In the summer monsoon region, it is known that convection generates vigorous gravity waves (Sato et al. 2009; Wright and Gille 2011). Such gravity waves play a significant role to transport both eastward and westward momentum to the middle and upper atmosphere, because convectively-generated gravity waves have a broad range of phase speed. Recent development of satellite observation techniques allows us to detect smaller-scale temperature disturbances due to gravity waves. In order to understand the dynamical role of such gravity waves, it is necessary to estimate the psudomomentum flux and the propagation properties. Generally, the satellite observations do not provide sufficient information on the psudomomentum flux and the wave propagation direction because observed quantities are temperature only. Momemtum flux estimation using satellite observations in previous studies (e.g. Ern et al. 2004) has large uncertainties. In this study, the wavelength and amplitude of gravity waves are locally estimated from the horizontal phase structure in order to clarify the propagation properties of convectively-generated gravity waves using AIRS high resolution temperature retrieval data (Hoffman and Alexander 2009), of which resolution is 3×3 times higher than AIRS operational Level 2 temperature data. The analysis is made for the summer Indian monsoon region. A wave detection method using S-transform, a kind of wavelet analyses (Stockwell et al. 1996) is applied to some cases where gravity waves are located near deep convections.

2011 年度気象学セミナー