Brazilian Surface and Upper-level Wind Characteristics Based on Ground and Model Observations from 1980–2014
Doctor of Philosophy (PhD)
Geography and Anthropology
The examination of temporal changes in surface winds has been analyzed by scientists for a variety of physical, biological, climatological, and socioeconomic reasons. This research uses surface and upper-level wind data from historical in-situ and climate models to examine the geographical and climatological characteristics of wind across Brazil during 1980–2014. Overall linear and quantile regression shows that surface wind speed trends are changing regionally across Brazil. Wind speeds across northeastern Brazil are increasing, while a decreasing trend is documented for interior and southeastern Brazil. The spatial and temporal trends found are possibly related to alterations in the physical landscape (urbanization and land-cover change) and the seasonal relationship between the Intertropical Convergence Zone and the South Atlantic Anticyclone. To further examine the role of the South Atlantic Anticyclone, an additional analysis was performed to show how the position of high pressure system affects surface conditions across Brazil. Results show that surface winds across northern Brazil are affected by an equatorward shift of the semi-permanent high pressure, while southern Brazil is more influenced by migrating anticyclones that were passing through the South Atlantic Basin. A spatial and temporal analysis of upper-level wind speed trends was conducted to examine how surface and marco-scale features have evolved over Brazil. An overall vertical profile shows a decreasing trend in lower-level winds (1000–850 hPa) that switches to a positive trend in the upper portions of the atmosphere (400–200 hPa). A geographical interpretation of upper-level wind trends was performed based on a three-dimensional model. The model depicts that seasonal wind trend patterns across Brazil occur within the proximity of the Bolivian high and subtropical jet (400–200 hPa). A regional analysis confirms the role of these two synoptic features.
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Gilliland, Joshua M., "Brazilian Surface and Upper-level Wind Characteristics Based on Ground and Model Observations from 1980–2014" (2017). LSU Doctoral Dissertations. 4410.
Keim, Barry D.