HR: 1340h
AN: A13A-0899    [Abstracts]
TI: Gravity Wave Characteristics Over Equator Observed During CPEA Campaign Using Simultaneous Multiple Stations Data
AU: * Venkat Ratnam, M
EM: vratnam@rish.kyoto-u.ac.jp
AF: Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Gokasho, Uji, 6110011 Japan
AU: Tsuda, T
EM: tsuda@rish.kyoto-u.ac.jp
AF: Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Gokasho, Uji, 6110011 Japan
AU: Shibagaki, Y
EM: sibagaki@maelab.osakac.ac.jp
AF: Department of elecommunications and Computer Networks, Osaka Electro-Communication University, Osaka, 572 8530 Japan
AU: Kozu, T
EM: kozu@ecs.shimane-u.ac.jp
AF: Faculty of Science and Engineering, Shimane University, Nishi-kawatsu, Matsue, 690 8504 Japan
AU: Mori, S
EM: mori@kobe-u.ac.jp
AF: Institute of Observational Research for Global Change (IORGC), Yokohama-city, Kanazawa, 236-0001 Japan
AB: 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.
DE: 3314 Convective processes
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3384 Acoustic-gravity waves
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005