Effect of Sun Angle on Solar Flux and Weather: A Study on Earth's Surface

[irishbob]

Homework Statement

The Sun is lower in the sky during the winter than it is during the summer. How does this change affect the flux of sunlight hitting a given area on the surface of Earth? How does this change affect the weather?

(I take it I'm supposed to consider the sun to have a uniform electric field, and that the area is normal.)

Homework Equations

Flux=EAcos(theta)

The Attempt at a Solution

So what I have written is "When the sun is lower in the sky, the angle theta between the sun and given area approaches 90, meaning cos(theta) approaches 0, meaning flux is smaller. The weather gets colder, since not as much heat is transferred from the sun.

So is this right? I can't really conceptualize this very well for some reason. Flux has kind of been a little confusing for me, since I don't really understand what you would use it for.

Also, I'm horrible at explaining things thoroughly, so please let me know if you don't think the answer is clear enough.

 

[gneill]

In this case "flux" as in solar flux, refers to the rate at which energy is delivered (in watts) per square meter cross section perpendicular to the source (the Sun). So the units are Watts/m².

This is a fairly constant value at the Earth's distance from the Sun (somewhere around 1360 W/m²). If you were to draw a big Gaussian surface around the Sun at the distance of the Earth's orbit, that would be the amount of solar energy in the form of light that is passing through it for every square meter of its surface. (Watts are joules per second). It's a pretty staggering amount of energy if you think about it.

Your description of the importance of angle of incidence is certainly on track. You might want to hit the important buzzwords, like latitude, angle of incidence, cross section (as in cross sectional area that a patch of surface presents to the incoming flux).

 

[irishbob]

Thanks! That's exactly what I needed. :D

 

[gomunkul51]

just my 2 cents: the farther away you are from the equator makes the angle between the normal to the differential surface of the Earth and the plane of the earth-sun system gets larger, thus the "dot product" becomes smaller... :)