2024-01-02 23:00:00
Albedo, also known as solar reflectivity, is the ability of a surface to reflect sunlight. The albedo of a surface also determines the amount of heat reflected from that surface. Albedo is an important aspect in the study of climate change. Albedo acts as an important climate regulator, because surfaces with higher albedo reflect more solar energy back into space than they absorb, helping to cool the planet.
Human activities affect the global albedo, and therefore, the climate. Indeed, air pollution, greenhouse gas emissions and changes in land use can modify the albedo of land surfaces, making them dark and contributing to increased heat absorption. on the planet, thus creating, in cities, hot zones called “urban heat islands”.
One of the most striking examples of this human influence on albedo is the melting of ice in the Arctic. Ice reflects much of the solar radiation, but areas of ice that have melted are replaced by free water, which absorbs much of the solar radiation.
Additionally, cities, with their bitumen and asphalt surfaces, have a lower albedo than surrounding natural areas, making them less reflective and hotter. This urban heat island is caused by changing land use around cities, the creation of roads and buildings, and other human activities. Cities covered with darker coverings (asphalt concrete, slate roofs, etc.) therefore tend to be warmer and absorb more energy.
In addition to the problems of climate and urban planning, there is a sector that needs quantitative albedo data: space. In fact, a launcher or a satellite in space is subject to vacuum. This implies that heat exchanges are exclusively radiative exchanges: heat dissipation by the radiation of a body according to Planck’s law weighted by emissivity, and solar contribution weighted by albedo. If the latter is not controlled, it represents, for a surface above the atmosphere, a value of approximately 1,300 W/m2. It is therefore necessary to protect once morest this with an adequate reflective coating.
For this, scientists need reliable tools to estimate albedo. Climatologists favor remote sensing methods, that is to say satellite methods. As for the town planning sector, the preferred method is an in situ field method, and on certain structural elements a laboratory measurement. For the aeronautics and space sector, these are essentially laboratory methods.
Albedo is an extremely important parameter to take into account in the fight once morest global warming and urban heat islands. This is essential information for the thermal design of a spacecraft. Its measurement meets strict normative requirements.
The article describes the concept of albedo and how to measure it in the laboratory using a spectrometer scanning the entire solar spectrum. The albedo is then calculated by weighting the spectral energy of the sun. Another approach, this one from the field, explains how, using solar radiation, we can measure the albedo
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