Computer Science – Sound
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.a13a0899v&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #A13A-0899
Computer Science
Sound
3314 Convective Processes, 3334 Middle Atmosphere Dynamics (0341, 0342), 3384 Acoustic-Gravity Waves
Scientific paper
The interaction between large-scale atmospheric circulation and convection has been recognized as crucial in understanding the perturbations ranging from meso-scale to planetary spatial scales in the tropical lower atmosphere (especially in UTLS region). Hence it is very important to understand various atmospheric processes that lead to tropical convection and its scale of affecting small scale (gravity waves) to large atmospheric circulation (Kelvin waves). In order to understand these processes, so many collocated simultaneous observations were necessary. Coupling Processes in Equatorial Atmosphere (CPEA) campaign conducted over Indonesia during April-May 2004 will provide good opportunity to find the link between these various atmospheric processes. The vertical and temporal variations of gravity waves are studied using intensive observations of upper air soundings conducted at Koto Tabang (0.2oS, 100.32oE) during CPEA campaign. Dominant oscillations in the gravity waves with periods 2-3 days and vertical wavelengths of about 3-5 km were detected in the temperature (T), zonal (U) and meridional (V) components. Clear downward phase propagation with respect to height is seen in lower stratosphere indicating upward propagating wave and there exists mixed upward and downward phase propagation in lower troposphere. The gravity wave energy is found to be significantly enhanced around 20 km altitude region. The variations in the convection, which is the major source for generation of gravity waves, is also studied using simultaneous X-band radar observations and also using outgoing-long wave radiation (OLR) measurements. Clear eastward propagation of convection from Indian ocean to the maritime continent is found with a phase velocity of 6.36m/s. The wave energy is found to be enhanced after passing cloud convection through the observational site with a delay of about 1.5 to 2 days. To delineate the other gravity wave characteristics, we used correlative analysis by using simultaneous intensive radiosonde soundings at other nearby stations located about 200-400km away from the Koto Tabang (one station namely Padang is at a distance of 75km from Koto Tabang). From this correlative analysis, the horizontal wavelength of the wave if found to be about 2000km and the horizontal and vertical group velocities of these waves are found to be in the range of 650-1000km/day and 1.5 to 2.3km/day, respectively (depending upon the event). The dominant direction of these waves is found to be from north-west to south-east direction. The process behind the observed phenomena will be discussed.
Kozu Tomotake
Mori Satoru
Ratnam Venkat M.
Shibagaki Yoshiaki
Tsuda Teruhisa
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