- Laboratory of Climatology, Department of Geography and Environmental Studies, University of Haifa, Haifa, Israel
- Affiliated Faculty at the Department of Statistics, Middle East Technical University , Ankara, Turkey
|ABSTRACT||Analysing and understanding the major causes and patterns of the spatial and temporal characteristics of the climatological dryness are one of the most important topic in the study of precipitation climatology and variability in time and space. Dryness is crucial mainly in semi-arid, dry sub-humid and moist semi-humid or semi-humid regions with water shortage, particularly those dominated by a warm/dry or hot/severe dry Mediterranean type climate regions.
The present study suggests a new approach for analysing dry spells and their annual distribution and introduces a new term is that of dry days since last rain (DDSLR), aiming at analysing and presenting the different annual variations the DDSLR across Turkey based on daily precipitation data recorded at 69 principal climatological and synoptic meteorological stations of the Turkish State Meteorological Service (TSMS) network of the Republic of Turkey during the period 1970 to 2011. Three different metrics of the dryness are examined; its severity, its consistency and its temporal uncertainty: The severity of the dryness measures the longest length of the dry period. The longer this period is, the more severe the dryness is. The consistency considers how frequently a dry period of a given length occurs. The higher this figure is, the more consistent the dryness is. Finally, the temporal uncertainty considers the span of time when a dry period of certain duration can be expected. The longer is this period, the higher is the temporal uncertainty.
Dryness may have many negative consequences on the environment, economy and societies in many regions around the world. Prolonged dry periods may affect water supply, causing large damages to the agriculture and the environment, enhance and intensify forest fires and land degradation. The majority of the Mediterranean basin is characterized by a concentration of precipitation in winter and also by relatively prolonged hot and dry summers, the so-called Mediterranean Climate (e.g., Aschmann, 1973). According to the Köppen climate classification, the driest month in summers receives less than one third than the wettest month in winter. Wigley and Farmer (1982) modified this criterion of the Köppen classification to define the Mediterranean climate as having winter season (DJF) rainfall more than three times that of summer (JJA). In the present study we use this criterion and define it as: Mediterranean Climate Index-MCI.|