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Meteorol Atmos Phys (2009) 105:211225 DOI 10.1007/s00703-009-0046-3
ORIGINAL PAPER
Winter mean temperature variability in Turkey associated with the North Atlantic Oscillation
Murat Trkes Ecmel Erlat
Received: 4 August 2008 / Accepted: 7 September 2009 / Published online: 22 September 2009 Springer-Verlag 2009
Abstract Changes and variability in seasonal average mean and monthly mean winter (DJF) air temperature series at 70 stations of Turkey and the circulation types at 500-hPa geopotential height level were investigated to explain atmospheric controls of temperature variations during the extreme (weak and strong) phases and normal (negative and positive) phases of the North Atlantic Oscillation (i.e., Ponta DelgadaReykjavik and the GibraltarReykjavik) indices. During the positive phases of the North Atlantic Oscillation indices (NAOIs), northeast-erly circulation increased, and thus spatially coherent and signicant cold signals dominate over the majority of Turkey. This pattern is closely linked to anomalously low 500-hPa heights over the region of the Icelandic Low, and anomalously high geopotential heights over the regions of the Azores High, the western Mediterranean basin and the Europe, in general including the Balkans and northwest Turkey. Contrarily, during the negative phases of the NAOIs, prevailing westerly winds that originate from the subtropical northeast Atlantic increase, and thus spatially coherent and signicant warm signals over the Anatolian peninsula appear. This pattern is closely linked to the increased cyclonic activity and associated increased westerly and southwesterly circulation causing warm maritime air advection over the Mediterranean basin toward Turkey.
1 Introduction
The atmospheric circulation is the principal control that determines the climate variability. Atmospheric circulation and teleconnection patterns can be characterized by using circulation indices, such as the indices developed for El NioSouthern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO) or the North SeaCaspian Pattern (NCP). Among them, the NAO is one of the most important circulation sources for short and/or long-term climatic variability in the North Atlantic, the Europe, and the Mediterranean regions, because of its importance in transporting heat and moisture to these regions or from them.
The NAO is closely connected to the interannual variability of climatic conditions, mainly during winter across wide regions of the North Atlantic Ocean, the North America, the Arctic, the Eurasia and the Mediterranean, including storminess and precipitation, ocean heat content, ocean currents and...