Um estudo das ondas de gravidade estratosféricas na região equatorial brasileira

Abstract

Gravity waves can be defined as undulating, almost periodic perturbations that propagate horizontally and vertically in the atmosphere. The mechanisms of gravity wave generation in regions near to the magnetic equator are little known, making it difficult to study their characteristics to structures mainly in the stratosphere. The main objective of this work was to investigate the seasonality of these disturbances and the sources of generation of these waves in our region. These studies are based on the signature of gravity waves in temperature profile data obtained from radiosonders installed in meteorological balloons launched from the Centro de Lançamentos da Barreira do Inferno (CLBI), located in Natal/RN (5,8° S; 35.5° W), we completed the data obtainedthrough the website http://weather.uwyo.edu/upperair/sounding.html, which provides survey data from both the northern hemisphere and the southern hemisphere. The experimental data were compared with the theoretical data generated from the semi-empirical model MSIS that does not take into account the presence of these waves in the atmosphere, thus obtaining the amplitudes and vertical wavelengths of the temperature fluctuations, from what was possible to determine the frequencies and to compare them with the cutoff frequency for these disorders, that is, the Brunt-Väisälä frequency, the study period was five years (2009 -2013), during that time interval 1435 daytime probes were performed , which allowed to classify 281 perturbations with periods between 4 -20 min, that is, compatible with gravity waves, it was also possible to obtain the profile of the potential energy density. The results obtained show that around 61% of these disorders were observed between January and June. It was searched through the images of Meteosat 9 satellite, to verify the presence or not of meteorological phenomena that could be associated as a possible mechanism of generation of these waves, among them convective phenomena such as the Zone of Intertropical Convergence (ITCZ). In addition, a numerical program was developed to simulate the amount of energy to be deposited in the troposphere in order to simulate the propagation of these waves, being verified that the amount of energy deposited in the troposphere by an ITCZ would be able to generate perturbations like those that we check the radiosonders data.