Predicting the future behavior of precipitation is of the utmost importance for planning agriculture or water resource management and in designing water structures. Determining the relationships between precipitation and the oceans may enable more accurate predictions. Therefore, oceanic and other persistent indices called teleconnection patterns can be used, namely the North Atlantic oscillation (NAO) and the Indian Ocean dipole (IOD). The NAO affects the precipitation patterns in the Atlantic Ocean and Mediterranean countries, such as in Turkey. The IOD is related to temperature and precipitation in the Indian Ocean coastal countries and in some areas far from the Indian Ocean. In this study, the effects of the NAO and IOD indices on precipitation in Turkey were investigated by means of cross-spectral analysis between the monthly total precipitation (mm) and monthly NAO and IOD index values. Phase shift values were also calculated for the selected periods and their accuracy was evaluated statistically, using the determination coefficient (R²) and Akaike information criterion (AIC) as performance criteria for the linear model. The results indicated strong correlations for the 13-, 14-, 16-, and 22–23-month periods between the NAO index and precipitation values; and for the 13-, 14-, 16–17-, and 20–21-month periods between the IOD index and precipitation values. After cross-spectral analysis between the NAO and IOD indices and precipitation values, the maximum phase shift values increased as the periods increased, while the maximum phase shift value for each period was almost half of the period value. Moreover, the maximum cross-power spectral density (CPSD) values increased as the periods increased. High CPSD values were observed in the west of Turkey for the NAO and in the east of Turkey for the IOD.

中文翻译：

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互谱分析法研究北大西洋涛动和印度洋偶极子对土耳其降水的影响

预测未来的降水行为对于规划农业或水资源管理以及设计水结构至关重要。确定降水与海洋之间的关系可以实现更准确的预测。因此，可以使用称为遥连接模式的海洋和其他持续性指标，即北大西洋振荡（NAO）和印度洋偶极子（IOD）。NAO影响大西洋和地中海国家（例如土耳其）的降水模式。IOD与印度洋沿岸国家以及远离印度洋的某些地区的温度和降水有关。在这个研究中，通过月总降水量（mm）与月NAO和IOD指数值之间的互谱分析，研究了NAO和IOD指数对土耳其降水的影响。还针对所选时段计算相移值，并使用确定系数（R ²）和Akaike信息准则（AIC）作为线性模型的性能准则。结果表明，NAO指数与降水量值在13、14、16和22-23个月之间有很强的相关性。在IOD指数和降水值之间的13、14、16-17和20-21个月期间。在NAO和IOD指数与降水量之间进行互谱分析后，最大相移值随周期增加而增加，而每个周期的最大相移值几乎是周期值的一半。此外，最大互功率谱密度（CPSD）值随着周期的增加而增加。NAO在土耳其西部观察到较高的CPSD值，而IOD在土耳其东部观察到较高的CPSD值。