how do the fluxes of radiation help explain why air temperature near the earth's surface is higher than it is 2km above the earth's surface
The difference in air temperature near the Earth's surface compared to 2 km above the surface can be explained by understanding the fluxes of radiation. To better understand this explanation, we need to consider two key factors: incoming solar radiation and outgoing terrestrial radiation.
1. Incoming Solar Radiation: The sun emits a wide range of electromagnetic radiation, including visible light. This solar radiation heats the Earth's surface upon contact. The Earth's surface absorbs some of the incoming solar radiation and reflects the rest.
2. Outgoing Terrestrial Radiation: After absorbing solar radiation, the Earth's surface releases energy back into space in the form of terrestrial radiation, also known as longwave radiation or infrared radiation. This terrestrial radiation is emitted by the Earth's surface, as well as the atmosphere, including the air.
Now, let's explore how these fluxes of radiation contribute to the difference in air temperature near the Earth's surface and 2 km above it:
1. Proximity to the Earth's Surface: The air temperature near the Earth's surface is higher because it receives direct heat from the warmed surface through conduction and convection. The Earth's surface absorbs a significant amount of solar radiation and heats up, transferring some of that heat energy to the air molecules directly in contact with it. As a result, the air near the surface tends to be warmer.
2. Atmospheric Composition: As we move higher in the atmosphere, the concentration of air molecules decreases, resulting in lower pressure and density. This decrease in air density leads to fewer air molecules available to absorb and retain heat, making the air temperature decrease with altitude.
3. Greenhouse Effect: The atmosphere contains various greenhouse gases, such as carbon dioxide and water vapor. These gases can absorb and re-emit a portion of the outgoing terrestrial radiation, trapping some of the heat in the lower atmosphere. This process is known as the greenhouse effect, which helps maintain the Earth's temperature within a habitable range. As a result, the air temperature near the Earth's surface is higher due to the greenhouse effect.
In summary, the difference in air temperature near the Earth's surface and 2 km above can be explained by considering the varying amounts of incoming solar radiation, the decrease in air density with altitude, and the greenhouse effect, which affects the absorption and re-emission of terrestrial radiation by the atmosphere.