Urban Heat Island — Chandigarh and Satellite Towns

Smaller cities, worse heat islands — evidence from India’s first planned city and five satellite towns

The counter-intuitive finding

Conventional wisdom says larger, more urbanised cities have stronger heat islands. This study found the opposite.

Chandigarh — India’s first planned city, its most urbanised centre in this study, with the highest proportion of built-up surface — experienced less surface urban heat island (SUHI) intensity than three of its much smaller satellite towns. Zirakpur, Kharar, and Mullanpur Garibdass, despite being a fraction of Chandigarh’s size, had the worst thermal environments of all six urban centres studied.

The reason: it is not how much built-up area a city has that determines its heat island — it is how that built-up area is spatially distributed relative to green spaces and water.

Study area

Six urban centres in the Chandigarh Capital Region, Punjab/Haryana, India — mapped across four time points: 1992, 2000, 2010, 2019.

Urban centre	Character
Chandigarh	India’s first planned city · highest vegetation ratio (0.75)
Panchkula	Second prime centre · adjacent to Shivalik forest ranges
Mohali	Largest satellite town · vegetation along river channels
Zirakpur	Fast-growing satellite town · lowest vegetation ratio (0.49)
Kharar	Small satellite town · 95% built-up area under distinguished SUHI by 2019
Mullanpur Garibdass	Smallest · highest SUHI intensity per unit area

Tools: Google Earth Engine · R · Landsat 4/5 and 8
Indices: Land Surface Temperature (LST) · Surface Urban Heat Island (SUHI) · Urban Thermal Field Variation Index (UTFVI) - Ecological Quality Indicator

From LST to SUHI to ecological quality

The analysis followed a three-step derivation:

LST (land surface temperature from Landsat thermal bands) → SUHI (relative temperature elevation above rural background, classified into six intensity grades) → UTFVI (Urban Thermal Field Variation Index — ecological quality experienced by residents, from excellent to worst)

Maps showing spatio-temporal land surface temperature across Chandigarh and five satellite towns at four time points — Land surface temperature — Chandigarh and satellite towns across 1992, 2000, 2010, 2019

Mean LST across the study area rose from 18.4°C to 26.7°C between 1992 and 2019 — a warming of over 8°C in less than three decades, driven almost entirely by agricultural land being converted to built-up surfaces.

SUHI intensity

The spatial pattern is striking. Within Chandigarh’s urban boundary, forest cover actually increased by 46% between 1992 and 2019 — a direct result of planned city greening. This, combined with the cooling effect of Sukhna Lake, kept SUHI intensity suppressed despite high urbanisation. Panchkula’s proximity to the Shivalik forest ranges provided a similar geographic cooling buffer.

In contrast, Zirakpur, Kharar, and Mullanpur Garibdass urbanised rapidly with no equivalent greening — producing dense built-up areas with no spatial interspersion of vegetation or water. By 2019, 95% of Kharar’s built-up area was under distinguished SUHI impact.

Ecological quality — UTFVI

Maps showing UTFVI-based ecological quality from excellent to worst across Chandigarh and satellite towns — Urban Thermal Field Variation Index — ecological quality across six urban centres

Excellent ecological quality zones were found only within Chandigarh, Panchkula, and partially in Mohali. For Zirakpur, Kharar, and Mullanpur Garibdass, excellent quality was restricted to peripheral cropland outside the urban boundary — meaning residents of these towns experienced predominantly poor to worst thermal environments within their own cities.

Key finding and planning implications

The intensity of heat island effects is not a simple function of city size or total built-up area. It is determined by the spatial distribution and pattern of built-up surfaces relative to green spaces and water across the urban landscape.

This has direct implications for satellite town development across India and the Global South — where rapid peri-urbanisation is creating new cities without the green infrastructure frameworks that Chandigarh benefited from at founding.

Practical recommendations from the study:

Integrate green space and water body targets into satellite town masterplans from the outset — retrofitting is significantly harder
Prioritise greening in high-SUHI zones identified by the spatial maps
Develop green belts along road networks and residential areas
Cool roofs and permeable pavements as immediate interventions in already built-up areas with no room for new vegetation

Note on publication status

This work was completed out of interest during doctoral studies but not submitted for publication. The spatial analysis, maps, and findings represent original research conducted solely by me during my time at Jawaharlal Nehru University.