What is the formula Of Solar Constant?
Answers
Answer:
The area of a circle is pi times the radius of the circle squared. In this case, the circle's radius is simply the radius of Earth, which is about 6,371 km (3,959 miles) on average. If we multiply this area by the amount of energy per unit area - the solar "insolation" mentioned above, we can determine the total amount of energy intercepted by Earth:

E = total energy intercepted (technically, energy flux = energy per unit time, in watts)
KS = solar insolation ("solar constant") = 1,361 watts per square meter
RE = radius of Earth = 6,371 km = 6,371,000 meters
Plugging in values and solving for E, we find that our planet intercepts about 174 petawatts of sunlight... quite a lot of energy!

Since Earth is not completely black, some of this energy is reflected away and not absorbed by our planet. Scientists use the term albedo to describe how much light a planet or surface reflects away. A planet completely covered with snow or ice would have an albedo close to 100%, while a completely dark planet would have an albedo close to zero. To determine how much energy Earth absorbs from sunlight, we must multiply the energy intercepted (that we calculated above) times one minus the albedo value; since albedo represents the light reflected away, one minus albedo equals the light energy absorbed. Our equation for total energy absorbed becomes:

Now that we have a value for the energy flowing into the Earth system, let's calculate the energy flowing out.
The sunlight Earth absorbs heats our planet. Any object with a temperature above absolute zero emits electromagnetic (EM) radiation. In the case of Earth, this EM radiation takes the form of longwave, infrared radiation (or IR "light").

Since the values for the solar constant (KS), Earth's albedo, and the Stefan-Boltzmann constant (σ) are all known, it is possible to solve this equation for temperature (T). Using a little more algebra, we can write the expression above as:

Earth's overall, average albedo is about 0.31 (or 31%). The value of the Stefan-Boltzmann constant (σ) is 5.6704 x 10-8 watts / m2 K4. Plugging these numbers and the value for KS into the equation, we can calculate Earth's expected temperature:

Converting to the more familiar Celcius and Fahrenheit temperature scales, we get:

Based on this calculation, Earth's expected average global temperature is well below the freezing point of water!
Earth's actual average global temperature is around 14° C (57° F). Our planet is warmer than predicted by 34° C (60° F). That's a pretty big difference!