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Assessment of the surface urban heat island

Conventionally, UHI studies relied on in situ air time series from 1988 to 2024, this research provides
temperature measurements from fixed weather stations. the most comprehensive long-term assessment of
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While valuable, this approach often suffers from SUHI dynamics in HCMC to date. This multi-decadal
sparse station networks, limiting its ability to capture approach allows us not only to confirm the existence of
the fine-scale spatial heterogeneity of urban thermal SUHI but also to meticulously quantify its evolution,
environments. Remote sensing technology offers a expansion, and changing intensity over time, an insight
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powerful alternative, providing synoptic, spatially unattainable from shorter-term studies. This deep
continuous data over large urban expanses with frequent historical perspective is critical for developing far-
revisit capabilities. Satellite-derived land surface sighted urban planning policies and effective climate
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temperature (LST) is a key parameter for SUHI studies, change adaptation strategies.
enabling the detailed mapping and monitoring of This study aims to contribute to this understanding
thermal patterns. The Landsat series of satellites, with by: (i) Assessing the spatiotemporal evolution of the
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its long-term archive and moderate-resolution thermal SUHI phenomenon in HCMC using a 36-year time
infrared bands, has been used extensively for LST series of Landsat imagery (1988–2024); (ii) quantifying
retrieval and SUHI analysis globally. 11,12 Concurrently, LST changes across the urban-rural gradient to
the normalized difference vegetation index (NDVI), analyze the expansion and intensification of the heat
another standard satellite-derived product, is used island; and (iii) investigating the correlation between
to quantify vegetation density and assess its cooling LST and NDVI to quantitatively evaluate the role of
effect. 13 vegetation in modulating surface temperatures. The
Numerous studies have investigated the SUHI findings are expected to provide a comprehensive,
phenomenon across diverse urban settings. For instance, updated perspective on SUHI dynamics in HCMC,
research in Bangkok, Thailand, using Landsat 8 imagery, offering crucial, data-driven insights for urban planners
revealed that LST in urban areas was typically 4°C higher and policymakers to develop effective strategies for
than in vegetated suburban areas. Similar investigations sustainable urban development and climate change
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in other Asian megacities, such as Shenzhen, China, and adaptation.
New Delhi, India, have also reported significant SUHI
effects, with urban LST exceeding that of vegetated 2. Materials and methods
areas by 3–4°C and correlating strongly with land
use changes and impervious surface expansion. 15,16 2.1. Study area
These studies underscore the commonality of the HCMC, located in the southeastern region of Vietnam,
SUHI phenomenon while also highlighting the city- is the nation’s largest city and a primary economic,
specific nature of its intensity and drivers, which are cultural, and educational hub. Characterized by
influenced by local geography, climate, and urban substantial growth and urban expansion, the city covers
form. Ho Chi Minh City (HCMC), Vietnam’s largest a total area of approximately 2,095 km (Figure 1).
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urban agglomeration and primary economic engine, has HCMC’s topography is generally flat, with about
undergone exceptionally rapid urbanization over recent 60% of its area lying below an average elevation
decades. With a population exceeding 10 million, this of 1.0 m. The city experiences a tropical monsoon
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growth has involved a significant transformation of climate with distinct wet (May–November) and dry
agricultural land into built-up areas, accompanied by (December–April) seasons. The population has grown
extensive infrastructure development. Such land use/ to over 9 million residents, with an average density of
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land cover (LULC) changes have inevitably impacted 4,481 people/km , and approximately 80% residing in
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the local climate, contributing to the emergence and urbanized areas. The rapid and often unplanned urban
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intensification of the SUHI phenomenon in HCMC. 19,20 sprawl has led to significant alterations in land use,
Previous research has provided a valuable foundation contributing to environmental challenges, including the
for understanding this issue. However, a continuous, SUHI effect.
multi-decadal assessment incorporating the most recent
data is needed to fully understand long-term trends and 2.2. Data collection and pre-processing
inform effective mitigation strategies. This study utilized multi-temporal Landsat satellite
The novelty and primary contribution of this imagery from Landsat 5 Thematic Mapper (TM),
study lie in its unprecedented temporal scale. By Landsat 7 Enhanced TM Plus (ETM+), and Landsat
employing a consistent methodology across a 36-year 8 Operational Land Imager/Thermal Infrared Sensor.

Volume 22 Issue 6 (2025) 211 doi: 10.36922/AJWEP025260210