Trend Analysis of Daily Maximum Rainfall Series in Çoruh Basin, Turkey

Abstract

In the present study, trends of daily maximum rainfall series in three time scales including annual,
seasonal and monthly time series were investigated by using Mann-Kendall (MK), modifed Mann-Kendall (mMK),
Theil–Sen (TH) and Sequential Mann-Kendall (SMK) trend tests. These tests are applied to daily maximum rainfall
data of fve stations located Çoruh Basin, Turkey. The MK and mMK tests are employed to quantify signifcance
of the trend, the TH test is used to determine magnitude of the trend and the SMK test is also applied for defning
starting year of the signifcant trend. The results of the MK and mMK tests showed that there are considerable
signifcant increasing trends of daily maximum rainfalls in months including January, March, July, August and
October. However, signifcant decreasing trends were detected in daily maximum rainfalls of May and December.
In annual and seasonal time scale, signifcant increasing trends were detected. The TH test also indicated that the
highest magnitude of the negative trends was occurred in daily maximum rainfalls of December while the highest
magnitude of the positive trends was found in daily maximum rainfalls of annual time scale. Furthermore, the SMK
test revealed that the signifcant positive and negative trends mostly began in the mid-1980s and the early 1990s

Keywords

• Çoruh basin,daily maximum rainfalls,mann-kendall test,modifed mann-kendall test,sequential mann-kendall test,theil-sen test

Çoruh Havza’sındaki Günlük Maksimum Yağış Serilerinin Trend Analizi

Abstract

Bu çalışmada, yıllık, mevsimlik ve aylık üç zaman dilimdeki günlük maksimum yağışların trendleri
Mann-Kendall (MK), modifye edilmiş Mann-Kendall (mMK), Theil-Sen (TH) ve Mann-Kendall Sıra Korelasyon
(MKSK) testleri kullanılarak araştırılmıştır. Bu testler, Çoruh havzasında bulunan 5 adet istasyonun günlük
maksimum yağış verilerine uygulanmıştır. MK ve mMK testleri trendlerin anlamlılığını belirlemede, TH testi
trendin büyüklüğünü hesaplamada ve MKSK testi ise ele alınan verilerdeki anlamlı trendlerin başladığı yılları
tespit etmede kullanılmıştır. MK ve mMK test sonuçlarına göre Ocak, Mart, Temmuz, Ağustos ve Ekim aylarına
ait günlük maksimum yağış değerlerinde istatistiksel anlamda bir artış varken Mayıs ve Aralık aylarının günlük
maksimum yağış verilerinde ise istatistiki anlamda önemli azalışlar söz konusudur. Yıllık ve mevsimlik zaman
ölçeğinde ise ele alınan verilerde istatistiksel anlamlı artış trendleri tespit edilmiştir. Ayrıca, TH testi günlük
maksimum yağışlardaki en büyük negatif (azalış) trendin Aralık ayında, en büyük pozitif (artışın) trendin ise
yıllık zaman diliminde meydana geldiğini belirtmektedir. Buna ek olarak, MKSK testide bu tespit edilen anlamlı
negatif ve pozitif trendlerin başlangıç yıllarının çoğunlukla 1980’lerin ortalarında ve 1990’ların başları olduğunu
göstermektedir

Keywords

• Çoruh havzası,günlük maksimum yağışlar,mann-kendall testi,mann-kendall sıra korelasyon testi,modifye edilmiş mann-kendall testi,theil-sen testi

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