Abstract
We relate the spatial and temporal distribution of lightning flash rates
and cloud top brightness temperature (CTBT) to concentric atmospheric
gravity wave (CGW) events observed at the Southern Space Observatory
(SSO) in Sao Martinho da Serra (29.44 degrees S, 53.82 degrees W, 488.7
m) in southern Brazil. The selected identified cases from 2017 to 2018
were observed by a hydroxyl (OH) all-sky imager. Backward ray tracing
shows that the time of gravity wave excitation agrees with the highest
values of lightning flash rates (indicating lightning jump) as well as
the coldest brightness temperatures that indicate the time of convective
overshoot. Radiosonde measurements show high convective available
potential energy (CAPE), associated with a maximum updraft velocity just
prior to the wave events. We find that these possible source locations
correspond to the positions and times that convective plumes overshot
the tropopause (seen in GOES-16 CTBT images). We also show that higher
spatial lightning density (i.e., number of lightning flashes at a given
longitude and latitude) agree with the overshoot locations from the GOES
satellite. We also find that the overshoot times from the GOES-16
satellite agree with the times lightning jumps were observed in the
lightning flash rate. Finally, we find that the periodicities in the
lightning flash rate agree with the periods of the observed CGWs, which
further strengthens the result that the CGWs were excited by the deep
convective systems determined from backward ray tracing.
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