Combined Use of Graphical and Statistical Approaches for Analyzing Historical Precipitation Changes in the Black Sea Region of Turkey

Abstract

Many statistical methods have been developed and used over time to analyze historical changes in hydrological time series, given the socioeconomic consequences of the changes in the water cycle components. The classical statistical methods, however, rely on many assumptions on the time series to be examined such as the normality, temporal and spatial independency and the constancy of the data distribution over time. When the assumptions are not fulfilled by the data, test results are not reliable. One way to relax these cumbersome assumptions and credibilize the results of statistical approaches is to make a combined use of graphical and statistical methods. To this end, two graphical methods of the refined cumulative sum of the difference between exceedance and non-exceedance counts of data points (CSD) and innovative trend analyses (ITA)-change boxes alongside the classical statistical Mann–Kendall (MK) method are used to analyze historical precipitation changes at 16 stations during 1960–2015 in the Black Sea region of Turkey. The results show a good match between the results of the graphical and statistical methods. The graphical CSD and ITA methods, however, are able to identify the hidden trends in the precipitation time series that cannot be detected using the statistical MK method.

Analyses of Precipitation and Evapotranspiration Changes across the Lake Kyoga Basin in East Africa

“…In other words, the significance of the trend was tested in terms of the difference between the exceedance and non-exceedance counts of data points [59][60][61]. Examples of recent studies that applied the method adopted in this study include Pirnia et al [62], Tang and Zhang [63], Vido et al [64], and Cengiz et al [65]. Statistically, the comparability of the adopted method with the MK test was demonstrated in previous studies [2,59].…”

Change-point detection and trend analysis in monthly, seasonal and annual air temperature and precipitation series in Bartın province in the western Black Sea region of Turkey

“…Compared to the southern part of Turkey, Ertugrul (2019) also found greater changes in the climate data of the Black Sea region of Turkey, and he warned about forest fire risk for the same region in the future. Cengiz et al (2020) analyzed the historical precipitation changes at 16 stations (also including Bartın) during 1960-2015 in the Black Sea region of Turkey using two different graphical methods. The authors stated that in Bartın province while there is no seasonal trend for a full-time series, there are statistically significant trends for the first half sub-series of spring and second half sub-series of autumn (−3.54 mm•year −1 and 6.47 mm•year −1 respectively).…”

“…Located in the Eastern Mediterranean basin, Turkey is considered to be adversely affected by the consequences of climate change (Önder et al 2009, Tayanç et al 2009, Türkeş & Tatlı 2009, Önol & Unal 2012, Demircan et al 2014, Önol et al 2014, Dabanlı 2018. The different climate variables of Bartın province have been investigated from various perspectives at both the regional and local scale (Ertuğrul et al 2014, Turoğlu 2014, Bolat et al 2018, Şensoy & Ateşoğlu 2018, Yozgatlıgil & Türkeş 2018, Balov & Altunkaynak 2019, Ay 2020, Cengiz et al 2020, Sönmez & Kale 2020, Yaman et al 2020. Ertuğrul et al (2014) evaluated whether the indication of climate change in Bartın's forests is occuring, based on the Standard Precipitation Index (SPI).…”

“…Ay (2020) carried out homogeneity and trend tests on the time series of monthly mean temperature and monthly total precipitation recorded in Düzce, Bolu, Zonguldak, Bartın, Kastamonu and Sinop provinces in the western Black Sea region of Turkey. Cengiz et al (2020) researched historical precipitation change using both graphical and statistical methods in the provinces of the Black Sea Region of Turkey. In a study on the annual streamflow of Filyos River, Sönmez & Kale (2018) used some climate variables of Bartın province.…”

Changes in precipitation and evapotranspiration over Lokok and Lokere catchments in Uganda

“…In this line, several studies have been conducted on trends and variability in climatic variables across the world. Examples of such studies were on the changes in historical precipitation in the Black Sea region of Turkey (Cengiz et al, 2020), trend and variability in rainfall and evapotranspiration over Mpologoma catchment in Uganda, East Africa (Mubialiwo et al, 2020), decadal and/or multi-decadal variability in gridded precipitation and potential evapotranspiration (PET) obtained from Cent-Trends and Princeton Global Forcing (PGF), respectively, across the Lake Kyoga Basin (LKB) (Onyutha et al, 2020) and the influence of several meteorological parameters on evapotranspiration in the humid zone of Pakistan (Adnan et al, 2020). Furthermore, Mahmood et al (2019) examined the climate variability and trend in the most parts of the lake Chad basin, Africa.…”