Abstract: A new method extracting gravity wave signals is investigated using typhoon data collected at six radiosonde stations. The extended empirical orthogonal function (EEOF) analysis is applied to the dataset, and the eigenvectors and their corresponding weights that represent planetary-scale wave modes are chosen to reconstruct the meteorological field. The reconstruction results indicate that polarization relationships between any two variables of temperature, zonal wind and meridional wind are different during different typhoon periods, i.e., the relationship is the same as that of Kelvin waves in easterly equatorial zonal winds, whereas it is the same as that of mixed Rossby-gravity waves in westerly equatorial zonal winds. New gravity wave signals are obtained by removing planetary-scale wave modes from the original data. Characteristic wavelength (λ^*) and spectra slope (s) for low frequency waves are calculated by fitting the vertical wavenumber spectrum. The obtained λ^* and s are approximately 1.7 km and 1, respectively, which are stable during different time periods and at different stations. Results of the present study indicate that gravity wave signals extracted using the method discussed here are consistent with results of the theoretical model of vertical wavenumber spectrum.