Wavelet transforms of meteorological parameters and gravity waves

The main purpose of this paper is to analyze some characteristics of gravity waves (GWs), and seasonal varia- tions of atmospheric waves over Istanbul by using wavelet techniques. Daily radiosonda data of Istanbul in the tro- posphere and lower stratosphere (1000 hPa-30 hPa) between 1993 and 1997 have been considered. Wavelet analysis based on a computer simulation of data is generally close to the real data when Daubechies wavelet series are used. Daily, monthly, seasonal and annual variations of pressure heights, air temperature and deviations from mean values have been analyzed. Variations show the effects of gravity waves for different pressure levels in the troposphere. These waves lead to the meso-scale wave-form structures in spring, au- tumn and winter. As a result of this study, wavelet series and transforms for data construction, definition of some disconti- nuities and the local effects on the signal have been compared with the results of previous studies. The most similar struc- ture between temperature, turbulence parameters and geo- potential height deviations has been defined at the 500-hPa pressure level. structures from turbulence data taken within and above a de- ciduous forest by Gao and Li (1993). This study demon- strates the usefulness of wavelet analysis in decomposing structures at different scales, hidden in time series data. The wavelet technique is a useful tool for analyzing time series with many different time scales or changes in variance. A practical step-by-step guide to wavelet analysis is given with examples taken from time series of the El Ni˜ no-Southern Os- cillation (ENSO) (Torrence and Compo, 1998).