Why is net radiation more in the tropics than in Polar Regions and why does incoming solar radiation pass more easily through the atmosphere?
polar region has relatively larger albedo meaning more SW radiation is reflected back and hence less net radiation at surface.
The sun angle is always high over the tropical oceans so the surface receives intense radiation throughout the year. With a high sun angle the albedo of the surface is low and absorption is high. When the sun's rays strike Earth's surface near the equator, the incoming solar radiation is more direct (nearly perpendicular or closer to a 90˚ angle). Therefore, the solar radiation is concentrated over a smaller surface area, causing warmer temperatures. At the poles, the ice, snow and cloud cover create a much higher albedo, and the poles reflect more and absorb less solar energy than the lower latitudes. Through all of these mechanisms, the poles absorb much less solar radiation than equatorial regions, which is why the poles are cold and the tropics are very warm. In the tropics there is a net energy surplus because the amount of sunlight absorbed is larger than the amount of heat radiated. In the Polar Regions, however, there is an annual energy deficit because the amount of heat radiated to space is larger than the amount of absorbed sunlight. Atmospheric gas molecules and aerosols deflect solar radiation from its original path, scattering (reflecting) some radiation back into deep space and some toward Earth's surface. Clouds reflect much more incoming solar radiation than they absorb. Some of this incoming radiation is reflected off clouds, some is absorbed by the atmosphere, and some passes through to the Earth's surface. Larger aerosol particles in the atmosphere interact with and absorb some of the radiation, causing the atmosphere to warm. Earth's atmosphere is composed primarily of nitrogen and oxygen. These gases are transparent to incoming solar radiation. They are also transparent to outgoing infrared radiation, which means that they do not absorb or emit solar or infrared radiation. The Earth's atmosphere is transparent to some wavelengths of microwave radiation, but not to others. The longer wavelengths (waves more similar to radio waves) pass through the Earth's atmosphere more easily than the shorter wavelength microwaves. Thus, most incoming solar radiation is transmitted through the atmosphere to the ground and solar radiation is not an effective heater of the atmosphere much better at absorbing this longer wavelength radiation. In the tropics there is a net energy surplus because the amount of sunlight absorbed is larger than the amount of heat radiated. In the Polar Regions, however, there is an annual energy deficit because the amount of heat radiated to space is larger than the amount of absorbed sunlight. The tropics refer to the region of Earth around the equator. The weather here is, on average, hot and humid. The curve of the planet leads to the tropics receiving more direct solar radiation than the rest of the Earth and more than the region re-radiates back to space.
- Badges
- Science topic
- Similar topics
- Geoscience
- Remote Sensing