Multivariate Long-Term Analysis of Hydroclimatic Variables in Eastern Anatolia Using ERA5-Land (1981–2020)

Öz

Climate change significantly affects the hydrological cycle components, and understanding these impacts at regional scales is crucial for sustainable water resources management. The Eastern Anatolia Region, Turkey's largest and highest geographical region, hosts the headwaters of the transboundary Euphrates and Tigris rivers, making it strategically vital for both national and regional water security. However, the region's harsh continental climate and complex topography limit the density of ground-based meteorological observations, creating substantial data gaps for hydro-climatological research. This study aims to characterize the hydro-climatological features of the Eastern Anatolia Region and detect long-term trends using ECMWF ReAnalysis 5th Generation – Land (ERA5-Land) high-resolution (0.1° × 0.1°) reanalysis data for the 1981-2020 period. Five key land surface variables were analyzed: 2-meter air temperature, total precipitation, soil moisture (0-7 cm and 7-28 cm layers), total evaporation, and surface plus subsurface runoff. The non-parametric Mann-Kendall test and Sen's slope estimator were employed for trend detection, while validation was performed against observations from 48 Turkish State Meteorological Service stations. Validation results demonstrated strong agreement between ERA5-Land and observed precipitation (R²=0.886), though a systematic positive bias (+87.4 mm/year, +17%) was identified. Regional climatology revealed an annual mean temperature of 7.26±0.96°C, precipitation of 767.5±94.8 mm, evaporation of 485.2±26.1 mm, and total runoff of 302.4±93.0 mm. Trend analysis detected a highly significant warming trend (+0.54°C/decade, p<0.001) across the entire region, accompanied by decreasing soil moisture (-0.0033 m³/m³/decade, p=0.031) and increasing evaporation (+7.0 mm/decade, p=0.029). These concurrent changes indicate an ongoing land desiccation process, suggesting increased agricultural drought risk and potential implications for transboundary water resources management.

Anahtar Kelimeler

• ERA5-Land
• Eastern Anatolia
• hydro-climatology
• Mann-Kendall
• trend analysis
• climate change

Destekleyen Kurum

None / Not applicable.

Etik Beyan

This study uses publicly available secondary data sources (ECMWF ERA5-Land reanalysis data and Turkish State Meteorological Service station observations). The study does not involve human or animal subjects, surveys, interviews, or personal data collection. Therefore, it does not require ethics committee approval according to the Higher Education Institutions Scientific Research and Publication Ethics Directive.

Doğu Anadolu’da Hidroklimatolojik Değişkenlerin ERA5-Land ile Çok Değişkenli Uzun Dönemli Analizi (1981–2020)

Öz

İklim değişikliği hidrolojik döngü bileşenlerini önemli ölçüde etkilemekte olup, bu etkilerin bölgesel ölçekte anlaşılması sürdürülebilir su kaynakları yönetimi açısından kritik önem taşımaktadır. Türkiye'nin en büyük ve en yüksek rakımlı coğrafi bölgesi olan Doğu Anadolu, sınır aşan Fırat ve Dicle nehirlerinin kaynak havzalarını barındırması nedeniyle hem ulusal hem de bölgesel su güvenliği açısından stratejik bir konumdadır. Bununla birlikte, bölgenin sert karasal iklimi ve karmaşık topoğrafyası, yer gözlem ağının yoğunluğunu sınırlandırmakta ve hidro-klimatolojik araştırmalar için önemli veri boşlukları oluşturmaktadır. Bu çalışma, yüksek çözünürlüklü (0,1° × 0,1°) ECMWF ReAnalysis 5th Generation – Land (ERA5-Land) reanaliz verilerini kullanarak Doğu Anadolu Bölgesi'nin 1981-2020 dönemi hidro-klimatolojik özelliklerini karakterize etmeyi ve uzun dönemli eğilimleri tespit etmeyi amaçlamaktadır. Çalışmada beş temel karasal yüzey değişkeni analiz edilmiştir: 2 metre hava sıcaklığı, toplam yağış, toprak nemi (0-7 cm ve 7-28 cm katmanları), toplam buharlaşma ve yüzey ile yeraltı akışı toplamı. Trend tespitinde parametrik olmayan Mann-Kendall testi ve Sen's slope tahmincisi kullanılmış, validasyon ise 48 Meteoroloji Genel Müdürlüğü (MGM) istasyonu gözlemleriyle gerçekleştirilmiştir. Validasyon sonuçları, ERA5-Land yağış verilerinin gözlemlerle güçlü uyum sergilediğini (R²=0,886) göstermekle birlikte, sistematik pozitif sapma (+87,4 mm/yıl, %17) tespit edilmiştir. Bölgesel klimatoloji, yıllık ortalama sıcaklığın 7,26±0,96°C, yağışın 767,5±94,8 mm, buharlaşmanın 485,2±26,1 mm ve toplam akışın 302,4±93,0 mm olduğunu ortaya koymuştur. Trend analizi, bölgenin tamamında istatistiksel olarak yüksek düzeyde anlamlı bir ısınma eğilimi (+0,54°C/10yıl, p<0.001), toprak neminde azalma (-0,0033 m³/m³/10yıl, p=0,031) ve buharlaşmada artış (+7,0 mm/10yıl, p=0,029) tespit etmiştir. Bu eş zamanlı değişimler, bölgede devam eden bir arazi kuraklaşması sürecine işaret etmekte olup, küresel ısınma süreci ile tarımsal kuraklık riskinin artması ve sınır aşan su kaynakları yönetimi üzerinde potansiyel etkileri olduğunu göstermektedir.

Anahtar Kelimeler

• ERA5-Land
• Doğu Anadolu
• hidro-klimatoloji
• Mann-Kendall
• trend analizi
• iklim değişikliği

Destekleyen Kurum

Yok / Bulunmamaktadır.

Etik Beyan

Bu çalışma halka açık ikincil veri kaynaklarını (ECMWF ERA5-Land reanaliz verileri ve Meteoroloji Genel Müdürlüğü istasyon gözlemleri) kullanmaktadır. Çalışmada insan veya hayvan katılımcı bulunmamakta, anket, görüşme veya kişisel veri toplanmamıştır. Bu nedenle Yükseköğretim Kurumları Bilimsel Araştırma ve Yayın Etiği Yönergesi kapsamında etik kurul onayı gerektirmemektedir.

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