Characteristics of the free atmosphere over Paraguay and its influence on the seasonal behaviour of precipitation | Caracteristicas de la atmosfera libre sobre Paraguay y su influencia en el comportamiento estacional de la precipitacion
Artículo académicoNombre
The main characteristics of the free atmosphere over Paraguay are described, using a record of seven years of radiosonde observations at Aeropuerto Silvio Pettirossi, located at 25° 15′S and 57° 31′W and at an altitude of 92 m. The results show a clear seasonal variation, with highest values of temperature and humidity, mainly in the lowest troposphere, during the summer months (December to March). Potential instability is characteristic of these months up to about 600 hPa. In the winter months (July to September) the temperature decreases significantly in the lower troposphere, the thickness of the west layer is reduced, and the atmosphere is potentially stable up to 300 hPa. At the level of 1000 hPa, the predominant wind direction is from the east during all the year, changing to a westerly component in the 850-100 hPa layer. In the lower stratosphere (70-20 hPa), the wind direction is from the west during the winter semester (May-October), rotating to an easterly component in the summer semester (November to April). The intensity of the westerlies near 200 hPa increases significantly during winter, reaching 33 ms-1 in July. This is consistent with the average location of the subtropical jet stream. Among the variables analyzed, are the height of the layer with potential instability, height of the west layer, wind shear, and Showalter index. They are related to the monthly rainfall distribution, which suggests that the most important rainfall events may be of convective origin.
