Recientes contribuciones a la detección de la distribución global de la energía de ondas atmosféricas a partir de radio ocultamientos GPSLEO

DE LA TORRE, A.; ALEXANDER, P.; LLAMEDO, P.; HIERRO, R.

Jornada; Jornadas de Trabajo sobre Ionosfera y Alta Atmósfera; 2010

In the last years, several studies on global energy distribution associated to atmospheric waves in the troposphere and stratosphere, based on radiosonde and satellite data, were performed. Nevertheless, no observational technique is able by itself to contemplate the whole spectrum of gravity waves (GW). The Global Positioning System radio occultation (GPS-RO) measurement principle may be applied to observe the Earth's atmosphere and climate. Since 2001, from CHAMP, SAC-C, GRACE and COSMIC Low Earth Orbit (LEO) satellites, atmospheric parameters such as temperature, pressure, water vapor and geopotential height have been systematically obtained. Simultaneous global coverage, sub-Kelvin temperature accuracy, high vertical resolution and insensitivity to clouds make this technique unique. Climatologies from global observations during long-term periods are essential to understand the role that GW play in atmosphere circulation.         In this talk, we present results of the global long-term mean potential energy per unit mass distribution associated to wave activity (WA) in the troposphere, lower and middle stratosphere, from GPS-RO temperature profiles retrieved during the last 8 years from the CHAMP satellite. We excluded temperature variations corresponding to the wavelike character of the quasi biennial oscillation. Possible limitations and distortions expected from our analysis are pointed out. Systematic annual and interannual features, clearly evidenced through years of observations as a function of height, latitude and time are shown. We confirm some previously reported characteristics, in addition to others not reported yet requiring a sufficiently long period of observation. In doing so, a new simple approach to estimate the committed error in the calculation of the mean relative temperature variance, independently of the experimental origin of the data, is proposed. The approach was developed through a statistical simulation from synthetic wave perturbations and temperature profiles from reanalyses. A systematic bias detected between true and calculated mean relative variance content is shown. Its variation with latitude and season is underlined and the possibility to apply these results in future climatologies is highlighted. From this global analysis, a systematic significant WA in the upper troposphere and lower stratosphere, mainly during winter, is detected in Argentina near to the Andes Range, between midlatitudes 30S–40S. The possible main GW sources in this region are: i) orographic forcing, ii) geostrophic adjustment and iii) deep convection. We discuss the relative importance of each of them. Finally, we show the seasonal and geographical behavior of GWA in the lower stratosphere over the southernmost Andes mountains, as well as their prolongation in the Antarctic Peninsula. The observed features complement observations in the same zone by other satellite passive remote sensing instruments, which are able to detect different height regions and other spectral intervals of the wave spectrum. The locations of significant cases indicate that topography is an important source and critical level filtering is shown to have a considerable attenuation effect.