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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 2
Ann. Geophys., 36, 301-310, 2018
https://doi.org/10.5194/angeo-36-301-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Space weather connections to near-Earth space and the...

Ann. Geophys., 36, 301-310, 2018
https://doi.org/10.5194/angeo-36-301-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 05 Mar 2018

Regular paper | 05 Mar 2018

Mesopause region temperature variability and its trend in southern Brazil

Mateus S. Venturini1, José V. Bageston2, Nattan R. Caetano1, Lucas V. Peres3, Hassan Bencherif4, and Nelson J. Schuch2 Mateus S. Venturini et al.
  • 1Aerospace Engineering, Federal University of Santa Maria, Av. Roraima, Santa Maria, Brazil
  • 2Southern Regional Space Research Center, National Institute for Space Research, Av. Roraima, Santa Maria, Brazil
  • 3Federal University of Western Pará, Rua Vera Paz, Santarém, Pará, Brazil
  • 4Université de La Réunion, LACy, UMR 8105, Réunion Island, France

Abstract. Nowadays, the study of the upper atmosphere is increasing, mostly because of the need to understand the patterns of Earth's atmosphere. Since studies on global warming have become very important for the development of new technologies, understanding all regions of the atmosphere becomes an unavoidable task. In this paper, we aim to analyze the temperature variability and its trend in the mesosphere and lower thermosphere (MLT) region during a period of 12 years (from 2003 to 2014). For this purpose, three different heights, i.e., 85, 90 and 95km, were focused on in order to investigate the upper atmosphere, and a geographic region different to other studies was chosen, in the southern region of Brazil, centered in the city of Santa Maria, RS (29°41′02′′S; 53°48′25′′W). In order to reach the objectives of this work, temperature data from the SABER instrument (Sounding of the Atmosphere using Broadband Emission Radiometry), aboard NASA's Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, were used. Finally, two cases were studied related to distinct grids of latitude/longitude used to obtain the mean temperature profiles. The first case considered a grid of 20° × 20° lat/long, centered in Santa Maria, RS, Brazil. In the second case, the region was reduced to a size of 15° × 15° in order to compare the results and discuss the two cases in terms of differences or similarities in temperature trends. Observations show that the size of the geographical area used for the average temperature profiles can influence the results of variability and trend of the temperature. In addition, reducing the time duration of analyses from 24 to 12h a day also influences the trend significantly. For the smaller geographical region (15° × 15°) and the 12h daily time window (09:00–21:00UT) it was found that the main contributions for the temperature variability at the three heights were the annual and semi-annual cycles and the solar flux influence. A smaller trend (−0.02±0.16%decade−1) was found at 90km height and small positive trends (0.58±0.26% and 0.41±0.19%decade−1) were found at altitudes of 85 and 95km, respectively.

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In the past years, the study of the temperature trend and its variability in the upper atmosphere has increased. However, most works were conducted in regions of medium and high latitude. Therefore, we aim to analyze a low-latitude region, the south of Brazil and surrounding areas. Using data from the TIMED/SABER instrument and applying the Trend-Run model for temperature trend analyses, no substantial temperature trend was found in the MLT region (80–100 km) from the years 2003 to 2014.
In the past years, the study of the temperature trend and its variability in the upper...
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