Question
Asked 17th Sep, 2022

How can i classify the temperatures of a land surface temperature map to find urban heat islands( I need precise ranges or ranges)?

I'm doing research for my degree thesis in architecture on the urban heat islands of the city of Naples - Italy.
I'm reclassifying the Land surface temeperature map in gis and I am looking for a method to classify the temperatures on the ground in a precise way, according to the classes that allow me to locate the heat islands.

Most recent answer

7th Oct, 2022
Yan Qing Zhang
Simon Fraser University
I just found one of my presentations on "using GIS technology to detect the most suitable experiment areas for global warming research" in 2005 at the GeoTech Event, in Vancouver, Canada. The method is "Weighting Factors for Aggregation".
Hope it would help you.

Popular answers (1)

27th Sep, 2022
Michel M. Verstraete
University of the Witwatersrand
Cara Rosa,
There are no universal thresholds to classify urban heat islands because each city will experience its own specific climate and environmental constraints. Since you are dealing with a single city, I suggest you start by determining the lowest and the highest temperatures in your data set, and then divide that range (Tmax - Tmin) in 3 equal intervals. For instance, if Tmin = 18 and Tmax = 24, your intervals would be 18 to 20, 20 to 22 and 22 to 24 C. In that case, all areas falling in the lower interval could be labeled 'cool', the areas falling in the next class could be called 'warm', and those belonging to the higher interval could be indicative of 'hot' conditions.
You should make sure that your data set covers a region around the city large enough to include agricultural fields or forests: those areas would provide you with a baseline environmental temperature away from the urban center. An obvious extension of this approach would be to map the city areas in single degree intervals, from blues through to greens, yellows, oranges and red. That will clearly indicate which areas are hotter.
A better approach would be to start from a preliminary question: why do you need to make a map of the urban heat island effect of Naples in the first place? If you were concerned by the health effect of temperature on morbidity and mortality of the inhabitants, for instance, then your temperature thresholds should be driven by medical rather than purely statistical considerations. Similarly, if your underlying concern were energy expenditures (cooling during the summer or heating during the winter), then your thresholds should relate to the corresponding critical rates of energy expenditure. In other words, your approach should depend on your ultimate goal.
Remember also that
- the urban heat island is quite time-dependent: it varies with cloudiness and synoptic conditions such as sea-breeze on a daily time scale, it is much more noticeable during the winter than the summer, and it may evolve on longer time scales, depending on the rates of urbanization and industrialization;
- land surface temperature is quite dependent on altitude, so you might want to acquire a topographic map of your area and look at the correlation between these two parameters;
- a land use map of the region will be useful to properly interpret your results, as the hotter area may not be the city center but some industrial area, depending on their relative rates of energy consumption.
I hope these comments may help you in your work. Michel.
3 Recommendations

All Answers (4)

21st Sep, 2022
Yan Qing Zhang
Simon Fraser University
It is important to give your definition of the hot spot or hot island. Then you can divide them into several classes. Based on the temperature conditions, label your result of a hot spot or hot island on the GIS map.
27th Sep, 2022
Rosa Cafaro
University of Naples Federico II
Yan Qing Zhang Thank you so much for your answer.
I have only the LST map of the city of Naples as input data and from this map I want to obtain the hot areas (heat isand). Is there a precise way to reclassify the LTS according to temperature ranges? an equation for which I will have a legend like:
- Low Temperature Zone
- ..
- Extremely High Temperature Zone
27th Sep, 2022
Michel M. Verstraete
University of the Witwatersrand
Cara Rosa,
There are no universal thresholds to classify urban heat islands because each city will experience its own specific climate and environmental constraints. Since you are dealing with a single city, I suggest you start by determining the lowest and the highest temperatures in your data set, and then divide that range (Tmax - Tmin) in 3 equal intervals. For instance, if Tmin = 18 and Tmax = 24, your intervals would be 18 to 20, 20 to 22 and 22 to 24 C. In that case, all areas falling in the lower interval could be labeled 'cool', the areas falling in the next class could be called 'warm', and those belonging to the higher interval could be indicative of 'hot' conditions.
You should make sure that your data set covers a region around the city large enough to include agricultural fields or forests: those areas would provide you with a baseline environmental temperature away from the urban center. An obvious extension of this approach would be to map the city areas in single degree intervals, from blues through to greens, yellows, oranges and red. That will clearly indicate which areas are hotter.
A better approach would be to start from a preliminary question: why do you need to make a map of the urban heat island effect of Naples in the first place? If you were concerned by the health effect of temperature on morbidity and mortality of the inhabitants, for instance, then your temperature thresholds should be driven by medical rather than purely statistical considerations. Similarly, if your underlying concern were energy expenditures (cooling during the summer or heating during the winter), then your thresholds should relate to the corresponding critical rates of energy expenditure. In other words, your approach should depend on your ultimate goal.
Remember also that
- the urban heat island is quite time-dependent: it varies with cloudiness and synoptic conditions such as sea-breeze on a daily time scale, it is much more noticeable during the winter than the summer, and it may evolve on longer time scales, depending on the rates of urbanization and industrialization;
- land surface temperature is quite dependent on altitude, so you might want to acquire a topographic map of your area and look at the correlation between these two parameters;
- a land use map of the region will be useful to properly interpret your results, as the hotter area may not be the city center but some industrial area, depending on their relative rates of energy consumption.
I hope these comments may help you in your work. Michel.
3 Recommendations
7th Oct, 2022
Yan Qing Zhang
Simon Fraser University
I just found one of my presentations on "using GIS technology to detect the most suitable experiment areas for global warming research" in 2005 at the GeoTech Event, in Vancouver, Canada. The method is "Weighting Factors for Aggregation".
Hope it would help you.

Similar questions and discussions

Scientists Support Ukraine
Discussion
Be the first to reply
  • Ijad MadischIjad Madisch
Like so many, I am shocked and saddened at seeing war break out in Europe. My thoughts – and those of the ResearchGate team – are with the people of Ukraine and everyone affected.
ResearchGate is an international company, whose purpose is to enable scientists across the world to work together openly and collaboratively, regardless of borders or nationality. We have people from over 40 countries on our staff of around 200, and being based in Berlin, we are profoundly aware of the human cost of conflicts, the echoes of which have shaped and scarred our home city. We join with the international community in condemning the actions of the Russian state.
We have been asking ourselves: What can we do?
From today, we will offer free advertising space worth $2.5 million on our network to humanitarian organizations working to respond to the crisis. ResearchGate benefits from over 50 million visitors every month, and we hope this initiative can help raise funds and awareness for those organizations that are having direct impact and need support.
We also want to use our platform to highlight the response from the scientific community. Personally, I have found the messages of support from scientists everywhere to be truly heartfelt, and I would like to highlight some of the community initiatives I’ve seen here:
Additionally, I’m posting here some of the organizations responding to the crisis and actively soliciting donations:
To help gather more support for these initiatives, please consider sharing this post further (you don’t need a ResearchGate account to see it), and I will continue to update it with other initiatives as I find them. You can also click “Recommend” below to help others in your ResearchGate network see it. And if you know of any other community initiatives that we can share here please let us know via this form: https://forms.gle/e37EHouWXFLyhYE8A
-Ijad Madisch, CEO & Co-Founder of ResearchGate
-----
Update 03/07:
This list outlines country-level initiatives from various academic institutions and research organizations, with a focus on programs and sponsorship for Ukrainian researchers:
How can environmental protection and biodiversity be improved by using current ecological technologies?
Discussion
1565 replies
  • Dariusz ProkopowiczDariusz Prokopowicz
Due to the current civilization progress in recent decades, acceleration of the development of industry, automotive, urban agglomerations, intensification of agricultural production, etc. and related greenhouse gas emissions, global warming, ozone layer depletion in the atecologicalecologicalmosphere, increase of environmental pollution, growing problem of smog in urban agglomerations, the increase in pollution of the seas and oceans to which unsorted waste is thrown away is cut out as part of the predatory economy of tropical forests in the Amazon and other largest natural forest ecosystems.
In addition, the secondary effect of global warming of the Earth's climate is the increasing, more frequent weather anomalies, including drought, leading to steppe and desertification of areas that were previously natural forest ecosystems or areas exploited by agriculture.
As a result of the above-mentioned processes, every year many species of flora and fauna disappear forever.
As a result, natural biodiversity diminishes, which for millions of years evolved evolutionally on Earth.
In this way the natural resources of the planet Earth are irretrievably in decline.
In view of the above, the issue of environmental protection and biodiversity is one of the most important challenges of humanity in the 21st century.
Classical economics must change towards a green economy based on the strategy of sustainable pro-ecological development.
Therefore, I am asking you for the following query:
How can environmental protection and biodiversity be improved by using current ecological technologies?
Please, answer, comments.
I invite you to the discussion.
Best wishes

Related Publications

Article
Full-text available
Urban heat islands (UHI) are one of the unequivocal effects of the ongoing process of climate change: anthropized areas suffer extreme heat events that affect the human perception of comfort. This study investigated the effects of road pavements as a passive countermeasure by comparing the air temperature (AT) and the predicted mean vote (PMV) for...
Article
Full-text available
The recent International Panel on Climate Change report predicts the highly urbanized Northeastern U.S. to be at high risk to heat waves. Since urban residents and infrastructure are known to be highly vulnerable to extreme heat, the goal of this paper is to understand the interaction between the synoptic-scale heat wave and the city-scale urban he...
Got a technical question?
Get high-quality answers from experts.