Physics

How does solar radiation reach the Earth?

Solar radiation refers to electromagnetic waves or the energy emitted by the Sun. Every place on Earth receives some part of sunlight at least part of the year. Factors affecting the amount of sunlight received include geographic location, time of day, season, local landscape, and weather. The Earth is round, so the sun hits the surface at different angles, ranging from 0 to 90 degrees. When rays strike vertically, maximum energy is emitted. Structures in cities like buildings, roads, and other infrastructure absorb and reflect the heat more than natural landscapes like forests and water bodies. This causes cities to experience higher temperatures than surrounding rural areas, creating an urban heat island.

Thermal Resonance and Its Effects on the Urban Heat Island Effect

Urban areas have materials like concrete, asphalt, and bricks. These materials have high thermal mass. They absorb and store heat during the day and release it slowly at night. This leads to higher nighttime temperatures. High concentrations of vehicles, industrial activities, and air conditioning units generate additional heat. This also contributes to the UHI effect.

Thermal Resonance

Thermal resonance occurs when a particle absorbs radiation at its resonant frequency. This causes it to be in an excited state. When molecules absorb energy, they oscillate more vigorously, increasing the material's temperature.

Excited State

The excited state of a molecule is a higher energy state. It is achieved when the molecule absorbs energy. For example, when materials like asphalt or concrete absorb infrared radiation, their molecules transition from a lower energy ground state to a higher energy excited state. This absorption increases thermal energy within the material, which is then retained and slowly released over time. Urban materials like concrete and asphalt have high thermal masses and specific heat capacities. These properties allow them to absorb significant amounts of solar radiation during the day. The molecular bonds within these materials resonate with specific frequencies of the absorbed radiation. This causes them to enter an excited state and store energy as heat.

Impact of Colored Infrastructure on Albedo

Some solar radiation reaching the surface of the Earth is reflected due to the properties of the surface. The ratio of the reflected intensity to the total incident radiation is called albedo. White and shiny surfaces have higher levels of albedo. This means less radiation received by the surface and thus lower average temperatures. In urban settings, buildings could be colored white to ensure that less radiation is absorbed.

Resonance and the Urban Heat Island Effect

Excited State: The excited state of a molecule is a higher energy state achieved when the molecule absorbs energy. For example, materials in urban environments, such as asphalt or concrete, absorb infrared radiation, causing their molecules to transition from a lower energy ground state to a higher energy excited state. This absorption increases the material's thermal energy, which is then retained and slowly released over time. Urban materials like concrete and asphalt, with high thermal masses and specific heat capacities, can absorb significant amounts of solar radiation. The molecular bonds within these materials resonate with specific frequencies of the absorbed radiation, storing energy as heat.

For more information, visit iTrees: Urban Heat Islands.