What is the heat island phenomenon?

In Yokohama, summer heat is becoming increasingly severe due to the overlap of the heat island phenomenon seen in urban areas.
On this page, we introduce the heat island phenomenon.

What is the heat island phenomenon?　／　Heat island countermeasures　／　City temperature observation　／　Thermal environment survey　／　Future forecast of city temperature

The heat island phenomenon is a phenomenon in which the temperature in urban areas is higher than in suburban areas.
When the isothermal line is drawn, the high temperature is like an island.
It is called the heat island (Hot Island).

※Partial processing based on "Heat Island Monitoring Report 2017 (JMA, 2018)"

The main cause of the heat island phenomenon.
①Artificialization of ground surface coating, (2) high density in urban forms, (3) increase in manpower waste heat
There are three types of things.

Paved surfaces such as asphalt and concrete, and the roof surface of buildings accumulate heat when exposed to sunlight during the summer day.
In addition, the heat stored on the paved surface during the day is released at night, preventing the temperature from falling at night.

※Quotation: “Revised Edition Guidelines for Measures against Heat Island (Ministry of the Environment, 2013)”

As the surrounding buildings become denser, the wind near the ground weakens, causing the spread of heat.
In addition, since the sky ratio is reduced, radiant cooling at night is prevented, making it easier for heat to accumulate.

※Quotation: “Revised Edition Guidelines for Measures against Heat Island (Ministry of the Environment, 2013)”

The artificial waste heat generated from buildings, automobiles, factories, etc., directly warms the atmosphere.
This is one of the causes of the rise in temperature.

※Quotation: “Revised Edition Guidelines for Measures against Heat Island (Ministry of the Environment, 2013)”