Seminário da Física 29/06/2021

Título: Atmospheric Concentric Gravity Waves over Brazil
Palestrante: Prosper K. Nyassor (INPE)

Data: 29/06/2021 às 16 horas via Zoom e via canal do PPGF no YouTube

Resumo: Atmospheric concentric (arc-like, semi-circular/elliptical, or nearly fully circular/elliptical) gravity waves (CGWs) observed using a network of all-sky imagers over Brazil are presented. These CGWs were observed in the OH airglow emission layer from three observation sites: São João do Cariri [7.39°S, 36.53°W], Cachoeira Paulista [22.40°S, 44.59°W], and São Martinho da Serra [29.44°S, 53.82°W]. The observed CGWs have horizontal wavelengths, H ∽ 19 – 80 km, phase speeds, c H ∽ 40 – 110 m/s, and periods, 6 – 13 min, suggesting these waves are small-scale GWs. Because CGWs are excited when a column of rising warm air in a cloud vertically pushes (overshoot) the tropopause into the stratosphere by ∼1–3 km, a possible nearby system of clouds were identified around where the CGWs were observed. It was observed that the centers of the CGWs were close to clouds with very cold tops (clouds top with very cold temperature indicate overshooting). Also, using backward ray tracing, each CGW trajectory was followed back in space and time to the origin of the CGWs. Interestingly, the ray tracing identified the same clouds with cold tops close to the CGW centers to be the origin of the CGWs, which strengthens the result that the CGWs were generated by these clouds.

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