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İstanbul Teknik Üniversitesi (2017)

A Comprehensive Evaluation Of The Observed And Modeled Precipitation Datasets For Turkey

GİRGİN Gizem

Titre : A Comprehensive Evaluation Of The Observed And Modeled Precipitation Datasets For Turkey

Türkiye İçin Gözleme Ve Modele Dayalı Yağış Veri Kümelerinin Kapsamlı Bir Değerlendirmesi

Auteur : GİRGİN Gizem

Université de soutenance : İstanbul Teknik Üniversitesi

Grade : M.Sc. THESIS 2017

Résumé
Precipitation, a crucial climate parameter, is in high demand for the research and operational activities in many different sectors as well as disciplines. However, the very high spatial variation and discontinuity in time makes prediction of precipitation very difficult. Various gridded global and regional precipitation data sets are available, but they have discrepancies resulting primarily from the differences in the number of stations and interpolation techniques used to create them. The primary objective of this research is to gain insight into how consistently these datasets represent the temporal and spatial distribution of precipitation in Turkey, which has a quite complex topography. The gridded datasets include those obtained from station and satellite measurements and those produced by reanalysis and climate models In this study, data sets are compared as spatially, seasonally and statistically. Ensemble mean of observation data sets is used as reference. Data sets are separated in two different periods considering their temporal availability as 1961-1990 and 1998-2007. All the analyses have been conducted according to these periods. In addition, statistical analyses have been performed for three regions named as Karadeniz, Akdeniz and Doğu Anadolu which are separated pursuant to climatologic dispersion of Turkey. Turkey maps for all data sets are used to illustrate the precipitation distribution. Spatial divergences are shown by maps extracting reference from the other data sets. Turkey avarega precipitation of data sets are compared within table for two periods. Seasonality is analyzed with seasonal mean table and monthly graph of all data sets. To understand the longitudinal and latitudinal differences, cross-section analysis has been carried out. Finally, Taylor Diagram is used for statistical analysis and agreements of data sets with reference data are examined. The preliminary results indicate that there is substantial differences between all type of data sets. The discrepancy amongst data sets is larger in the northern and eastern parts of the country that are more mountainous. In addition, the discrepancy is usually large in the winter and spring months. The model and reanalysis data sets have a tendency to produce higher precipitation values than the observations. The major spatial difference between the model and observation-based datasets takes place in the mountainous areas lacking an adequately dense station network. The most outstanding example is the northeastern Black Sea region. All of the analysis results that the most concurrent data set with the reference is the distributed station data named as TR_STA_GRIDDED.

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