Why Do Aerial Images of Earth Appear Blue Despite Equal RGB Scattering?

In summary, the graph allegedly obtained from MODTRAN supports the idea that the scattering of blue photons by the atmosphere is more significant than for other colors, hence aerial images of Earth look bluesh. The sun is at the Zenith and the detector is looking straight down towards the ground, so the scattered light is backscattered to the detector.
  • #1
AlexVM
5
0
It is common knowledge that the scattering of blue photons by the atmosphere is more significant than for other colors hence aerial images of Earth look bluesh.
The graph below obtained from MODTRAN 'allegedly' supports this fact.

While trying to quantify this effect, I've preformed several calculations
According to my calculations, since the camera counts photons and since one has to divide energy by hc/lambda to obtain #photons we obtain a monotonically decreasing scattering function multiplied by the monotonically increasing lambda function, which yields a relatively constant product (high energy at low wavelengths represent same photon number as low energy at high wavelengths).

This product, multiplied by each of the 3 color bands (R, G and B) gives a similar result for all channels.
In other words, the sun scattering is relatively equal for all three RGB channels of a standard CCD camera.My question is why are the images bluesh?
Am I missing something??

Thanks!

SolarScattering.jpg
 
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  • #2
What is lambda function? Function of what?
 
  • #3
AlexVM said:
It is common knowledge that the scattering of blue photons by the atmosphere is more significant than for other colors hence aerial images of Earth look bluesh.
The graph below obtained from MODTRAN 'allegedly' supports this fact.

Where was the sun relative to the detector in this simulation?
 
  • #4
The sun is at the Zenith and the detector is looking straight down towards the ground.
 
  • #5
AlexVM said:
The sun is at the Zenith and the detector is looking straight down towards the ground.

Ok, but what is the angle between the sun-ground axis and detector-ground axis?
 
  • #6
All three points are on the same vector - the angle is zero.
 
  • #7
So the sun is behind the detector- thus, the light scattered from sunlight is backscattered to the detector. Angles matter- the sky is most blue when you are looking approximately at a right angle to the sun. Try running MODTRAN with a few different angles and compare the curves, and only plot the range 400 - 700 nm, since digital cameras have IR cut filters.. I'm assuming you don't have any particulate matter included in your simulation...
 

Related to Why Do Aerial Images of Earth Appear Blue Despite Equal RGB Scattering?

1. What is path radiance in atmosphere?

Path radiance in atmosphere refers to the radiance emitted or scattered by particles in the atmosphere along the path of a light beam. It is a measure of the amount of light that reaches an observer from a specific direction after being scattered or absorbed by the atmosphere.

2. How is path radiance in atmosphere different from path radiance in space?

Path radiance in atmosphere is affected by the presence of particles such as dust, water vapor, and pollutants in the atmosphere, which can increase or decrease the amount of light reaching an observer. In contrast, path radiance in space is mainly affected by the distance between the observer and the light source.

3. What factors affect path radiance in atmosphere?

Path radiance in atmosphere is affected by the sun's position, atmospheric conditions such as cloud cover and aerosol content, and the type and concentration of particles in the atmosphere. It can also be affected by surface characteristics, such as the reflectivity of the Earth's surface.

4. How is path radiance in atmosphere measured?

Path radiance in atmosphere can be measured using remote sensing techniques, such as satellite or airborne sensors that detect and measure the amount of light scattered by the atmosphere. It can also be measured using ground-based instruments, such as radiometers and spectrometers.

5. Why is path radiance in atmosphere important to study?

Path radiance in atmosphere is an important factor in understanding and predicting the Earth's climate and weather patterns. It also plays a crucial role in remote sensing applications, such as monitoring air quality, studying the Earth's surface, and detecting changes in the environment. Understanding path radiance in atmosphere can also help improve the accuracy of satellite imagery and weather forecasting models.

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