Análise energética à superfície em casos de linhas de instabilidade na Floresta Amazônica.

Abstract

Squall Lines are mesoscale convective systems that form in tropical and mid-latitudes. They are characterized by cumulonimbus clouds in various stages of development, organized linearly or scattered, and associated with intense convective activity. The Planetary Boundary Layer is part of the troposphere influenced by the Earth's surface, responding in about an hour to heating, cooling, and friction. Its thickness varies from a few dozen meters at night to over 2 kilometers during the day, depending on the location. These factors significantly impact the thermodynamic structure and surface fluxes of the boundary layer, especially in tropical regions such as the Amazon. This study analyzed changes in the planetary boundary layer in six events classified as LIP2 squall lines in central Amazonia between 2014 and 2015, using high-frequency data from the ATTO project and images from the GOES-13 satellite. The analyses indicated relevant variations with reductions of up to 3.8 K in potential temperature and up to 3.0 g/kg in specific humidity after the passage of the systems. Turbulent kinetic energy (TKE) showed extremely variable behavior, with peaks exceeding 30 m²/s² in certain events. Sensible heat fluxes reached values of up to 220 W/m², while latent heat flux reached 525 W/m². The radiation balance exceeded 800 W/m² before the passages, followed by subsequent abrupt drops. In the radiation balance, the shortwave incident component (K↓) experienced reductions of more than 750 W/m² in a matter of minutes, reflecting the intense cloudiness associated with squall lines. Reflected shortwave radiation (K↑) varied around 10% of K↓, highlighting the increase in atmospheric reflectivity during periods of greater cloud cover.