lämpösaarekeilmiötä

The urban heat island effect, or lämpösaarekeilmiö in Finnish, describes the phenomenon where metropolitan areas are significantly warmer than their surrounding rural areas. This temperature difference is usually most pronounced at night and during winter.

Several factors contribute to the urban heat island effect. One primary cause is the replacement of natural vegetation with impervious surfaces like asphalt and concrete. These materials absorb and retain more solar radiation than vegetated land, leading to higher surface and air temperatures. Buildings also play a role by trapping heat and creating a "canyon effect" that reduces wind speed, hindering the dissipation of heat. Additionally, waste heat generated by human activities, such as from vehicles, industrial processes, and air conditioning systems, further contributes to the elevated temperatures in urban environments.

The consequences of the urban heat island effect can be varied. It can lead to increased energy consumption for cooling during warmer months, exacerbating air pollution and greenhouse gas emissions. Heat stress can also negatively impact human health, particularly for vulnerable populations. Conversely, in colder climates, the effect can sometimes reduce heating energy demand in winter, though this benefit is often outweighed by the negative impacts. Mitigation strategies include increasing urban green spaces, using cool pavements and roofing materials, and optimizing building design to reduce heat absorption and waste heat.