资源环境科技发展态势分析平台

Drought may occur in almost every climatic region on Earth at any time. Understanding the nature and magnitude of the dryness and drought events are crucial mainly in semi-arid regions characterized by water shortage and warm/hot and dry Mediterranean type climate. The present article analyses the major patterns of the spatial and temporal characteristics of the climatological dryness in Turkey.

This study adopts a relatively new approach for characterizing the dryness over a certain region; dry days since last rain (DDSLR). The DDSLR in a certain place can be evaluated using three different metrics; its severity, consistency and temporal uncertainty enabling to present intra-and inter-annual variations of the dryness. The DDSLR is also coupled with the Mediterranean Climate Index (MCI) approach, measuring the seasonality of rainfall. Analyses were based on daily precipitation data recorded at 69 principal climatological and synoptic meteorological stations of the Turkish Meteorological Service network during the period 1970-2011.

The spatial distributions of the MCI and the various DDSLR metrics are presented and analysed. Overall, the three metrics of the DDSLR show their highest values in southern parts of Turkey along the Mediterranean and the borders with Syria and Iraq. These dryness indices are even larger than in central Turkey which receives less annual rainfall. On the other hand, dryness is at its minimum along the Black Sea in northern Turkey.

Logarithmic equations of the type f((DDSLR)) = a x ln(MCI) + b were fitted to describe the dependence of these metrics on the MCI. All regressions are highly significant and enable to evaluate these metrics even in regions without daily data. Finally, linear trends of the longest DDSLR in each year were calculated and reveal trends toward more severe dry conditions in north-western Turkey and less severe dry conditions in east Turkey.