Water features as the main SUHI hindering factor across 50 global cities

Abstract

We propose a cloud-based, open-source, user-friendly, highly-customizable, and globally-available 30-m system, named SUHI-GEE. This system can conduct stepwise regressions of 20+ different literature-based factors to derive SUHI main contributing factors within each city and across cities. We implemented SUHI-GEE over 50 major cities in 38 different countries in 2022, studying the normal/average, hot and extreme temperatures' occurrences. We found out that the global average of 2.46 variables influencing >60% SUHI on normal conditions has decreased to 1.98 and 1.6 under hot and extreme conditions, respectively. Urban fabric, studied in terms of the Normalized Difference Built-up Index (NDBI), was the most influential factor under the three conditions (i.e., normal, hot and extreme) explaining >51% of the SUHI values. It is followed by urban vegetation variables, represented mainly by the Normalized Difference Vegetation Index (NDVI), even though its influence decreased ∼8% over hot temperatures and ∼ 19% over extreme temperatures. Under these conditions, urban water variables have showed a continuously increased relationship to SUHI, with the highest found in the Seasonal Water with an increase of 6% and 2% under hot and extreme conditions, respectively. Future efforts should mainly focus on the availability of water to curb SUHI impacts.