Abstract
Abstract Using stratospheric temperature profiles derived from GPS radio occultation (RO) measurements made by the German CHAMP satellite from June 2001 to May 2006, we studied the climatological behavior of atmospheric wave activity in the tropics. The wave potential energy, E p, is calculated from temperature fluctuations with vertical scales shorter than 7 km in a longitude and latitude cell of 20° × 10° at 19–26 km. E p is then averaged every 3 months (June–July–August (JJA), September–October–November (SON), December–January–February (DJF), March–April–May (MAM)), and the averages are compared with the cloud top temperature from outgoing long-wave radiation (OLR) and the convective rain rate from the TRMM precipitation radar (PR). E p at 19–26 km in the western Pacific to Indian Ocean is found to show a clear seasonal variation, with a large E p during DJF and MAM and a considerably enhanced E p in SON; it becomes minimum during JJA near the equator, when the center of the enhanced E p region appears over north India and the Indochina peninsula. Localized enhancement of E p seems to be mainly due to atmospheric gravity waves. In addition, the longitudinally elongated portion of E p is partially affected by Kelvin wave-like disturbances with short horizontal scales. In DJF and MAM, the convective clouds are located over the western Pacific and around Indonesia, at which time the Kelvin wavelike disturbances are effectively generated. The spatial and seasonal variations of E p are closely related to the distribution of clouds, implying that convective wave generation is very important in the tropics. However, wave-mean flow interactions due to the wind shear of the QBO become important in the lower stratosphere, which considerably modifies our analysis of the E p distribution at 19–26 km. Therefore, both wave generation and propagation characteristics must be taken into account in describing the climatological behavior of atmospheric wave activity in the equatorial stratosphere.
Highlights
Active convection in the tropics generates various waves, such as Kelvin waves, tides, gravity waves, among others
A biennial cycle can clearly be recognized in Fig. 2; for example, the Ep in the western Pacific was enhanced in December–January– February (DJF) in 2001/2002, 2003/2004, and 2005/2006, but it was suppressed in 2002/2003 and 2004/2005, which seem to be a result of the wave-mean flow interaction with the quasi-biennial oscillation (QBO), as reported by de la Torre et al (2006), who used Challenging Mini-Payload (CHAMP) GPS radio occultation (RO) data
Concluding Remarks Using temperature profiles observed with CHAMP GPS
Summary
Active convection in the tropics generates various waves, such as Kelvin waves, tides, gravity waves, among others. The stratospheric wave activity generally showed an annual variation, but it was largely affected by the QBO as the wave energy was enhanced just below zonal wind contours, corresponding to eastward shear.
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