Seasonality, persistency, regionalization, and control mechanism of extreme rainfall over complex terrain

Extreme rainfall has enormous importance in hazard management as well as the design of critical infrastructures for urban and rural areas. Also, complex terrain has a vast influence on spatial and temporal patterns of extreme rainfall. In this study, therefore, many different properties such as spatial similarity (regionalization) and temporal variability (trends and seasonality) of extreme rainfall were quantified over Turkey in which topography heavily influences meteorological parameters in short distances due to orientation and height of mountain chains. Moreover, spatial and temporal extreme rainfall characteristics are poorly quantified and investigated in Turkey. Principal component analyses (PCA) were used in order to reveal the parameters that have influence on rainfall, and three components were observed based on Kaiser Rule. The three PC explain the effect of topography, large-scale weather systems, and seasonality on extreme rainfall. Model-based clustering via retained component scores were used to generate the extreme rainfall regions. Eight different extreme rainfall regions have been obtained with different return periods and growth curves calculated based on regional frequency analysis via generalized extreme values distribution (GEV) distribution based on the goodness-of-fit measure. SWM (Southwest Mediterranean) and HEBS (Humid Eastern Black Sea) are remarkable regions than other extreme rainfall regions in terms of the magnitude of extreme rainfall because of the interaction of topography with tracks of weather systems. The circular statistic shows a strong gradient in terms of extreme rainfall seasonality between the coastal and interior parts of Anatolia. Moreover, positive trends and persistence in extreme rainfall have been detected in all regions as a signal of the increase in natural hazards. In general, orographic barriers and their interaction with large-scale weather systems shape the spatiotemporal variability of extreme rainfall and creating a negative gradient between interior and frontal parts of the Anatolian plateau.