Cooling capacity assessment in Karet Tengsin Platinum Integrated Area

The increasing trend of urbanisation has resulted in land use changes and increased urban activities, which led to the emergence of the Urban Heat Island (UHI) phenomenon. The readiness of urban design and planning in mitigating UHI becomes crucial, to reduce the demand for cooling energy and enhance productivity. This study aimed to calculate the cooling capacity index of the Karet Tengsin Platinum Area design, using InVEST 3.12.1, based on shading, evapotranspiration, albedo, and distance from cooling islands, and it has a range of 0-1. The index was further analysed, using the kernel density method, to examine the spatial density patterns to identify the priority features that need to be intervened to mitigate UHI in the Area. The research findings show that, the Karet Tengsin Platinum Area design has a cooling capacity index ranging from 0.22 to 0.83, dominated with a low index value, below 0.3, indicating that, this area has poor cooling capacity. Low index values are distributed in built-up areas, which show that, the materials used in built-up areas need to be prioritised as features that need to be intervened to enhance the cooling capacity. Additionally, this study also discusses urban cooling strategies, through other features that are less explored in the modelling. This study method can be used as a reference for urban designers in integrating urban cooling approaches, as UHI mitigation strategies, in urban area planning and design.


Introduction
The urbanisation trend is increasing day by day.In Indonesia as a whole, in 2020, 56.7% of the population lived in urban areas, and the percentage is expected to increase to 66.6% by 2035 [1].Rapid urbanisation has led to an increased demand for built-up land, resulting in significant land use changes in urban areas and increased urban activities.This increase, in turn, affects energy consumption in urban areas.Excess heat energy is often unable to be absorbed and is instead reflected by built-up surfaces in urban areas, leading to an increase in temperature and the emergence of the Urban Heat Island (UHI) phenomenon.
UHI is a phenomenon caused by human activities and urban physical characteristics, such as dense land cover, construction materials or abnormal airflow patterns, which result in higher air temperature in cities than the surrounding areas, both rural and suburban [2].The increase in UHI has implications for the decreasing quality of urban life, such as increased potential health risks, reduced air quality and water quality, increased cooling energy demand, and reduced economic growth [3].Research conducted by Nandi & Dede [4] shows that, areas with high UHI are typically associated with those with high urban activities, including Central Business Districts (CBDs).A study conducted by Kamruzzaman et al. [5] also shows that, Transit Oriented Development (TOD) areas experienced a higher level of UHI effect, compared to non-TOD area.
Karet Tengsin Platinum Integrated area, located in Central Jakarta, Indonesia, is a superblock area with a strategic position in the CBD and within the TOD radius, flanked by three main arteries.Presently, the area exhibits relatively low Surface Urban Heat Island (SUHI) intensity (1.5-3° Celsius), compared to other parts of Jakarta, including Kemayoran and Taman Sari (6-7.5°Celsius) [6].However, the strategic location has spurred rapid development, necessitating preparedness to mitigate potential future impacts, including a potential increase in UHI intensity.Additionally, in tandem with the area's sustainable development vision outlined in its masterplans [7], assessing its design performance in mitigating the UHI effect becomes crucial.
Cooling capacity is a crucial factor for mitigating UHI effects.Green Urban Infrastructure (GUI), a combination of green infrastructure and building systems, plays a significant role in providing cooling to urban areas experiencing UHI [8].GUI achieves this through shading, evapotranspiration, air movement optimisation, and heat exchange alteration [9].Although previous studies have emphasised the importance of GUI in natural cooling, only a limited number of research on integrated multiple cooling elements are available, rendering it difficult to analyse their collective contribution.This study aimed to calculate the cooling capacity index of Karet Tengsin Platinum Integrated Area Design and identify priority features for comprehensive UHI mitigation, taking various cooling elements into consideration.

Study Area
Karet Tengsin Platinum Integrated area is a mixed-use superblock in the Tanah Abang District, Central Jakarta, Indonesia.The area has a triangular shape with a total area of approximately 53.3 hectares.Based on the masterplan [7], this area would be separated into several types of land uses, 74.03% as built-up areas such as retail, residential, mixed-use, and utilities; and the remaining 25.97% as green areas.

Materials
In this research, there were several types of data required, as follows: 1. Land Use/Land Cover (LULC): In this study, land use maps were sourced from the Karet Tengsin Platinum Area Urban Design Guideline [7] with spatial resolution of 4.7 m.The proposed land uses were simplified into 8 types, grouped into 3 feature categories; grass, wide-canopy trees, and slender-canopy trees standing for green feature components, water bodies standing for blue feature components, and high-rise building, low-rise buildings, pedestrian areas, and roads standing for grey feature components.2. Biophysical Table : The biophysical table ( [10].c.The green area value was assumed to be 1, for areas without pavement, and 0 for areas with pavement.d.The shade value was assumed to be 1 for green areas and 0 for non-green areas.e.The albedo value was determined, based on the study conducted by Zawadzka et al. 2021 [10], Bradley et al. 2002 [11], and Sanjuan et al. 2021 [12].The albedo values for each land use type were estimated from an existing condition, assuming that the lowest solar reflection value was for water, followed by paved areas and low-rise buildings, due to their dark colour, and the highest value was for high-rise buildings, due to their bright colour, with vegetated areas falling in the middle range.

Evapotranspiration: Data related to evapotranspiration maps were obtained by referring to the
Global PET data at https://cgiarcsi.community/data/global-aridity-and-pet-database/ [13].4. Maximum Cooling Distance: The distance at which green areas with a size exceeding 2 hectares exhibit a cooling effect.The value was obtained by referring to the recommended value, which is 100 meters.5. Air Mixing Distance: The radius at which the average air temperature is considered for air mixing.
The value was obtained by referring to the recommended value, which was 2000 meters.6. UHI Magnitude: The extent of the UHI phenomenon, that refers to the disparity between the highest temperature recorded within the urban area and the rural reference temperature.The value was obtained by referring to the Global_Surface_UHI_Explorer (earthengine.app)[6], which was 3.06°C.7. Non-UHI Reference Temperature: The air temperature where the UHI effect is not present in the comparison area.Data was obtained from the average temperature data of [14] Indonesia's Meteorology, Climatology, and Geophysical Agency (BMKG) in Tanjung Priok for the past 5 years (2018-2022) in the summer month (June) and the rainy season month (December), with Tanjung Priok area assumed as the unaffected reference area.The value used was 28.63°C.

Cooling Capacity Assessment
This study assessed the cooling capacity of the Karet Tengsin Platinum Integrated area design, conducted using urban cooling modelling in the InVEST 3.12.1 application.Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) is a modeling application used to map and assess ecosystem services.Urban cooling modeling is one of the types of modeling available in the InVEST application, which calculates the cooling capacity index based on shade, evapotranspiration, albedo, and distance from cooling islands [9,15].These factors are calculated using equation ( 1) with different weights for each factor, based on their respective impacts on the cooling effect [16].
The values of these indices shall be between 0 and 1, with 0 being the lowest and 1 the highest.The shading factor shows the proportion of tree canopy (with a minimum height of 2 m) related to different land use type, with values ranging from 0 to 1.The albedo factor measures the solar radiation absorbed by any type of land use, with values ranging from 0 and 1. [17].The Evapotranspiration Index (ETI) is calculated as a normalised potential for evapotranspiration, based on equation ( 2), with ET0 as reference evapotranspiration, Kc as crop coefficient associated with each land use type, and ETmax as the maximum value of the ET0 raster.
Subsequently, the index values will be divided into four classes: very poor, poor, fair, and very good, with equal value intervals for each class, based on the minimum-maximum value for a simpler visualisation and interpretation of the results, while ensuring that, the classes are more representative of the actual distribution of the data.The assessment of UHI mitigation readiness for the area will be determined by calculating the percentage distribution of all classes of the cooling capacity index.

Cooling Capacity Index Spatial Density Patterns Analysis
The cooling capacity values were randomly distributed throughout the entire area, therefore the existing values were further analysed, using kernel density in the ArcGIS application, to see the density patterns of each index.For each cooling capacity index value, the Kernel Density tools calculated the magnitude per unit area from the features, using the kernel function to fit a smooth tapered surface to each cooling capacity index value [18].Subsequently, the density patterns of the indices were overlaid with two land use categories: green-blue features and grey features.The grouping was done to simplify the classification process and to focus on specific features that have or do not have cooling effect, to mitigate UHI.This analysis was used to identify priority features that need to be intervened to mitigate UHI in the Area.Based on the simulation results, it was found that the cooling capacity index values range from 0.22 to 0.83, with a distribution dominated by low index values (below 0.3) and an average index of 0.28.The range of cooling capacity index values in the area is only found in the extreme classes, which are very good and very poor.This can occur due to the variation in weight and values assigned to each factor in different land use types, which tends to be unbalanced.The cooling capacity index is predominantly found in the very poor cooling capacity index class (0.22-0.372), which is covering 92.8% of the area.This shows that, the design of the area still has a low capacity for UHI mitigation and needs to be further analysed to identify priority features that need to be intervened.6  Referring to Table 3 and Figure 5, it can be observed that, areas exhibiting good and very good cooling capacity index values (56.8%) have a significant presence of green and blue features.This result shows that, the green features in the area can provide natural cooling effects through natural shading in certain areas.This is because, most of the green features are designed to be large-canopy trees.Ronchi et al, 2020 [19] also found that, selecting tree species with high shading capacity is more important to maximise the cooling effect of green space.Meanwhile, according to Gilner et al., 2015 [20], trees showing both advantages of providing a high leaf-area density and a high rate of transpiration are more effective in cooling the air temperatures.However, it is unfortunate that the green features have a low intensity in the area, only 25.97% of the total area.As it is assumed that, the cooling effect only occurs within a 100 m radius of green features, this situation limits the coverage of the cooling effect.That assumptions refer to the research conducted by Zardo et al, 2017 [9] which revealed that, the presence of a cooling effect can still be seen, within a radius of approximately 100 meters, or five times the height of a tree.But the distance value of the cooling island is influenced by several factors, such as the size of the green open space, vegetation cover, vegetation shape, and the direction of the measurement [20].This makes it important to consider the arrangement of the intensity and distribution of green open spaces, as well as the types and coverage of vegetation in an area.Compared to smaller parks, bigger parks have higher cooling capacities and a larger proportion of urban areas devoted to parks provides more extensive cooling advantages.However, even in limited spaces, it is still advisable to use small green areas [21].According to a study conducted by Aram et al. 2019 [22] the greatest distance and intensity of the cooling effect are observed in large urban parks with an area of more than 10 hectares, with a temperature decrease of between 1-2°C, which extends over 350 m from the park boundary.However, it is certainly challenging to achieve this, especially in urban areas with limited space and high built-up intensity, such as the Karet Tengsin Platinum area.Therefore, urban greening solutions, such as green roofs, green walls, and green facades become crucial to implement in the context of enhancing the cooling effect in urban areas.As the proportion of green roof area increased from 25% to 100%, there was a linear reduction in the daytime peak temperature of the roof surface, ranging from 0.75°C to 3.25°C [23].Therefore, Karet Tengsin Platinum Urban Design Guideline should accommodate this solution to address the limited space challenge.

Cooling Capacity Index Spatial Density Pattern
The green and blue features can also be combined to make them cooler.A series of green and blue areas that are aligned with the prevailing wind direction can help circulate cool air throughout the city, allowing individual locations at higher altitudes known as "cool corridors" to have cooling effects [21].Compared with open areas, Blue-green Infrastructure offers a more significant microclimate advantage, resulting in reducing air temperatures by as much as 1.6°C [24].These techniques can be applied, for examples in rain gardens, bioswales, bio lakes, water retaining basins, rainwater harvesting systems, and wetlands.This integration can help increase the cooling effect through a combination process of absorption of solar radiation and raising the evaporation process [25].
Another alternative to enhance the cooling effect is through shading, which can be achieved using various features, including green features, shading features, and urban geometry factors.Shading features such as tenant umbrellas, tents, and curtains cannot directly reduce surface temperature, but this technique can significantly lower radiative temperature.So does the urban configuration, the shadow cast by tall buildings can provide shading for the surrounding areas [26].Several urban configuration factors such as size, spacing, shape, and orientation of buildings and streets also can provide cooling effects in different ways, such as absorption of sunlight by urban surfaces, maximising the wind movement, and the efficiency of heat dissipation from buildings and pavements [3].
However, it should be noted that, the simulation results assume that, only green features can provide shading effects in the area, while other features are considered incapable of doing it.This limitation is one of the drawbacks of urban cooling modelling in the InVEST 3.12.1 application [10].Meanwhile, the calculation of cooling effects generated by other features is only based on the level of reflectivity (albedo) and evapotranspiration, which has a lower weight, compared to shading.Furthermore, other factors, such as wind movement and residual energy are also not considered in the simulations [9].However, other features such as shading features and urban geometry factors can still be added with strategies for maximising the cooling effect in the area.
Regardless of the limitations, other components besides green features can still be considered as the priority intervention to mitigate UHI in the area, especially in areas with poor and very poor cooling capacity index values.Based on Figure 5 and Table 3, it can also be seen that, grey features are most distributed in areas with poor and very poor cooling capacity index values (60.3%).This result shows that, the materials used in the built-up area of the design are unable to provide cooling effects, especially through altering heat exchange.This is because, most grey features in the area have dark colours and low albedo values, resulting in more absorption of heat from sunlight into building materials and pavement compared to reflection, thus making the area hotter.Conventional road pavements, such as asphalt and concrete typically have hard, impermeable, thick, and heavy surfaces, which tend to have low solar reflectivity, ranging from 5% to 20%.These pavements can reach surface temperatures of 48°C to 67°C during summer days [26].Multiple studies also showed that, raising the surface albedo by 0.1 can result in a reduction of 3-5°C in concrete or asphalt surface temperatures [27].Therefore, it is important to regulate buildings or pavements to use cool materials which have high albedo values.
In other ways, there are several strategies to provide a cooling effect through altering heat exchange, which is less explored in the simulations in this study, such as using efficient energy technology, using renewable energy resources, and improving transportation systems.Using efficient energy technology such as district cooling, building management system, efficient energy equipment, and passive cooling strategies can decrease heat losses and increase energy savings.The anthropogenic factors that contribute to the UHI effect can also be regulated with increased use of renewable energy sources.Improving transportation systems by promoting public transport, integrating route systems, promoting active mobility, and reducing the number of vehicles can also enhance fuel combustion efficiency and reduce the residual energy that is converted into heat [28].
Although physical solutions are often the first option that comes to mind when considering effective cooling solutions, it is important to invest in more sustainable cooling solutions and combine different approaches to create the right environment for long-term benefits [29].Regulation, involvement, funding, and research are some of the approaches which might be used to ensure an efficient implementation of any city cooling intervention [21].In 2020, World Bank stated that, besides the technical issues, there are several barriers to implement urban cooling strategies, such as lack of cooling solutions awareness, lack of comprehensive policy guidance or regulatory frameworks, and limited financing/incentives for cities and building owners [3].However, these challenges are rare to be considered in the cooling capacity assessment, especially in the simulation context.Therefore, more attention is needed to address these challenges in the context of implementing an urban cooling strategy.

Conclusions
The results of cooling capacity assessments indicate that, the Platinum Karet Tengsin Integrated Area Design is not adequately prepared for UHI.In order to achieve the sustainable development vision of this area, the priority features that should be intervened are grey features, especially in terms of the materials used.Other features that could also be intervened are intensely green and blue features, arranging buildings configuration, adding some shading features, and improving energy efficiency.The non-physical feature also needs to be integrated with the physical features strategy, to enable the successful implementation of any urban cooling intervention.All these strategies also need to be implemented, while considering the limited space issues of this area, through the integration of features with built-up areas to enhance land efficiency.However, this study shows the importance of integrating urban cooling approaches, as UHI mitigation strategies, in urban planning and design.Therefore, this approach can be used, or further developed by the urban planner or designer, to make a city more sustainable and resilient.

Figure 2 . 3 .
Figure 2. Distribution of cooling capacity index Figure 3. Distribution of cooling capacity index class

Figure 4 .Figure 5 .
Figure 4. Cooling capacity index density pattern class map

Table 2 .
Cooling capacity index class distribution area

Table 3 .
Distribution of land use in each cooling capacity index density pattern class Land