Abstract
Abstract. We first study the seasonal and geographical behavior of gravity wave activity in the lower stratosphere over the southernmost Andes mountains and their prolongation in the Antarctic Peninsula by global positioning system (GPS) radio occultation (RO) temperature profiles, obtained between years 2002 and 2005 by the CHAllenging Minisatellite Payload (CHAMP) mission. 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. Comparisons with previous GPS RO studies in smaller areas than the one covered in our analysis are also established. Significant seasonal variation of wave activity is observed in our work, in agreement with results from other instruments. The locations of significant cases indicate that topography is an important source. Some strong wave activity is also found over open ocean. Critical level filtering is shown to have an attenuation effect, implying that a large fraction of the observed activity can be considered to be an outcome of mountain waves. The studied region has a significant advantage as compared to other regions of our planet: it generates wavefronts nearly aligned with the North-South direction (almost parallel to the mountains), whereby this geometry favors the wave detection by the nearly meridional line of sight characterizing most of the GPS RO observations used. A distribution of the observed gravity waves in terms of amplitudes and wavelengths is also presented.
Highlights
Gravity wave (GW) drag in general circulation models has been usually treated with parameterizations
Last decade studies that rely on remote sensing techniques on board of satellites have shown that there is an extratropical zone in the Southern Hemisphere, close to the Patagonian Andes, their prolongation in the Antarctic Peninsula and towards the South Atlantic Ocean, that exhibits a strong wave activity in the upper troposphere and lower stratosphere in winter and spring
As there are far more data points at very negative rotation angles and the nonuniform distribution there might mislead any immediate conclusions, we developed some kind of normalized analysis according to the number of samples as explained below
Summary
Gravity wave (GW) drag in general circulation models has been usually treated with parameterizations. Last decade studies that rely on remote sensing techniques on board of satellites have shown that there is an extratropical zone in the Southern Hemisphere, close to the Patagonian Andes, their prolongation in the Antarctic Peninsula and towards the South Atlantic Ocean, that exhibits a strong wave activity in the upper troposphere and lower stratosphere in winter and spring (see references below). Jiang et al (2002b) found in a global UARS MLS data study a strong wave activity close to the southern Andes and the Antarctic Peninsula between 35 S and 75 S during the winters of 1992–1997. This should complement previous works, as these included either a fraction of the geographical area of interest or other instruments, which cover different altitudes or spectral regions of the wave spectrum
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