Yüzey Sıcaklıkları Üzerinde Kentsel Yeşil Alanların Soğutma Etkisi: Bornova Örneği

Öz

Bu çalışma, küresel kentleşme ve iklim değişikliğinin birlikte yarattığı kentsel ısı adası (UHI) olgusunu, İzmir’in Bornova ilçesindeki yeşil alanların serinletici etkisi üzerinden incelemektedir. Araştırmada problem, geçirimsiz yüzeylerin artışıyla yükselen yüzey sıcaklıklarının enerji tüketimi, hava kirliliği ve halk sağlığı üzerindeki olumsuz yansımaları olarak tanımlanmış; kuramsal temel, yeşil alanların park serinletme etkisi (PCI) oluşturarak kentsel mikroiklimi iyileştirdiği yaklaşımına dayandırılmıştır. Bu amaçla, farklı büyüklük ve özelliklere sahip 27 kentsel yeşil alana ait 2024 yılı temmuz dönemine ilişkin Landsat 8 ve Sentinel-2 uydu görüntüleri değerlendirilmiş; ArcGIS 10.8.2 yazılımı ile yüzey sıcaklıkları hesaplanmış, PCI değerleri üç farklı tampon mesafe (100, 200, 300 m) için belirlenmiş ve SPSS Statistics 30 yazılımı ile regresyon analizleri yapılmıştır. Bulgular, yüzey sıcaklıklarının en yüksek değerlerinin yoğun yapılaşmış ve sanayi bölgelerinde (38,20-41,01 °C), en düşük değerlerin ise orman örtüsüne sahip alanlarda (24,36-27,40 °C) görüldüğünü ortaya koymuştur. Yeşil alanların serinletici etkisi en fazla 5,9 °C’ye ulaşmış, ancak bitki örtüsü kaybı yaşayan geniş ölçekli bazı yeşil alanlarda beklenen etki gözlenmemiştir. İstatistiksel analizler, serinletme etkisini en güçlü biçimde açıklayan değişkenin yeşil yüzey oranı olduğunu, alan büyüklüğünün negatif yönde ve çoğunlukla anlamlı bir etkiye sahip bulunduğunu, şekil indeksinin ise anlamlı bir belirleyici olmadığını göstermiştir. Sonuç olarak, kentsel yeşil alanların soğutma kapasitesinin homojen olmadığı, özellikle bitki örtüsünün yoğunluğu ve mekânsal organizasyonunun büyüklükten daha belirleyici olduğu saptanmış; bu durum, kentsel planlama süreçlerinde küçük ölçekli dahi olsa zengin bitki örtüsüne sahip ve doğru konumlandırılmış yeşil alanların UHI etkisini azaltmada kritik rol oynayabileceğini ortaya koymaktadır.

Anahtar Kelimeler

• Kentsel Isı Adası
• Park Serinletme Etkisi
• Yüzey Sıcaklığı
• Şekil İndeksi
• İzmir

The Cooling Effect of Urban Green Spaces on Land Surface Temperatures: The Case of Bornova

Öz

This study examines the urban heat island (UHI) phenomenon, arising from the combined effects of global urbanization and climate change, through the cooling influence of green spaces in the Bornova district of İzmir. The research problem is defined as the adverse consequences of rising surface temperatures -driven by the expansion of impervious surfaces- on energy consumption, air pollution, and public health. The theoretical framework is grounded in the notion that green spaces improve the urban microclimate by forming park cooling islands (PCI). To investigate the cooling effects of urban green spaces, Landsat 8 and Sentinel-2 satellite images from July 2024 were analyzed for 27 urban green areas differing in size and characteristics. Surface temperatures were calculated using ArcGIS 10.8.2, PCI values were determined for three buffer distances (100, 200, and 300 m), and regression analyses were conducted with the SPSS Statistic 30 software. The results indicated that the highest surface temperature values were calculated in densely developed and industrial regions (38.20-41.01 °C), whereas the lowest values were found in areas with forest cover (24.36-27.40 °C). The maximum cooling effect of green spaces reached 5.9 °C; however, in some large-scale green spaces with vegetation loss, the expected effect was not observed. Statistical analyses indicated that the proportion of green cover is the strongest predictor of cooling performance, while area size displayed a negative and mostly significant influence, and the shape index was not a meaningful determinant. Overall, the study concludes that the cooling capacity of urban green spaces is not homogeneous. Rather, the density and spatial configuration of vegetation are more decisive than area size. This highlights that, even at smaller scales, well-vegetated and strategically located green spaces can play a critical role in mitigating UHI effects within urban planning processes.

Anahtar Kelimeler

• Urban Heat Island
• Park Cooling Island
• Land Surface Temperature
• Shape Index
• İzmir

Kaynakça

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