• Introduction to course
• Atmospheric Phenomena Demonstration

The fundamental detection of volcanic clouds can be summarized by:

input light source -> medium -> output signal -> instrument

This can be more formally described by the Beer-Bouger-Lambert Law.

Vout = Vin * exp (-tm); where
m = 1/cosq, and q = the solar zenith angle
t = optical depth

Let's look at the BBL Law in action, using an example which simulates the process of observing a cloud by satellite sensor.

In Bohren's experiment, two petri dishes with water are placed on a projector screen. In one is added milk, and the other ink, producing a white and a black mixture, respectively. Yet, the projected image of these are identical (gray). Why?

The milk dish is white due to scattering of light, while the ink dish is black due to absorption. However, on the screen one is measuring the transmission of light through the dishes, which is affected by both factors. This transmission, or Vout, is called extinction.

Extinction = scattering + absorption

Therefore, the signal received by a satellite instrument must be interpreted with this in mind, and in order to fully characterize the target (cloud), both effects must be considered.