Why do we get more solar radiation near the poles than at the equator even though it is further from the sun there and solar radiation vary from equator to poles if so why?
I don't know in what way you mean "more solar radiation near the poles than the equator". I don't know of any sense in which that is true. Can you supply a reference or argument for that statement?
In general:
The power incident on a surface that is oriented perpendicular to the direction to the sun at a given distance from the sun is constant.
If the surface is not perpendicular, then the power intercepted by the same surface is less due to the tilt. This effect goes like cosine of the angle between the direction to the sun and the perpendicular to the surface area. See this figure for a sense of how that works: https://en.wikipedia.org/wiki/Solar_irradiance#/media/File:Seasons.too.png
At the poles, the sun is never higher in the sky than 23.5 degrees above the horizon so this effect is cosine(90-23.5) which is about 0.4 (so 60% less than if the sun were directly overhead).
The extra distance (maximum amount=radius of the earth) away from the sun that the poles are also makes the intensity less, but it is a tiny effect b/c the radius of the earth is so small compared to the distance to the sun. The ratio "radius of earth"/"distance to sun"=0.000043 and the intensity goes down as distance from the sun squared so the fraction by which the intensity is smaller due to this is about 0.0000000018.
There are also many other contributions to the effective heating by solar radiation at a location, including cloud cover, reflectivity of the surface, refraction in the atmosphere, etc. but the cosine effect is one of the biggest.
- Badges
- Science topic
- Similar topics
- Mathematics