Planning for a cooler future : heat risk assessment and mitigation in Lahti
Negi, Ankur (2024)
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2024100225989
https://urn.fi/URN:NBN:fi:amk-2024100225989
Tiivistelmä
With the rapidly changing climate, heat risk is increasing rapidly in colder regions as well. Finland is projected to see higher rise in temperatures than the global average and thus needs to be prepared to mitigate these risks. This study aims to assess the current and future heat risk in the urban core of Lahti, Finland, using social vulnerabilities and exposure indicators to identify hotspots and suggest strategies to mitigate the heat risk.
The analysis, supported by temperature data from 2017 to 2024 provided by Juuso Suomi (University of Turku), confirms the upward trend in temperatures. This trend aligns with the projections of Ruosteenoja and Jylhä (2021). Projections from the EC-Earth3-veg GCM under the SSP2 - 4.5 scenario predict a significant increase in maximum mean monthly temperatures for the summer months in Lahti.
Risk profiling for Lahti reveals a notable increase in high and very high-risk categories from 9.79% (84 assessment units) in the present scenario to 23.65% (203 assessment units) by 2040. This rise in risk is primarily attributed to the projected increase in air temperatures, as vulnerabilities and exposure remain relatively similar in both scenarios. The relatively low change in exposure highlights the effectiveness of the Lahti masterplan. The study also utilizes local climate zone (LCZ) classification to understand the relationship between LCZ and land surface temperature (LST) data obtained from LANDSAT. It is observed that LCZ classes 1, 2, 8, and 10, and land cover class F, consistently exhibit high LST. Despite LST's limitations as a sole heat risk indicator, its correlation with LCZ classes can inform urban design of future masterplans to mitigate heat stress.
Microclimate analysis, carried out in a smaller area near the Lahti Town Hall using ENVI-met, highlights the increase in heat risk as well as the cooling impact of vegetation and its significance in improving outdoor thermal comfort. This analysis underscores the importance of integrating green infrastructure, such as urban trees and green spaces, into urban planning to counteract rising temperatures. Simulation with higher albedo road surfaces reveals that an increase in albedo is inversely proportional to thermal comfort at the street level.
The study advocates for urban infrastructure design changes to reduce heat absorption and improve thermal comfort. Utilizing seasonal shading structures and green infrastructure can significantly alleviate heat stress at pedestrian levels. The incorporation of microclimate analysis in planning and design processes enables planners to model and quantify the cooling effects of various interventions, ensuring optimal solutions for reducing surface and air temperatures. Future studies can consider building level analysis to analyse indoor thermal comfort of the people.
The analysis, supported by temperature data from 2017 to 2024 provided by Juuso Suomi (University of Turku), confirms the upward trend in temperatures. This trend aligns with the projections of Ruosteenoja and Jylhä (2021). Projections from the EC-Earth3-veg GCM under the SSP2 - 4.5 scenario predict a significant increase in maximum mean monthly temperatures for the summer months in Lahti.
Risk profiling for Lahti reveals a notable increase in high and very high-risk categories from 9.79% (84 assessment units) in the present scenario to 23.65% (203 assessment units) by 2040. This rise in risk is primarily attributed to the projected increase in air temperatures, as vulnerabilities and exposure remain relatively similar in both scenarios. The relatively low change in exposure highlights the effectiveness of the Lahti masterplan. The study also utilizes local climate zone (LCZ) classification to understand the relationship between LCZ and land surface temperature (LST) data obtained from LANDSAT. It is observed that LCZ classes 1, 2, 8, and 10, and land cover class F, consistently exhibit high LST. Despite LST's limitations as a sole heat risk indicator, its correlation with LCZ classes can inform urban design of future masterplans to mitigate heat stress.
Microclimate analysis, carried out in a smaller area near the Lahti Town Hall using ENVI-met, highlights the increase in heat risk as well as the cooling impact of vegetation and its significance in improving outdoor thermal comfort. This analysis underscores the importance of integrating green infrastructure, such as urban trees and green spaces, into urban planning to counteract rising temperatures. Simulation with higher albedo road surfaces reveals that an increase in albedo is inversely proportional to thermal comfort at the street level.
The study advocates for urban infrastructure design changes to reduce heat absorption and improve thermal comfort. Utilizing seasonal shading structures and green infrastructure can significantly alleviate heat stress at pedestrian levels. The incorporation of microclimate analysis in planning and design processes enables planners to model and quantify the cooling effects of various interventions, ensuring optimal solutions for reducing surface and air temperatures. Future studies can consider building level analysis to analyse indoor thermal comfort of the people.