İSTANBUL VE ANKARA'NIN SICAKLIK KAYITLARINDAKİ KENTSEL ETKİNİN DEĞERLENDİRİLMESİ: BİREYSEL OLARAK METROPOLLER KENTSELLEŞMEYE YANITTA NASIL FARKLILIK GÖSTEREBİLİR?

Abstract

Bu çalışma, Türkiye'nin stratejik metropolleri olan İstanbul ve Ankara'nın kentsel ve kırsal bölgelerindeki sıcaklık değişkenliğini, 2011-2018 dönemini kapsayan periyot için uydu, yer gözlemleri ve Avrupa Orta Vadeli Hava Tahmin Merkezi (ECMWF) reanaliz verilerini kullanarak incelemektedir. Bu çalışmanın uygulaması iki temel bileşenden oluşmaktadır. İlk olarak, istasyon gözlemlerinden sağlanan saatlik 2 metre ortalama sıcaklık verileri kullanılarak kentsel ve kırsal istasyonların yıllık, mevsimsel ve aylık sıcaklık özelliklerindeki farklılıklar şehir özelinde analiz edilmiştir. İkinci olarak, GHS Yerleşim Modeli 1 km çözünürlüğünde veri seti kullanılarak kentsel ve kırsal grid noktaları belirlenmiş ve MODIS-Terra günlük yüzey sıcaklık verileriyle kentsel ve kırsal grid noktaları arasındaki uzun vadeli farklılıkları ortaya konmuştur. Ayrıca, grid tabanlı analizde, her şehirde kentsel ve kırsal alanlarda günlük maksimum sıcaklığın belirli bir eşiği aşan gün sayısını karşılaştırmak için yüksek çözünürlüklü CHIRTS-günlük sıcaklık ürünü kullanılmıştır. Sonuçlar, kentsel ısı adası (UHI) etkisi olarak adlandırılan kentsel ve kırsal alanlar arasındaki sıcaklık farkı değişkenliği incelenmiştir. Ancak, bu değişkenlik, kentsel alanların toplam çalışma alanının yaklaşık %20'sini oluşturduğu İstanbul için kentsel alanların %4'ten daha az olduğu Ankara'ya göre çok daha yüksek tespit edilmiştir. İstanbul'daki kentsel kullanımı dikkate aldığımızda, gözlemlenen sıcaklık değerlerinin, olasılık dağılım fonksiyonunun (PDF) daha sıcak bir tarafına kaydığına dair net bir sinyal bulunmakta ve bu durum kernel yoğunluk kestirimi analizi ile ortaya konmaktadır. Ancak, Ankara için karşılık gelen PDF analizinde dikkate değer bir değişiklik görülmemektedir. Uzun vadeli UHI analizleri de bu bulguları desteklemekte olup, İstanbul'un kentsel ve kırsal konumları arasındaki yıllık, mevsimsel ve aylık sıcaklık farkı, Ankara'ya kıyasla daha belirgindir. Bu çalışma, farklı şehirlerde kentsel etkinin geniş bir genelleştirmesinden kaçınmanın önemini aktarmaktadır.

Keywords

• Kentsel Isı Adası
• Kentleşme
• Sıcaklık
• Uzaktan Algılama
• Arazi Örtüsü

ASSESSMENT OF THE URBAN IMPACT ON THE TEMPERATURE RECORDS OF ISTANBUL AND ANKARA: HOW CAN INDIVIDUAL METROPOLES DIFFER IN RESPOND TO URBANIZATION?

Abstract

This study examines the temperature variability over urban and rural sites of Istanbul and Ankara, two strategic metropoles in Turkiye, using multiple data sources, including satellite, ground observations, and a reanalysis product for the period of 2011-2018. The practice of this study is twi-formed. Firstly, we introduce a location-based analysis, in which we identify the differences in annual, seasonal, and monthly temperature characteristics of urban and rural stations using hourly 2-meter mean temperature provided from station observation data. Secondly, in the grid-based analysis, we utilize the GHS Settlement Model grid classification dataset with a resolution of 1 km to determine urban-rural grids and employ the MODIS-Terra daily land surface temperature data to reveal the long-term dissimilarity of the urban and rural grids. Also included in the grid-based analysis is the CHIRTS-daily temperature product at high resolution, which we use to compare the number of days where the daily maximum temperature exceeds a specified threshold at urban and rural grids in each city. Results reveal the variability of the temperature difference between the corresponding urban and rural grids, which we refer to as the urban heat island (UHI) effect. However, this variability is higher for Istanbul, where urban land use constitutes approximately 20% of the grids, compared to Ankara, where the percentage of the grids represented by urbanization is less than 4%. When we consider the urban land use in Istanbul, there is a clear signal of a shift in the location parameter of observed temperature values to the warmer side of the probability distribution function (PDF), as revealed by the kernel density estimation analysis. Yet, for Ankara, we do not see a notable change in the corresponding PDF. Long-term UHI analyses also support these, as the difference in annual, seasonal, and monthly temperature between urban and rural locations of Istanbul is more pronounced than in Ankara. This study communicates the importance of avoiding a broad generalization of the urban impact in different cities.

Keywords

• Urban Heat Island
• Urbanization
• Heat
• Remote Sensing
• Land Cover

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