%0 Journal Article
%4 sid.inpe.br/mtc-m21b/2017/05.22.18.57
%2 sid.inpe.br/mtc-m21b/2017/05.22.18.57.54
%@doi 10.1002/2016JA023638
%@issn 2169-9402
%T Strong temperature gradients and vertical wind shear on MLT region associated to instability source at 23°S
%D 2017
%8 Apr.
%9 journal article
%A Andrioli, Vânia Fátima,
%A Batista, Paulo Prado,
%A Xu, Jiyao,
%A Yang, Guotao,
%A Chi, Wang,
%A Zhengkuan, Liu,
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Chinese Academy of Sciences
%@affiliation Chinese Academy of Sciences
%@affiliation Chinese Academy of Sciences
%@affiliation Chinese Academy of Sciences
%@electronicmailaddress vania.andrioli@inpe.br
%@electronicmailaddress paulo.batista@inpe.br
%B Journal of Geophysical Research: Space Physics
%V 122
%N 4
%P 4500-4511
%K convective instability, dynamical instability, mesopause instabilities, meteor radar wind, Na lidar temperature.
%X Na lidar temperature measurements were taken successfully from 2007 to 2009 in the mesopause region over São José dos Campos (23.1°S, 45.9°W). Strong gradients on these vertical temperature profiles are often observed. A simple theoretical study has shown that temperature gradient of at least −8 K/km is required concurrently with the typical tidal wind shear in order to generate dynamical instability in the MLT region. We have studied vertical shear in horizontal wind related to atmospheric tides, inferred by meteor radar, with the aim of analyzing instability occurrence. These wind measurements were taken from an all-sky meteor radar at Cachoeira Paulista (22.7°S, 45°W). Two years of simultaneous data, wind and temperature, were used in this analysis which represent 79 days, totalizing 589 h of simultaneous observations. We realize that the condition for the local Richardson number (Ri) dropping below the critical value of instability (Ri < 0.25) is often reached in 98% of the analyzed cases. The mean probabilities for occurrence of convective and dynamical instabilities, in the altitude region between 82 and 98 km, were observed to be about 3% and 17.5%, respectively. Additionally, vertical distribution of these probabilities has revealed a weak occurrence of dynamical instability around 90 km, and this fact can be related to the double mesopause typically observed in this site.
%@language en
%3 andrioli_strong.pdf