Re: [Phys-L] solar constant

["David Marx" <marx@phy.ilstu.edu>]

The solar irradiance has been averaging around 1366 W/m^2 for the past 60
years.  Before that, it was as much as 3 W/m^2 lower.  Here is a graph...
http://www.climate4you.com/images/SolarIrradianceReconstructedSince1610.gif

This number is the irradiance arriving at the top of the Earth's atmosphere. 
The actual average insolation on the ground is about 8 times smaller due to
(1) the curvature of the Earth, (2) only half the Earth illuminated at a given
time, and (3) atmospheric reflection/absorption.

If you want to measure the local insolation, you can get one of these...
http://en.wikipedia.org/wiki/Pyranometer


> The solar constant is around 1370 W/m2. I believe this is the average value
over the entire Earth in one year. I have two questions.
> 1. How can I find the approximate value on a given day at a given location
(latitude)? Is there some formula or way to estimate? I realize this might
not be easy.
> which leads to:
>
> 2. Is there a "simple" experiment kids can do to measure the solar constant
(solar cell, heating water, etc.)?
> This has some good concepts for energy, heat, and optics in both physics and
astronomy.
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