systematic review of Urban Heat Island Studies in Greater Accra Region, Ghana.

 

A SYSTEMATIC REVIEW OF URBAN HEAT ISLAND STUDIES IN

GREATER ACCRA REGION, GHANA.

                          by

                SANUSI AHMED

                    AFFILIATIONS

UNIVERSITÉ DE STRASBOURG, STRASBOURG, FRANCE

(FACULTÉ DE GÉOGRAPHIE ET D'AMÉNAGEMENT)

UNIVERSITÉ LUMIÈRE LYON 2, LYON, FRANCE

(CENTRE INTERNATIONAL D’ETUDES FRANÇAISES)

CENTRAL UNIVERSITY, ACCRA, GHANA

(DEPARTMENT OF ENVIRONMENT AND DEVELOPMENT STUDIES)

ORCID id: 0009-0001-1728-5028

Email: sanusiahmed05@gmail.com

Abbreviation 3

Abstract 4

1. Introduction 5

1.1 Study area 6

1.2 Study area 7

2. Literature search and screening 8

3. Results and discussion 8

4. Conclusion 11

5. Recommendation 12

References 14

Abbreviation

UHI= Urban Heat Island

AUHI= Atmospheric Urban Heat Island

SUHI= Surface Urban Heat Island

GIS= Geographic Information System

GSS= Ghana Statistical Service

CBD= Central Business District

A SYSTEMATIC REVIEW OF URBAN HEAT ISLAND STUDIES IN GREATER ACCRA REGION, GHANA

 Author: * Sanusi Ahmed , email: sanusiahmed05@gmail.com

Abstract

 This study comprehensively reviews the state of the art on Urban Heat Island research in the Greater Accra region of Ghana. It identifies potential research limitations and gaps in previous studies and analyses key drivers of Urban Heat Island. The systematic review focuses on four major studies. I reviewed and analysed in detail the key drivers of Urban Heat Island, the methods of measurement, key findings, and critiquing the methods and limitations of the studies. In all the four major studies reviewed, there exist major research limitations and gaps. Some important recommendations have been enumerated for future studies. Quantum GIS tools and techniques was employed in the systematic review to better understand the area of interest, Greater Accra Region. The Ghana populated places points data was accessed on Humanitarian Data Exchange (HDX) website. This dataset, sourced from Open street map, provides point feature for populated places and can be downloaded by visiting the linked HDX page and clicking on the download link: hotosm_gha_populated_places_points_shp.zip

Keywords

Review, Urbanisation, Urban Heat Island, Accra, Land Cover, urban expansion, Remote Sensing, Land Surface Temperature, Atmospheric Temperature.

Citation: Sanusi. A., (2025). A systematic review of Urban Heat Island Studies in Greater Accra Region, Ghana. DOI: 10.13140/RG.2.2.21747.39201.

 Introduction

 Ghana as a developing nation, has seen drastic increase in rural to urban migration. This has exacerbated the problem of urban congestion and housing in Greater Accra Region. The expansion of settlements and encroachment of individuals on unauthorised places in Accra have led to destruction of natural landscape of the city. Accra has experienced a decline in green spaces as well as vegetation cover. The Urban Heat Island phenomenon is where an urban area is significantly warmer than its surrounding peri-urban and rural areas [1]. The urban growth is accompanied by uncontrolled land use and land cover for developmental activities such as industrialisation, construction of roads and buildings with high thermal capacity materials creating impervious surfaces [2]. Greater Accra is the most urbanised region in Ghana [3]. According to [4] , rapid Urbanisation is one of the most crucial issues in the world of the 21st century. According to [5], Urban Heat Island can be categorised as Atmospheric Urban Heat Island (AUHI) and Surface Urban Heat Island (SUHI). As climate change accelerates, global temperatures continue to rise, reshaping urban environments and leading to more frequent, intense, and prolonged extreme heat events [6,7,8,9]. In urban areas, the Urban Heat Island effects, driven by dense construction, minimal green spaces, and large populations, intensifies heat, increasing energy demands, degrading air quality, and heightening health risks [10]. Accra continues to face worsening extreme heat due to unchecked urban sprawl [11]. In the course of history, cities have been developing, and their physical characteristics have undergone various transformations because of varying events [12] . The population of Ghana has since independence, grown rapidly, a situation which has culminated in the rapid Urbanisation of several towns across the country [13].

1.1 Study area

Figure 1. Land cover map of Greater Accra Region

1.2 Study area

Figure 2. Populated places in Greater Accra Region

2. Literature search and screening

To begin with, different scholarly articles and theses on Urban Heat Island were assessed and extracted from Google scholar, ResearchGate, Academia.edu, and ScienceDirect. These databases mentioned above enabled me to intensively search and extracted previous studies on Urban Heat Island in the Greater Accra Region of Ghana. Eight studies were initially assessed and extracted for this systematic review and after a thorough manual reading was carried out on the eight extracted articles, four were deemed relevant for this review. The selection of the four extracted articles was based on the following criteria;1. the article must address the review objective, 2. the article must be relevant to the scope of the review.

3. Results and discussion

The key findings of the four extracted articles provided substantial information on the existence of Urban Heat Island in the greater Accra region. All the four articles confirmed some key drivers of Urban Heat Island such as rapid urbanisation, urban expansion, and land cover change.

Article 1: Assessment of Urban Heat Island Warming in the greater Accra Region [14]. The study uses remote sensing and integrated Geographic Information System techniques in analysing satellite imagery. It also uses Landsat Satellite Imagery captured in 1991, 2002, and 2017 and in-situ daily minimum and maximum temperature data spanning the period of 1980 to 2017. Extreme temperature indices were assessed with the ClimPACT2 software. Land use change was identified as a key driver of Urban Heat Island couple with rapid urban expansion and land cover transformations. Urbanisation and loss of vegetation were also identified as key drivers of the Urban Heat Island in Accra. While the study provides important findings on surface temperature increase and urban expansion in the greater Accra, there exist some limitations and gap. The study relied on two stations in assessing daily minimum and maximum extreme temperature data from the stations at Accra and Tema. The two stations would not be enough to capture air temperature extreme across the whole Greater Accra Region. While the study uses Landsat images from 1991, 2002, and 2017, it would not reflect or express the year-to-year variability and seasonal cycles. It also over relied on remotely sensed data in the absence of ground truthing, which would ensure the accuracy of the data remotely collected. Moreover, there is absence of modelling in the study carried out, which is very vital for future predictions.

Article 2: Estimating the expansion of urban areas and Urban Heat Islands in Ghana: a case study [15]. The study highlights important key findings on how urban expansion has influenced surface temperatures in two major cities, Accra and Kumasi from 2002 to 2017. It analyses Urban sprawl and Urban Heat Island effects in the two cities mentioned above. It uses Landsat 7 and 8 satellite imagery. It also uses object-based image analysis for land cover classification and a single channel algorithm. The study shows that both cities depict presence and expansion of Urban Heat Island. It shows an increase in Urban sprawl leading to landscape changes. The urban sprawl expansion has contributed to the loss of vegetated areas and been replaced with concrete and built-up areas in Accra and Kumasi. While the study contributed enormously to understanding the presence or existence of Urban Heat Island and its key drivers in the two cities, it has some shortcomings. The land cover classification solely focused on object-based analysis, that may misclassify areas. There is not a single, universally accepted algorithm for object-based image analysis, making it harder to compare results across different studies or implement a standardized methodology [16].

  Moreover, seasonal and interannual variability were not fully addressed, as a result, the findings on Urban Heat Island may reflect anomalies. In addition, the study does not assess urban morphology, topography, or biodiversity that affect urban Heat Island dynamics.

Article 3: Evaluation of the effect of urbanisation on urban thermal behaviour using Urban Heat Island indicators: a case of the CBD of Accra [17]. This study investigates how urbanisation in the Central Business District of Accra affects the local climate. The study uses Urban Heat Island indicators to evaluate the thermal behaviour of the city and identifies areas experiencing higher temperatures due to urban development. The study shows an important finding on how rapid urbanisation and loss of greenery in Accra’s CBD amount to urban thermal behaviour. The study combined weather data and expert interviews that could aid in future research. The key limitations of the study are that; the study only focused on the Central Business District of Accra, which may not represent whole patterns across the whole Accra, secondly, the study did not analyse seasonal variations in urban heat island intensity, which will be difficult to generalise conclusions beyond the specific measurement period, In addition, the study also touched on surface temperature with some measured atmospheric temperature that is only limited in certain areas within Accra’s Central Business District which could not represent whole patterns across the whole Accra, which may not fully capture human thermal comfort and actual heat stress dynamics.

Article 4: Assessment of Urban Heat Island and Urban Pollution Island Synergy during the dry season in Greater Accra, Ghana [18]: provides important findings on how heat and fine particulate pollution (PM 2.5) interact. The study shows that during the dry season, heat and pollution engages and increases, making the daytime pollution high by increasing the night-time heat. The study provides substantial findings on presence of both Urban Heat Island and Urban Pollution Island such as particulate matter (PM 2.5). Like other previous studies, there are some limitations such as limited spatial coverage and sensor network, season specific focus in the sense that it did not extend across different seasons like the wet season, hence the synergy between Urban Heat Island and Urban Pollution Island might differ during the rainy months or in a full year context, non-inclusion of other pollutants, lack of meteorological context and finally, time resolution and diurnal limitations.

4. Conclusion

This systematic review on Urban Heat Island studies in Greater Accra Region of Ghana shows that rapid Urbanisation, urban expansion, land cover change and vegetation loss are the main drivers of Urban Heat Island in the region (see figure 1 and 2 above). Based on the four major articles examined, remote sensing and Geographic Information System techniques and methods were the primary tools used to measure Urban Heat Island, which indicates the scarcity of dense, long-term ground-based temperature monitoring equipment in Ghana. This systematic review also confirms the presence of Surface Urban Heat Island with little or no Atmospheric Urban Heat Island measurement across the four major articles examined, indicating a major implication for Environmental quality and human health.

It was indicated that spatial coverage is mostly limited to a few monitoring stations, as a result this may not capture the region’s diverse microclimate. Moreover, the limited seasonal and interannual variability analysis, insufficient integration of urban morphology and topography, and the exclusion of key meteorological and socio-economic frameworks inhibits the development of a holistic understanding of Urban Heat Island dynamics in the Greater Accra Region. With all the review findings enumerated, there is therefore the need to expand both the depth and breadth of Urban Heat Island studies in the Greater Accra Region.

5. Recommendation

Firstly, there should be an integration and expansion of ground-based monitoring networks in the studies of Urban Heat Island in the Greater Accra Region. By doing so, both surface and atmospheric temperatures could be captured at multiple scales. There should be an integrated measurement approaches in Urban Heat Island studies in the Greater Accra Region. The combination of remote sensing with in-situ temperature measurements as well as the integration of both Surface Urban Heat Island and Atmospheric Urban Heat Island assessment would help link land surface change with human thermal comfort and public health impacts.

Secondly, future studies on urban Heat Island in the Region should focus on longitudinal studies that would capture year to year change and seasonal cycles for better understanding of Urban Heat Island persistence and fluctuation patterns.

Moreover, there should be an integration of urban morphology and topography in future studies on urban Heat Island in the Greater Accra Region. There should also be incorporation of socioeconomic and public health dimensions in future studies. By linking Urban Heat Island mapping with demographic, and vulnerability data to identifying heat vulnerable communities in the region.

Acknowledgments: All thanks to the Almighty Allah, the Lord of all that exist, Most Gracious, Most Merciful, for His guidance, protection and knowledge that He bestowed upon me in conducting this systematic review.

Funding

This research received no external funding.

Author contribution

Not Applicable.

Conflict of interest

The author declare no conflict of interest.

Data availability statement

The Ghana populated places points data was accessed on Humanitarian Data Exchange (HDX) website. This dataset, sourced from Open street map, provides point feature for populated places and can be downloaded by visiting the linked HDX page and clicking on the download link: hotosm_gha_populated_places_points_shp.zip

Sample availability

The author declare that no physical sample were used in this study.

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