actually, one can observe land breezes whose intensities are equal or even larger than sea breezes. Thus, the mountain contribution for the intensity of the breeze circulations in the nighttime is extremely non-linear. The expansion work that is actually associated with these circulations contributes only with 7% for the total work. Consequently, the larger part of the total work is associated with the compression work performed by the atmosphere in order to compensate long-wave cooling and much of the energy available for the circulations is consumed to overcome dissipation.