City Heat: Exploring Urban Heat Island in Jakarta
A great city is not to be confounded with a populous one.
Aristotle
When people talk about Jakarta, they often refer to it ambiguously as a city. While that’s true in a general sense, if we dive deeper into the specifics — especially from an administrative geography perspective — Jakarta is actually a province. It is the smallest province in Indonesia, divided into five administrative cities, each governed by a mayor. These cities are easy to remember; North Jakarta, East Jakarta, South Jakarta, West Jakarta, and Central Jakarta, with names simply based on their compass directions.
Central Jakarta is the hub of government activity. It houses the Presidential Palace, various ministries, and other legal and governmental institutions that carry out official duties. Each of cities in Jakarta also serve as the basis of economic activities in various sector. Skyscrapers dominate the landscape, with office buildings, hotels ranging from 1 to 5 stars, traditional and international restaurants, modern city parks, amusement parks, indie coffee shops, colonial-era buildings, slums, and townhouses all contributing to the diverse character of Jakarta province.
Due to Jakarta’s bustling nature, it has grown into a populous city. The residents of Jakarta, known as Jakartans, live and work in the province, spending most of their time enjoying urban recreational activities because Jakarta primarily offers urbanized experiences. The city lacks natural features like mountains, and while there are beaches and mangrove forests, they aren’t particularly appealing for Jakartans. Jakarta’s beaches are muddy and often unpleasant, so don’t compare them to the pristine beaches of Bali.
For recreation, most Jakartans, especially the younger generation, prefer malls, urban parks, or hanging out in public spaces and indie coffee shops. This trend has become a cultural phenomenon among young people in Jakarta, dating back to 2017 and continuing today.
The bustling economic growth in Jakarta, which drives urban expansion, not only shapes the culture and its people but also has a significant impact on the environment. Walk through Jakarta at any time — whether it’s 9 a.m., noon, 3 p.m., or even 9 p.m. — and you’ll feel the heat. Jakarta’s climate is naturally hot and humid, given its location in a tropical country, but human activities have intensified the heat.
Massive urbanization has led to a city dominated by buildings, asphalt, and concrete structures. Combined with the pollution from private transportation — cars and motorcycles that Jakartans rely on to get around — this has amplified the effects of the urban heat island (UHI) phenomenon. The result is a city where the heat feels much more extreme, no matter the time of day.
What is urban heat island (UHI)? UHI is a phenomenon that occurs in every big cities, or technically areas which experiences significantly higher temperatures than their surrounding rural areas due to anthropogenic activities and the built environment. The causes of UHI phenomenon is anthropogenic related. Because urban areas tend to have fewer trees and green spaces which reduce the amount of cooling through evapotranspiration. Urban areas are built with materials such as asphalt, concrete, and buildings which absorb and retain more heat than natural surfaces such as soil and vegetation. Materials like asphalt, concrete, and buildings have high capacities and thermal conductivity, causing them to store heat during the day and release it slowly at night.
Waste heat from human activities, such as vehicles, factories, air conditioners, and other urban processes, plays a major role in increasing cities temperatures. In Jakarta, where the tropical climate is naturally hot, air conditioning is practically a necessity. With over 3,400 skyscrapers, each almost certainly fitted with air conditioning, the amount of waste heat generated by these buildings is staggering.
Additionally, Jakarta’s dense concentration of tall buildings and narrow streets creates urban “canyons” that trap heat, restrict airflow, and reduce natural cooling, leading to localized heat pockets. Now factor in the heat produced by over 17.4 million vehicles used by Jakartans daily. This combination of waste heat from buildings and transportation escalates the overall temperature, further intensifying the urban heat island effect, making the city feel even hotter and more uncomfortable.
To mitigate the urban heat island effect, several strategies can be implemented. Using materials that reflect more sunlight and absorb less heat, green roofs, urban planning, and planting trees. The latter is the most effective — and yet challenging approaches. Planting more trees and developing green spaces can help cool urban areas through shading and evapotranspiration. While Jakarta does have green spaces, they are not evenly distributed throughout the city. Below is a Proportion of Vegetation (Pv) map for Jakarta, which estimates the abundance of vegetation across different areas, highlighting the disparities in green space distribution.
If you’re a technical person, you may find this equation useful for calculating the Pv, which you can apply to your area of interest:
NDVI = NDVI for the area
NDVIs = Minimum NDVI (representing bare soils or no vegetation)
NDVIs = Maximum NDVI (representing full vegetation coverage)
Before calculating Pv, make sure to calculate the NDVI first.
Pv values range from 0 to 1, where 0 indicates no vegetation and 1 represents full or maximum vegetation coverage. Intermediate values reflect partial vegetation cover. Unfortunately, Jakarta does not reach full vegetation coverage, with a highest Pv value of 0.53 and a lowest of 0.16. The average Pv values across Jakarta’s cities are relatively close but show some variation. Central Jakarta has an average Pv of 0.24, North Jakarta and West Jakarta 0.25, and East Jakarta and South Jakarta both have average Pv of 0.28.
Jakarta’s green spaces include land uses such as city parks, forests, golf courses, zoos, gardens, and areas with flooded vegetation, like swamps. However, these green spaces are unevenly distributed throughout the city, which limits their potential to significantly mitigate the urban heat island effect.
Vegetation coverage significantly affects the actual temperature of the land surface, known as Land Surface Temperature (LST). LST refers to the temperature of the Earth’s surface, including the ground or vegetation canopy, as measured from space by detecting the thermal infrared energy radiating from the surface. It’s important not to confuse LST with air temperature, as LST specifically measures the temperature of the land, not the air above it. Vegetation helps regulate LST by providing shade and through processes like evapotranspiration, which can cool the surrounding environment.
The equation used for calculating LST from satellite data is typically derived from the thermal infrared (TIR) bands and is shown below.
BT = Brightness Temperature (°C)
ε = Land Surface Emissivity
The eastern part of Jakarta exhibits a high LST value, with East Jakarta having an average LST of 28.10 °C. In contrast, North Jakarta shows the lowest average LST at 26.18 °C. The relationship between land use, land cover, and the urban heat island effect is evident in these differences. North Jakarta, for example, benefits from a more evenly distributed mix of parks, amusement parks, lakes, and swampy, flooded vegetation, which help to reduce the urban heat island effect by providing natural cooling, even though the area doesn’t meet ideal ecological standards.
Areas with higher LST values, typically represented in reddish colors on the map, are dominated by concrete structures and buildings, which trap and radiate heat. Among Jakarta’s five cities, East Jakarta is the most populous, with 3.31 million inhabitants, contributing to its higher LST due to dense urbanization and limited green space compared to other areas in the province.
Land Surface Temperature (LST) is crucial to examine urban heat island effect. LST value for specific city can be use to calculate Urban Heat Island Normalized (UHIn), which is calculated based on the difference between urban and rural LST. This formula normalizes the UHI intensity by expressing it as a fraction of the total LST range in the region.
Ts = Land Surface Temperature (LST)
Tstd = LST’s standart deviation value
Tm = LST’s mean value
North Jakarta, due to its land use and land cover, experiences the lowest urban heat island effect, while East Jakarta faces the highest. This finding might be surprising to young Jakartans, who often hold the stigma that the northern part of the city is unbearably hot. Contrary to this belief, the data shows that North Jakarta has the lowest Land Surface Temperature (LST) and urban heat island effect compared to other Jakarta cities. This is largely because North Jakarta’s green spaces, including parks, lakes, and swampy areas, contribute to a cooling effect that mitigates the intensity of heat, contrary to the common perception.
Urban Thermal Field Variance Index (UTFVI)
The Urban Thermal Field Variance Index (UTFVI) is a critical parameter used to quantify the spatial differences in Land Surface Temperature (LST) within urban areas. It helps assess urban heat island (UHI) intensity and can be a valuable tool for identifying ecological conditions in specific regions. Urban planners can utilize UTFVI to better understand thermal variability, assess the impact of heat in urban areas, and guide future urban planning efforts.
The equation for calculating UTFVI is as follows:
Where,
Ts = Land Surface Temperature (LST)
Tm = LST’s mean value
There is qualitative parameter that help in interpreting the UTFVI index, making it a useful tool for urban heat island (UHI) analysis. These qualitative parameter provides insight into the ecological status and urban heat severity in specific areas. The table below presents the interpretation of different UTFVI values:
The UTFVI map above was created using the equation provided for calculating the Urban Thermal Field Variance Index (UTFVI). Across Jakarta, the highest UTFVI value is 0.33, while the lowest is 0.13. The map shows the average UTFVI values for each of Jakarta’s cities: North Jakarta stands at 0.22, East Jakarta at 0.28, and South Jakarta, West Jakarta, and Central Jakarta each at 0.25.
What’s concerning is that Jakarta as a whole exceeds the critical UTFVI threshold of 0.045, which places the city in the “Dangerous” category, indicating severe urban heat island effects and serious ecological disruption. This confirms what many Jakartans already experience — the city is highly prone to extreme heat. While the residents of Jakarta have adapted to these conditions, it’s a worrying sign for long-term livability, as continuous exposure to such environmental stress can have detrimental effects on both human health and the urban ecosystem.
Addressing these high UTFVI values through better urban planning, green space expansion, and sustainable infrastructure is crucial for improving Jakarta’s ecological status.
Source:
[1] Carlson, T. N., & Ripley, D. A. (1997). On the relation between NDVI, fractional vegetation cover, and leaf area index. Remote Sensing of Environment, 62(3), 241–252. https://doi.org/10.1016/S0034-4257(97)00104-1
[2] Li, Z., Wang, N., Li, Q., & Zhao, C. (2018). Calibration of top-of-atmosphere radiance for remote sensing applications. Remote Sensing, 10(9), 1360. https://doi.org/10.3390/rs10091360
[3] Nguyen, T. M., Lin, T. H., & Chan, H. P. (2019). The environmental effects of urban development in Hanoi, Vietnam from satellite and meteorological observations from 1999–2016. Sustainability, 11(6), 1768.
[4] Sobrino, J. A., Jiménez-Muñoz, J. C., & Paolini, L. (2004). Land surface temperature retrieval from LANDSAT TM 5. Remote Sensing of Environment, 90(4), 434–440. https://doi.org/10.1016/j.rse.2004.02.003
[5] Tucker, C. J. (1979). Red and photographic infrared linear combinations for monitoring vegetation. Remote Sensing of Environment, 8(2), 127–150. https://doi.org/10.1016/0034-4257(79)90013-0
[6] Wan, Z., & Dozier, J. (1996). A generalized split-window algorithm for retrieving land-surface temperature from space. IEEE Transactions on Geoscience and Remote Sensing, 34(4), 892–905. https://doi.org/10.1109/36.508406
[7] Wang, F., Xu, Y., Xu, W., & Liu, J. (2015). Brightness temperature estimation and its application in land surface temperature retrieval. Journal of Applied Remote Sensing, 9(1), 097697. https://doi.org/10.1117/1.JRS.9.097697
[8] Zhang, H., & Wang, Y. (2008). An analysis of urban thermal field variance using high-resolution thermal infrared remote sensing data. International Journal of Remote Sensing, 29(17–18), 5315–5338. https://doi.org/10.1080/01431160802036510
[9] Zhang, Y., Zheng, B., Zhang, H., & Zhao, X. (2013). The normalized urban heat island intensity index: A new metric to quantify UHI. Building and Environment, 69, 79–87. https://doi.org/10.1016/j.buildenv.2013.08.021
Software and Plugin:
[1] Congedo, Luca, (2021). Semi-Automatic Classification Plugin: A Python tool for the download and processing of remote sensing images in QGIS. Journal of Open Source Software, 6(64), 3172, https://doi.org/10.21105/joss.03172
[2] QGIS.org (2024). QGIS Geographic Information System. Open Source Geospatial Foundation Project. http://qgis.org
Dataset:
[1] Badan Pusat Statistik Provinsi DKI Jakarta. (n.d.). Jumlah penduduk menurut kabupaten/kota di Provinsi DKI Jakarta. Badan Pusat Statistik. Retrieved September 17, 2024, from https://jakarta.bps.go.id/id/statistics-table/2/MTI3MCMy/jumlah-penduduk-menurut-kabupaten-kota-di-provinsi-dki-jakarta-.html
[2] Landsat-8 image courtesy of the U.S. Geological Survey
