HARMONIC-ANALYSIS OF PRECIPITATION, PRESSURE AND TEMPERATURE OVER TURKEY

Monthly averages of temperature, precipitation and pressure values fro m ground-based measurements for long-term data observed in different g eographical regions in Turkey have been investigated. The main purpose of this study is to define the role of small-and lar ge-scale phenome na (local and synoptic fluctuations) on precipitation, pressure and te mperature variations and their periods. Hence, the Fourier transformat ion analysis of the monthly average value of meteorological parameters has been considered, and phase angles and amplitudes have been calcul ated. The first-order harmonics of temperature, :precipitation and pre ssure values show large-scale effects, while higher-or der harmonics s how the effects of small-scale variations. The variations of first-six th-order harmonic amplitudes and phases provide a useful means of unde rstanding the la ge-and local-scale effects on meteorological paramete rs. The phase angle can be used to determine the time of the year when the maximum or minimum of a given harmonic occurs. The analysis helps us distinguish different precipitation, pressure and temperature regi mes and transition regions. Local-and large-scale phenomena and some u nusual seasonal patterns ape also defined. This analysis also shows st rong annual variations of precipitation in the Southern and Western pa rt of Anatolia and that strong semi-annual fluctuations are predominan t in the eastern part of Turkey. Strong annual influence on pressure v ariations is mostly observed in the coastal part of Turkey. The domina nce of the first three harmonics of pressure is smaller over most of t he terrestrial stations. Temperature variations are mostly influenced by the annual fluctuations in eastern and south-eastern Anatolia. The urban heat island caused by developing metropolitan areas refers to lo cal warming effects and heat islands. The local effects are observed i n the western part of Turkey.