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Abstract:The North Atlantic Oscillation (NAO) is a large-scale mode of natural climate variability governing the path of Atlantic mid-latitude storm tracks and precipitation regimes in the Atlantic and Mediterranean sectors. The primary focus of this study is to investigate the variability of lake levels in seven lakes scattered across Turkey using the method of continuous wavelet transforms and global spectra. The long winter (December, January, February and March) lake-level series and the NAO index (NAOI) series were subjected to wavelet transform. The global wavelet spectrum (energy spectrum of periodicities) of lake levels and winter NAOI anomalies, in most cases, revealed a significant correlation. It was shown that the Tuz, Sapanca, and Uluabat lakes reflect much stronger influences of the NAO than the other four lakes. In contrast, weak correlations were found in the coastal areas of the Mediterranean and eastern Turkey. The periodic structures of Turkish lake levels in relation to the NAO revealed a spectrum between the 1-year and 10-year scale level. Although the periodicities of more than 10-year scale levels were detected, explaining significant relations between the NAO and these long-term periodicities remains a challenging task. The results of this study are consistent with the earlier studies concerning the teleconnection between the NAO and climate variables in Turkey.

In order to explain many secret events of natural phenomena, analyzing non-stationary series is generally an attractive issue for various research areas. The wavelet transform technique, which has been widely used last two decades, gives better results than former techniques for the analysis of earth science phenomena and for feature detection of real measurements. In this study, a new technique is offered for streamflow modeling by using the discrete wavelet transform. This new technique depends on the feature detection characteristic of the wavelet transform. The model was applied to two geographical locations with different climates. The results were compared with energy variation and error values of models. The new technique offers a good advantage through a physical interpretation. This technique is applied to streamflow regression models, because they are simple and widely used in practical applications. However, one can apply this technique to other models.Streamflow prediction, discrete wavelet transform, hydrological modeling,

Ozetqeikinci Diinya Savqi'ndan bu zamana, bilgi-iglem giivenligi ve gifreleme sistemlerine ilgi gitgide arlmaktadrr. IBM'in DES ve Triple DES'inin yaninda RSA firmasmm RCX simetrik algoritmalar serisi ve MD5 benzeri HASH algoritmalan gifreleme alaninda (Inemli yer edinmislerdir. Fakat daha hidl mikro-iglemcilerin geligimi, nano-teknoloji ve kuantwn bilgisayarlar gibi geliven teknolojiler, veri giivenligi alaninin kendini yenilemesini kaginilmaz kilmaktadr. Bu galigmada, igaret igleme ve goliintii silugtirma alanlannda kullanilan dalgacik doniigiimii metodu, veri kangtima yontemi o l d denenmigtir. Sonuglar, bilinen gifreleme sistemlerinin giivenilirlik algoribna hizi gihi parametreleri ile karylqtinlmigtir. AbstractSince 11. World War, IT security and cryptology systems are getting important day by day. Beside DES and Triple DES of IBM Inc., RCX series of symmetric algorithms and MD5 variant HASH algorithms of RSA Inc. have widely used in cryptology research area. However, recent technology concepts such as faster micrapmcessors, nano-technology and quantum computers make the change inevitable. In the present study, Wavelet Transform method prefening signal processing and image compression areas, is used as data scrambling procedure. The results were compared by parameters such as reliability, algorithm speed.